Association of phosphatidylinositol 3-kinase composed of p110beta-catalytic and p85-regulatory subunits with the small GTPase Rab5.
A family of phosphatidylinositol 3-kinases (PI 3-kinase), comprising three major classes (I-III) in terms of substrate specificity and regulation, play important roles in a variety of cell functions. We previously reported that the class-I heterodimeric PI 3-kinase consisting of p110beta-catalytic and p85-regulatory subunits is synergistically activated by two different types of membrane receptors, one possessing tyrosine kinase activity and the other activating trimeric G proteins. Here we report an additional unique feature of the p110beta/p85 PI 3-kinase. The small GTPase Rab5 was identified as a binding protein for the p110beta-catalytic subunit in a yeast two-hybrid screening system. The interaction appears to require at least two separated amino-acid sequences present specifically in the beta isoform of p110 and the GTP-bound form of Rab5. The expressions of constitutively active and dominant negative mutants of Rab5 in THP-1 cells induce the stimulation and inhibition, respectively, of protein kinase B activity, which is dependent on the PI 3-kinase product phosphatidylinositol 3,4,5-triphosphate. These results suggest that there is a specific interaction between GTP-bound Rab5 and the p110beta/p85 PI 3-kinase, leading to efficient coupling of the lipid kinase product to its downstream target, protein kinase B.
Kurosu
H
H
Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Katada
T
T
D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002460:Cell Line; D004789:Enzyme Activation; D005799:Genes, Dominant; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006801:Humans; D009154:Mutation / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D020696:rab5 GTP-Binding Proteins