Insulin dependent tyrosine phosphorylation of the tyrosine internalisation motif of TGN38 creates a specific SH2 domain binding site.
Tyrosine-based motifs are involved in both protein targeting and, via SH2 domain binding, intracellular signalling. To date there has only been one example of such a motif acting as both an intracellular sorting signal and SH2 binding determinant, namely that of the T cell costimulation receptor, CTLA-4. We show that insulin stimulation of cultured rat hepatoma cells results in increased cell surface expression of TGN38. Furthermore, the cytosolic domain of TGN38 can be phosphorylated by the insulin receptor in vitro and tyrosine phosphorylated TGN38 can specifically bind to the SH2 domains of the spleen tyrosine kinase Syk. These data imply that tyrosine-based motifs may play a broader role than has previously been accepted and could help to integrate trafficking and signalling events.
Stephens
D J
DJ
Department of Biochemistry, University of Bristol, School of Medical Sciences, UK.
Banting
G
G
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D004705:Endocytosis; D006023:Glycoproteins; D007328:Insulin / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins; D010766:Phosphorylation; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism*; D018909:src Homology Domains
D006023:Glycoproteins; D007328:Insulin; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C513045:Tgoln2 protein, rat; D014443:Tyrosine; D011972:Receptor, Insulin