title: Phosphotyrosine phosphatase activity associated with c-Src in large multimeric complexes isolated from adrenal medullary chromaffin cells.
abstract: Chromaffin cells, which secrete catecholamines in response to acetylcholine, express high levels of the Src-family tyrosine kinases. These kinases contain protein-protein interaction domains which bind signal transduction proteins that participate in a variety of cellular processes. To determine if signalling proteins bind c-Src in chromaffin cells, we examined c-Src immunocomplexes for co-precipitating proteins. We discovered a phosphotyrosine phosphatase (PTPase; EC 3.1.3.48) activity which associates with specific subcellular pools of c-Src in vivo and which preferentially binds the SH2 (Src homology 2) domain of c-Src in vitro. Known PTPases were not identified by blotting of c-Src immunocomplexes with a panel of anti-PTPase antibodies, suggesting that the PTPase may be a novel family member. The c-Src-PTPase complex is enriched in the plasma membrane fraction and exists in several large complexes, as revealed by gel-filtration analysis. This PTPase activity is altered rapidly following stimulation by secretagogues, decreasing within 30 s and returning to basal levels by 60 s of stimulation. Both the subcellular localization and rapid activity changes suggest that the c-Src-associated PTPase may function in early signalling events emanating from the nicotinic acetylcholine receptor. In support of this is the co-precipitation of a PTPase activity with the nicotinic acetylcholine receptor and co-chromatography of this receptor with one or the c-Src-PTPase complexes.
authors.affiliation: Department of Microbiology, University of Virginia, Charlottesville 22908, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: van Hoek
authors.forename: C S
authors.initials: CS
authors.lastname: Allen
authors.forename: S J
authors.initials: SJ
authors.lastname: Parsons
mesh_terms: D000313:Adrenal Medulla / Q000737:chemistry / Q000166:cytology / Q000201:enzymology*; D000818:Animals; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D000081247:CSK Tyrosine-Protein Kinase; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000737:chemistry / Q000201:enzymology*; D009097:Multienzyme Complexes / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D010449:Peptide Mapping; D017027:Protein Tyrosine Phosphatases / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism*; D013347:Subcellular Fractions / Q000737:chemistry / Q000201:enzymology; D019061:src-Family Kinases
chemical_list: D000911:Antibodies, Monoclonal; D009097:Multienzyme Complexes; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D017027:Protein Tyrosine Phosphatases