SHP protein tyrosine phosphatase expression in rat uterine tissue.
OBJECTIVE
Enhanced tyrosine phosphorylation of phospholipase C-gamma1 (PLCgamma1) is associated with increased spontaneous contractile activity. PLCgamma1 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 PLCgamma1: 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 PLCgamma1 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-I1 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 PLCgamma1.


CONCLUSIONS
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 PLCgamma1 phosphotyrosine levels in the rat uterus.
Phillippe
Mark
M
Department of Obstetrics and Gynecology, University of Vermont College of Medicine, Burlington, Vermont 05405, USA. Mark.Phillippe@uvm.edu
Bradley
Diana F
DF
Engle
Daniel
D
Sweet
Leigh
L
D000818:Animals; D015153:Blotting, Western; D004971:Estrus; D005260:Female; D005865:Gestational Age; D007163:Immunosorbent Techniques; D047908:Intracellular Signaling Peptides and Proteins / Q000032:analysis*; D051966:Phospholipase C gamma / Q000032:analysis; D011247:Pregnancy; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014599:Uterus / Q000201:enzymology*
D047908:Intracellular Signaling Peptides and Proteins; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516727:Ptpn11 protein, rat; C509250:Ptpn6 protein, rat; D051966:Phospholipase C gamma