title: Presence and tyrosine phosphorylation of c-met receptor in human sperm.
abstract: The c-met receptor is a p190MET tyrosine kinase proto-oncoprotein that through its binding to its ligand, designated hepatocyte growth factor (HGF), induces mitogenic, motogenic, and morphogenic activities in a variety of cell types. The present study was conducted to examine whether or not the c-met receptor is expressed and tyrosine phosphorylated in the human sperm cell. The Western blot analysis, using a monoclonal antibody (MAb2) directed against the extracellular domain of the c-met receptor, showed a specific band of 195 kDa corresponding to the intact c-met receptor in the detergent-solubilized human sperm preparation (HSP). This protein band was not recognized by the control myeloma lg (immunoglobin). In the immunoprecipitation procedure, a similar specific band of 195 kDa and a 145-kDa band corresponding to the beta-subunit of c-met receptor were seen. In the indirect immunofluorescence technique, the c-met receptor was localized predominantly in the acrosomal region of the sperm cell. The c-met receptor was tyrosine phosphorylated/autophosphorylated during capacitation and in the cell-free in vitro kinase assay. Incubation of human sperm with hepatocyte growth factor (HGF) or MAb2 to c-met receptor enhanced the degree of tyrosine phosphorylation/autophosphorylation of the c-met receptor up to 5.1-fold. These findings indicate that the c-met receptor is present in the acrosomal region of human sperm cell and is tyrosine phosphorylated, which is enhanced by HGF and the receptor antibody. The c-met system may have an important role in sperm function.
authors.affiliation: Department of Obstetrics and Gynecology, Medical College of Ohio, Toledo 43614-5806, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Herness
authors.forename: R K
authors.initials: RK
authors.lastname: Naz
mesh_terms: D015153:Blotting, Western; D005306:Fertilization / Q000502:physiology; D006801:Humans; D008297:Male; D010766:Phosphorylation; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism* / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D014443:Tyrosine; D019859:Proto-Oncogene Proteins c-met