Phosphotyrosine Protein Research Articles

EGF-like peptide-enhanced cell movement in Dictyostelium is mediated by protein kinases and the activity of several cytoskeletal proteins

DdEGFL1, a synthetic epidermal growth factor-like (EGFL) peptide based on the first EGFL repeat of the extracellular matrix, cysteine-rich, calmodulin-binding protein CyrA, has previously been shown to sustain the threonine phosphorylation of a 210kDa protein during the starvation of Dictyostelium cells. Immunoprecipitation coupled with a LC/MS/MS analysis identified the 210kDa protein as vinculin B (VinB). VinB shares sequence similarity with mammalian vinculin, a protein that links the actin cytoskeleton to the plasma membrane. Both threonine phosphorylated VinB (P-VinB) and VinB-GFP localized to the cytoplasm and cytoskeleton of Dictyostelium amoebae. VinB-GFP was also shown to be threonine phosphorylated and co-immunoprecipitated with established vinculin-binding cytoskeletal proteins (e.g. myosin II heavy chain, actin, alpha-actinin, talin). P-VinB and VinB-GFP were detected in DdEGFL1 pull-down assays, which also identified a 135kDa phosphothreonine protein and two phosphotyrosine proteins (35 and 32kDa) as potential components of the DdEGFL1 signaling pathway. DdEGFL1-enhanced cell movement required the cytoskeletal proteins talin B and paxillin B and tyrosine kinase activity mediated by PKA signaling, however VinB threonine phosphorylation was shown to be independent of PI3K/PLA2 signaling and PI3K and PKA kinase activity. Finally, VinB-GFP over-expression suppressed DdEGFL1-enhanced random cell movement, but not folic acid-mediated chemotaxis. Together, this study provides the first evidence for VinB function plus new insight into the signaling pathway(s) mediating EGFL repeat/peptide-enhanced cell movement in Dictyostelium. This information is integrated into an emerging model that summarizes existing knowledge.

Abstract 4805: Distinctive phospho-proteome signatures in non-small cell lung carcinoma tumors

Abstract Non-small cell lung carcinoma (NSCLC) is a major, lethal cancer worldwide. Various molecular and cellular abnormalities are found in NSCLC, and an established theme is the alteration of protein phosphotyrosine (pY), as exemplified by elevated epidermal growth factor receptor (EGFR) activity recognized in a subset of NSCLC. In order to gain a broad perspective of pY-mediated signaling networks in NSCLC, mass spectrometry was used to analyze pY-containing peptides affinity purified from protease-digested xenograft tumors. Seventeen tumors representing the major NSCLC subtypes adenocarcinoma (ADC) and squamous cell carcinoma (SCC) were characterized. The major classes of pY proteins detected were cytoskeletal, protein kinases, and adhesion proteins. Pathways and cellular functions enriched in the data set included focal adhesion, adherens junction, and ErbB signaling. Five receptor tyrosine kinases (RTKs) were detected, with EGFR and EPHA2 most prevalent. Src-family kinases (YES, LYN, FRK and LCK) and focal adhesion kinase (FAK) comprised the majority of non-receptor tyrosine kinases measured. Analysis of individual pY sites on 14 tyrosine kinases indicates their activation by kinase domain activation loop phosphorylation, but also revealed additional pY sites suggestive of regulation by trafficking/endocytosis and inter- and intra-molecular protein-protein interactions involving, for example, SH2 and SH3 domains, and extra-kinase domain regions. Analysis of tumors based on protein-pY suggested subtypes distinguished by their activated tyrosine kinase networks. Genetic analysis of 3 tumors that displayed EGFR-associated phospho-proteome signatures confirmed that they carried either EGFR activating mutations (in two ADCs) or increased gene copy number (in one SCC). Western blot analysis of protein pY confirmed different patterns of cellular protein pY among the tumor phospho-types in agreement with the phospho-proteomic analysis. Quantification of kinase and substrate pY sites, according to their integrated extracted ion currents, revealed a set of phosphorylations that constituted a molecular signature that differentiated between the ADC and SCC subtypes. In summary, quantitative phospho-proteomic profiling of NSCLC tumors is feasible and may have utility in the categorization of individual tumors according to their networks of activated tyrosine kinases and substrates. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4805. doi:1538-7445.AM2012-4805

Comparative Proteomic Profiling of Human Breast Cell Lines

Although epidemiological studies have suggested that the isoflavone genistein found in soy may be protective against breast cancer, its effects on molecular processes involved in cell proliferation have not been clearly elucidated. Using comparative shotgun proteomics, we examined the proteome of non‐cancerous breast MCF10A cells, estrogen receptor‐positive breast cancer T47D cells, and Hras transfected MCF10A cells after treatment with 3, 10, and 30 μM genistein for 18 h. While genistein induced G1‐phase arrest in MCF10A‐Hras and G2/M‐phase arrest in T47D cells, it did not alter the cell cycle distribution in MCF10A cells. The arrest in G1‐phase of MCF10A‐Hras cells coincided with downregulation of the proliferation marker Ki67, epidermal growth factor receptor, various components of the mitogen‐activated protein kinase family of enzymes and low molecular weight phosphotyrosine protein phosphatase (ACP1), The arrest in G2/M‐phase of T47D cells was accompanied by upregulation of caspase‐8 and mSH2, suggesting that genistein may induce a G2/M checkpoint/proapoptotic response involving the mismatch repair system. Taken together, these findings suggest a differential response to genistein in cancerous cells and non‐malignant epithelial cells, and demonstrate the utility of comparative shotgun proteomics for investigating the cancer preventative effects of bioactive components.

Src homology 2 domain proteomimetics: developing phosphopeptide selective receptors

SH2 domains are the paradigm of phosphotyrosine protein recognition modules and are involved in mediating numerous cancer-promoting protein–protein complexes. In an effort to develop protein-selective receptors for inhibition of protein complexation events, we herein report the de novo rational and computationally aided design of SH2 domain proteomimetics. Lead mimetics exhibit target phosphopeptide selectivity (Ka ≈ 107 M−1) and potently disrupt SH2 domain:phosphopeptide interactions.

Neurons and a Subset of Interstitial Cells of Cajal in the Enteric Nervous System Highly Express Stam2 Gene

Signal transducing adaptor molecule 2 (STAM2) is a phosphotyrosine protein, which is a member of the endosomal sorting complex required for transport (ESCRT-0) and is involved in the sorting process of the mono-ubiquitinated endosomal cargo for degradation in the lysosome. Analysis of gene trap mice carrying lacZ in frame with Stam2 revealed beta-galactosidase activity in the enteric nervous system (both in the myenteric and submucosal plexus) throughout the digestive tract. STAM2 immunostaining confirmed that the observed beta-galactosidase activity coincided with high Stam2 expression. To identify cell types with high Stam2 expression, STAM2 immunostaining was colocalized with the neuronal markers microtubule-associated protein 2 and protein gene product 9.5 and with c-kit as a marker for interstitial cells of Cajal (ICCs). STAM2 and c-kit positive cells comprised a subset of ICCs in the enteric nervous system. Qualitative and quantitative analysis of the morphology of the enteric nervous system in the homozygous mice carrying gene trap insertion in the Stam2 gene did not reveal phenotype changes; therefore, STAM2 function in the digestive tube remains elusive.

Amyloid-β oligomers stimulate microglia through a tyrosine kinase dependent mechanism

Alzheimer's disease (AD) has been well characterized by the presence of reactive microglia, often associated with β-amyloid (Aβ) plaque deposition. The oligomeric form of Aβ peptide (Aβo) has neurotoxic effects in the presence of microglia and is suggested to potentiate proinflammatory changes in microglia in AD. Primary murine microglia cultures stimulated with Aβo displayed increased protein phosphotyrosine and secreted tumor necrosis factor (TNF)-α levels which were attenuated by the Src/Abl inhibitor, dasatinib. Intracerebroventricular infusions of Aβo into C57BL6/J mice stimulated increased microgliosis and protein phosphotyrosine levels that were also attenuated by dasatinib administration. The rodent findings were validated in human AD brains versus age-matched controls demonstrating reactive microglial association with Aβo deposits and increased microglial protein phosphotyrosine and phospho-Src levels. These data suggest a role for Aβo in microglial activation through a tyrosine kinase-dependant pathway both in rodent models and human disease. Use of a selective nonreceptor tyrosine kinase inhibitor such as dasatinib to attenuate microglial-dependent proinflammatory changes may prove to be an important step toward developing anti-inflammatory treatments for AD.

Comparison of Three Quantitative Phosphoproteomic Strategies to Study Receptor Tyrosine Kinase Signaling

There are three quantitative phosphoproteomic strategies most commonly used to study receptor tyrosine kinase (RTK) signaling. These strategies quantify changes in: (1) all three forms of phosphosites (phosphoserine, phosphothreonine and phosphotyrosine) following enrichment of phosphopeptides by titanium dioxide or immobilized metal affinity chromatography; (2) phosphotyrosine sites following anti- phosphotyrosine antibody enrichment of phosphotyrosine peptides; or (3) phosphotyrosine proteins and their binding partners following anti-phosphotyrosine protein immunoprecipitation. However, it is not clear from literature which strategy is more effective. In this study, we assessed the utility of these three phosphoproteomic strategies in RTK signaling studies by using EphB receptor signaling as an example. We used all three strategies with stable isotope labeling with amino acids in cell culture (SILAC) to compare changes in phosphoproteomes upon EphB receptor activation. We used bioinformatic analysis to compare results from the three analyses. Our results show that the three strategies provide complementary information about RTK pathways.

Identification of NO induced and capacitation associated tyrosine phosphoproteins in buffalo (Bubalus bubalis) spermatozoa

To acquire the fertilizing competence, spermatozoa must undergo a cascade of physiological and biochemical changes collectively defined as capacitation. Compelling evidence signifies that the global increase in protein tyrosine phosphorylation is the driving factor for capacitation. In our laboratory, we previously demonstrated that nitric oxide (NO) induces capacitation in buffalo sperm and is associated with an increase in protein tyrosine phosphorylation. The aim of the present study is to identify the proteins undergo tyrosine phosphorylation during NO induced buffalo sperm capacitation using 2-D immunoblotting and mass spectrometry. The percentage of progressively motile and capacitated sperm was more in presence of l-arginine. Along with known tyrosine phosphoproteins like ATP synthase subunit beta, pyruvate dehydrogenase E1 component subunit beta, GST mu 3, F-actin capping protein subunit beta 2, GPD2 and VDAC2, interestingly novel tyrosine phosphoprotein substrates such as actin, serine/threonine-protein phosphatase PP1-gamma catalytic subunit, and glutamine synthetase were also identified which might be specific to the NO induced signaling and also emphasizes the species specificity with respect to tyrosine phosphorylation of proteins during capacitation. In conclusion, this study forms an essential step in delineating the proteins undergo tyrosine phosphorylation in response to NO induced signaling pathways during capacitation of buffalo sperm.

Low Molecular Weight Phosphotyrosine Protein Phosphatases as Emerging Targets for the Design of Novel Therapeutic Agents

ADVERTISEMENT RETURN TO ISSUEPREVPerspectiveNEXTLow Molecular Weight Phosphotyrosine Protein Phosphatases as Emerging Targets for the Design of Novel Therapeutic AgentsRosanna Maccari* and Rosaria OttanàView Author Information Dipartimento Farmaco-Chimico, Faculty of Pharmacy, University of Messina, Polo Universitario dell’Annunziata, 98168 Messina, Italy* Telephone: +39906766406. Fax: +39906766402. E-mail: [email protected]Cite this: J. Med. Chem. 2012, 55, 1, 2–22Publication Date (Web):October 11, 2011Publication History Received13 May 2011Published online26 October 2011Published inissue 12 January 2012https://doi.org/10.1021/jm200607gCopyright © 2011 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views3185Altmetric-Citations26LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (4 MB) Get e-AlertsSUBJECTS:Cell and molecular biology,Inhibitors,Monomers,Peptides and proteins,Post-translational modification Get e-Alerts

Effect of Incorporation of Additives in Tris‐Based Egg Yolk Extender on Buffalo (Bubalus bubalis) Sperm Tyrosine Phosphorylation During Cryopreservation

Phosphorylation of tyrosine residues on sperm protein is a known indicator of capacitation and a major intracellular signalling event. There is evidence that sperm cryopreservation promotes tyrosine phosphorylation and is associated with reduced fertility of spermatozoa. Under this study, cryoprotective role of different additives namely taurine, trehalose, catalase and 4-bromophenacyl bromide on buffalo sperm quality was evaluated. Buffalo semen was cryopreserved in tris-based egg yolk extender supplemented with additives like taurine (50 mm) or trehalose (100 mm) or 4-bromophenacyl bromide (200 μm) or catalase (100 U/ml) and used for assessment of levels of tyrosine phosphorylation in frozen-thawed spermatozoa. The results obtained were compared with the level of protein tyrosine phosphorylation of semen cryopreserved in tris-based egg yolk extender without additives. Proteins were extracted from a total number of nine ejaculates from three individual buffalo bulls chosen at random and analysed for tyrosine phospho-proteins using SDS-PAGE followed by immunoblotting. Monoclonal anti-phosphotyrosine antibody (Clone pT-154) was used as primary antibody followed by treatment with HRP-conjugated secondary antibody. Signals were detected on X-ray film using chemiluminescence. Nine proteins (p20, p30, p32, p38, p49, p56, p59, p72 and p86) were found to be tyrosine phosphorylated in cryopreserved spermatozoa. Supplementation of additives significantly (p<0.05) reduced the level of protein tyrosine phosphorylation in spermatozoa. Moreover, this study showed improved (p<0.05) post-thaw motility, viability and membrane integrity of spermatozoa on addition of these additives. The results obtained clearly indicate reduced level of capacitation like changes on supplementation of additives in terms of protein tyrosine phosphorylation.

Nucleocytoplasmic transfer of cyclin dependent kinase 5 and its binding to puromycin-sensitive aminopeptidase in Dictyostelium discoideum

The Dictyostelium discoideum homolog of mammalian cyclin dependent kinase 5 (Cdk5) has previously been shown to be required for optimal growth and differentiation in this model organism, however, the subcellular localization of the protein has not previously been studied. In this study, immunolocalizations and a GFP fusion construct localized Cdk5 predominantly to the nucleus of vegetative cells. Western blots showed that Cdk5 was present in both nuclear and non-nuclear fractions, suggesting a functional role in both cellular locales. During the early stages of mitosis, Cdk5 gradually moved from a punctate nucleoplasmic distribution to localize adjacent to the inner nuclear envelope. During anaphase and telophase, Cdk5 localized to the cytoplasm and was not detected in the nucleoplasm. Cdk5 returned to the nucleus during cytokinesis. Proteolytic activity has been shown to be a critical regulator of the cell cycle. Immunoprecipitations coupled with immunolocalizations identified puromycin-sensitive aminopeptidase A (PsaA) as a potential Cdk5 binding partner in Dictyostelium. Immunoprecipitations also identified two phosphotyrosine proteins (35 and 18kDa) that may interact with Cdk5 in vivo. Together, this work provides new insight into the localization of Cdk5, its function during cell division, and its binding to a proteolytic enzyme in Dictyostelium.

Crystal structures of YwqE from Bacillus subtilis and CpsB from Streptococcus pneumoniae, unique metal-dependent tyrosine phosphatases

Unique metal-dependent protein tyrosine phosphatases that belong to the polymerase and histindinol phosphatase (PHP) family are present in Gram-positive bacteria. They are distinct from the Cys-based, low-molecular-weight phosphotyrosine protein phosphatases (LMPTPs). Two representative members of the PHP family tyrosine phosphatases are YwqE from Bacillus subtilis and CpsB from Streptococcus pneumoniae. YwqE is involved in polysaccharide biosynthesis, bacterial DNA metabolism, and DNA damage response in B. subtilis. CpsB regulates capsular polysaccharide biosynthesis via tyrosine dephosphorylation of CpsD, its cognate tyrosine kinase, in S. pneumoniae. To gain insights into the active site and possible conformational changes of the metal-dependent tyrosine phosphatases from Gram-positive bacteria, we have determined the crystal structures of B. subtilis YwqE (in both the apo form and the phosphate-bound form) and S. pneumoniae CpsB (in the sulfate-bound form). Comparisons of the three structures reveal conformational plasticity of two active site loops. Furthermore, in both structures of the phosphate-bound YwqE and the sulfate-bound CpsB, the phosphate (or sulfate) ion is bound to a cluster of three metal ions in the active site, thus providing insight into the pre-catalytic state.

Abstract 4464: Ciclopirox Olamine alters PEAK-1-mediated cytoskeleton organization and invasion of metastatic cancer cells

Abstract The majority of cancer patients die from metastatic disease because there are no drugs available to prevent the spread of cancer and eradicate metastases in patients. The antimycotic drug ciclopirox olamine (CPX) is under investigation as a repositioned drug candidate which has anti-tumor and anti-angiogenesis activity in experimental models. Because CPX has been FDA tested and shows exceptionally low side effects in patients even at high doses, it has significant potential as both a therapeutic to prevent cancer recurrence after surgical resection and for the long term systemic treatment of cancer patients with overt metastatic disease. However, CPX has not yet been tested for its ability to inhibit metastatic cell function. In this study we examined the ability of CPX to inhibit metastatic cancer cell migration, invasion, and proliferation, and evaluated the signal transduction pathways that regulate these processes. Interestingly, CPX was observed to inhibit the expression of the tyrosine kinase, pseudopodium-enriched atypical kinase 1 (PEAK1), which is necessary for proper remodeling of the actin cytoskeleton and focal adhesion dynamics in metastatic cancer cells (PNAS, 107(24), 10920-5). Associated with the decrease in PEAK1 expression by CPX was decreased total cellular tyrosine phosphoprotein content, pseudopodium protrusion, cancer cell spreading, movement, and proliferation on extracellular matrix proteins. Collectively, our findings indicate that at therapeutic doses, CPX potently alters cytoskeletal signaling, cancer cell movement, and proliferation by modulating PEAK1 activity. These findings are important in light of the fact that PEAK1 amplification and cytoskeleton modulation have been linked to anchorage-independent cell growth, cell migration, and tumor progression in human gastrointestinal cancers. The exceptional safety record of CPX and our findings support the notion that CPX has significant potential as a repositioned therapeutic agent to combat cancer recurrence and spread in patients. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4464. doi:10.1158/1538-7445.AM2011-4464

Abstract 5128: Physical EGFR network mapping and dynamic regulation in lung cancer cells

Abstract Aberrant activation of Epidermal Growth Factor Receptor (EGFR) through somatic mutations plays a critical role in the development and progression in lung cancer. A better understanding of the downstream signaling network driven by EGFR mutations could uncover novel therapeutics targets and/or resistance mechanisms. We characterized a physical EGFR network by integrating (i) protein-protein interaction data derived from tandem affinity purification (TAP) and liquid chromatography mass spectrometry (LC-MS/MS) and (ii) global phospho-tyrosine protein profile identified by immunoaffinity purification of tyrosine phosphorylated peptides coupled to LC-MS/MS. All experiments were performed in lung cancer cell lines harboring activating EGFR mutations and highly sensitive to EGFR inhibitors. We identified 266 proteins in this network including other ERBB family member (ERBB2 and ERBB3), adaptors (GRB2, SHC1, MIG6 and STS1), heat shock proteins and chaperones (HSP90 isoforms, CDC37 and BIP), proteins involved in RTK endocytosis (AP family proteins), and phosphatases (PTPN12 and PTPRA). We found ERBB3 bound EGFR but not ERBB2 while PI3K subunits are exclusively in complex with ERBB3 suggesting ERBB3 is a key linkage between EGFR and downstream PI3K/AKT signaling. CDC37, as a co-chaperone of HSP90, bound multiple kinases suggesting possible functional importance in these cells. ARHGEF5, an activator of RHO pathway signaling, was found to interact with GRB2 and SHC1. MIG6 (also known as ERRFI1 and RALT), a known negative regulator of ERB signaling, interacts with numerous components of this network, including EGFR, GRB2, STS1, SHC1, ERBB2. We found that forced expression of MIG6 in PC9 and HCC827 cells inhibits EGFR-ERK signaling. Interestingly, cells maintain AKT signaling independently of EGFR through unknown mechanism. These cells become resistance to EGFR inhibitors but are sensitized to PI3K/mTOR inhibition. STS1, a tyrosine phosphatase, can also regulate EGFR signal pathway and lead to resistance to EGFR inhibitor. Updated work will be presented. Supported by the SPORE in Lung Cancer (P50-CA119997), National Functional Genomics Center, and Austrian Proteomics Platform GZ 200.145/1-VI/1/2006, part of the GEN-AU initiative of the BM:WF. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5128. doi:10.1158/1538-7445.AM2011-5128

Abstract 5121: A targeted approach to identify activators of class IA phosphoinositide-3-kinase in cancers using tandem mass spectrometry

Abstract A majority of human cancers exhibit aberrant activation of the phosphoinositide 3-Kinase (PI3K) pathway. In many cases this activation is due to mutations or amplifications in upstream activators of PI3K resulting in activation by direct binding of phosphotyrosine proteins (e.g., receptor tyrosine kinases (RTK) or adaptors such as IRS-1/2 or Gab1/2) to the p85 regulatory subunit of PI3K. To date, experiments to identify the mechanisms of PI3K activation in cancer have remained difficult and cumbersome. Since inhibitors of many of these RTKs are either already approved or in clinical trials, identification of the major upstream activators of PI3K in a given tumor could suggest the appropriate therapeutic intervention. Here we present a quantitative mass spectrometry approach (targeted ion MS/MS – TIMM) for identifying the upstream activators of PI3K in cancer cell lines grown on plastic as well as in tumor Xenografts. Importantly, we show that in a series of non small cell lung carcinoma cell lines, it is possible to predict the appropriate drug for treating the cells based on the upstream activator of PI3K as revealed by TIMM. Specifically, we identified how PI3K is activated in MET amplified, EGFR and EML4-ALK driven non-small cell lung cancers (NSCLCs) both in vitro and in vivo, and were successful in identifying the optimal RTK inhibitor treatment for the H1703 NSCLC cell line. Additionally, this technology revealed that TORC1 inhibition leads to activation of PI3K via IRS-2, not IRS-1 in KRAS mutant cell lines. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5121. doi:10.1158/1538-7445.AM2011-5121

Particle stimulation dephosphorylates glutathione S-transferase pi 1 of epithelial cells

Environmental pollutant exposure is associated with adverse respiratory outcomes. The phosphorylation of enzymes activates or deactivates many cellular processes and is related to the development of lung diseases such as asthma and chronic obstructive pulmonary disease. However, little is known about protein phosphorylation of bronchial epithelial cells in response to airborne particulates. Herein, we screened differentially phosphorylated proteins in TiO 2-treated epithelial cells and validated the change in GSTP1 protein phosphorylation. Two-dimensional electrophoresis was adopted for differential display proteomics of TiO 2-treated BEAS-2B cell lysates. Phosphoproteins were screened using Pro-Q ® Diamond phosphoprotein gel stain and identified by MALDI-TOF/TOF analysis. Immunoprecipitation and immunoblotting were performed for quantitative measurement of GSTP1 phosphorylation in cell lysates. Normalized relative intensities of nine phosphorylated proteins increased after TiO 2 treatment, whereas those of 12 proteins decreased in the BEAS-2B cell lysates. From gene ontology and pathway analysis, proteins involved in signal transduction were commonly identified, followed by cytoskeletal proteins, proteins from oxidation and antioxidation pathways, proteins catalyzing reductions, and those involved in cellular process, transport, and modification. Immunoblotting with anti-GSTP1 antibody demonstrated no change in GSTP1 protein levels in the lysates of BEAS-2B cells after treatment with TiO 2 particles; blotting with anti-phosphoserine and anti-phosphotyrosine antibodies showed dose-dependent decreases in phosphoserine and phosphotyrosine proteins. Stimulation with particulates phosphorylated and dephosphorylated several proteins in epithelial cells, and serine and tyrosine protein phosphorylation of GSTP1 decreased. These data indicate that airborne particles affect the pattern of phosphorylation of proteins involved in defense or apoptosis of respiratory epithelium.

Evidence of Abnormal Tyrosine Phosphorylated Proteins in the Urine of Patients With Bladder Cancer: The Road Toward a New Diagnostic Tool?

Since changes in protein phosphorylation are a common feature of cancer cells, we analyzed phosphoproteins in the tissue and urine of patients with bladder cancer and assessed the diagnostic relevance of abnormally phosphorylated proteins as tumor markers. Enrolled in this study were 66 patients and 82 healthy volunteers. From the first 14 patients with bladder cancer we obtained samples of malignant and normal bladder tissue. All patients and volunteers provided a urine sample. Protein extracts of tissue specimens were separated by 2-dimensional gel electrophoresis for comparative analysis of neoplastic and normal tissue. Phosphoproteins were studied by Western blot and characterized by mass spectrometry. Urine samples were analyzed by 1-dimensional gel electrophoresis. Phosphoproteins were measured by affinity dot blotting. Profound changes in the pattern of protein tyrosine phosphorylation were consistently, reproducibly observed in bladder cancer tissues. A total of 24 phosphorylated proteins were differentially expressed in cancer tissue and identified by mass spectrometry. Phosphoproteins were fairly stable in urine samples, leading to accumulation. Urinary tyrosine phosphoproteins showed the most remarkable changes in patients with cancer with an approximately 5-fold increase compared to levels in healthy controls. To our knowledge we investigated for the first time the diagnostic potential of tissue and urinary tyrosine phosphoproteins for bladder carcinoma. Results indicate that phosphorylated proteins may represent a new, valuable class of urinary biomarkers for bladder cancer.

Analysis of dynamic tyrosine phosphoproteome in LFA‐1 triggered migrating t‐cells

The ordered, directional migration of T-lymphocytes is a key process during immune surveillance and response. This requires cell adhesion to the high endothelial venules or to the extracellular matrix by a series of surface receptor/ligand interactions involving adhesion molecules of the integrin family including lymphocyte function associated molecule-1 (LFA-1) and intercellular adhesion molecules (ICAMs). Reversible protein phosphorylation is emerging as a key player in the regulation of biological functions with tyrosine phosphorylation playing a crucial role in signal transduction. Thus, the study of this type of post-translational modification at the proteomic level has great biological significance. In this work, phospho-enriched cell lysates from LFA-1-triggered migrating human T-cells were subjected to immunoaffinity purification of tyrosine phosphorylated proteins, mass spectrometric, and bioinformatic analysis. In addition to the identification of several well-documented proteins, the analysis suggested involvement of a number of new and novel proteins in LFA-1 induced T-cell migration. This dataset expands the list of the signaling components of the LFA-1 induced phosphotyrosine protein complexes in migrating T-cells that will be extremely useful in the study of their specific roles within LFA-1 associated signaling pathways. Identification of proteins previously not reported in the context of LFA-1 stimulated signal transduction might provide new insights into understanding the LFA-1 signaling networks and aid in the search for new potential therapeutic targets.

Effects of a Synthetic bFGF Antagonist Peptide on the Proteome of 3T3 Cells Stimulated with bFGF

It has been known that basic fibroblast growth factor (bFGF) plays an important role in tumor progression mainly due to its strong mitogenic activity. Antagonists targeting bFGF have been considered a potential strategy for cancer therapy via inhibiting cell proliferation induced by bFGF. We have previously obtained a high-affinity bFGF-binding peptide (named as P7) with strong inhibitory activity against bFGF-induced cell proliferation from the phage display random heptapeptide library. The aim of the present investigation was to synthesize the peptide P7 by solid phase method and explore the mechanisms of the inhibitory effect of P7-targeting bFGF stimulation on Balb/c 3T3 cells via proteomic analysis. Seven differentially expressed protein were identified, among which four were decreased by bFGF stimulation alone and increased by addition of P7, the other three were up-regulated by bFGF treatment alone and down-regulated by addition of P7. Among the identified proteins, epidermal fatty acid-binding protein (E-FABP) and low molecular weight phosphotyrosine protein phosphatase (LMW-PTP) take part in the regulation of cell proliferation. The results suggested P7 inhibited the bioactivities of bFGF possibly via influencing the expression of cellular proteins related to cell proliferation.

Identification of capacitation associated tyrosine phosphoproteins in buffalo ( Bubalus bubalis) and cattle spermatozoa

At ejaculation mammalian sperm lack fertilizing ability as they are released in a functionally immature form. The capacity to fertilize eggs is only acquired after they have been educated in the female reproductive tract and this phenomenon is termed as capacitation. Sperm capacitation includes a cascade of biochemical modifications, including cholesterol efflux, Ca 2+ influx and cAMP/PKA-dependent/independent protein tyrosine phosphorylation which is specifically considered as the biochemical marker for capacitation. The identification of tyrosine phosphoproteins shall be useful in delineating their physiological role in different events associated with sperm capacitation. The present study was conducted to identify the tyrosine phosphoproteins in the capacitated buffalo and cattle spermatozoa using 2D immunoblotting and mass spectrometry. Among several proteins identified in the buffalo capacitated sperm, serine/threonine-protein phosphatase PP1-gamma catalytic subunit, MGC157332 protein, alpha-enolase, 3-oxoacid CoA transferase 2 and actin-like protein 7A were identified as new tyrosine phosphorylation substrates in mammalian spermatozoa. Cattle sperm also contain proteins such as serine/threonine-protein phosphatase PP1-alpha catalytic subunit and membrane metallo-endopeptidase-like 1 which have not been reported as tyrosine phosphorylated in any other species. Though the presence of serine/threonine-protein phosphatase PP1-alpha catalytic subunit was demonstrated for the first time in mammalian sperm, further studies are required for its existence and possible role in different sperm functions.