Cloning of human p55 gamma, a regulatory subunit of phosphatidylinositol 3-kinase, by a yeast two-hybrid library screen with the insulin-like growth factor-I receptor

Gene. 1998 Mar 16;209(1-2):175-83. doi: 10.1016/s0378-1119(98)00045-6.


We have used the yeast two-hybrid system to identify proteins that interact with the intracellular domain of the insulin-like growth factor-I receptor (IGFIR). In a search of a human fetal brain library we identified a cDNA encoding a protein that is the human homologue of mouse p55PIK, a regulatory subunit of phosphatidylinositol 3-kinase (hp55 gamma). The hp55 gamma protein interacts strongly with the activated IGFIR but not with the kinase-negative mutant receptor. hp55 gamma also interacts with the insulin receptor (IR) in the yeast two-hybrid system. The putative hp55 gamma protein is composed of a unique amino terminal region followed by a proline-rich motif and two Src homology 2 (SH2) domains, which are highly homologous to those in mouse p55PIK, rat p55 gamma, human p85 alpha and bovine p85 beta; it contains no SH3 domain. hp55 gamma mRNAs are expressed in most human fetal and adult tissues with particularly high abundance in adult testis. Splice variant(s) of hp55 gamma, one of which has a deletion of 36 amino acids at the amino terminus and another which has an insertion of 59 amino acids at position 256 between the SH2 domains, were also identified. A GST-hp55 gamma fusion protein interacts in vitro with both the activated IGFIR and IR derived from mammalian cells. Our findings suggest that hp55 gamma interacts with the IGFIR and IR and may be involved in PI 3-kinase activation by these receptors.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3T3 Cells
  • Adult
  • Amino Acid Sequence
  • Animals
  • Brain / enzymology
  • Cattle
  • Cloning, Molecular
  • Fetus
  • Gene Library
  • Humans
  • Macromolecular Substances
  • Male
  • Mice
  • Molecular Sequence Data
  • Organ Specificity
  • Phosphatidylinositol 3-Kinases / biosynthesis
  • Phosphatidylinositol 3-Kinases / chemistry
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Proline
  • RNA, Messenger / biosynthesis
  • Rats
  • Receptor, IGF Type 1 / metabolism*
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Testis / enzymology
  • Transcription, Genetic*
  • Transfection
  • src Homology Domains


  • Macromolecular Substances
  • RNA, Messenger
  • Recombinant Fusion Proteins
  • Proline
  • Receptor, IGF Type 1

Associated data

  • GENBANK/AF028785