Sealy Center for Cancer Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555-1074, USA.
Am J Physiol Cell Physiol. 2010 Aug;299(2):C454-63. doi: 10.1152/ajpcell.00148.2010. Epub 2010 Jun 2.
An important step in carcinoma progression is loss of cell-cell adhesion leading to increased invasion and metastasis. We show here that the protein tyrosine phosphatase, PTP-PEST, is a critical regulator of cell-cell junction integrity and epithelial cell motility. Using colon carcinoma cells, we show that the expression level of PTP-PEST regulates cell motility. Either transient small interfering RNA or stable short hairpin RNA knockdown of PTP-PEST enhances haptotactic and chemotactic migration of KM12C colon carcinoma cells. Furthermore, KM12C cells with stably knocked down PTP-PEST exhibit a mesenchymal-like phenotype with prominent membrane ruffles and lamellae. In contrast, ectopic expression of PTP-PEST in KM20 or DLD-1 cells, which lack detectable endogenous PTP-PEST expression, suppresses haptotactic migration. Importantly, we find that PTP-PEST localizes in adherens junctions. Concomitant with enhanced motility, stable knockdown of PTP-PEST causes a disruption of cell-cell junctions. These effects are due to a defect in junctional assembly and not to a loss of E-cadherin expression. Adherens junction assembly is impaired following calcium switch in KM12C cells with stably knocked down PTP-PEST and is accompanied by an increase in the activity of Rac1 and a suppression of RhoA activity in response to cadherin engagement. Taken together, these results suggest that PTP-PEST functions as a suppressor of epithelial cell motility by controlling Rho GTPase activity and the assembly of adherens junctions.
在癌的进展过程中，一个重要步骤是细胞间黏附的丧失，导致侵袭和转移的增加。我们在这里表明，蛋白酪氨酸磷酸酶 PTP-PEST 是细胞间连接完整性和上皮细胞迁移的关键调节因子。使用结肠癌细胞，我们表明 PTP-PEST 的表达水平调节细胞迁移。瞬时小干扰 RNA 或稳定短发夹 RNA 敲低 PTP-PEST 增强了 KM12C 结肠癌细胞的趋化性和趋药性迁移。此外，稳定敲低 PTP-PEST 的 KM12C 细胞表现出间充质样表型，具有明显的细胞膜皱襞和薄片。相比之下，在缺乏可检测到的内源性 PTP-PEST 表达的 KM20 或 DLD-1 细胞中异位表达 PTP-PEST 抑制了趋化性迁移。重要的是，我们发现 PTP-PEST 定位于黏着连接。与增强的迁移一致，稳定敲低 PTP-PEST 导致细胞-细胞连接的破坏。这些影响是由于连接组装的缺陷，而不是 E-钙黏蛋白表达的丧失。在稳定敲低 PTP-PEST 的 KM12C 细胞中，钙转换后黏着连接的组装受到损害，并且 Rac1 的活性增加，而 RhoA 的活性受到 E-钙黏蛋白结合的抑制。总之，这些结果表明 PTP-PEST 通过控制 Rho GTPase 活性和黏着连接的组装，作为上皮细胞迁移的抑制剂发挥作用。
