Lysophosphatidic acid modulates the association of PTP1B with N-cadherin/catenin complex in SKOV3 ovarian cancer cells

LPA (lysophosphatidic acid) is a natural phospholipid that plays important roles in promoting cancer cell proliferation, invasion and metastases. We previously reported that LPA induces ovarian cancer cell dispersal and disruption of AJ (adherens junction) through the activation of SFK (Src family kinases). In this study, we have investigated the regulatory mechanisms during the early phase of LPA-induced cell dispersal. An in vitro model of the ovarian cancer cell line SKOV3 for cell dispersal was used. LPA induces rapid AJ disruption by increasing the internalization of N-cadherin-beta-catenin. By using immunoprecipitations, LPA was shown to induce increased tyrosine phosphorylation of beta-catenin and alter the balance of beta-catenin-bound SFK and PTP1B (phosphotyrosine phosphatase 1B). The altered balance of tyrosine kinase/phosphatase correlated with a concomitant disintegration of the beta-catenin-alpha-catenin, but not the beta-catenin-N-cadherin complex. This disintegration of beta-catenin from alpha-catenin and the cell dispersal caused by LPA can be rescued by blocking SFK activity with the chemical inhibitor, PP2. More importantly, PP2 also restores the level of PTP1B bound to beta-catenin. We propose that LPA signalling alters AJ stability by changing the dynamics of tyrosine kinase/phosphatase bound to AJ proteins. This work provides further understanding of the early signalling events regulating ovarian cancer cell dispersal and AJ disruption induced by LPA.