Pattern Of Tyrosine Phosphorylation Research Articles

P-109 Nanoflakes of molybdenum disulfide functionalized with catechins modulate the sperm capacitation resulting in an improvement of the IVF outcomes in a swine in vitro model

Abstract Study question Are there any potential effects derived from the exposure of spermatozoa to MoS2/catechins nanoflakes during the process of capacitation? Summary answer The spermatozoa exposure to MoS2/catechin nanoflakes do not induce toxicity on spermatozoa and modulate sperm capacitation in a swine in vitro model. What is known already Molybdenum disulfide (MoS2)is a 2D graphene-like material widely used in a pletora of applications, such as energy storage, catalysts, sensors, lubricants and friction reducers. The unique features of this nanomaterial suggest interesting applications in the biomedical field. To date, there are no data regarding the potential effects of MoS2 nanoflakes on the reproductive field. Study design, size, duration To evaluate the potential effects derived from the interaction between the sperm cells and this material, spermatozoa were exposed to MoS2/Catechins nanoflakes at 10, 1, 0.1 ppm, using catechins as control, during capacitation. Different sperm capacitation events were studied, mainly related to their physic-chemical properties (membrane) and biochemical pathways (intracellular signaling), and then IVF experiments were performed with MoS2/catechins and catechins (0.1 ppm). Ten independent experiments were carried out between November 2020 and November 2021. Participants/materials, setting, methods The sonochemical exfoliation of bulk MoS2 in water-soluble MoS2 nanoflakes was obtained with a flavonoid, catechin (CT), that acts as stabilizing agent remaining anchored onto the surface of the MoS2 sheets. Sperm cells from different animals were included in this study. To evaluate the parameters exposed, different techniques were used: fluorescence microscopy, flow cytometry, western blot and in vitro fertilization assay. Main results and the role of chance No significant differences were found in terms of sperm membrane modifications (acrosome damage and membrane disorder) and sperm biochemical pathways (PKA activity, tyrosine phosphorylation patterns, intracellular calcium concentration and mitochondrial activity) between the groups of study compared to the control group. From the results arise that MoS2/CT nanoflakes do not induce any negative effect on the parameters evaluated related to sperm capacitation. Moreover, the addition of MoS2/CT nanoflakes and CT alone at a specific concentration (0.1 ppm) has demonstrated to increase the spermatozoa fertilizing ability in an IVF assay by increasing the number of fertilized oocytes with respect to the control group. Limitations, reasons for caution Despite the promising results in terms of IVF outcomes, further studies are needed to investigate the nature of the interaction between spermatozoa and the MoS2, as well as the potential effects on embryonic development. Wider implications of the findings Our findings open new interesting perspectives regarding the use of 2D graphene-like materials obtained using natural/bio compounds, to implement new strategies to manage sperm capacitation. Trial registration number not applicable

Is stallion epididymal fluid phosphoproteome affected by the equine reproductive season?

Phosphorylation and dephosphorylation of proteins are considered to be the most important processes in sperm maturation during epididymal transit. The main aim of this study was to isolate and identify phosphoproteins from the epididymal milieu obtained from reproductively mature stallions during and out of the breeding season. With the use of 1D-PAGE and nanoLC-MS/MS, we identified phosphoproteins that fulfil various functions: regulatory, transport, motility, ubiquitination, chaperone, antioxidant, apoptotic and enzymatic. Moreover, we characterized tyrosine, serine and threonine phosphorylation patterns, taking into consideration the seasonal and epididymal segment variables. The intensity of phosphorylation and profiles of phosphoproteins varied in subsequent regions of the epididymis. With the use of western and immunoblot tests, we demonstrated that fourteen proteins underwent phosphorylation both during and out of the breeding season. However, significant differences (p≤0.05) in the phosphorylation status were demonstrated in the case of 44 kDa (glutamine synthetase), 38 kDa (malate dehydrogenase), 34 kDa (clusterin/inorganic pyrophosphatase), 31 kDa (clusterin/ /ubiquitin thioesterase), 29 kDa (14-3-3 protein/purine nucleotide phosphorylase) for the season factor and 55 (Rab GDP dissociation inhibitor alpha) and 31 kDa ((clusterin/ubiquitin thioesterase) proteins for the segment factor. The occurrence of the other phosphoproteins was spontaneous among individuals and in both seasons.

Influence of the Season and Region Factor on Phosphoproteome of Stallion Epididymal Sperm

Simple SummaryPhosphorylation and dephosphorylation of proteins are considered to be the most important processes in sperm maturation during the epididymal transit. We demonstrated that 27 proteins underwent phosphorylation both in and out of the breeding season. Differences in the phosphorylation status were demonstrated in the case of endoplasmic reticulum chaperone BiP, albumin, protein disulfide-isomerase A3, nesprin-1, peroxiredoxin-5, and protein bicaudal D homolog.Epididymal maturation can be defined as a scope of changes occurring during epididymal transit that prepare spermatozoa to undergo capacitation. One of the most common post-translational modifications involved in the sperm maturation process and their ability to fertilise an oocyte is the phosphorylation of sperm proteins. The aim of this study was to compare tyrosine, serine, and threonine phosphorylation patterns of sperm proteins isolated from three subsequent segments of the stallion epididymis, during and out of the breeding season. Intensities of phosphorylation signals and phosphoproteins profiles varied in consecutive regions of the epididymis. However, significant differences in the phosphorylation status were demonstrated in case of endoplasmic reticulum chaperone BiP (75 and 32 kDa), protein disulfide-isomerase A3 (50 kDa), nesprin-1 (23 kDa), peroxiredoxin-5 (17 kDa), and protein bicaudal D homolog (15 kDa) for season x type of phosphorylated residues variables. Significant differences in the phosphorylation status were also demonstrated in case of endoplasmic reticulum chaperone BiP and albumin (61 kDa), protein disulfide-isomerase A3 (50 kDa), and protein bicaudal D homolog (15 kDa) for region x type of phosphorylated residues variables.

P–113 α-tubulin and tyrosine phosphorylation immunolocalization on human sperm from a globozoospermic patient with proper embryo development after ICSI

Abstract Study question Can novel sperm biomarkers, such as α-tubulin and tyrosine phosphorylation, help to predict the fertilizing potential osf a globozoospermic sample? Summary answer The characterization of α-tubulin and tyrosine phosphorylation provide additional information that could be useful to determine the fertilizing capacity of the globozoospermic samples. What is known already Globozoospermia is a severe disorder characterized by the acrosome absence and other sperm alterations such as tail structural disorders and chromatin condensation abnormalities. This set of defects makes globozoospermia correlates with primary infertility and low fertilisation rates. Therefore, additional studies are necessary to know how the globozoospermia affects the disposition of α-tubulin and tyrosine phosphorylation and the relationship between embryo development and pregnancy. In this context, previous studies have independently described different patterns of α-tubulin and tyrosine phosphorylation in normozoospermic samples. Specifically, the continuous α-tubulin distribution along the flagellum and tyrosine phosphorylation have been recently linked to proper sperm functionality. Study design, size, duration We conducted a prospective study. The sample was obtained from a globozoospermic patient in October 2019. This sample was divided into two fractions, one proceeded to ICSI and the another was fixed to characterize α-tubulin and tyrosine phosphorylation using confocal microscopy. A total of 200 sperm were analyzed for each biomarker. Participants/materials, setting, methods A 38-year-old man requested assisted reproduction in IVF Spain after a failed treatment with no fertilized oocytes. The clinical procedure was performed at IVF Spain and the characterization studies were made at the University of Alicante. The flagellar cytoskeleton was assessed using anti-α-tubulin antibody (Sigma-Aldrich) at a 1:600 dilution. Besides, tyrosine phosphorylation was detected using anti-phosphotyrosine primary antibody (PY20, Sigma-Aldrich) at a 1:500 dilution. Spermatozoa were evaluated using a confocal microscope (Zeiss LSM 800). Main results and the role of chance Regarding the α-tubulin characterization, only the 33% of spermatozoa showed continuous labelling in the tail and in the 67% the fluorescence appeared in the terminal piece of the flagellum. Otherwise, we only observed 0.5% of positive tyrosine phosphorylation in the studied cells, whereas the 99.5% of sperm analyzed did not show positive fluorescence. The clinical parameters showed a fertilization rate of 20% with only one embryo after the MII oocyte artificial activation by calcium ionophore. The embryo development was further adequate, and it acquired Bt5AA status on day five. Unfortunately, the pregnancy did not ensue after the embryo transfer. Limitations, reasons for caution The main limitation of this study was that due to the very low frequency of globozoospermia (<0.01%) this research was conducted only in one patient. Thus, the present results are preliminary. We need to characterize the aforementioned biomarkers in additional globozoospermic samples to establish relationships with clinical parameters. Wider implications of the findings: The study of potential candidate biomarkers like α-tubulin and tyrosine phosphorylation in globozoospermia and the linkage with clinical parameters would facilitate the diagnosis and improve the selection of more effective treatment techniques. Trial registration number Not applicable

A Functional Interplay Between Pyk2 and Src Family Kinases Links Ca2+ Signaling To Protein Tyrosine Phosphorylation In Thrombin-Stimulated Platelets

IntroductionThrombin and other soluble agonists promote platelet activation by binding to G-protein-coupled receptors, which typically recruit phospholipase C and trigger cytosolic Ca2+ increase and protein kinase C stimulation. Platelets also express several tyrosine kinases, including different members of the Src family (mainly Src and Lyn) and of the focal adhesion family (such as FAK and Pyk2), which are known to be activated upon stimulation with thrombin. Both Src family kinases (SFKs) and Pyk2 are required for thrombin-induced aggregation and thromboxane A2 production, and both of them have been shown to be regulated by intracellular Ca2+ (Xiang et al, J Biol Chem 2012; Canobbio et al, Blood 2013). However, the hierarchy of protein tyrosine kinases activation, as well as the molecular mechanism linking agonist-induced increase of cytosolic Ca2+ to protein tyrosine phosphorylation is poorly understood. In this study, we investigated the interplay between intracellular Ca2+, Pyk2 and SFKs in the regulation of protein tyrosine phosphorylation in thrombin-stimulated platelets. ResultsIn the presence of the ADP scavenger apyrase, thrombin caused the time-dependent tyrosine phosphorylation of several proteins in aspirin-treated human, as well as mouse platelets. This effect was severely reduced by the intracellular Ca2+ chelator BAPTA-AM and by the SFKs inhibitor PP2, and was totally suppressed only when BAPTA-AM and PP2 were used in combination, indicating that cytosolic Ca2+ and SFKs activity cooperate in the regulation of the whole process of protein tyrosine phosphorylation elicited by thrombin. Analysis of SFKs activity in human and mouse platelets with an anti-pY416Src antibody, that detects the autophosphorylation site in the catalytic domain, revealed that cytosolic Ca2+ is upstream SFKs activation upon thrombin stimulation. Accordingly, SFKs phosphorylation in the catalytic domain was also directly promoted by the Ca2+ ionophore A23187. Immunoblotting analysis on high resolution gels allowed to distinguish between Src and Lyn, and revealed that PP2 prevented phosphorylation of both kinases, but BAPTA-AM only inhibited Src , but not Lyn phosphorylation caused by thrombin. The Ca2+ ionophore A23187 also triggered the phosphorylation and activation of the Ca2+-dependent focal adhesion kinase Pyk2, and stimulation with thrombin promoted Pyk2 activation by a Ca2+-dependent mechanism. However, thrombin- or A23187-induced activation of Pyk2 was also reduced by the SFKs inhibitor PP2, and both PP2 and BAPTA-AM were required to completely suppress Pyk2 activation. In platelets from Pyk2 knockout mice, stimulation of SFKs by thrombin was strongly reduced, as it was the overall pattern of protein tyrosine phosphorylation. Importantly, also SFKs activation caused by Ca2+ionophore was significantly impaired in Pyk2-deficient platelets. Finally, in the absence of Pyk2, thrombin-induced aggregation was reduced to a level comparable to that of wild type platelets treated with PP2, although inhibition of SFKs by PP2 further reduced aggregation of Pyk2-deficient platelets. ConclusionsThese results indicate that in thrombin-stimulated platelets intracellular Ca2+ increase promotes Pyk2 stimulation, which initiates SFKs activation and establishes a positive loop which reinforces the Pyk2/SFKs axis to allow the subsequent massive tyrosine phosphorylation of multiple platelet substrates. Disclosures:No relevant conflicts of interest to declare.

Proteomic analysis of tyrosine phosphorylation induced by exogenous expression of oncogenic kinase fusions identified in lung adenocarcinoma.

Kinase fusions are considered oncogenic drivers in numerous types of cancer. In lung adenocarcinoma 5-10% of patients harbor kinase fusions. The most frequently detected kinase fusion involves the Anaplastic Lymphoma Kinase (ALK) and Echinoderm Microtubule-associated protein-Like 4 (EML4). In addition, oncogenic kinase fusions involving the tyrosine kinases RET and ROS1 are found in smaller subsets of patients. In this study, we employed quantitative mass spectrometry-based phosphoproteomics to define the cellular tyrosine phosphorylation patterns induced by different oncogenic kinase fusions identified in patients with lung adenocarcinoma. We show that exogenous expression of the kinase fusions in HEK 293T cells leads to widespread tyrosine phosphorylation. Direct comparison of different kinase fusions demonstrates that the kinase part and not the fusion partner primarily defines the phosphorylation pattern. The tyrosine phosphorylation patterns differed between ALK, ROS1, and RET fusions, suggesting that oncogenic signaling induced by these kinases involves the modulation of different cellular processes.

Boar sperm incubation with reduced glutathione (GSH) differentially modulates protein tyrosine phosphorylation patterns and reorganization of calcium in sperm, in vitro fertilization, and embryo development depending on concentrations

The sperm in the female's reproductive tract undergo changes to fertilize the oocyte (sperm capacitation). These changes are regulated by redox system. However, some assisted reproductive technologies require sperm capacitation under in vitro conditions, though this increases the generation of ROS. Therefore, the aim of this study was to evaluate the effect of GSH as an antioxidant agent during the capacitation of boar sperm [evaluated by calcium compartmentalization, tyrosine phosphorylation (Tyr-P), motility, viability, and acrosomal integrity], in vitro fertilization (evaluated by penetration, monospermy, and efficiency %), and later embryo development (evaluated by cleavage and blastocyst rates, total number of cells per blastocyst and blastocyst diameter). Four experimental groups with different GSH concentrations (0-control, 0.5, 1, and 5 mM) were formed. When 1-GSH was added to the medium, the percentage of capacitated sperm increased after 4 h of incubation; the localization of Tyr-P was modified at 1 h and 4 h of incubation depending on the GSH concentration. Percentages of total and progressive sperm motility also increased at 4 h of incubation, but only in the 5-GSH group compared to control. Viability, acrosomal integrity, and general Tyr-P (Western blot) not differ among the experimental groups. The addition of GSH during gamete interaction increased penetration, monospermy, and efficiency rates in the 1-GSH group compared to the others. However, the effect of GSH was not observed in cleavage and blastocyst rates compared to the control. In conclusion, adding GSH modulates sperm capacitation (by means of calcium compartmentalization and tyrosine phosphorilation pattern) depending on its concentration, and improves IVF output at 1-GSH during gamete interaction.

Regulation of mitotic spindle orientation by phosphorylation of end binding protein 1

End binding protein 1 (EB1) is a key regulator of microtubule dynamics that orchestrates hierarchical interaction networks at microtubule plus ends to control proper cell division. EB1 activity is known to be regulated by serine/threonine phosphorylation; however, how tyrosine phosphorylation affects EB1 activity remains poorly understood. In this study, we mapped the tyrosine phosphorylation pattern of EB1 in synchronized cells and identified two tyrosine phosphorylation sites (Y217 and Y247) in mitotic cells. Using phospho-deficient (Y/F) and phospho-mimic (Y/D) mutants, we revealed that Y247, but not Y217, is critical for astral microtubule stability. The Y247D mutant contributed to increased spindle angle, indicative of defects in spindle orientation. Time-lapse microscopy revealed that the Y247D mutant significantly delayed mitotic progression by increasing the duration times of prometaphase and metaphase. Structural analysis suggests that Y247 mutants lead to instability of the hydrophobic cavity in the EB homology (EBH) domain, thereby affecting its interactions with p150glued, a protein essential for Gαi/LGN/NuMA complex capture. These findings uncover a crucial role for EB1 phosphorylation in the regulation of mitotic spindle orientation and cell division.

The role of Aquaporin-4 in T cell activation

Abstract Aquaporins (AQPs) are membrane channels that mediate a variety of biological processes via water and other small molecule movement. Several aquaglyceroporins have been shown to regulate key immune functions. However, the role of AQP4 in immune cells is poorly characterized. We recently reported that AQP4 is expressed by both naïve and memory CD4 and CD8 T cells. Furthermore, AQP4 blockade with a small molecule inhibitor, AER-270, reduced T cell activation and proliferation leading to a significant prolongation of fully MHC-mismatched murine heart allograft survival. The goal of this study was to determine the mechanisms by which AQP4 facilitates T cell activation and TCR signaling. Wild-type (WT) but not AQP4−/− T cells treated with AER-270 were protected from lysis in a hypoosmotic shock assay demonstrating AQP4 requirement for water transport in T cells. Following αCD3/αCD28 stimulation, AQP4−/− T cells demonstrated inferior activation compared to WT T cells. Similar decreased activation was observed after treatment of WT T cells with AER-270. Consistent with reduced T cell activation, AQP4 inhibition diminished Ca2+flux in WT but not AQP4−/− T cells in response to TCR crosslinking. AQP4 inhibition also resulted in altered pattern of protein tyrosine phosphorylation at 2 min following TCR crosslinking. These results indicate that despite T cell expression of several water channels, AQP4 function is critical for optimal T cell activation and functions. Our study identifies a novel role of water channels in T cell biology and suggests AQP4 inhibition as a promising strategy to modulate T cell alloresponses following transplantation.

Boar sperm protein tyrosine phosphorylation in the presence of egg yolk soluble and low density lipoprotein fractions during cooling

Increased protein tyrosine phosphorylation and the appearance of a phosphorylated protein of 32 kD (p32) are reported among the capacitation-like changes in cryopreserved boar sperm. Egg yolk freezing extenders are composed by two fractions: insoluble granules and soluble plasma, which contains the low density lipoproteins (LDL) proposed as responsible for the egg yolk cryoprotective action. The aim of this work was to analyze the effects of complete egg yolk and its insoluble, soluble and LDL fractions on boar sperm quality and protein tyrosine phosphorylation after the first stage of a standard cryopreservation protocol. Semen samples in Androstar® Plus diluent were centrifuged and resuspended in the different egg yolk extenders. Temperature was decreased from 17 °C to 5 °C and sperm quality, protein tyrosine phosphorylation and protein pattern were analyzed. Results showed that complete egg yolk as well as soluble and LDL egg yolk fractions maintained sperm quality after temperature decrease. Cooling without any lipid component or in the presence of the insoluble fraction, significantly reduced sperm motility. About sperm protein tyrosine phosphorylation analysis, the p32 band appeared before treatments or after cooling in Androstar® Plus diluent. Complete egg yolk and its insoluble fraction interfered with sperm tyrosine phosphorylation even after cells were extensively washed. Analysis of extenders revealed a high amount of tyrosine phosphorylated proteins in the insoluble fraction, which may have co-precipitate with sperm in experiments. Samples submitted to temperature decrease from 17 °C to 5 °C in the presence of soluble and LDL egg yolk fractions in Androstar® Plus diluent did not show any change in the p32 band associated with sperm capacitation. However, a tyrosine-phosphorylated protein of 33 kD present in clarified egg yolk was also observed in sperm treated with this extender. Protein transference from plasma and LDL egg yolk extenders was also observed in sperm protein profile. Results suggested that soluble and LDL fractions might have a protective action preventing sperm protein tyrosine phosphorylation during cooling from 17 °C to 5 °C. Further studies are needed to expand the knowledge of the LDL protection mechanism as well as to determine the possible benefits of clarified egg yolk in freezing protocols.

IgG-Independent Co-aggregation of FcεRI and FcγRIIB Results in LYN- and SHIP1-Dependent Tyrosine Phosphorylation of FcγRIIB in Murine Bone Marrow-Derived Mast Cells.

Activation of the high-affinity receptor for IgE (FcεRI) follows a bell-shaped dose-response curve. Upon supra-optimal stimulation, mast cell effector responses are down-regulated by inhibitory molecules like the SH2-containing inositol-5′-phosphatase SHIP1 and the SRC-family-kinase LYN. To identify further molecules involved in a negative regulatory signalosome, we screened for proteins showing the same pattern of tyrosine phosphorylation as SHIP1, which is tyrosine-phosphorylated strongest upon supra-optimal antigen (Ag) stimulation. The low-affinity IgG receptor, FcγRIIB, was found to be most strongly phosphorylated under supra-optimal conditions. This phosphorylation is the consequence of passive, Ag/IgE-dependent and progressive co-localization of FcεRI and FcγRIIB, which is not dependent on IgG. Upon supra-optimal FcεRI cross-linking, FcγRIIB phosphorylation is executed by LYN and protected from dephosphorylation by SHIP1. Analysis of FcγRIIB-deficient bone marrow-derived mast cells revealed an ambiguous phenotype upon FcεRI cross-linking. Absence of FcγRIIB significantly diminished the level of SHIP1 phosphorylation and resulted in augmented Ca2+ mobilization. Though, degranulation and IL-6 production were only weakly altered. Altogether our data establish the LYN/FcγRIIB/SHIP1 signalosome in the context of FcεRI activation, particularly at supra-optimal Ag concentrations. The fact that SHIP1 tyrosine phosphorylation/activation not only depends on FcγRIIB, highlights the necessity for its tight backup control.

A threshold model for receptor tyrosine kinase signaling specificity and cell fate determination.

Upon ligand engagement, the single-pass transmembrane receptor tyrosine kinases (RTKs) dimerize to transmit qualitatively and quantitatively different intracellular signals that alter the transcriptional landscape and thereby determine the cellular response. The molecular mechanisms underlying these fundamental events are not well understood. Considering recent insights into the structural biology of fibroblast growth factor signaling, we propose a threshold model for RTK signaling specificity in which quantitative differences in the strength/longevity of ligand-induced receptor dimers on the cell surface lead to quantitative differences in the phosphorylation of activation loop (A-loop) tyrosines as well as qualitative differences in the phosphorylation of tyrosines mediating substrate recruitment. In this model, quantitative differences on A-loop tyrosine phosphorylation result in gradations in kinase activation, leading to the generation of intracellular signals of varying amplitude/duration. In contrast, qualitative differences in the pattern of tyrosine phosphorylation on the receptor result in the recruitment/activation of distinct substrates/intracellular pathways. Commensurate with both the dynamics of the intracellular signal and the types of intracellular pathways activated, unique transcriptional signatures are established. Our model provides a framework for engineering clinically useful ligands that can tune receptor dimerization stability so as to bias the cellular transcriptome to achieve a desired cellular output.

Murine sperm capacitation, oocyte penetration and decondensation following moderate alcohol intake.

Male chronic alcohol abuse causes testicular failure and infertility. We analyzed the effects of moderate sub-chronic alcohol intake on sperm morphology, capacitation, fertilization and sperm head decondensation. CF-1 male mice were administered 15% ethanol in drinking water for 15 days; control mice received ethanol-free water. Similar patterns of tyrosine phosphorylation were observed in capacitated spermatozoa of control and treated males. Percentage of hyperactivation (H) and spontaneous (SAR) and progesterone-induced (IAR) acrosome reaction significantly decreased at 120 and 150 min of capacitation in treated males compared to controls (H: 14.1 ± 2.5 vs 23.7 ± 2.6, P < 0.05; SAR-T120 min: 17.9 ± 2.5 vs 32.9 ± 4.1, P < 0.01; IAR-150 min: 43.3 ± 3.5 vs 73.1 ± 1.1, P < 0.001, n = 6). During in vitro fertilization (2.5, 3.5 and 4.5 h post-insemination), there was an increased percentage of fertilized oocytes (with a decondensed sperm head and one or two pronuclei) in treated males (P < 0.001, n = 7). After 60 min of in vitro decondensation with glutathione plus heparin, the percentage of decondensed sperm heads was significantly higher in treated males than in controls (mean ± s.d.: 57.1 ± 5.6 vs 48.3 ± 4.5, P < 0.05, n = 5). The percentage of morphologically normal sperm heads was significantly decreased in treated males with respect to controls (P < 0.001, n = 9). These results show that short-term moderate alcohol consumption in outbred mice affect sperm morphology, hyperactivation, acrosomal exocytosis, and the dynamics of in vitro fertilization and in vitro sperm nuclear decondensation.

Activation Status of Receptor Tyrosine Kinases as an Early Predictive Marker of Response to Chemotherapy in Osteosarcoma

Receptor tyrosine kinases (RTKs) are membrane receptors that play a vital role in various biological processes, in particular, cell survival, cell proliferation, and cell differentiation. These cellular processes are composed of multitiered signaling cascades of kinases starting from ligand binding to extracellular domains of RTKs that activate the entire pathways through tyrosine phosphorylation of the receptors and downstream effectors. A previous study reported that, based on proteomics data, RTKs were a major candidate target for osteosarcoma. In this study, activation profiles of six candidate RTKs, including c-Met, c-Kit, VEGFR2, HER2, FGFR1, and PDGFRα, were directly examined from chemonaive fresh frozen tissues of 32 osteosarcoma patients using a multiplex immunoassay. That examination revealed distinct patterns of tyrosine phosphorylation of RTKs in osteosarcoma cases. Unsupervised hierarchical clustering was calculated using Pearson uncentered correlation coefficient to classify RTKs into two groups—Group A (c-Met, c-Kit, VEGFR2, and HER2) and Group B (FGFR1 and PDGFRα)—based on tyrosine phosphorylation patterns. Nonactivation of all Group A RTKs was associated with shorter overall survival in stage IIB osteosarcoma patients. Percentages of tumor necrosis in patients with inactive Group A RTKs were significantly lower than those in patients with at least one active Group A RTK. Paired primary osteosarcoma cells with fresh osteosarcoma tissue were extracted and cultured for cytotoxicity testing. Primary cells with active Group A RTKs tended to be sensitive to doxorubicin and cisplatin. We also found that osteosarcoma cells with active Group A RTKs were more proliferative than cells with inactive Group A RTKs. These findings indicate that the activation pattern of Group A RTKs is a potential risk stratification and chemoresponse predictor and might be used to guide the optimum chemotherapy regimen for osteosarcoma patients.

Phosphoproteomic Profiling Reveals ALK and MET as Novel Actionable Targets across Synovial Sarcoma Subtypes.

Despite intensive multimodal treatment of sarcomas, a heterogeneous group of malignant tumors arising from connective tissue, survival remains poor. Candidate-based targeted treatments have demonstrated limited clinical success, urging an unbiased and comprehensive analysis of oncogenic signaling networks to reveal therapeutic targets and personalized treatment strategies. Here we applied mass spectrometry-based phosphoproteomic profiling to the largest and most heterogeneous set of sarcoma cell lines characterized to date and identified novel tyrosine phosphorylation patterns, enhanced tyrosine kinases in specific subtypes, and potential driver kinases. ALK was identified as a novel driver in the Aska-SS synovial sarcoma (SS) cell line via expression of an ALK variant with a large extracellular domain deletion (ALKΔ2-17). Functional ALK dependency was confirmed in vitro and in vivo with selective inhibitors. Importantly, ALK immunopositivity was detected in 6 of 43 (14%) of SS patient specimens, one of which exhibited an ALK rearrangement. High PDGFRα phosphorylation also characterized SS cell lines, which was accompanied by enhanced MET activation in Yamato-SS cells. Although Yamato-SS cells were sensitive to crizotinib (ALK/MET-inhibitor) but not pazopanib (VEGFR/PDGFR-inhibitor) monotherapy in vitro, synergistic effects were observed upon drug combination. In vivo, both drugs were individually effective, with pazopanib efficacy likely attributable to reduced angiogenesis. MET or PDGFRα expression was detected in 58% and 84% of SS patients, respectively, with coexpression in 56%. Consequently, our integrated approach has led to the identification of ALK and MET as promising therapeutic targets in SS. Cancer Res; 77(16); 4279-92. ©2017 AACR.

Structural Elucidation of the Binding of the Vav‐SH2 Domain to the EphA2 Cytoplasmic Region

The Vav guanine nucleotide exchange factors (GEFs) facilitate the GDP/GTP exchange of the Rac/Rho family of small GTPases to modulate cytoskeletal organization, cell morphology and mobility. In endothelial cells, Vav interacts with the EphA2 receptor tyrosine kinase (RTK) with its C‐terminal SH2 domain and plays a crucial role in EphA2‐mediated angiogenesis in cancers. Two closely‐spaced tyrosines in the juxtamembrane segment (JM) of the EphA2 cytoplasmic region, Y588 and Y594, were the postulated Vav‐SH2 recognition sites. Quantitative mass spectrometry data suggests that both JM tyrosines are phosphorylated with high stoichiometry in mammalian cells. However, they exhibit different rates of dephosphorylation by human cytoplasmic protein tyrosine phosphatases (HCPTPs). To characterize the role of each JM phosphotyrosine in Vav‐SH2 binding, isothermal titration calorimetry (ITC) and 15N‐HSQC titration experiments were performed using bacterially expressed Vav1‐SH2 and synthetic JM peptides with different tyrosine phosphorylation patterns. The ITC data indicates Vav1‐SH2 binds preferentially to the doubly phosphorylated and the Y594‐phosphorylated version of JM peptide (JMpYpY and JMYpY), with a KD 10‐fold smaller than the Y588‐phosphorylated version (JMpYY). The 15N‐HSQC spectra suggests all three versions of synthetic JM phosphopeptides bind Vav‐SH2 in similar fashions. The chemical shift perturbation (CSP) analysis of the titration spectra reveals both the primary and secondary phosphotyrosine binding pockets of Vav1‐SH2 are involved in JM phosphopeptide recognition, suggesting each phosphotyrosine has its designated binding pocket. Subsequent 3D NOESY‐HSQC experiments and crystallization trials are undergoing in order to resolve the peptide configuration in the complex of the Vav‐SH2 domain and the JM phosphopeptides.Support or Funding InformationPurdue University Center for Cancer Research

SH2 Domain Histochemistry.

Among posttranslational modifications, the phosphorylation of tyrosine residues is a key modification in cell signaling. Because of its biological importance, characterization of the cellular state of tyrosine phosphorylation is of great interest. Based on the unique properties of endogenously expressed SH2 domains recognizing tyrosine phosphorylated signaling proteins with high specificity we have developed an alternative approach, coined SH2 profiling, enabling us to decipher complex patterns of tyrosine phosphorylation in various normal and cancerous tissues. So far, SH2 profiling has largely been applied for the analysis of protein extracts with the limitation that information on spatial distribution and intensity of tyrosine phosphorylation within a tissue is lost. Here, we describe a novel SH2 domain based strategy for differential characterization of the state of tyrosine phosphorylation in formaldehyde-fixed and paraffin-embedded tissues. This approach demonstrates that SH2 domains may serve as very valuable tools for the analysis of the differential state of tyrosine phosphorylation in primary tissues fixed and processed under conditions frequently applied by routine pathology laboratories.

Resolution of Novel Pancreatic Ductal Adenocarcinoma Subtypes by Global Phosphotyrosine Profiling

Comprehensive characterization of signaling in pancreatic ductal adenocarcinoma (PDAC) promises to enhance our understanding of the molecular aberrations driving this devastating disease, and may identify novel therapeutic targets as well as biomarkers that enable stratification of patients for optimal therapy. Here, we use immunoaffinity-coupled high-resolution mass spectrometry to characterize global tyrosine phosphorylation patterns across two large panels of human PDAC cell lines: the ATCC series (19 cell lines) and TKCC series (17 cell lines). This resulted in the identification and quantification of over 1800 class 1 tyrosine phosphorylation sites and the consistent segregation of both PDAC cell line series into three subtypes with distinct tyrosine phosphorylation profiles. Subtype-selective signaling networks were characterized by identification of subtype-enriched phosphosites together with pathway and network analyses. This revealed that the three subtypes characteristic of the ATCC series were associated with perturbations in signaling networks associated with cell-cell adhesion and epithelial-mesenchyme transition, mRNA metabolism, and receptor tyrosine kinase (RTK) signaling, respectively. Specifically, the third subtype exhibited enhanced tyrosine phosphorylation of multiple RTKs including the EGFR, ERBB3 and MET. Interestingly, a similar RTK-enriched subtype was identified in the TKCC series, and 'classifier' sites for each series identified using Random Forest models were able to predict the subtypes of the alternate series with high accuracy, highlighting the conservation of the three subtypes across the two series. Finally, RTK-enriched cell lines from both series exhibited enhanced sensitivity to the small molecule EGFR inhibitor erlotinib, indicating that their phosphosignature may provide a predictive biomarker for response to this targeted therapy. These studies highlight how resolution of subtype-selective signaling networks can provide a novel taxonomy for particular cancers, and provide insights into PDAC biology that can be exploited for improved patient management.

Protein modification in the post-mating spermatophore of the signal crayfish Pacifastacus leniusculus: insight into the tyrosine phosphorylation in a non-motile spermatozoon

After mating, spermatophores of signal crayfish are stored on the body of the female for a period before fertilization. This study compared the post-mating protein profile and pattern of protein tyrosine phosphorylation of the signal crayfish spermatophore to that of the freshly ejaculated spermatophore and found substantial differences. Two major bands of tyrosine-phosphorylated proteins of molecular weights 10 and 50kDa were observed in the freshly ejaculated spermatophore of the signal crayfish. While the tyrosine-phosphorylated protein band with molecular weight 10kDa was formed by protein(s) of similar pH, the band with molecular weight of 50kDa consisted of proteins of varying pH. In the post-mating spermatophore, the band with molecular weight of 50kDa was not detected, and an increase in the level of protein tyrosine phosphorylation was observed in the 10kDa band. The microtubular radial arms of the spermatozoon showed a positive reaction to an anti-tyrosine antibody conjugated with gold particles in both the freshly ejaculated and post-mating spermatophores. In conclusion, the male gamete of the signal crayfish undergoes molecular modification during post-mating storage on the body of the female including changes in the level of protein expression and protein tyrosine phosphorylation. Structural similarity of the radial arms in the crayfish immotile spermatozoon with flagellum, which is the main site of protein tyrosine phosphorylation in the mammalian motile spermatozoa, raises questions regarding evolution and function of such organelles across the animal kingdom that must be addressed in the future studies.

Nuclear Translocation of Crk Adaptor Proteins by the Influenza A Virus NS1 Protein.

The non-structural protein-1 (NS1) of many influenza A strains, especially those of avian origin, contains an SH3 ligand motif, which binds tightly to the cellular adaptor proteins Crk (Chicken tumor virus number 10 (CT10) regulator of kinase) and Crk-like adapter protein (CrkL). This interaction has been shown to potentiate NS1-induced activation of the phosphatidylinositol 3-kinase (PI3K), but additional effects on the host cell physiology may exist. Here we show that NS1 can induce an efficient translocation of Crk proteins from the cytoplasm into the nucleus, which results in an altered pattern of nuclear protein tyrosine phosphorylation. This was not observed using NS1 proteins deficient in SH3 binding or engineered to be exclusively cytoplasmic, indicating a physical role for NS1 as a carrier in the nuclear translocation of Crk. These data further emphasize the role of Crk proteins as host cell interaction partners of NS1, and highlight the potential for host cell manipulation gained by a viral protein simply via acquiring a short SH3 binding motif.