Protein Phosphorylation In Cells Research Articles

Toxoplasma gondii and Neospora caninum induce different host cell responses at proteome-wide phosphorylation events; a step forward for uncovering the biological differences between these closely related parasites.

Toxoplasma gondii and Neospora caninum are closely related intracellular protozoan parasites and tissue cyst-forming Coccidia of the phylum Apicomplexa. There are remarkable similarities between the morphology, genomes and transcriptomes of both parasites. Toxoplasma is zoonotic, with a wide host range and is mainly transmitted horizontally between its definitive host, the cat, and its intermediate hosts. Neospora causes disease within a narrow host range and with reduced virulence potential to the hosts. The dog is the definitive host of Neospora and its epidemiology in cattle mainly depends on vertical transmission. What causes these biological differences is not well understood. Since these parasites secrete an array of secretory proteins, including kinases, during infection to manipulate host cell responses. Host-parasite interactions due to phosphorylation of host cell proteins by T. gondii kinases enhance virulence and maintenance of infection. In this study, proteome-wide phosphorylation events of host cell proteins were investigated in response to infection with T. gondii and N. caninum using phosphoproteomic analyses, followed by pathway analysis on host signalling pathways. A few interesting differences in host responses at both the qualitative and quantitative levels were identified between the two infections; about one third of the phosphoproteomes, approximately 21% of the phospho-motifs and several pathways such as glycolysis/gluconeogenesis and mTOR pathways of the host cell were found differentially enriched between infection with these parasites. Identifying the differences in host-parasite interactions represents a promising step forward for uncovering the biological dissimilarities between both parasites.

Abstract 2328: Race specific hyper-activation of CCR9-mediated survival signals and its impact on efficacy of docetaxel in prostate cancer

Abstract Current approaches to treat and manage prostate cancer (PCa) have failed to reduce racial disparity primarily due to undefined molecular mechanism. We have shown higher expression of chemokine receptor-9 in PCa cells and CCR9 expression was higher in PCa cells (MDA-PCa-2b) derived from African American (AA) patient compared to PCa cells derived form European American (EA) patients (LNCaP and PC3). Using antibody microarray we observed hyper activation of survival molecules and down-regulation of apoptotic molecules in AA PCa cells compared to EA PCa cell lines, following CCL25 stimulation. Comparative heat map analysis showed significant increase (~2-3 fold) in phosphorylation of pro-survival proteins in AA cells compared to EA cells treated with CCL25, which was further confirmed by western blot analysis. Furthermore, CCL25 treated PCa cells showed decreased expression of pro-apoptotic proteins (Bim, Bid, Bak), which was significantly abrogated by CCR9 shRNA. This effect was more pronounced in AA cells compared to EA cells. Efficacy of docetaxel (DTX) was higher after CCR9 blockade in presence of CCL25 compared to cells treated with CCL25 without blocking CCR9. Improvement in efficacy of DTX was due to inhibition of cell survival and activation of pro-apoptotic signals following CCR9 blockade. These observations suggest potential involvement of CCR9 mediated molecular pathways in disparity associated with outcome of PCa. Citation Format: Neeraj Kapur, Hina Mir, Guru Sonpavde, Shailesh Singh. Race specific hyper-activation of CCR9-mediated survival signals and its impact on efficacy of docetaxel in prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2328. doi:10.1158/1538-7445.AM2017-2328

Abstract 216: Tracking expression, post-translational modifications and interactions of EGF signalling proteins in A431 cells with antibody microarrays

Abstract Elucidation of epidermal growth factor (EGF) signalling pathways in cancer cells has helped to define the mechanisms for their neoplastic transformation and potential drug targets for therapeutic intervention. Antibody microarrays are promising tools to evaluate alterations in the levels and phosphorylation status of hundreds of proteins of interest with only microgram amounts of crude cell and tissue lysate protein. However, interpretations of the results from traditional antibody microarray approaches have been hampered by the problems associated with sample preparation and protein detection, even when reliable antibodies are deployed in these arrays. The Kinex™ KAM-900P antibody microarray permitted semi-quantitative measurements of the expressions, post-translational modifications and interactions of proteins with 100 µg or less of lysate proteins. These microarrays utilize approximately 878 different pan- and phosphosite-specific antibodies for tracking protein kinases, phosphatases and other low abundance regulatory proteins. Multiple detection protocols were developed with the KAM-900P slides to enable high depth profiling of protein levels, phosphorylation and protein-protein interactions in A431 cells in response to EGF treatment. One method (KAM) involved the capture of in vitro biotin-labeled proteins, followed by their detection with a secondary dye-labeled anti-biotin antibody. False positive signals from associated proteins in complexes with the targets were reduced by chemical cleavage with NTCB prior to their capture on the array, and this also produced more uniformity of the dye signals for protein targets despite vast differences in their sizes. Transient changes in protein phosphorylation in EGF treated cells that were typically lost when processed by conventional methods were better preserved by chemical cleavage right at time of sample homogenization. Biotin-labeling and subsequent detection of the protein on the array with a dye-labeled secondary antibody further reduced non-specific background signals, allowed for a greater dynamic range of detection, and enhanced discrimination of subtle changes. In conjunction with other detection protocols, such as the usage of dye-labeled reporter antibodies for generic protein-tyrosine phosphorylation in sandwich antibody microarrays (SAM format) or generic protein phosphorylation with nanoparticles such as pAMIGO (PAM format), it is also feasible to monitor changes in general post-translational modifications of target proteins or their specific association with other adapter, scaffolding and chaperone proteins of interest for which antibody probes are available. Citation Format: Lambert Yue, Steven Pelech. Tracking expression, post-translational modifications and interactions of EGF signalling proteins in A431 cells with antibody microarrays [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 216. doi:10.1158/1538-7445.AM2017-216

Abstract 3935: Dissecting small cell lung carcinoma heterogeneity and chemotherapy resistance with mass cytometry

Abstract Introduction: Small cell lung cancer (SCLC) is a high grade neuroendocrine carcinoma of the lung responsible for up to 25% of lung cancer deaths. Treatment in SCLC has not changed significantly in the last 20 years. SCLC initially responds well to chemotherapy, but inevitably recurs. Characterization of tumor heterogeneity and changes in SCLC cell signaling and phenotypes after chemotherapy could yield new insights and therapeutic options. Mass cytometry uses metal labeled antibodies to profile expression and phosphorylation of more than 40 proteins in single cells and offers the opportunity to identify new subpopulations including potential cancer stem cell populations as well as targets for novel therapies in SCLC. Methods: Nude mice with SCLC patient derived xenografts (PDXs) were treated with one cycle of carboplatin/etoposide or saline injection. Tumors were harvested at ~2000mm3, disaggregated, and cryopreserved. PDX samples were stained with a 22 marker panel and an intercalator dye to identify nucleated cells. This panel measured phospho-signaling, neuroendocrine, immune, and mesenchymal cell markers, and functional markers including ki67 and cleaved caspase 3. ViSNE analysis and biaxial gating were used to identify major subpopulations of interest. Results: PDX tumors released viable tumor and stromal cells suitable for cryopreservation and mass cytometry. ACK buffer and enzymatic dissociation yielded the best quality cells by depleting red blood cells. Mouse cells, including leukocytes, were excluded using mouse MHC1 gating and iridium intercalator was used to identify nucleated cells. Single cell protein expression and phosphorylation was analyzed using viSNE and yielded at least 9 distinct subpopulations based on density islands with neuroendocrine (CD56+) and non-neuroendocrine (CD56-) populations. Chemotherapy treated cells had dramatic changes in subpopulation distribution compared to matched mock treated tumor. This included 2-3 fold expansion of SOX2+, CD117+, and pSTAT3+ populations with chemotherapy treatment. A small CD44+ tumor subpopulation identified in the chemotherapy treated cells was not present in the matched mock treated tumor suggesting a potential chemotherapy resistant/ stem- like subpopulation. Kinase activity showed stable p-AKT overall, but increased p-S6 in the chemotherapy treated cells. Conclusions: Mass cytometry was able to identify multiple neuroendocrine and non-neuroendocrine cell populations from SCLC PDXs and characterize their signaling. Chemotherapy treated PDX had differential subpopulation distribution with enrichment of multiple stem-like signaling factors. This work demonstrates the utility of mass cytometry and viSNE as novel techniques to identify subpopulations associated with chemotherapy resistance for future targeting and demonstrates the feasibility of this technique for characterizing signaling heterogeneity in human SCLC tumors. Citation Format: Jonathan M. Lehman, Nalin Leelatian, Bradford Harris, Megan Hoeksema, Zou Yong, Deon B. Doxie, Jonathan M. Irish, Pierre P. Massion. Dissecting small cell lung carcinoma heterogeneity and chemotherapy resistance with mass cytometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3935. doi:10.1158/1538-7445.AM2017-3935

Connexin 43 mediates changes in protein phosphorylation in HK-2 cells during chronic cadmium exposure

Connexin 43 (Cx43) is believed to play a role in the mechanisms of toxicity of many chemical species, include cadmium (Cd). In this study, human renal proximal tubule (HK-2) cells were exposed to Cd (1μM, 10 days). Of the 584 protein residues detected using a Phospho Explorer antibody microarray (PEX100), more than half changed their levels of phosphorylation after chronic Cd exposure. Cx43 siRNA attenuated Cd-induced apoptosis and inhibited proliferation, while also attenuating changes in the levels of phosphorylation of many protein residues. According to DAVID Bioinformatics Resources analysis and KEGG PATHWAY database, AKT signal pathway may be the important one. Focusing on the AKT pathway confirmed that Cx43 mediated increased levels of p-PTENSer380/Ser382/Thr383 and decreased levels of p-AKTThr308, p-AKTTyr326, p-ASK1Ser83, and p-p27Thr187, thereby possibly contributing to the Cd-induced apoptosis and inhibited proliferation. These results suggested that AKT pathway was the dominant pathway involved in Cx43-mediated chronic Cd toxicity.

Tu1779 - An ex vivo Model to Determine Stat Protein Phosphorylation in Human Colorectal Mononuclear Mucosal Cells Obtained From Biopsies

Tu1779 - An ex vivo Model to Determine Stat Protein Phosphorylation in Human Colorectal Mononuclear Mucosal Cells Obtained From Biopsies

Vertebrate Lonesome Kinase Regulated Extracellular Matrix Protein Phosphorylation, Cell Shape, and Adhesion in Trabecular Meshwork Cells.

Glaucoma, a leading cause of irreversible blindness, is commonly associated with elevated intraocular pressure (IOP) due to impaired aqueous humor (AH) drainage through the trabecular meshwork (TM). Although dysregulated production and organization of extracellular matrix (ECM) is presumed to increase resistance to AH outflow and elevate IOP by altering TM cell contractile and adhesive properties, it is not known whether regulation of ECM protein phosphorylation via the secretory vertebrate lonesome kinase (VLK) influences TM cellular characteristics. Here, we tested this possibility. Experiments carried out in this study reveal that the 32 kDa protein is a prominent VLK isoform detectable in lysates and conditioned media (CM) of human TM cells. Increased levels of VLK were observed in CM of TM cells subjected to cyclic mechanical stretch, or treated with dexamethasone, TGF-β2, and TM cells expressing constitutively active RhoA GTPase. Downregulation of VLK expression in TM cells using siRNA decreased tyrosine phosphorylation (TyrP) of ECM proteins and focal adhesions, and induced changes in cell shape in association with reduced levels of actin stress fibers and phospho-paxillin. VLK was also demonstrated to regulate TGF-β2-induced TyrP of ECM proteins. Taken together, these results suggest that VLK secretion can be regulated by external cues, intracellular signal proteins, and mechanical stretch, and VLK can in turn regulate TyrP of ECM proteins secreted by TM cells and control cell shape, actin stress fibers, and focal adhesions. These observations indicate a potential role for VLK in homeostasis of AH outflow and IOP, and in the pathobiology of glaucoma. J. Cell. Physiol. 232: 2447-2460, 2017. © 2016 Wiley Periodicals, Inc.

Interactome Mapping Guided by Tissue-Specific Phosphorylation in Age-Related Macular Degeneration.

The current study aims to determine the molecular mechanisms of age-related macular degeneration (AMD) using the phosphorylation network. Specifically, we examined novel biomarkers for oxidative stress by protein interaction mapping using in vitro and in vivo models that mimic the complex and progressive characteristics of AMD. We hypothesized that the early apoptotic reactions could be initiated by protein phosphorylation in region-dependent (peripheral retina vs. macular) and tissue-dependent (retinal pigment epithelium vs. retina) manner under chronic oxidative stress. The analysis of protein interactome and oxidative biomarkers showed the presence of tissue- and region-specific post-translational mechanisms that contribute to AMD progression and suggested new therapeutic targets that include ubiquitin, erythropoietin, vitronectin, MMP2, crystalline, nitric oxide, and prohibitin. Phosphorylation of specific target proteins in RPE cells is a central regulatory mechanism as a survival tool under chronic oxidative imbalance. The current interactome map demonstrates a positive correlation between oxidative stress-mediated phosphorylation and AMD progression and provides a basis for understanding oxidative stress-induced cytoskeletal changes and the mechanism of aggregate formation induced by protein phosphorylation. This information could provide an effective therapeutic approach to treat age-related neurodegeneration.

Anti-androgen 2-hydroxyflutamide modulates cadherin, catenin and androgen receptor phosphorylation in androgen-sensitive LNCaP and androgen-independent PC3 prostate cancer cell lines acting via PI3K/Akt and MAPK/ERK1/2 pathways

This study aimed to investigate rapid effect of anti-androgen 2-hydroxyflutamide (HF) on cadherin/catenin complex and androgen receptor (AR) phosphorylation in prostate cancer cell lines. In addition, a role of PI3K/Akt and MAPK/ERK1/2 pathways in mediating these effects was explored. We have demonstrated that in androgen-sensitive LNCaP cells HF induced rapid increase of E-cadherin phosphorylation at Ser 838/840 (p<0.05) in MAPK/ERK1/2-dependent manner, whereas phosphorylation of β-catenin at Tyr 654 was unchanged. Concomitantly, the reduction of the level of AR phosphorylated at Ser210/213 was found (p<0.01). In androgen-independent PC3 cells HF decreased Tyr 860 N-cadherin and Tyr 645 β-catenin phosphorylation (p<0.01), acting via both MAPK/ERK1/2 and PI3K/Akt pathways. Further, we evidenced that MAPK/ERK1/2 and PI3K/Akt pathways were differentially influenced by HF in LNCaP and PC3 cells. In LNCaP cells, both Akt (p<0.01) and ERK1/2 (p<0.001) phosphorylation were negatively regulated and this effect was mediated by Raf-1 (p<0.05). In contrast, in PC3 cells HF stimulated Akt (p<0.001) and ERK1/2 (p<0.001) activation, but had no effect on the crosstalk between PI3K/Akt and MEK/ERK1/2 pathways at the Raf-1 kinase level. Our findings expand the role of anti-androgen into non-genomic signaling, creating a link between anti-androgen action and phosphorylation of adherens junction proteins in prostate cancer cells.

In Gel Kinase Assay.

Proper spatiotemporal regulation of protein phosphorylation in cells and tissues is required for normal development and homeostasis. We present the protocol 'In Gel Kinase Assay', which is useful for protein kinase activity measurements from crude protein extracts. We have successfully used 'In Gel Kinase Assay' protocol to show that the Arabidopsis thaliana sextuple mutant in the PYRABACTIN RESISTANCE1/PYR1-LIKE/REGULATORY COMPONENTS OF ABA RECEPTORS (PYR/PYL/RCAR-ABA receptors; line pyr/pyl112458) is impaired in ABA-mediated activation of SnRK2.2, SnRK2.3 and OST1/SnRK2.6, as much as the triple mutant snrk2.2/2.3/2.6 (Gonzalez-Guzman et al., 2012).

P1.02-055 Synthetic Lethality Dictates the Mutual Exclusivity of Oncogenic Mutations in Lung Adenocarcinoma

EGFR mutations are present in ∼15% and KRAS mutations in ∼30% of lung adenocarcinomas (LACs). Yet, as several observers have noted, no individual LAC appears to carry mutations in both, even in the setting of resistance to EGFR kinase inhibitors. The typical explanation given is that the two genes are entirely functionally redundant, thereby eliminating any selective advantage to mutation of both. In this study we tested an alternative hypothesis for this mutual exclusivity: that co-occurrence of mutations in both KRAS and EGFR is deleterious to the evolving cancer cell. Furthermore, we aimed to characterize the specific cellular effects and signaling pathways induced by mutant KRAS and EGFR co-induction and determine whether this information could be used to design new strategies to inhibit LACs. Next-generation sequence data for over 600 human LACs were acquired from public sources and analyzed for co-incidence of KRAS and EGFR mutation and the relationship to smoking status. Transgenic mice that express both mutant oncogenes specifically in the lung epithelium were generated to test the effects on LAC development. LAC cell lines with endogenous mutations in either KRAS or EGFR were engineered with lentiviral vectors to conditionally express the second oncogene and assessed for cell viability, gene expression and protein phosphorylation changes. Temporal phosphoproteome assessment of cells co-expressing both oncogenes is currently ongoing to determine the specific signaling pathways affected. We confirmed the mutual exclusivity of KRAS and EGFR mutations and demonstrated that this relationship is not due to limited power to detect concurrent mutations in either smokers or non-smokers. While no effect on tumor latency was observed in transgenic mice that express both mutant oncogenes, the resulting tumors preferentially expressed only one of the two transgenic oncogenes, indicating negative selection against co-expression. Introduction of the second oncogene into LAC cells expressing either mutant KRAS or EGFR stimulated the loss of cell viability. The most prominent features accompanying loss of cell viability were vacuolization, other changes in cell morphology, and increased macropinocytosis. Activation of ERK, p38 and JNK was observed in cells expressing both mutants suggesting that an overly active MAPK signaling pathway may mediate this synthetic lethal phenotype. Lastly, this effect is dependent on functionally active EGFR, since inhibition of the EGFR tyrosine kinase with erlotinib rescued cells from the detrimental effects of co-expression. Together, our findings indicate that mutual exclusivity of oncogenic mutations may reveal unexpected vulnerabilities and therapeutic possibilities.

Quantitative Proteomics Reveals the Dynamics of Protein Phosphorylation in Human Bronchial Epithelial Cells during Internalization, Phagosomal Escape, and Intracellular Replication of Staphylococcus aureus.

Internalization of Staphylococcus aureus by nonprofessional phagocytic cells is a major suspected cause of persistent and difficult-to-treat infections, including pneumonia. In this study, we established an infection model with 16HBE14o- human bronchial epithelial cells and demonstrated internalization, escape from phagosomal clearance, and intracellular replication of S. aureus HG001 within the first 4 h postinfection. We used quantitative phosphoproteomics to identify characteristic signaling networks in the host at different infection stages. Although we found only minor changes in protein abundance, the infection was accompanied by highly dynamic alterations in phosphorylation events primarily in proteins that are associated with pathways of cytoskeleton dynamics, cell-cell and cell-matrix contacts, vesicle trafficking, autophagy, and GTPase signaling. Analyses of host protein kinases by kinase-substrate mapping, active regulatory site immunoblotting, and prediction algorithms highlighted known and novel host kinases with putative critical roles in S. aureus infection-accompanied signaling including FAK, PKA, PKC, and CDK. Targeted pharmacological inhibition of these kinases resulted in a significant reduction of intracellular S. aureus cells. The current study constitutes a valuable resource for better understanding the infection-relevant molecular pathomechanisms of airway cells and for developing novel host-centric anti-infective strategies for treating S. aureus infections.

Bile acid receptor TGR5, NADPH Oxidase NOX5-S and CREB Mediate Bile Acid-Induced DNA Damage In Barrett's Esophageal Adenocarcinoma Cells.

The mechanisms whereby bile acid reflux may accelerate the progression from Barrett’s esophagus (BE) to esophageal adenocarcinoma (EA) are not fully understood. In this study we found that bile acid taurodeoxycholic acid (TDCA) significantly increased the tail moment (TM) and histone H2AX phosphorylation in FLO-1 EA cells, an increase which was significantly decreased by knockdown of TGR5. Overexpression of TGR5 significantly increased TDCA-induced TM increase and H2AX phosphorylation. In addition, NADPH oxidase inhibitor diphenylene iodonium significantly inhibited the TDCA-induced increase in TM and H2AX phosphorylation. TDCA-induced increase in TM and H2AX phosphorylation was significantly decreased by knockdown of NOX5-S and overexpression of NOX5-S significantly increased TDCA-induced increase in the tail moment and H2AX phosphorylation. Furthermore, TDCA significantly increased cAMP response element binding protein (CREB) phosphorylation in FLO-1 cells. Knockdown of CREB significantly decreased TDCA-induced increase in NOX5-S mRNA and the tail moment. Conversely, overexpression of CREB significantly increased TDCA-induced TM increase. We conclude that TDCA-induced DNA damage may depend on the activation of TGR5, CREB and NOX5-S. It is possible that in Barrett’s patients bile acids may activate NOX5-S and increase reactive oxygen species (ROS) production via activation of TGR5 and CREB. NOX5-S-derived ROS may cause DNA damage, thereby contributing to the progression from BE to EA.

Biphasic Regulation of Yes-associated Protein (YAP) Cellular Localization, Phosphorylation, and Activity by G Protein-coupled Receptor Agonists in Intestinal Epithelial Cells: A NOVEL ROLE FOR PROTEIN KINASE D (PKD)

We examined the regulation of Yes-associated protein (YAP) localization, phosphorylation, and transcriptional activity in intestinal epithelial cells. Our results show that stimulation of intestinal epithelial IEC-18 cells with the G protein-coupled receptor (GPCR) agonist angiotensin II, a potent mitogen for these cells, induced rapid translocation of YAP from the nucleus to the cytoplasm (within 15 min) and a concomitant increase in YAP phosphorylation at Ser(127) and Ser(397) Angiotensin II elicited YAP phosphorylation and cytoplasmic accumulation in a dose-dependent manner (ED50 = 0.3 nm). Similar YAP responses were provoked by stimulation with vasopressin or serum. Treatment of the cells with the protein kinase D (PKD) family inhibitors CRT0066101 and kb NB 142-70 prevented the increase in YAP phosphorylation on Ser(127) and Ser(397) via Lats2, YAP cytoplasmic accumulation, and increase in the mRNA levels of YAP/TEAD-regulated genes (Ctgf and Areg). Furthermore, siRNA-mediated knockdown of PKD1, PKD2, and PKD3 markedly attenuated YAP nuclear-cytoplasmic shuttling, phosphorylation at Ser(127), and induction of Ctgf and Areg expression in response to GPCR activation. These results identify a novel role for the PKD family in the control of biphasic localization, phosphorylation, and transcriptional activity of YAP in intestinal epithelial cells. In turn, YAP and TAZ are necessary for the stimulation of the proliferative response of intestinal epithelial cells to GPCR agonists that act via PKD. The discovery of interaction between YAP and PKD pathways identifies a novel cross-talk in signal transduction and demonstrates, for the first time, that the PKDs feed into the YAP pathway.

Etoposide induces pancreatic β-cells cytotoxicity via the JNK/ERK/GSK-3 signaling-mediated mitochondria-dependent apoptosis pathway

Etoposide is widely used in the treatment of the different types of tumors such as pancreatic cancer. However, etoposide also causes several unwanted side-effects in normal viable cells, including pancreatic β-cells, which are vulnerable to chemical-induced injuries, and the molecular mechanisms underlying etoposide-induced apoptosis are still unclear. Here, the results showed that in RIN-m5F cells (a β-cell-derived cell line), the number of viable cells was significantly decreased after 24h of etoposide treatment and underwent mitochondria-dependent apoptotic signals accompanied by mitochondrial dysfunction, and increases in the population of sub-G1 hypodiploid cells and apoptotic cells, caspase-3 activity, and the activation of caspase cascades. Etoposide also increased the phosphorylation levels of glycogen synthase kinase (GSK)-3α/β in treated RIN-m5F cells. Pretreatment with LiCl, a GSK-3 inhibitor, prevented etoposide-induced mitochondria-dependent apoptosis and GSK-3 protein phosphorylation in RIN-m5F cells. Furthermore, exposure of the cells to etoposide induced the phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-related kinase (ERK)1/2 but not p38-MAPK, which was suppressed by the specific JNK inhibitor (SP600125) and ERK1/2 inhibitor (PD98059), respectively. Additionally, pretreatment with both SP600125 and PD98059 effectively suppressed etoposide-induced β-cell cytotoxicity, apoptosis, and GSK-3 protein phosphorylation; however, LiCl did not reverse JNK and ERK1/2 phosphorylation. Taken together, these results suggest that etoposide is capable of causing cytotoxicity on pancreatic β-cells by inducing apoptosis through the JNK/ERK-mediated GSK-3 downstream-triggered mitochondria-dependent signaling pathway.

Abstract 1822: Circadian regulation of estrogen receptor alpha protein and phosphorylation in mammary carcinoma cells

Abstract Circadian regulation of nuclear receptors in peripheral tissues is important in the timing of key physiological processes. However few studies have examined circadian regulation of estrogen receptor alpha (ERa) protein in cancer or normal tissues, and no studies have evaluated ERα phosphorylation during the circadian cycle. In addition to transcription, protein turnover and posttranslational modifications are important regulatory mechanisms in the circadian control of protein function. ERα protein is important in regulation of the peripheral clock proteins Period (PER), Cryptochrome (CRY), CLOCK, and brain and muscle arnt-like protein-1 (BMAL1). Several key ERα phosphorylation sites, serine 118 and serine 167, important in regulating ERα function contain consensus sequences for two kinases, casein kinase 1 and 2 (CK1, CK2), that regulate the peripheral clock proteins levels. The present study examined ERα protein levels and phosphorylation in human and rat mammary carcinoma cells following entrainment by 50% serum shock that results in circadian oscillation of clock genes in vitro. In human MCF-7 breast cancer cells, ERα protein levels exhibited circadian regulation after serum shock with an approx. 60% decrease at 4 hours, recovery to baseline level or above at 16 hours, and a 30% decline from baseline at 24 hours. Estradiol treatment resulted in a longer sustained suppression of ERα protein levels. Rat MAT mammary carcinoma cells exhibited a similar circadian regulation of ERα protein following serum shock. In MCF-7 cells, serine 118 phosphorylation was elevated 2-7 fold 4 hours after serum shock with a subsequent return to baseline levels by 12 hours. Estradiol treatment resulted in a more robust circadian cycle of serine 118 phosphorylation of up to 40 fold with peaks occurring between 4-8 hours and at 16-24 hours. A reverse phosphorylation pattern occurred for serine 167 phosphorylation. Serum shock resulted in a single induction up to 23 fold of serine 167 phosphorylation at 8-12 hours that was suppressed by estradiol. In rat MAT cells, serum shock resulted in circadian oscillation of serine 167 phosphorylation up to 3 fold with peaks at 8 and 20 hours that was similar when cells were treated with estradiol. For both MCF-7 cells and MAT cells, it was noted that peak levels of ERa protein and ERα phosphorylation were out of phase. Estradiol induction of cyclin D1 and c-myc mRNA demonstrated functional ERα signaling following serum shock. These data demonstrate a very significant circadian regulation of ERα protein levels and ERα phosphorylation in mammary carcinoma cells following entrainment by serum shock that likely contribute to time-dependent effects on peripheral clock function and ERα signaling in mammary cancer.[A.Y. and Y.Z. contributed equally to this work.] Citation Format: Alix Youngblood, Yifang Zhang, Murali Anbalagan, Dawei Tian, Brian G. Rowan. Circadian regulation of estrogen receptor alpha protein and phosphorylation in mammary carcinoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1822.

Impact of Human Mutant TGFβ1/Fc Protein on Memory and Regulatory T Cell Homeostasis Following Lymphodepletion in Nonhuman Primates.

Transforming growth factor β1 (TGFβ1) plays a key role in T cell homeostasis and peripheral tolerance. We evaluated the influence of a novel human mutant TGFβ1/Fc (human IgG4 Fc) fusion protein on memory CD4+ and CD8+ T cell (Tmem) responses in vitro and their recovery following antithymocyte globulin (ATG)-mediated lymphodepletion in monkeys. TGFβ1/Fc induced Smad2/3 protein phosphorylation in rhesus and human peripheral blood mononuclear cells and augmented the suppressive effect of rapamycin on rhesus Tmem proliferation after either alloactivation or anti-CD3/CD28 stimulation. In combination with IL-2, the incidence of CD4+ CD25hi Foxp3hi regulatory T cells (Treg) and Treg:Th17 ratios were increased. In lymphodepleted monkeys, whole blood trough levels of infused TGFβ1/Fc were maintained between 2 and 7 μg/mL for 35 days. Following ATG administration, total T cell numbers were reduced markedly. In those given TGFβ1/Fc infusion, CD8+ T cell recovery to predepletion levels was delayed compared to controls. Additionally, numbers of CD4+ CD25hi CD127lo Treg increased at 4-6 weeks after depletion but subsequently declined to predepletion levels by 12 weeks. In all monkeys, CD4+ CD25hi Foxp3hi Treg/CD4+ IL-17+ cell ratios were reduced, particularly after stopping TGFβ1/Fc infusion. Thus, human TGFβ1/Fc infusion may delay Tmem recovery following lymphodepletion in nonhuman primates. Combined (low-dose) IL-2 infusion may be required to improve the Treg:Th17 ratio following lymphodepletion.

Defining the functional binding sites of interleukin 12 receptor β1 and interleukin 23 receptor to Janus kinases.

The interleukin (IL)-12-type cytokines IL-12 and IL-23 are involved in T-helper (Th) 1 and Th17 immunity, respectively. They share the IL-12 receptor β1 (IL-12Rβ1) as one component of their receptor signaling complexes, with IL-12Rβ2 as second receptor for IL-12 and IL-23R for IL-23 signal transduction. Stimulation with IL-12 and IL-23 results in activation of receptor-associated Janus kinases (Jak) and phosphorylation of STAT proteins in target cells. The Janus kinase tyrosine kinase (Tyk) 2 associates with IL-12Rβ1, whereas Jak2 binds to IL-23R and also to IL-12Rβ2. Receptor association of Jak2 is mediated by Box1 and Box2 motifs located within the intracellular domain of the receptor chains. Here we define the Box1 and Box2 motifs in IL-12Rβ1 and an unusual Jak2-binding site in IL-23R by the use of deletion and site-directed mutagenesis. Our data show that nonfunctional box motifs abolish IL-12- and IL-23-induced STAT3 phosphorylation and cytokine-dependent proliferation of Ba/F3 cells. Coimmunoprecipitation of Tyk2 by IL-12Rβ1 and Jak2 by IL‑23R supported these findings. In addition, our data demonstrate that association of Jak2 with IL-23R is mandatory for IL-12 and/or IL-23 signaling, whereas Tyk2 seems to be dispensable.

The G Protein-Coupled Estrogen Receptor Agonist G-1 Inhibits Nuclear Estrogen Receptor Activity and Stimulates Novel Phosphoproteomic Signatures.

Estrogen exerts cellular effects through both nuclear (ESR1 and ESR2) and membrane-bound estrogen receptors (G-protein coupled estrogen receptor, GPER); however, it is unclear if they act independently or engage in crosstalk to influence hormonal responses. To investigate each receptor's role in proliferation, transcriptional activation, and protein phosphorylation in breast cancer cells (MCF-7), we employed selective agonists for ESR1 propyl-pyrazole-triol (PPT), ESR2 diarylpropionitrile (DPN), and GPER (G-1) and also determined the impact of xenoestrogens bisphenol-A (BPA) and genistein on these effects. As anticipated, 17β-estradiol (E2), PPT, DPN, BPA, and genistein each enhanced proliferation and activation of an ERE-driven reporter gene whereas G-1 had no significant impact. However, G-1 significantly reduced E2-, PPT-, DPN-, BPA-, and genistein-induced proliferation and ERE activation at doses greater than 500 nM indicating that G-1 mediated inhibition is not ESR isotype specific. As membrane receptors initiate cascades of phosphorylation events, we performed a global phosphoproteomic analysis on cells exposed to E2 or G-1 to identify potential targets of receptor crosstalk via downstream protein phosphorylation targets. Of the 211 phosphorylated proteins identified, 40 and 13 phosphoproteins were specifically modified by E2 and G-1, respectively. Subnetwork enrichment analysis revealed several processes related to cell cycle were specifically enriched by G-1 compared with E2. Further there existed a number of newly identified proteins that were specifically phosphorylated by G-1. These phosphorylation networks highlight specific proteins that may modulate the inhibitory effects of G-1 and suggest a novel role for interference with nuclear receptor activity driven by E2 and xenoestrogens.

Dynamics of PKA phosphorylation and gain of function in cardiac pacemaker cells: a computational model analysis.

Cardiac pacemaker cell function is regulated by a coupled-clock system that integrates molecular cues on the cell-membrane surface (i.e., membrane clock) and on the sarcoplasmic reticulum (SR) (i.e., Ca(2+) clock). A recent study has shown that cotransfection of spontaneous beating cells (HEK293 cells and neonatal rat myocytes) with R524Q-mutant human hyperpolarization-activated cyclic nucleotide-gated molecules (the dominant component of funny channels) increases the funny channel's sensitivity to cAMP and leads to a decrease in spontaneous action potential (AP) cycle length (i.e., tachycardia). We hypothesize that in rabbit pacemaker cells, the same behavior is expected, and because of the coupled-clock system, the resultant steady-state decrease in AP cycle length will embody contributions from both clocks: the initial decrease in the spontaneous AP beating interval, arising from increased sensitivity of the f-channel to cAMP, will be accompanied by an increase in the adenylyl cyclase (AC)-cAMP-PKA-dependent phosphorylation activity, which will further decrease this interval. To test our hypothesis, we used the recently developed Yaniv-Lakatta pacemaker cell numerical model. This model predicts the cAMP signaling dynamics, as well as the kinetics and magnitude of protein phosphorylation in both normal and mutant pacemaker cells. We found that R524Q-mutant pacemaker cells have a shorter AP firing rate than that of wild-type cells and that gain in pacemaker function is the net effect of the R514Q mutation on the functioning of the coupled-clock system. Specifically, our results directly support the hypothesis that changes in Ca(2+)-activated AC-cAMP-PKA signaling are involved in the development of tachycardia in R524Q-mutant pacemaker cells.