SHP Protein Tyrosine Phosphatase Expression in Rat Uterine Tissue

Objective: Enhanced tyrosine phosphorylation of phosopholipase C-γ1 (PLCγ1) is associated with increased spontaneous contractile activity. PLCγ1 phosphorylation is regulated by cellular protein tyrosine kinases and tyrosine phosphatases (PTPs). The studies in this report were undertaken to characterize the expression of two PTPs known to bind to PLCγ1: Src-homology phosphatase type-1 (SHP-1) and type-2 (SHP-2). Methods: Uterine and other tissues were obtained from non-pregnant (estrus) and pregnant (gestational day 12 through day 1 postpartum) Sprague-Dawley rats. PTP activity in myometrial homogenates was determined using an in vitro fluorometric PTP assay with and without bpV(phen) (a nonselective PTP inhibitor), or PTP-Inhibitor 1 (PTP-I1, a SHP selective inhibitor). Western blots were performed using polyclonal antibodies to SHP-1 and SHP-2. Immunoprecipitation studies were performed to demonstrate an association between PLCγ1 and the SHP proteins. Results: The in vitro PTP assays demonstrated comparable enzyme activity in myometrium from estrus and pregnant animals. BpV(phen) produced a 93% reduction in PTP activity (P