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SHP Protein Tyrosine Phosphatase Expression in Rat Uterine Tissue

Department of Obstetrics and Gynecology, University of Vermont College of medicine, Given Building, Room C-256, 89 Beaumont Ave., Burlington, VT 05405 Mark.Phillippe{at}uvm.edu

Diana F. Bradley

Daniel Engle

Leigh Sweet

Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Burlington, Vermont

Objective: Enhanced tyrosine phosphorylation of phosopholipase C-1 (PLC1) is associated with increased spontaneous contractile activity. PLC1 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 PLC1: 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 PLC1 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 <.05); similarly, PTP-11 produced an 86% reduction in enzyme activity (P <.05). Western blots confirmed robust expression of both SHP-1 and SHP-2 protein in rat uterus. SHP-1 expression decreased significantly at the end of gestation; in contrast, SHP-2 levels remained stable. Immunoprecipitation studies confirmed an association between the SHP proteins and PLC1.

Conclusion: These studies have demonstrated that SHP-1 and SHP-2 are expressed in rat myometrium and appear to be responsible for the PTP activity in this tissue, thereby providing a molecular mechanism for the modulation of PLC1 phosphotyrosine levels in the rat uterus.

Key Words: SHP-1 protein tyrosine phosphatase • SHP-2 protein tyrosine phosphatase • phospholipase C-1 • rat uterus

Journal of the Society for Gynecologic Investigation, Vol. 13, No. 5, 338-342 (2006)
DOI: 10.1016/j.jsgi.2006.04.008


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