Regulation and Function of PTP-PEST in colon carcinoma

描述(由申请人提供)：蛋白酪氨酸磷酸酶(PTPase)是一类很少被研究的假定的肿瘤抑制因子。肿瘤进展的一个关键步骤是失去细胞-细胞接触，导致高度侵袭性表型。细胞-细胞接触处酪氨酸激酶信号的增加通过破坏黏附连接而导致结肠癌的侵袭。钙粘附素参与通过调节Rho GTP酶促进细胞间的黏附和接触抑制细胞的运动。P120连环蛋白是一种酪氨酸磷酸化的钙粘附素结合蛋白，调节Rho GTP酶活性。P120ctn与钙粘附素的结合稳定了粘连连接。RTK信号的升高增加了细胞质的p120ctn，并通过使Rho GTP酶活性从粘连连接到前沿而导致细胞的分散和侵袭。P120ctn基因非定位化与侵袭性结肠癌有关。然而，控制p120ctn酪氨酸磷酸化的机制以及这如何影响连接完整性、Rho GTP酶活性和随后的结肠癌细胞侵袭的机制还知之甚少。PTP-PEST是一种胞质PTPase，与p120ctn一样，通过Rho GTP酶调节细胞运动。我们的初步证据表明，PTP-PEST靶向于结肠癌细胞中的p120ctn。此外，PTP-PEST基因在结肠癌细胞中发生突变，导致功能蛋白丢失。PTP-PEST表达的缺失如何与运动性和Rho GTP酶活性相关尚不清楚。我们的长期目标是了解PTP-PEST如何促进结肠癌的进展。本研究的目的是研究PTP-PEST如何控制黏附连接中Rho GTP酶的活性以限制结肠癌的侵袭，以及PTP-PEST表达的变化如何影响侵袭潜能。这一建议的具体目的是：1)确定PTP-PEST的定位如何影响黏附连接的完整性和细胞运动；2)阐明PTP-PEST如何调节钙粘素参与下游的rac1和RhoA活性；3)检测PTP-PEST表达如何影响结肠癌细胞的侵袭和转移潜能。结肠癌有效治疗的一个主要障碍是需要有针对性的治疗。我们的工作将使PTP-PEST成为治疗结肠癌的潜在候选者，作为一种侵袭抑制因子。这些目标的完成将有助于更好地理解PTP-PEST控制结肠癌侵袭的细胞和生化机制。此外，我们的研究将为未来研究PTP-PEST作为一个潜在的生物标志物和作为基于基因治疗的方法来规避结肠癌侵袭奠定基础。

DESCRIPTION (provided by applicant): Protein tyrosine phosphatases (PTPases) are a largely understudied class of putative tumor suppressors. A critical step in tumor progression is the loss of cell-cell contacts leading to a highly invasive phenotype. Increased tyrosine kinase signaling at cell-cell contacts contributes to the invasion of colon carcinomas through disruption of adherens junctions. Cadherin engagement promotes cell-cell adhesion and contact inhibition of cell motility through regulation of Rho GTPases. p120 catenin is a tyrosine phosphorylated cadherin binding protein that regulates Rho GTPase activity. Binding of p120ctn to cadherins stabilizes adherens junctions. Elevated RTK signaling increases cytoplasmic p120ctn and leads to cell scattering and invasion by delocalizing Rho GTPase activity from adherens junctions to the leading edge. The delocalization of p120ctn is associated with aggressive colon cancer. However, the mechanisms that control tyrosine phosphorylation of p120ctn and how this affects junctional integrity, Rho GTPase activity and subsequent invasion of colon carcinoma cells are poorly understood. PTP-PEST is a cytoplasmic PTPase that, like p120ctn, regulates cell motility through Rho GTPases. Our preliminary evidence indicates that PTP-PEST targets p120ctn in colon carcinoma cells. In addition, the PTP-PEST gene is mutated in colon cancer cells leading to a loss of functional protein. How loss of PTP-PEST expression correlates with motility and Rho GTPase activity is not known. Our long-term goal is to understand how PTP-PEST contributes to colon cancer progression. The purpose of this proposal is to investigate how PTP-PEST controls Rho GTPase activity in adherens junctions to limit colon carcinoma invasion and how changes in PTP-PEST expression influence invasive potential. The specific aims of this proposal are: 1) Determine how localization of PTP-PEST affects integrity of adherens junctions and cell motility 2) Elucidate how PTP- PEST modulates Rac1 and RhoA activity downstream of cadherin engagement and 3) Examine how PTP- PEST expression affects the invasive and metastatic potential of colon carcinoma cells. A major barrier to effective treatment of colon cancer is a need for targeted therapies. Our work will establish PTP-PEST as a potential candidate for the treatment of colon cancer as a suppressor of invasion. Completion of the proposed aims will lead to a better understanding of the cellular and biochemical mechanisms by which PTP- PEST functions to control colon carcinoma invasion. Moreover, our studies will lay a foundation for future studies investigating PTP-PEST as a potential biomarker and as a candidate for gene therapy based approaches to circumvent colon carcinoma invasion.