Effects of overexpression of PTP36, a putative protein tyrosine phosphatase, on cell adhesion, cell growth, and cytoskeletons in HeLa cells

Non-receptor-type putative protein tyrosine phosphatase-36 (PTP36), also kn own as PTPD2/Pez, possesses a domain homologous to the N-terminal half of b and 4.1 protein. To gain insight into the biological function of PTP36, we established a HeLa cell line, HtTA/P36-9, in which the overexpression of PT P36 was inducible. PTP36 expressed in HeLa cells was enriched in the cytosk eleton near the plasma membrane. There was little endogenous PTP36 detectab le in uninduced HtTA/P36-9 cells or in the parental HeLa cells. Upon induct ion of PTP36 overexpression, HtTA/P36-9 cells spread less well, grew more s lowly, and adhered to the extracellular matrix proteins less well than unin duced cells. Moreover, decreases in the actin stress fibers and the number of focal adhesions were observed. The tyrosine phosphorylation of the focal adhesion kinase induced by lysophosphatidic acid was suppressed in the HtT A/P36-9 cells overexpressing PTP36. These results indicate that PTP36 affec ts cytoskeletons, cell adhesion, and cell growth, thus suggesting that PTP3 6 is involved in their regulatory processes.