A transmembrane osteoclastic protein-tyrosine phosphatase regulates osteoclast activity in part by promoting osteoclast survival through c-Src-dependent activation of NFκB and JNK2

This study evaluated the effects of overexpression of wild-type (WT) or phosphatase-deficient (PD) mutant of an osteoclastic protein-tyrosine phosphatase (PTP-oc) in RAW/C4 cells. Osteoclast-like cells derived from WT-PTP-oc overexpressing clones increased, while those derived from PD-PTP-oc expressing clones decreased, their resorption activity. WT-PTP-oc clones had lower apoptosis, lower caspase 3/7 activity, reduced c-Src tyr-527 phosphorylation (PY527) and IκBα cellular levels, and increased NFκB activation and JNK phosphorylation. Overexpression of PD-PTP-oc or PTP-oc siRNA treatment increased apoptosis, caspase 3/7 activity, PY527 and IκBα levels, and decreased NFκB and JNK2 activation. Inhibition of the c-Src kinase blocked the PTP-oc-mediated NFκB and JNK2 activation. Blocking the NFκB activation had no effect on the JNK2 activation. Inhibiting the NFκB and/or JNK2 pathway prevented the PTP-oc-mediated reduction in apoptosis. In conclusion, PTP-oc activates osteoclast activity in part by promoting osteoclast survival through the PTP-oc-mediated c-Src-dependent activation of NFκB and JNK2.