TI  - Interaction of <prot>p85</prot> subunit of  <prot>PI 3-kinase</prot>  with  <prot>insulin</prot>  and  <prot>IGF-1</prot>  receptors
      analysed by using the two-hybrid system.
PG  - 51-5
AB  - Interaction of the <prot>p85</prot> subunit of   <prot>PI 3-kinase</prot>   with the  <prot><prot>insulin</prot> receptor</prot>
      (<prot>IR</prot>)  and the  <prot><prot>IGF-1</prot> receptor</prot> (<prot>IGF-1R</prot>)  was investigated using the two-hybrid
      system by assessing for his3 and lacZ activation in S. cerevisiae. The
      experiments were performed with the cytoplasmic beta domain (wild type or
      mutated) of <prot>IR</prot> and <prot>IGF-1R</prot> and <prot>p85</prot> or its subdomains (N + C-SH2, N-SH2,
      C-SH2, SH3 + N-SH2). The results of his3 activation indicated that   <prot>p85</prot> , N
      + C-SH2 and C-SH2  interact with both  <prot><prot>IR</prot> beta</prot>  and   <prot><prot>IGF-1R</prot> beta</prot>  , whereas
       N-SH2 and SH3 + N-SH2  interact only with  <prot><prot>IR</prot> beta</prot> . Interaction of  <prot>p85</prot>  and
       N+C-SH2  with   <prot>IR beta</prot>   (<prot>delta C-43</prot>) or   <prot><prot>IGF-1R</prot> beta</prot>(<prot>delta C-43</prot>)   in which the
      C-terminal 43 amino acids (including the YXXM motif) were deleted,
      persisted. The internal binding site thus revealed was not altered by
      further mutating Y960/F for <prot>IR</prot> or Y950/F for <prot>IGF-1R</prot>. Activation of lacZ
      upon interaction of   <prot>p85</prot>   with  <prot>IR beta</prot>(<prot>delta C-43</prot>)  was 4-fold less as
      compared to  <prot>IR beta</prot> . This activation with <prot>p85</prot> and <prot><prot>IGF-1R</prot> beta</prot> was 4-fold
      less as compared to <prot>IR beta</prot> and was somewhat increased (2-fold) for <prot><prot>IGF-1R</prot>
      beta</prot> (<prot>delta C-4</prot>3). Thus, the C-terminal domain in  <prot>IGF-1R</prot>  appears to exert
      a negative control on binding of  <prot>p85</prot>  thereby providing a possible
      regulatory mechanism for direct activation of the <prot>PI 3-kinase</prot> pathway.
AD  - Institut Cochin de Genetique Moleculaire, INSERM U257, Paris, France.
