TI  - Thymocyte activation induces the association of   <prot>phosphatidylinositol
      3-kinase</prot>   and  <prot>pp120</prot>  with  <prot>CD5</prot> .
PG  - 679-86
AB  - <prot>CD5</prot> is a glycoprotein expressed on thymocytes, T cells, and a subset of B
      cells. Antibody-mediated cross-linking studies or studies on <prot>CD5</prot> knockout
      mice implicate <prot>CD5</prot> as a co-stimulatory or negative regulatory molecule.
      <prot>CD5</prot> is rapidly phosphorylated on tyrosine (Y) residues following Tcell
      activation. Y429 and Y441 occur in an imperfect <prot>immunoreceptor
      tyrosine-based activation motif</prot> (<prot>ITAM</prot>)-like sequence. We investigated
      whether  <prot>phosphatidylinositol (PI) 3-kinase</prot> , which binds to
      tyrosine-phosphorylated  <prot>ITAM</prot> , interacts with <prot>CD5</prot> following T cell
      activation.  <prot>PI 3-kinase</prot>  activity and the regulatory <prot>p85</prot> subunit of <prot>PI
      3-kinase</prot> associated with  <prot>CD5</prot>  in pervanadate-stimulated, but not in
      unstimulated thymocytes. Cellular <prot>p85</prot> as well as the recombinant Src
      homology 2 (SH2) domains of <prot>p85</prot> bound a tyrosine-phosphorylated peptide
      encompassing Y463 with approximately threefold greater affinity than a
      doubly tyrosine-phosphorylated Y429-Y441 peptide. Binding of the C-SH2
      domain to the Y463 phosphopeptide, together with preferential binding of
      the N-SH2 domain to the Y429-Y441 phosphopeptide, suggests a bivalent
      interaction. A <prot>120-kDa phosphoprotein</prot> ( <prot>pp120</prot> ) associated with  <prot>CD5</prot>  and
      specifically with the Y429-Y441 phosphopeptide in stimulated thymocytes.
      We conclude that stimulation of thymocytes with pervanadate induces the
      recruitment of  <prot>PI 3-kinase</prot>  and  <prot>pp120</prot>  to   <prot>CD5</prot>  .
AD  - Department of Medical Physiology and Biochemistry, University of
