Thy-1 associated pp85--90 is a potential docking site for SH2 domain-containing signal transduction molecules.
Thy-1, a glycosylphosphatidylinositol (GPI)-anchored glycoprotein expressed at high levels on thymocytes, has been implicated in positive and negative signal transduction. We show that Thy-1 associates with a protein of 85--90 kDa, which is prominently phosphorylated in vitro as well as in vivo following the stimulation of thymocytes with pervanadate. pp85--90 is not identical to known proteins that are phosphorylated following T cell activation. The SH2 domains of fyn, csk, phosphatidylinositol 3'-kinase, rasGAP, vav and lck bind to pp85--90 with varying affinities. The SH2 domains of ZAP70, SHP-1 and PLC gamma 1 and the SH3 domains of lck, vav and HS1 did not bind to pp85--90. The molecular weight, iso-electric point, efficient phosphorylation by fyn and lck and preferential binding to the SH2 domain of fyn compared to that of lck indicate that Thy-1-associated pp85-90 may be identical to a recently cloned, fyn-associated transmembrane adaptor protein, PAG-85.
Department of Medical Physiology and Biochemistry, University of Stellenbosch Medical School, Tygerberg, South Africa. gad@gerga.sun.ac.za
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Durrheim
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Garnett
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Dennehy
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Beyers
D000818:Animals; D001665:Binding Sites; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005982:Glutathione Transferase / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008213:Lymphocyte Activation; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry; D051076:Proto-Oncogene Proteins c-fyn; D051381:Rats; D011917:Rats, Inbred Lew; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism; D018800:Thy-1 Antigens / Q000737:chemistry* / Q000378:metabolism*; D018909:src Homology Domains
D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D018800:Thy-1 Antigens; D005982:Glutathione Transferase; C494961:Fyn protein, rat; D051076:Proto-Oncogene Proteins c-fyn