title: Direct association of p110 beta phosphatidylinositol 3-kinase with p85 is mediated by an N-terminal fragment of p110 beta.
abstract: Phosphatidylinositol (PI) 3-kinase is a heterodimeric enzyme of 85-kDa (p85) and 110-kDa (p110) subunits implicated in mitogenic signal transduction by virtue of its activation in cells transformed by diverse viral oncoproteins and treated with various growth factors. We have identified a domain in p110 that mediates association with p85 in vitro and in intact cells. A glutathione S-transferase fusion protein containing the N-terminal 171 amino-acids of p110 beta bound to free p85 in cell lysates. This fusion protein also bound directly to p85 immobilized on nitrocellulose filters. An epitope-tagged fragment containing amino acids 31 to 150 of p110 beta associated with p85 upon expression in intact cells. Expression of either an N-terminal fragment of p110 beta or the p85 inter-SH2 domain, which mediates association with p110, reduced the association of endogenous PI 3-kinase activity with the activated platelet-derived growth factor receptor in intact cells. Hence, these defined regions of p85 and p110 mediate the interaction between the two subunits of PI 3-kinase.
authors.affiliation: Department of Pharmacology, New York University Medical Center, NY 10016.
authors.forename: P
authors.initials: P
authors.lastname: Hu
authors.forename: J
authors.initials: J
authors.lastname: Schlessinger
mesh_terms: D000595:Amino Acid Sequence; D000906:Antibodies; D002460:Cell Line; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000096:biosynthesis / Q000302:isolation & purification; D006801:Humans; D015151:Immunoblotting; D007668:Kidney; D046911:Macromolecular Substances; D008961:Models, Structural; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D015398:Signal Transduction; D014162:Transfection
chemical_list: D000906:Antibodies; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor)