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

• Published in: Gene Vol. 209; no. 1; pp. 175 - 183
• Main Authors: Dey, Bhakta R, Furlanetto, Richard W, Nissley, S.Peter
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 16.03.1998
• Subjects: 3T3 Cells; Adult; Amino Acid Sequence; Animals; Brain - enzymology; Cattle; Cloning, Molecular; Fetus; Gene Library; Humans; insulin receptor; IRS-1; Macromolecular Substances; Male; Mice; Molecular Sequence Data; Organ Specificity; p55 PIK; p85 α; p85 β; Phosphatidylinositol 3-Kinases - biosynthesis; Phosphatidylinositol 3-Kinases - chemistry; Phosphatidylinositol 3-Kinases - metabolism; Proline; Rats; Receptor, IGF Type 1 - metabolism; Recombinant Fusion Proteins - biosynthesis; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - metabolism; RNA, Messenger - biosynthesis; Saccharomyces cerevisiae; Sequence Alignment; Sequence Homology, Amino Acid; src Homology Domains; Testis - enzymology; Transcription, Genetic; Transfection; IGFIR, insulin-like growth factor-I receptor; IRS-1, insulin receptor substrate-1; GST, glutathione- S-transferase; IRS-1; p55 PIK; AD, activation domain; p85 α; insulin receptor; p85 β; IGF, insulin-like growth factor; IR, insulin receptor
• ISSN: 0378-1119; 1879-0038
• 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 p55 PIK, a regulatory subunit of phosphatidylinositol 3-kinase (hp55 γ). The hp55 γ protein interacts strongly with the activated IGFIR but not with the kinase-negative mutant receptor. hp55 γ also interacts with the insulin receptor (IR) in the yeast two-hybrid system. The putative hp55 γ 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 p55 PIK, rat p55 γ, human p85 α and bovine p85 β; it contains no SH3 domain. hp55 γ mRNAs are expressed in most human fetal and adult tissues with particularly high abundance in adult testis. Splice variant(s) of hp55 γ, 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 γ fusion protein interacts in vitro with both the activated IGFIR and IR derived from mammalian cells. Our findings suggest that hp55 γ interacts with the IGFIR and IR and may be involved in PI 3-kinase activation by these receptors.