Prostatitis No.1 traditional chinese medicine significantly exhibited anti-inflammation role on prostatitis through miR-205-5p/YES1

Prostatitis is one common male disease with a high prevalence. Traditional Chinese medicine (TCM) has been used as an alternative method for the treatment. However, the molecular mechanism of Prostatitis No.1 Traditional Chinese Medicine (P1TCM) on prostatitis is still unclear. For this purpose, the rat models were constructed and treated with PITCM of control, model, low (10 g/kg/d), medium (20 g/kg/d), and high (40 g/kg/d), as well as the transfections of medium dosage+NC mimic, and medium dosage+miR-205-5p mimic, medium dosage+NC mimic+pc-NC, medium dosage+miR-205-5p mimic+pc-NC, and medium dosage+miR-205-5p mimic+pc-v-YES-1 Yamaguchi sarcoma viral oncogene homolog 1 (YES1). Real-time quantitative PCR (qPCR) and western blotting analyses were carried out to evaluate the expression of miR-205-5p and YES1, respectively. The levels of interleukin-1β (IL-1β) and tumor necrosis factor-alpha (TNF-α) were assessed by enzyme-linked immunosorbent assay (ELISA). The targeting role of miR-205-5p on YES1 was predicted by StarBase and verified by a dual-luciferase reporter gene assay. Results showed that the optimal treatment of P1TCM relieved the damage of prostate tissue, decreased the immunity and inflammation factors, and reduced the expression level of miR-205-5p in prostate tissue and serum. miR-205-5p mimics significantly relieved tissue damage and reduced immunity and inflammatory functions. miR-205-5p targeted YES1. YES1 was significantly upregulated in medium dosage treatment compared with Control, while downregulated compared with the Model. YES1 was also upregulated in prostatitis patients. The pc-YES1 reversed the function of the miR-205-5p mimic. In conclusion, P1TCM significantly relieved the tissue damage and reduced prostate patients' inflammatory functions through miR-205-5p/YES1, which might be essential for clinical studies.

An RGDKGE-Containing Cryptic Collagen Fragment Regulates Phosphorylation of Large Tumor Suppressor Kinase-1 and Controls Ovarian Tumor Growth by a Yes-Associated Protein-Dependent Mechanism

The growth and spread of malignant tumors, such as ovarian carcinomas, are governed in part by complex interconnected signaling cascades occurring between stromal and tumor cells. These reciprocal cross-talk signaling networks operating within the local tissue microenvironment may enhance malignant tumor progression. Understanding how novel bioactive molecules generated within the tumor microenvironment regulate signaling pathways in distinct cellular compartments is critical for the development of more effective treatment paradigms. Herein, we provide evidence that blocking cellular interactions with an RGDKGE-containing collagen peptide that selectively binds integrin β3 on ovarian tumor cells enhances the phosphorylation of the hippo effector kinase large tumor suppressor kinase-1 and reduces nuclear accumulation of yes-associated protein and its target gene c-Myc. Selectively targeting this RGDKGE-containing collagen fragment inhibited ovarian tumor growth and the development of ascites fluid in vivo. These findings suggest that this bioactive collagen fragment may represent a previously unknown regulator of the hippo effector kinase large tumor suppressor kinase-1 and regulate ovarian tumor growth by a yes-associated protein-dependent mechanism. Taken together, these data not only provide new mechanistic insight into how a unique collagen fragment may regulate ovarian cancer, but in addition may help provide a useful new alternative strategy to control ovarian tumor progression based on selectively disrupting a previously unappreciated signaling cascade.

Suppression of IL-17A-induced CCL20 production by cytokine inducible SH2-containing protein 1 in epidermal keratinocytes

BACKGROUND

Lesions of atopic dermatitis have fewer Th17 cells than those of psoriasis, resulting in frequent skin infections. Expression of CCL20, a chemokine that is important for recruiting Th17 cells, is suppressed in the lesions of atopic dermatitis. We previously reported that IL-4 induces the expression of cytokine-inducible SH2-containing protein 1 (CIS1), a member of the CIS/SOCS family, in epidermal keratinocytes.

OBJECTIVE

To investigate whether CIS1 influences CCL20 production in epidermal keratinocytes.

METHODS

Expression of CIS1 was examined in atopic dermatitis skin and in cultured keratinocytes. The effects of overexpression of CIS1 on CCL20 production by IL-17A, and on signaling pathways inhibited by CIS1, were assessed in vitro.

RESULTS

Expression of CIS1 was enhanced in the basal layer of the lesional epidermis of skin with atopic dermatitis. When CIS1 was expressed in keratinocytes using adenoviral vectors, IL-17A-induced CCL20 expression, but not HBD2 or S100A7 expression, was significantly suppressed. TNF-α/IL-1-induced CCL20 production was not altered by CIS1. Overexpression of CIS1 attenuated IL-17A-induced ERK phosphorylation. ERK phosphorylation was mediated by the Act1 and Src family kinase pathways. CIS1 overexpression suppressed Src phosphorylation. Among the Src family kinases, the Yes kinase may have an important role because knockdown of Yes in epidermal keratinocytes resulted in suppression of ERK phosphorylation and CCL20 mRNA expression by IL-17A.

CONCLUSION

CIS1 induced by Th2 cytokines has the ability to change the response of epidermal keratinocytes to IL-17A by suppression of Src family kinases.

Functionalizable Antifouling Coatings as Tunable Platforms for the Stress-Driven Manipulation of Living Cell Machinery

Cells are continuously sensing their microenvironment and subsequently respond to different physicochemical cues by the activation or inhibition of different signaling pathways. To study a very complex cellular response, it is necessary to diminish background environmental influences and highlight the particular event. However, surface-driven nonspecific interactions of the abundant biomolecules from the environment influence the targeted cell response significantly. Yes-associated protein (YAP) translocation may serve as a marker of human hepatocellular carcinoma (Huh7) cell responses to the extracellular matrix and surface-mediated stresses. Here, we propose a platform of tunable functionable antifouling poly(carboxybetain) (pCB)-based brushes to achieve a molecularly clean background for studying arginine, glycine, and aspartic acid (RGD)-induced YAP-connected mechanotransduction. Using two different sets of RGD-functionalized zwitterionic antifouling coatings with varying compositions of the antifouling layer, a clear correlation of YAP distribution with RGD functionalization concentrations was observed. On the other hand, commonly used surface passivation by the oligo(ethylene glycol)-based self-assembled monolayer (SAM) shows no potential to induce dependency of the YAP distribution on RGD concentrations. The results indicate that the antifouling background is a crucial component of surface-based cellular response studies, and pCB-based zwitterionic antifouling brush architectures may serve as a potential next-generation easily functionable surface platform for the monitoring and quantification of cellular processes.

Modular mimicry and engagement of the Hippo pathway by Marburg virus VP40: Implications for filovirus biology and budding

Ebola (EBOV) and Marburg (MARV) are members of the Filoviridae family, which continue to emerge and cause sporadic outbreaks of hemorrhagic fever with high mortality rates. Filoviruses utilize their VP40 matrix protein to drive virion assembly and budding, in part, by recruitment of specific WW-domain-bearing host proteins via its conserved PPxY Late (L) domain motif. Here, we screened an array of 115 mammalian, bacterially expressed and purified WW-domains using a PPxY-containing peptide from MARV VP40 (mVP40) to identify novel host interactors. Using this unbiased approach, we identified Yes Associated Protein (YAP) and Transcriptional co-Activator with PDZ-binding motif (TAZ) as novel mVP40 PPxY interactors. YAP and TAZ function as downstream transcriptional effectors of the Hippo signaling pathway that regulates cell proliferation, migration and apoptosis. We demonstrate that ectopic expression of YAP or TAZ along with mVP40 leads to significant inhibition of budding of mVP40 VLPs in a WW-domain/PPxY dependent manner. Moreover, YAP colocalized with mVP40 in the cytoplasm, and inhibition of mVP40 VLP budding was more pronounced when YAP was localized predominantly in the cytoplasm rather than in the nucleus. A key regulator of YAP nuclear/cytoplasmic localization and function is angiomotin (Amot); a multi-PPxY containing protein that strongly interacts with YAP WW-domains. Interestingly, we found that expression of PPxY-containing Amot rescued mVP40 VLP egress from either YAP- or TAZ-mediated inhibition in a PPxY-dependent manner. Importantly, using a stable Amot-knockdown cell line, we found that expression of Amot was critical for efficient egress of mVP40 VLPs as well as egress and spread of authentic MARV in infected cell cultures. In sum, we identified novel negative (YAP/TAZ) and positive (Amot) regulators of MARV VP40-mediated egress, that likely function in part, via competition between host and viral PPxY motifs binding to modular host WW-domains. These findings not only impact our mechanistic understanding of virus budding and spread, but also may impact the development of new antiviral strategies.

By screening an array of 115 mammalian WW-domains with the PPxY motif from MARV VP40 (mVP40), we identified YAP1 and TAZ, transcriptional effectors of the Hippo pathway, as mVP40 interactors, and demonstrated that ectopically expressed YAP1 or TAZ inhibited budding of mVP40 virus-like particles (VLPs) in a WW-domain/PPxY dependent manner. Angiomotin (Amot), a multi-PPxY containing regulator of YAP1 nuclear/cytoplasmic localization and function, rescued mVP40 VLP egress from either YAP1- or TAZ-mediated inhibition in a PPxY-dependent manner. Indeed, endogenous Amot expression was critical for egress of mVP40 VLPs and authentic MARV. In sum, we have revealed a link between the Hippo pathway and filovirus egress by identifying negative (YAP/TAZ) and positive (Amot) regulators of MARV VP40-mediated egress.

Circ_Lrp6, a Circular RNA Enriched in Vascular Smooth Muscle Cells, Acts as a Sponge Regulating miRNA-145 Function

RATIONALE

microRNAs (miRNAs) modulate gene expression by repressing translation of targeted genes. Previous work has established a role for miRNAs in regulating vascular smooth muscle cell (VSMC) activity. Whether circular RNAs are involved in the modulation of miRNA activity in VSMCs is unknown.

OBJECTIVE

We aimed to identify circular RNAs interacting with miRNAs enriched in VSMCs and modulating the cells' activity.

METHODS AND RESULTS

RNA sequencing and bioinformatics identified several circular RNAs enriched in VSMCs; however, only one, possessing multiple putative binding sites for miR-145, was highly conserved between mouse and man. This circular RNA gemmed from alternative splicing of Lrp6 (lipoprotein receptor 6), a gene highly expressed in vessels and implicated in vascular pathologies and was thus named circ_Lrp6. Its role as a miR-145 sponge was confirmed by determining reciprocal interaction through RNA immunoprecipitation, stimulated emission depletion microscopy, and competitive luciferase assays; functional inhibition of miR-145 was assessed by measuring expression of the target genes ITGβ8 (integrin-β8), FASCIN (fascin actin-bundling protein 1), KLF4 (Kruppel-like factor 4), Yes1 (YES proto-oncogene 1), and Lox (lysyl oxidase). The interaction was preferentially localized to P-bodies, sites of mRNA degradation. Using loss- and gain-of-function approaches, we found that circ_Lrp6 hindered miR-145-mediated regulation of VSMC migration, proliferation, and differentiation. Differential expression of miR-145 and circ_Lrp6 in murine and human vascular diseases suggests that the ratio of circ_Lrp6 bound to miR-145 versus unbound could play a role in vascular pathogenesis. Viral delivery of circ_Lrp6 shRNA prevented intimal hyperplasia in mouse carotids.

CONCLUSIONS

circ_Lrp6 is an intracellular modulator and a natural sponge for miR-145, counterbalancing the functions of the miRNA in VSMCs.

Yes1 signaling mediates the resistance to Trastuzumab/Lap atinib in breast cancer

Background

Overexpression of human epidermal growth factor receptor 2 (HER2) is observed in approximately 15–23% of breast cancers and these cancers are classified as HER2-positive breast cancer. Trastuzumab is the first-line targeted therapeutic drug for HER2-positive breast cancer and has improved patient overall survival. However, acquired resistance to trastuzumab is still a critical issue in breast cancer treatment. We previously established a trastuzumab-resistant breast cancer cell line (named as BT-474-R) from a trastuzumab-sensitive HER2-amplified cell line BT-474. Lapatinib is also a molecular-targeted drug for HER2-positive breast cancer, which acquired the resistance to trastuzumab. Acquired resistance to lapatinib is also an issue to be conquered.

Methods

We established trastuzumab/lapatinib-dual resistant cell line (named as BT-474-RL2) by additionally treating BT-474-R with lapatinib. We analyzed the mechanisms of resistance to trastuzumab and lapatinib. Besides, we analyzed the effect of the detected resistance mechanism in HER2-positive breast cancer patients.

Results

Proto-oncogene tyrosine-protein kinase Yes1, which is one of the Src family members, was amplified, overexpressed and activated in BT-474-R and BT-474-RL2. Silencing of Yes1 by siRNA induced both BT-474-R and BT-474-RL2 to restore the sensitivity to trastuzumab and lapatinib. Pharmaceutical inhibition of Yes1 by the Src inhibitor dasatinib was also effective to restore the sensitivity to trastuzumab and lapatinib in the two resistant cell lines. Combination treatment with dasatinib and trastuzumab induced down-regulation of signaling molecules such as HER2 and Akt. Moreover, the combination treatments induced G1-phase cell-cycle arrest and apoptosis. Consistent with cell line data, high expression of Yes1 mRNA was correlated with worse prognosis in patients with HER2-positive breast cancer.

Conclusion

Yes1 plays an important role in acquired resistance to trastuzumab and lapatinib in HER2-positive breast cancer. Our data suggest that pharmacological inhibition of Yes1 may be an effective strategy to overcome resistance to trastuzumab and lapatinib.

Activated Hippo/Yes-Associated Protein Pathway Promotes Cell Proliferation and Anti-apoptosis in Endometrial Stromal Cells of Endometriosis

CONTEXT

The imbalance in cell proliferation and apoptosis is considered an important role in the pathogenesis of endometriosis, but the exact mechanisms remains unclear. A newly established signaling pathway–Hippo/Yes-associated protein (YAP) pathway plays a critical role in the proliferation and apoptosis processes. However, studies focusing on Hippo/YAP pathway and endometriosis are lacking.

OBJECTIVE

The objective was to explore the function of the Hippo/YAP pathway in endometriosis.

SETTING AND DESIGN

The expression of YAP was first investigated in endometrium of women with or without endometriosis. The role of YAP in cell proliferation and apoptosis is identified by transfection of endometrial stromal cells (ESCs) in vitro, subsequent Verteporfin treatments in eutopic ESCs in vitro, and endometriosis animal model of nude mice in vivo.

RESULTS

Our results revealed that increased expression of YAP and decreased expression of p-YAP in ectopic and eutopic endometrium compared with normal endometrium. YAP knockdown in eutopic ESCs decreased cell proliferation and enhanced cell apoptosis companied with decreased expression of TEAD1, CTGF, and B-cell lymphoma/leukemia (BCL)-2; whereas overexpression of YAP resulted in increased proliferation and decreased apoptosis of normal ESCs with increased expression of TEAD1, CTGF, and BCL-2. By chromatin immunoprecipitation qPCR CTGF and BCL-2 were identified as directly downstream target genes of YAP-TEAD1 active complex. Eutopic ESCs treated with Verteporfin revealed decreased proliferation and enhanced apoptosis whereas in endometriosis animal models of nude mice treated with Verteporfin, the size of endometriotic lesions was significantly reduced.

CONCLUSIONS

Our study suggests that the Hippo/YAP-signaling pathway plays a critical role in the pathogenesis of endometriosis and should present a novel therapeutic method against endometriosis.

Up-regulation of microRNA-210 inhibits proliferation of hepatocellular carcinoma cells by targeting YES1

AIM: To determine the expression of microRNA-210 (miR-210) in hepatocellular carcinoma (HCC) and to examine its role using HCC cells.

METHODS: The expression of miR-210 was determined in 21 pairs of HCC samples and the corresponding surrounding non-tumor tissues. The effects of miR-210 on proliferation and cell cycle progression were examined using HepG2 and HuH7 cells. Over-expression and inhibition of miR-210 was achieved by transfection of the cells with miR-210 mimic or inhibitor. Luciferase reporter constructs were used to identify the miR-210 interacting site on Yes1. Yes1 expression was examined after miR-210 transfection, as well as in the HCC samples.

RESULTS: miR-210 was significantly up-regulated by 3.4 fold (P < 0.01) in the tumor samples. The over-expression of miR-210 significantly reduced cell proliferation compared to the mock-treated cells (68.9% ± 7.4% and 53.6% ± 5.0%, P < 0.05 for the HepG2 and HuH7 cells respectively). Analysis of the HuH7 cells transfected with miR-210 mimic by flow cytometry showed that the cells took a longer time to reach the G2/M phase. The interaction between miR-210 and the 3’UTR of the Yes1 transcript was confirmed using a luciferase reporter assay. Over-expression of miR-210 reduced the expression of Yes1 protein in both HuH7 and HepG2 cells. Tumors with a greater than four-fold increase in the expression of miR-210 showed consistently lower expressions of Yes1 in the tumors. In nocodazole-treated cells with a significant G2/M cell population, Yes1 protein was significantly reduced and pre-inhibition of miR-210 in HuH7 cells was able to prevent the reduction of Yes1 protein expression. Knock-down of Yes1 by siRNA also led to reduced cell proliferation (70.8% ± 7.5%, P < 0.05 in the HuH7 cells).

CONCLUSION: Up-regulation of miR-210 inhibits cell proliferation. Yes1 is a target of miR-210 and affects cell proliferation in HCC.

Individual Src-family tyrosine kinases direct the degradation or protection of the clock protein Timeless via differential ubiquitylation

Timeless was originally identified in Drosophila as an essential component of circadian cycle regulation, where its function is tightly controlled at the protein level by tyrosine phosphorylation and subsequent degradation. In mammals, Timeless has also been implicated in circadian rhythms as well as cell cycle control and embryonic development. Here we report that mammalian Timeless is an SH3 domain-binding protein and substrate for several members of the Src protein-tyrosine kinase family, including Fyn, Hck, c-Src and c-Yes. Co-expression of Tim with Fyn or Hck was followed by ubiquitylation and subsequent degradation in human 293T cells. While c-Src and c-Yes also promoted Tim ubiquitylation, in this case ubiquitylation correlated with Tim protein accumulation rather than degradation. Both c-Src and c-Yes selectively promoted modification of Tim through Lys63-linked polyubiquitin, which may explain the differential effects on Tim protein turnover. These data show distinct and opposing roles for individual Src-family members in the regulation of Tim protein levels, suggesting a unique mechanism for the regulation of Tim function in mammals.

c-Yes regulates cell adhesion at the apical ectoplasmic specialization-blood-testis barrier axis via its effects on protein recruitment and distribution

During spermatogenesis, extensive restructuring takes place at the cell-cell interface since developing germ cells migrate progressively from the basal to the adluminal compartment of the seminiferous epithelium. Since germ cells per se are not motile cells, their movement relies almost exclusively on the Sertoli cell. Nonetheless, extensive exchanges in signaling take place between these cells in the seminiferous epithelium. c-Yes, a nonreceptor protein tyrosine kinase belonging to the Src family kinases (SFKs) and a crucial signaling protein, was recently shown to be upregulated at the Sertoli cell-cell interface at the blood-testis barrier (BTB) at stages VIII-IX of the seminiferous epithelial cycle of spermatogenesis. It was also highly expressed at the Sertoli cell-spermatid interface known as apical ectoplasmic specialization (apical ES) at stage V to early stage VIII of the epithelial cycle during spermiogenesis. Herein, it was shown that the knockdown of c-Yes by RNAi in vitro and in vivo affected both Sertoli cell adhesion at the BTB and spermatid adhesion at the apical ES, causing a disruption of the Sertoli cell tight junction-permeability barrier function, germ cell loss from the seminiferous epithelium, and also a loss of spermatid polarity. These effects were shown to be mediated by changes in distribution and/or localization of adhesion proteins at the BTB (e.g., occludin, N-cadherin) and at the apical ES (e.g., nectin-3) and possibly the result of changes in the underlying actin filaments at the BTB and the apical ES. These findings implicate that c-Yes is a likely target of male contraceptive research.

LKB1/STK11 inactivation leads to expansion of a prometastatic tumor subpopulation in melanoma

Germline mutations in LKB1 (STK11) are associated with the Peutz-Jeghers syndrome (PJS), which includes aberrant mucocutaneous pigmentation, and somatic LKB1 mutations occur in 10% of cutaneous melanoma. By somatically inactivating Lkb1 with K-Ras activation (±p53 loss) in murine melanocytes, we observed variably pigmented and highly metastatic melanoma with 100% penetrance. LKB1 deficiency resulted in increased phosphorylation of the SRC family kinase (SFK) YES, increased expression of WNT target genes, and expansion of a CD24(+) cell population, which showed increased metastatic behavior in vitro and in vivo relative to isogenic CD24(-) cells. These results suggest that LKB1 inactivation in the context of RAS activation facilitates metastasis by inducing an SFK-dependent expansion of a prometastatic, CD24(+) tumor subpopulation.

SRC-induced disassembly of adherens junctions requires localized phosphorylation and degradation of the rac activator tiam1

The Rac activator Tiam1 is required for adherens junction (AJ) maintenance, and its depletion results in AJ disassembly. Conversely, the oncoprotein Src potently induces AJ disassembly and epithelial-mesenchymal transition (EMT). Here, we show that Tiam1 is phosphorylated on Y384 by Src. This occurs predominantly at AJs, is required for Src-induced AJ disassembly and cell migration, and creates a docking site on Tiam1 for Grb2. We find that Tiam1 is associated with ERK. Following recruitment of the Grb2-Sos1 complex, ERK becomes activated and triggers the localized degradation of Tiam1 at AJs, likely involving calpain proteases. Furthermore, we demonstrate that, in human tumors, Y384 phosphorylation positively correlates with Src activity, and total Tiam1 levels are inversely correlated. Thus, our data implicate Tiam1 phosphorylation and consequent degradation in Src-mediated EMT and resultant cell motility and establish a paradigm for regulating local concentrations of Rho-GEFs.

The cysteine-cluster motif of c-Yes, Lyn and FAK as a suppressive module for the kinases

The Src family of non-receptor protein tyrosine kinases plays a critical role in the progression of human cancers so that the development of its specific inhibitors is important as a therapeutic tool. We previously reported that cysteine residues in the cysteine-cluster (CC) motif of v-Src were critical for the kinase inactivation by the SH-alkylating agents such as N-(9-acridinyl) maleimide (NAM), whereas other cysteine residues were dispensable. We found similar CC-motifs in other Src-family kinases and a non-Src-family kinase, FAK. In this study, we explored the function of the CC-motif in Yes, Lyn and FAK. While Src has four cysteines in the CC-motif, c-Yes and Lyn have three and two of the four cysteines, respectively. Two conserved cysteines of the Src family kinases, corresponding to Cys487 and Cys498 of Src, were essential for the resistance to the inactivation of the kinase activity by NAM, whereas the first cysteine of c-Yes, which is absent in Lyn, was less important. FAK has similar CC-motifs with two cysteines and both cysteines were again essential for the resistance to the inactivation of the kinase activity by NAM. Taken together, modification of cysteine residues of the CC-motif causes a repressor effect on the catalytic activity of the Src family kinases and FAK.

Yes and PI3K bind CD95 to signal invasion of glioblastoma

Invasion of surrounding brain tissue by isolated tumor cells represents one of the main obstacles to a curative therapy of glioblastoma multiforme. Here we unravel a mechanism regulating glioma infiltration. Tumor interaction with the surrounding brain tissue induces CD95 Ligand expression. Binding of CD95 Ligand to CD95 on glioblastoma cells recruits the Src family member Yes and the p85 subunit of phosphatidylinositol 3-kinase to CD95, which signal invasion via the glycogen synthase kinase 3-beta pathway and subsequent expression of matrix metalloproteinases. In a murine syngeneic model of intracranial GBM, neutralization of CD95 activity dramatically reduced the number of invading cells. Our results uncover CD95 as an activator of PI3K and, most importantly, as a crucial trigger of basal invasion of glioblastoma in vivo.

Differential mitotic activation of endogenous c-Src, c-Yes, and Lyn in HeLa cells

Src-family tyrosine kinases (SFKs) play an important role in mitosis. Despite overlapping expression of multiple SFK members, little is known about how individual SFK members are activated in M phase. Here, we examined mitotic activation of endogenous c-Src, c-Yes, and Lyn, which are co-expressed in HeLa cells. c-Src, c-Yes, and Lyn were activated at different levels in M phase, and the activation was inhibited by Cdc2 inactivation. Mitotic c-Src and c-Yes exhibited normal- and retarded-electrophoretic-mobility forms on SDS-polyacrylamide gels, whereas Lyn did not show mobility retardation. Like c-Src, the retardation of electrophoretic mobility of c-Yes was caused by Cdc2-mediated phosphorylation. The normal- and retarded-mobility forms of c-Src were comparably activated, but activation of the retarded-mobility form of c-Yes was higher than that of the normal-mobility form of c-Yes. Thus, these results suggest that endogenous c-Src, c-Yes, and Lyn are differentially activated through Cdc2 activation during M phase.

The membrane targeting and spatial activation of Src, Yes and Fyn is influenced by palmitoylation and distinct RhoB/RhoD endosome requirements

Src activation is a tightly regulated process which requires RhoB endosome-associated actin assembly and transit to the cell periphery. We show here that although two other ubiquitous Src family kinases (SFKs) Yes and Fyn also require intact actin filaments for peripheral membrane targeting, they display distinct spatial activation and endosomal requirements. Unlike Src, both Yes and Fyn are constitutively membrane-localized to some extent, and Fyn is present in RhoD-positive endosomes whereas Yes does not visibly colocalize with either of the endosomal markers RhoB or RhoD. By modulating amino acid acceptor sites for palmitoylation in Src, Yes and Fyn, we show that Src S3C/S6C, which is palmitoylated (unlike wild-type Src) behaves in a manner more similar to Fyn, by predominantly colocalizing with RhoD endosomes, and the targeting of both Fyn and Src S3C/S6C is inhibited by siRNA-mediated knockdown of RhoD. Moreover, Fyn C3S/C6S, which is no longer palmitoylated, behaves much more like Src by colocalizing with RhoB endosomes and by requiring RhoB for activation and membrane translocation. These data imply that distinct modes of spatial activation and membrane delivery, at least partly under the control of specific acylation attachment sequences and endosome sub-type requirements, define distinct properties of the three ubiquitously expressed SFKs.

Purinergic agonists stimulate lens Na-K-ATPase-mediated transport via a Src tyrosine kinase-dependent pathway

The Na-K-ATPase is vital for maintenance of lens transparency. Past studies using intact lens suggested the involvement of tyrosine kinases in short-term regulation of Na-K-ATPase. Furthermore, in vitro phosphorylation of a lens epithelial membrane preparation by Src family kinases (SFKs), a family of nonreceptor tyrosine kinases, resulted in modification of Na-K-ATPase activity. Here, the effect of purinergic agonists, ATP and UTP, on Na-K-ATPase function and SFK activation was examined in the rabbit lens. Na-K-ATPase function was examined using two different approaches, measurement of ouabain-sensitive potassium ((86)Rb) uptake by the intact lens, and Na-K-ATPase activity in lens epithelial homogenates. ATP and UTP caused a significant increase in ouabain-sensitive potassium ((86)Rb) uptake. Na-K-ATPase activity was increased in the epithelium of lenses pretreated with ATP. Lenses treated with ATP or UTP displayed activation of SFKs as evidenced by increased Western blot band density of active SFK (phosphorylated at the active loop Y416) and decreased band density of inactive SFKs (phosphorylated at the COOH terminal). A single PY416-Src immunoreactive band at approximately 60 kDa was observed, suggesting not all Src family members are activated. Immunoprecipitation studies showed that band density of active Src, and to a lesser extent active Fyn, was significantly increased, while active Yes did not change. Preincubation of the lenses with SFK inhibitor PP2 abolished the ATP-induced increase in ouabain-sensitive potassium ((86)Rb) uptake. The results suggest selective activation of Src and/or Fyn is part of a signaling mechanism initiated by purinergic agonists that increases Na-K-ATPase-mediated transport in the organ-cultured lens.

Post‐translational modification of POU domain transcription factor Oct‐4 by SUMO‐1

POU domain transcription factor Oct-4 plays a crucial role in maintaining self-renewal and pluripotency of embryonic stem (ES) cells in a concentration-dependent manner. However, the molecular mechanism controlling Oct-4 levels in ES cells remains largely unknown. To explore the molecular mechanism regulating Oct-4 function, we constructed a mouse ES cell cDNA library and performed yeast two-hybrid screening using the POU domain of Oct-4 as bait. Here, we present novel evidence for Oct-4 interaction with Ubc9, an E2 conjugation enzyme for SUMO modification, and its modification by SUMO-1. The SUMO acceptor site was identified at lysine residue 118. Importantly, disruption of Oct-4 sumoylation reduced Oct-4 protein stability and self-renewal capacity in ES cells. Interestingly, expression of cYes was found to reduce when Oct-4 sumoylation was disrupted or Oct-4 expression downregulated in ES cells. We further demonstrate that Oct-4 was recruited to the cYes promoter region, suggesting that cYes might be a novel downstream gene of Oct-4. Taken together, we first demonstrate the post-translational modification of endogenous Oct-4 by SUMO and the role of sumoylation in regulating Oct-4 protein stability and function. Our findings provide new evidence for the important role of post-translational modification in controlling Oct-4 function in ES cells.

Exercise affects the gene expression profiles of human white blood cells

White blood cells (WBCs) express tens of thousands of genes, whose expression levels are modified by genetic and external factors. The purpose of the present study was to investigate the effects of acute exercise on gene expression profiles (GEPs) of WBCs and to identify suitable genes that may serve as surrogate markers for monitoring exercise and training load. Five male participants performed an exhaustive treadmill test (ET) at 80% of their maximal O2uptake (V̇o2 max) and a moderate treadmill test (MT) at 60% V̇o2 maxfor exactly the same time ∼2 wk later. WBCs were isolated by the erythrocyte lysis method. GEPs were measured using the Affymetrix GeneChip technology. After scaling, normalization, and filtering, groupwise comparisons of gene expression intensities were performed, and several measurements were validated by real-time PCR. We found 450 genes upregulated and 150 downregulated (>1.5-fold change; ANOVA with Benjamini-Hochberg correction, P < 0.05) after ET that were closely associated with the gene ontology lists “response to stress” and “inflammatory response”. Analysis of mean expression levels after MT showed that the extent of up- and downregulation was workload dependent. The genes for the stress (heat shock) proteins HSPA1A and HSPH1 and for the matrix metalloproteinase MMP-9 showed the most prominent increases, whereas the YES1 oncogene (YES1) and CD160 (BY55) were most strongly reduced. Despite different methodological approaches used, the consistency of our results with the expression data of another study (Connolly PH, Caiozzo VJ, Zaldivar F, Nemet D, Larson J, Hung SP, Heck JD, Hatfield GW, Cooper DM. J Appl Physiol 97: 1461–1469, 2004) suggests that expression fingerprints are useful tools for monitoring exercise and training loads and thereby help to avoid training-associated health risks.

ERK1/2 regulates ANG II-dependent cell proliferation via cytoplasmic activation of RSK2 and nuclear activation of elk1

In a concurrently submitted article, we show that ANG II-induced ERK1/2 activation is mediated by both c-Src/Yes/Fyn and heterotrimeric G protein/PKCζ-dependent signaling. Furthermore, we show that heterotrimeric G protein/PKCζ-activated ERK1/2 is destined for the nucleus while ERK1/2 activated by c-Src/Yes/Fyn-dependent signaling remains in the cytoplasm. Interestingly, both mechanisms of activation are required for maximum ANG II-induced cell proliferation. In this study, we sought to determine the mechanisms by which ERK1/2 facilitate cell proliferation via these distinct nuclear and cytoplasmic events, using cells that were lacking either c-Src/Yes/Fyn or heterotrimeric G protein/PKCζ-dependent ERK1/2 activation. A loss of c-Src/Yes/Fyn blocked ANG II-dependent RSK2 activation, RSK2 nuclear translocation, serum-response factor (SRF) phosphorylation, a portion of c-fos transcriptional activity and c-Fos phosphorylation. Blocking ANG II-induced heterotrimeric G protein/PKCζ activity resulted in a loss of ERK1/2 nuclear translocation, elk1 phosphorylation, and the remaining portion of c-fos transcriptional activity not dependent on c-Src/Yes/Fyn. Inhibition of RSK with the potent and selective inhibitor, SL0101, attenuated ANG II-induced cell proliferation, and, in combination with a PKCζ pseudosubstrate, completely attenuated cell proliferation. Thus we conclude that ERK1/2 mediate ANG II-dependent cell proliferation via distinct cytoplasmic and nuclear signaling events, which are in turn governed by c-Src/Yes/Fyn and heterotrimeric G protein/PKCζ-dependent signaling, respectively.

ANG II-induced cell proliferation is dually mediated by c-Src/Yes/Fyn-regulated ERK1/2 activation in the cytoplasm and PKCζ-controlled ERK1/2 activity within the nucleus

High-affinity binding of angiotensin II (ANG II) to the ANG II type 1 receptor (AT1R) results in the activation of ERK1/2 mitogen-activated protein kinases (MAPK). However, the precise mechanism of ANG II-induced ERK1/2 activation has not been fully characterized. Here, we investigated the signaling events leading to ANG II-induced ERK1/2 activation using a c-Src/Yes/Fyn tyrosine kinase-deficient mouse embryonic fibroblast (MEF) cell line stably transfected with the AT1R (SYF/AT1). ERK1/2 activation was reduced by ∼50% within these cells compared with wild-type controls (WT/AT1). The remaining ∼50% of intracellular ERK1/2 activation was dependent upon heterotrimeric G protein and protein kinase C zeta (PKCζ) activation. Therefore, ANG II-induced ERK1/2 activation occurs via two independent mechanisms. We next investigated whether a loss of either c-Src/Yes/Fyn or PKCζ signaling affected ERK1/2 nuclear translocation and cell proliferation in response to ANG II. ANG II-induced cell proliferation was markedly reduced in SYF/AT1cells compared with WT/AT1cells ( P < 0.01), but interestingly, ERK2 nuclear translocation was normal. ANG II-induced nuclear translocation of ERK2 was blocked via pretreatment of WT/AT1cells with a PKCζ pseudosubstrate. ANG II-induced cell proliferation was significantly reduced in PKCζ pseudosubstrate-treated WT/AT1cells ( P < 0.01) and was completely blocked in SYF/AT1cells treated with this same compound. Thus ANG II-induced cell proliferation appears to be regulated by both ERK1/2-driven nuclear and cytoplasmic events. In response to ANG II, the ability of ERK1/2 to remain within the cytoplasm or translocate into the nucleus is controlled by c-Src/Yes/Fyn or heterotrimeric G protein/PKCζ signaling, respectively.

Comparison of gene expression profiles between primary tumor and metastatic lesions in gastric cancer patients using laser microdissection and cDNA microarray

AIM: To study the differential gene expression profiles of target cells in primary gastric cancer and its metastatic lymph nodes using laser microdissection (LMD) in combination with cDNA microarray.

METHODS: Normal gastric tissue samples from 30 healthy individuals, 36 cancer tissue samples from primary gastric carcinoma and lymph node metastasis tissue samples from 58 patients during gastric cancer resection were obtained using LMD in combination with cDNA microarray independently. After P27-based amplification, aRNA from 36 of 58 patients (group 1) with lymph node metastasis and metastatic tissue specimens from the remaining 22 patients (group 2) were applied to cDNA microarray. Semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemical assay verified the results of microarray in group 2 and further identified genes differentially expressed in the progression of gastric cancer.

RESULTS: The expression of 10 genes was up-regulated while the expression of 15 genes was down-regulated in 22 gastric carcinoma samples compared with that of genes in the normal controls. The results were confirmed at the level of mRNA and protein, and suggested that four genes (OPCML, RNASE1, YES1 and ACK1) could play a key role in the tumorigenesis and metastasis of gastric cancer. The expression pattern of 3 genes (OPCML, RNASE1 and YES1) was similar to tumor suppressor genes. For example, the expression level of these genes was the highest in normal gastric epithelium, which was decreased in primary carcinoma, and further decreased in metastatic lymph nodes. On the contrary, the expression pattern of gene ACK1 was similar to that of oncogene. Four genes were further identified as differentially expressed genes in the majority of the cases in the progression of gastric cancer.

CONCLUSION: LMD in combination with cDNA microarray provides a unique support foe the identification of early expression profiles of differential genes and the expression pattern of 3 genes (OPCML, RNASE1 and YES1) associated with the progression of gastric cancer. Further study is needed to reveal the molecular mechanism of lymph node metastasis in patients with gastric cancer.

Wnt-5a/Ca2+-induced NFAT activity is counteracted by Wnt-5a/Yes-Cdc42-casein kinase 1alpha signaling in human mammary epithelial cells

Wnt-5a has been shown to influence the metastatic behavior of human breast cancer cells, and the loss of Wnt-5a expression is associated with metastatic disease. We show here that NFAT1, a transcription factor connected with breast cancer metastasis, is activated by Wnt-5a through a Ca2+ signaling pathway in human breast epithelial cells. This activation was simultaneously counteracted by a Wnt-5a-induced Yes/Cdc42 signaling pathway. The observation that inhibition of the Wnt-5a/Yes/Cdc42 signal prolonged the duration of ionomycin-induced NFAT1 activation revealed the general importance of this pathway. The Wnt-5a-induced inhibition of NFAT1 did not require glycogen synthase kinase 3beta, JNK, or Pak1 activity or modulation of the cytoskeleton. Instead, we observed that Wnt-5a induced a complex formation of NFAT1/casein kinase 1alpha, even upon treatment with ionomycin, which was blocked upon inhibition of the Wnt-5a/Yes/Cdc42 signaling pathway. Our results explain why Wnt-5a/Ca2+-induced NFAT activity is hard to detect and suggest a novel mechanism by which Wnt-5a can suppress tumor-specific, agonist-induced NFAT activity and thus the metastatic behavior of breast cancer cells.

Verotoxin-1 stimulation of macrophage-like THP-1 cells up-regulates tissue factor expression through activation of c-Yes tyrosine kinase: Possible signal transduction in tissue factor up-regulation

Verotoxin (VT)-producing Escherichia coli (E. coli) O157:H7 infections are frequently complicated by thrombotic angiopathy, hemolytic uremic syndrome (HUS) and neurological symptoms. The present data demonstrate that VT-1 (Shiga toxin) stimulation of macrophage-like THP-1 cells up-regulates the activity, antigen and mRNA levels of tissue factor (TF), a key cofactor of the coagulation-inflammation-thrombosis circuit. This up-regulation is accompanied by phosphorylation of phosphatidylinositol 3-kinase (PI3-kinase), IkappaB kinase beta (IKKbeta) and extracellular signal-regulated kinase 2 (ERK2). Changes in TF mRNA levels were in parallel with the activation of NF-kappaB/Rel and Egr-1 activation, but not with AP-1. Inhibition of PI3-kinase attenuated VT-1-induced phosphorylation of IKKbeta and ERK2, and the up-regulation of TF mRNA levels. VT-1 stimulation rapidly activated c-Yes tyrosine kinase, a member of the Src family. Treatment of the cells with c-Yes antisense oligos attenuated the VT-1-induced phosphorylation of PI3-kinase, IKKbeta and ERK2, activations of NF-kappaB/Rel and Egr-1, and up-regulation of TF mRNA levels. These results suggest that VT-1-induced macrophage stimulation activates c-Yes, which then up-regulates TF expression through activation of the IKKbeta/proteasome/NF-kappaB/Rel and MEK/ERK2/Egr-1 pathways via activation of PI3-kinase. Induction of macrophage TF expression by VT-1 may play an important role in the acceleration of the coagulation-inflammation-thrombosis circuit during infections by VT-producing E. coli.

Involvement of the SH3 domain in Ca2+-mediated regulation of Src family kinases

When cells are treated with Ca(2+) and Ca(2+)-ionophore, c-Src kinase activity increases, whereas c-Yes kinase activity decreases. This opposite modulation can be reproduced in an in vitro reconstitution assay and is dependent on Ca(2+) and on soluble factors present in cell lysates. Since c-Src and c-Yes share a high degree of homology, with the exception of their N-terminal "unique" domains, their activity was thought to be coordinately regulated. To assess the mechanism of regulation we generated stable cell lines expressing eight different constructs containing wild type c-Src and c-Yes, as well as swaps of the unique domain alone, unique and Src homology 3 (SH3) domains together and the SH3 domain alone. Swapping of the unique domains was not sufficient to reverse the regulation of the chimeric molecules. On the other hand, chimeras containing swaps of the unique plus the SH3 domains displayed reverse regulation, implicating both domains in the regulation of kinase activity by Ca(2+). To rule out the participation of the unique domain, we used chimeric molecules with swapped SH3 domains only and found that the SH3 domain is necessary and sufficient to confer Ca(2+)-mediated regulation of Src and Yes tyrosine kinases.

Inhibition of SRC expression and activity inhibits tumor progression and metastasis of human pancreatic adenocarcinoma cells in an orthotopic nude mouse model

The nonreceptor protein tyrosine kinase Src is overexpressed in 70% of pancreatic adenocarcinomas. Here, we describe the effect of molecular and pharmacological down-regulation of Src on incidence, growth, and metastasis of pancreatic tumor cells in an orthotopic model. Src expression in L3.6pl human pancreatic tumor cells was reduced by stable expression of a plasmid encoding small interfering RNA (siRNA) to c-src. In stable siRNA clones, Src expression was reduced >80%, with no change in expression of the related kinases c-Yes and c-Lyn, and proliferation rates were similar in all clones. Phosphorylation of Akt and p44/42 Erk mitogen-activated protein kinase and production of VEGF and IL-8 in culture supernatants were also reduced (P < 0.005). On orthotopic implantation of varying cell numbers into nude mice, tumor incidence was unchanged; however, in the siRNA clones, large tumors failed to develop, and incidence of metastasis was significantly reduced, suggesting that c-Src activity is critical to tumor progression. To examine this possibility further, animals bearing established wild-type tumors were treated with the Src/Abl-selective inhibitor BMS-354825 (dasatinib). Tumor size was decreased, and incidence of metastases was significantly reduced in treated mice compared with controls. These results demonstrate that Src activation contributes to pancreatic tumor progression in this model, offering Src as a candidate for targeted therapy.

Alternatively spliced FGFR-1 isoforms differentially modulate endothelial cell activation of c-YES

Ligand activation of fibroblast growth factor receptor-1 (FGFR-1) induces an angiogenic response following activation of multiple intracellular signaling substrates, including the Src family of nonreceptor tyrosine kinases (SFK). However, the direct association between FGFR-1 and SFK and the involvement of SFK in FGFR-1-dependent cell proliferation have been controversial. Structural variants of FGFR-1 are generated by alternative splicing which results in two major isoforms, containing either three (FGFR-1alpha) or two (FGFR-1beta) immunoglobulin-like domains in the extracellular region. To determine whether alternatively spliced FGFR-1 isoforms differentially activate SFK, we have examined FGF receptor-negative endothelial cells stably transfected with human cDNA encoding either FGFR-1alpha or FGFR-1beta. Transient activation of c-YES, the predominant SFK expressed in these endothelial cells, was restricted to FGFR-1beta transfectants following exposure to acidic fibroblast growth factor (FGF-1). Co-immunoprecipitation studies revealed that c-YES directly associated with FGFR-1beta. The Src homology (SH)2 domain (and not the SH3 domain) of c-YES was able to recognize tyrosine phosphorylated FGFR-1beta. FGFR-1beta-specific activation of c-YES was accompanied by its association with and activation of cortactin. FGF-1 treatment of both FGFR-1alpha and FGFR-1beta transfectants induced SFK-independent cellular proliferation and growth in low density cultures. At high density, under both anchorage-dependent and -independent conditions, FGF-1 failed to induce proliferation and growth of FGFR-1alpha transfectants. In contrast, FGF-1 induced proliferation, growth, and formation of cord-like structures in high density cultures of FGFR-1beta transfectants in an SFK-dependent manner. In vitro cord formation on Matrigel was restricted to FGFR-1beta transfectants in an SFK-dependent manner. Formation of vascular structures in vivo was limited to endothelial cells transfected with FGFR-1beta. Collectively, these results emphasize the roles of alternatively spliced FGFR-1 structural isoforms and activation of SFK as modulators of endothelial cell growth during the formation of neovascular structures.

Docking-based Substrate Recognition by the Catalytic Domain of a Protein Tyrosine Kinase, C-terminal Src Kinase (Csk)

Protein tyrosine kinases are key enzymes of mammalian signal transduction. Substrate specificity is a fundamental property that determines the specificity and fidelity of signaling by protein tyrosine kinases. However, how protein tyrosine kinases recognize the protein substrates is not well understood. C-terminal Src kinase (Csk) specifically phosphorylates Src family kinases on a C-terminal Tyr residue, which down-regulates their activities. We have previously determined that Csk recognizes Src using a substrate-docking site away from the active site. In the current study, we identified the docking determinants in Src recognized by the Csk substrate-docking site and demonstrated an interaction between the docking determinants of Src and the Csk substrate-docking site for this recognition. A similar mechanism was confirmed for Csk recognition of another Src family kinase, Yes. Although both Csk and MAP kinases used docking sites for substrate recognition, their docking sites consisted of different substructures in the catalytic domain. These results helped establish a docking-based substrate recognition mechanism for Csk. This model may provide a framework for understanding substrate recognition and specificity of other protein tyrosine kinases.

Src family kinase members have a common response to histone deacetylase inhibitors in human colon cancer cells

Histone deacetylase inhibitors (HDIs) induce cell cycle arrest, differentiation and/or apoptosis in numerous cancer cell types and have shown promise in clinical trials. These agents are particularly novel, given their ability to selectively influence gene expression. Previously, we demonstrated that the HDIs butyrate and trichostatin A (TSA) directly repress c-Src proto-oncogene expression in many cancer cell lines. Activation and/or overexpression of c-Src have been frequently observed in numerous malignancies, especially of the colon. Therefore, our observation was particularly interesting since butyrate is a naturally abundant component of the large intestine and has been suggested to be a cancer-preventive agent. However, c-Src is not the only Src family kinase (SFK) member to be implicated in the development of human cancers, including those of the colon. Therefore, the relative expression levels of known SFKs were examined in a panel of human colon cancer cell lines. We found a surprisingly diverse expression pattern but noted that most cell lines expressed relatively high levels of at least 2 SFKs. When the effects of butyrate and TSA were examined in representative cell lines, the expression of all SFKs was repressed in a dose- and time-dependent manner. Further, detailed examination of Lck, Yes and Lyn demonstrated that this repression had a direct effect on transcription and was independent of new protein synthesis. These results mirror our earlier data obtained with c-Src and suggest that SFKs are a major target of HDIs and likely account in part for the anticancer effects of these promising new drugs.

Abl collaborates with Src family kinases to stimulate actin-based motility of vaccinia virus

Local activation of Src at the plasma membrane by extracellular vaccinia virus results in a signalling cascade that acts to stimulate actin polymerization beneath the virus to enhance its cell-to-cell spread. Initiation of this signalling cascade involves Src-mediated phosphorylation of tyrosine 112 and 132 of the viral membrane protein A36R. Here we show that recruitment of Src is dependent on its myristoylation and an interaction with A36R upstream of tyrosine 112 and 132. We further show that Src, Fyn and Yes have unique specificities towards these tyrosine residues. Using cell lines deficient in Src, Fyn and Yes, we demonstrate that multiple Src family members can stimulate vaccinia-induced actin polymerization and also uncover a role for Abl family kinases. Additionally, Abl and Arg are able to phosphorylate A36R in vitro and are recruited to vaccinia-induced actin tails. The ability of multiple families of tyrosine kinases to directly phosphorylate A36R ensures robust cell-to-cell spread of vaccinia virus will occur under a variety of cellular conditions.

Recombinant O-GlcNAc transferase isoforms: identification of O-GlcNAcase, yes tyrosine kinase, and tau as isoform-specific substrates

O-linked N-acetylglucosaminyltransferase (OGT) catalyzes the transfer of O-linked GlcNAc to serine or threonine residues of a variety of substrate proteins, including nuclear pore proteins, transcription factors, and proteins implicated in diabetes and neurodegenerative disorders. We have identified two nucleocytoplasmic isoforms of OGT (ncOGT and sOGT) and one isoform that localizes to the mitochondria (mOGT). These three isoforms contain identical catalytic regions but differ in the number of tetratricopeptide repeat motifs found at the N-terminus of each enzyme. We expressed each of these OGT isoforms in a soluble form in Escherichia coli and have used them to identify novel targets including the Src-family tyrosine kinase yes and O-GlcNAc-ase. We demonstrate that some substrate proteins, such as Nup62 and casein kinase II, are glycosylated by both ncOGT and mOGT, while others such as O-GlcNAcase and tau are specifically modified by ncOGT. The yes kinase was specifically modified by mOGT. The short isoform of OGT (sOGT) did not glycosylate any of the substrates tested, although it retains a potentially active catalytic domain. Our findings demonstrate the potential utility of recombinant OGT in identifying new targets and illustrate the necessity to examine all active isoforms of the enzyme. The identification of a tyrosine kinase and O-GlcNAcase as OGT targets suggests the potential for OGT participation in numerous signal transduction cascades.

Integrin alpha4beta1 promotes focal adhesion kinase-independent cell motility via alpha4 cytoplasmic domain-specific activation of c-Src

The fibronectin binding integrins alpha5beta1 and alpha4beta1 generate signals pivotal for cell migration through distinct yet undefined mechanisms. For alpha5beta1, beta1-mediated activation of focal adhesion kinase (FAK) promotes c-Src recruitment to FAK and the formation of a FAK-Src signaling complex. Herein, we show that FAK expression is essential for alpha5beta1-stimulated cell motility and that exogenous expression of human alpha4 in FAK-null fibroblasts forms a functional alpha4beta1 receptor that promotes robust cell motility equal to the alpha5beta1 stimulation of wild-type and FAK-reconstituted fibroblasts. alpha4beta1-stimulated FAK-null cell spreading and motility were dependent on the integrity of the alpha4 cytoplasmic domain, independent of direct paxillin binding to alpha4, and were not affected by PRNK expression, a dominant-negative inhibitor of Pyk2. alpha4 cytoplasmic domain-initiated signaling led to a approximately 4-fold activation of c-Src which did not require paxillin binding to alpha4. Notably, alpha4-stimulated cell motility was inhibited by catalytically inactive receptor protein-tyrosine phosphatase alpha overexpression and blocked by the p50Csk phosphorylation of c-Src at Tyr-529. alpha4beta1-stimulated cell motility of triple-null Src(-/-), c-Yes(-/-), and Fyn(-/-) fibroblasts was dependent on c-Src reexpression that resulted in p130Cas tyrosine phosphorylation and Rac GTPase loading. As p130Cas phosphorylation and Rac activation are common downstream targets for alpha5beta1-stimulated FAK activation, our results support the existence of a novel alpha4 cytoplasmic domain connection leading to c-Src activation which functions as a FAK-independent linkage to a common motility-promoting signaling pathway.

Muscarinic M2 receptors mediate transactivation of EGF receptor through Fyn kinase and without matrix metalloproteases

Transactivation of epidermal growth factor receptor (EGFR) by G protein-coupled receptors (GPCRs) has been attributed to the activation of matrix metalloproteases (MMPs) and the release of EGF family ligands such as HB-EGF. This mode of transactivation leads to signalling downstream of EGFR which is indistinguishable from that induced by the ligand. Here we provide evidence that in the COS-7 cell model EGFR transactivation via the muscarinic M2 receptor (M2R) is independent of MMPs and results in an incomplete EGFR signalling including ERK and Akt but not PLCgamma1. Using dominant-negative mutants of c-Src and Fyn and Src-deficient SYF cells as well as by co-immunoprecipitation studies, we can demonstrate that the M2R-mediated transactivation of EGFR specifically involves Fyn but not c-Src or Yes. This specific role of Fyn can be verified in SH-SY5Y human neuroblastoma cells with endogenously expressed M2 receptors.

Activation of the lutropin/choriogonadotropin receptor in MA-10 cells leads to the tyrosine phosphorylation of the focal adhesion kinase by a pathway that involves Src family kinases

We show that activation of the endogenous or recombinant lutropin/choriogonadotropin receptor (LHR) in mouse Leydig tumor cells (MA-10 cells) leads to the tyrosine phosphorylation of the focal adhesion kinase (FAK) and one of its substrates (paxillin). Using specific antibodies to the five tyrosine residues of FAK that become phosphorylated, we show that activation of the LHR increases the phosphorylation of Tyr576 and Tyr577, but it does not affect the phosphorylation of Tyr397, Tyr861, or Tyr925. Because FAK is a prominent substrate for the Src family of tyrosine kinases (SFKs) we tested for their involvement in the LHR-mediated phosphorylation of FAK-Tyr576. Src is not detectable in MA-10 cells, but two other prominent members of this family (Fyn and Yes) are present. The LHR-mediated phosphorylation of FAK-Tyr576 is readily inhibited by PP2 (a pharmacological inhibitor of SFKs) and by dominant-negative mutants of SKFs. Moreover, activation of the LHR in MA-10 cells results in the stimulation of the activity of Fyn and Yes, and overexpression of either of these two tyrosine kinases enhances the LHR-mediated phosphorylation of FAK-Tyr576. Studies involving activation of other G protein-coupled receptors, overexpression of the different Galpha-subunits, and the use of second messenger analogs suggest that the LHR-induced phosphorylation of FAK-Tyr576 in MA-10 cells is mediated by SFKs, and that this family of kinases is, in turn, independently or cooperatively activated by the LHR-induced stimulation of Gs and Gq/11-mediated pathways.