PTP-PEST controls motility, adherens junction assembly, and Rho GTPase activity in colon cancer cells

• Published in: American Journal of Physiology: Cell Physiology Vol. 299; no. 2; pp. C454 - C463
• Main Authors: Espejo, Rosario, Rengifo-Cam, William, Schaller, Michael D, Evers, B Mark, Sastry, Sarita K
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.08.2010
• Subjects: Adherens Junctions - enzymology; Adherens Junctions - metabolism; Adherens Junctions - physiology; Animals; Cell adhesion & migration; Cell Line, Tumor; Cell Migration Inhibition - physiology; Cell Movement - physiology; Cells, Cultured; Colonic Neoplasms - enzymology; Colonic Neoplasms - metabolism; Colonic Neoplasms - pathology; Colorectal cancer; Enzyme Activation - physiology; Extracellular Matrix, Cell Interactions; Gene expression; Genotype & phenotype; HCT116 Cells; Humans; Metastasis; Physiology; Protein Tyrosine Phosphatase, Non-Receptor Type 12 - physiology; Proteins; Rats; rho GTP-Binding Proteins - antagonists & inhibitors; rho GTP-Binding Proteins - metabolism; Ribonucleic acid; RNA
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00148.2010

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.