SMART: PI3K_p85B domain annotation

PI3K_p85B PI3-kinase family, p85-binding domain

SMART accession number:	SM00143
Description:	Region of p110 PI3K that binds the p85 subunit.
Interpro abstract (IPR003113):	Phosphatidylinositol 3-kinases (PI3Ks) are lipid kinases that phosphorylate 4,5-bisphonate (PI(4,5) P2 or PIP2) at the 3-position of the inositol ring, and thus generate phosphatidylinositol 3,4,5-trisphosphate (PIP3), which, in turns, initiates a vast array of signaling events. PI3Ks can be grouped into three classes based on their domain organisation. Class I PI3Ks are heterodimers consisting of a p110 catalytic subunit and a regulatory subunit of either the p85 type (associated with the class IA p110 isoforms p110alpha, p110beta or p110delta) or the p101 type (associated with the class IB p110 isoform p110gamma). Common to all catalytic subunits are an N-terminal adaptor-binding domain (ABD) that binds to p85, a Ras-binding domain (RBD), a putative membrane-binding domain (C2), a helical domain of unknown function, and a kinase catalytic domain [(PUBMED:17626883), (PUBMED:18079394), (PUBMED:20081827)]. PI3K ABD is a small globular domain of about 100 residues in length with an alpha/beta-sandwich topology [(PUBMED:17626883), (PUBMED:18079394), (PUBMED:20081827)].
Family alignment:	View or

There are 101 PI3K_p85B domains in 101 proteins in SMART's nrdb database.

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Evolution (species in which this domain is found)
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Go to specific node: Caenorhabditis elegans, Drosophila melanogaster, Homo sapiens, Mus musculus, Rattus norvegicus, Takifugu rubripes
Cellular role (predicted cellular role)
Binding / catalysis: protein-binding, p85-binding
Literature (relevant references for this domain)
Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.
- Rodriguez-Viciana P, Warne PH, Vanhaesebroeck B, Waterfield MD, Downward J
- Activation of phosphoinositide 3-kinase by interaction with Ras and by point mutation.
- EMBO J. 1996; 15: 2442-51
- Display abstract
- We have reported previously that Ras interacts with the catalytic subunit of phosphoinositide 3-kinase (PI 3-kinase) in a GTP-dependent manner. The affinity of the interaction of Ras-GTP with p85alpha/p110alpha is shown here to be approximately 150 nM. The site of interaction on the p110alpha and beta isoforms of PI 3-kinase lies between amino acid residues 133 and 314. A point mutation in this region, K227E, blocks the GTP-dependent interaction of PI 3-kinase p110alpha with Ras in vitro and the ability of Ras to activate PI 3-kinase in intact cells. In addition, this mutation elevates the basal activity of PI 3-kinase in intact cells, suggesting a direct influence of the Ras binding site on the catalytic activity of PI 3-kinase. Using an in vitro reconstitution assay, it is shown that the interaction of Ras-GTP, but not Ras-GDP, with PI 3-kinase leads to an increase in its enzymatic activity. This stimulation is synergistic with the effect of tyrosine phosphopeptide binding to p85, particularly at suboptimal peptide concentrations. These data show that PI 3-kinase is regulated by a number of mechanisms, and that Ras contributes to the activation of this lipid kinase synergistically with tyrosine kinases.
- Dhand R et al.
- PI 3-kinase: structural and functional analysis of intersubunit interactions.
- EMBO J. 1994; 13: 511-21
- Display abstract
- Phosphatidylinositol (PI) 3-kinase has an 85 kDa subunit (p85 alpha) which mediates its association with activated protein tyrosine kinase receptors through SH2 domains, and an 110 kDa subunit (p110) which has intrinsic catalytic activity. Here p85 alpha and a related protein p85 beta are shown to form stable complexes with recombinant p110 in vivo and in vitro. Using a panel of glutathione S-transferase (GST) fusion proteins of the inter-SH2 region of p85, 104 amino acids were found to bind directly the p110 protein, while deletion mutants within this region further defined the binding site to a sequence of 35 amino acids. Transient expression of the mutant p85 alpha protein in mouse L cells showed it was unable to bind PI 3-kinase activity in vivo. Mapping of the complementary site of interaction on the p110 protein defined 88 amino acids in the N-terminal region of p110 which mediate the binding of this subunit to either the p85 alpha or the p85 beta proteins. The inter-SH2 region of p85 is predicted to be an independently folded module of a coiled-coil of two long anti-parallel alpha-helices. The predicted structure of p85 suggests a basis for the intersubunit interaction and the relevance of this interaction with respect to the regulation of the PI 3-kinase complex is discussed.
- Hu P, Schlessinger J
- Direct association of p110 beta phosphatidylinositol 3-kinase with p85 is mediated by an N-terminal fragment of p110 beta.
- Mol Cell Biol. 1994; 14: 2577-83
- Display 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.
- Klippel A, Escobedo JA, Hirano M, Williams LT
- The interaction of small domains between the subunits of phosphatidylinositol 3-kinase determines enzyme activity.
- Mol Cell Biol. 1994; 14: 2675-85
- Display abstract
- Previous studies have suggested that the two subunits of phosphatidylinositol (PI) 3-kinase, p85 and p110, function as localizing and catalytic subunits, respectively. Using recombinant p85 and p110 molecules, we have reconstituted the specific interaction between the two subunits of mouse PI 3-kinase in cells and in vitro. We have previously shown that the region between the two Src homology 2 (SH2) domains of p85 is able to form a functional complex with the 110-kDa subunit in vivo. In this report, we identify the corresponding domain in p110 which directs the binding to p85. We demonstrate that the interactive domains in p85 and p110 are less than 103 and 124 amino acids, respectively, in size. We also show that the association of p85 and p110 mediated by these domains is critical for PI 3-kinase activity. Surprisingly, a complex between a 102-amino-acid segment of p85 and the full-length p110 molecule is catalytically active, whereas p110 alone has no activity. In addition to the catalytic domain in the carboxy-terminal region, 123 amino acids at the amino terminus of p110 were required for catalytic activity and were sufficient for the interaction with p85. These results indicate that the 85-kDa subunit, previously thought to have only a linking role in localizing the p110 catalytic subunit, is an important component of the catalytic complex.
- Kodaki T, Woscholski R, Hallberg B, Rodriguez-Viciana P, Downward J, Parker PJ
- The activation of phosphatidylinositol 3-kinase by Ras.
- Curr Biol. 1994; 4: 798-806
- Display abstract
- BACKGROUND: Activation of the mammalian phosphatidylinositol 3-kinase complex can play a critical role in transducing growth factor responses. The lipid kinase complex, which is made up of p85 alpha and p110 alpha regulatory and catalytic subunits, becomes associated with a number of activated receptor protein tyrosine kinases, but the mechanism of its activation has not yet been defined. Recent evidence indicates that Ras can bind to the p85 alpha/p110 alpha complex. We describe here the functional regulation of the mammalian phosphatidylinositol 3-kinase complex by Ras. RESULTS: Expression of p110 alpha, the catalytic subunit of phosphatidylinositol 3-kinase, in the fission yeast, Schizosaccharomyces pombe, has been used to demonstrate an inhibitory effect of p85 alpha on p110 alpha activity in intact cells; inhibition did not result from a decrease in p110 alpha expression. In this cellular context, we have investigated the effect of a constitutively active mutant of Ras, v-Ras, either on p85 alpha or p110 alpha-alone, or on the p85 alpha/p110 alpha complex. In the presence of the p85 alpha/p110 alpha complex, v-Ras suppressed cell growth, but an effector-domain mutant of v-Ras did not. The growth-suppressive effect of v-Ras was not seen for any other combination of expressed proteins. The phenotype induced by v-Ras was consistent with activation of the p85 alpha/p110 alpha complex: it was sensitive to the phosphatidylinositol 3-kinase inhibitor, wortmannin, and the cells accumulated 3-phosphorylated polyphosphoinositides. Activation of purified p85 alpha/p110 alpha by purified recombinant Ras in vitro was also demonstrated. CONCLUSIONS: The phosphatidylinositol 3-kinase complex, p85 alpha/p110 alpha, shows a suppressed catalytic function in vivo when compared with free p110 alpha. This complex can, however, be activated by Ras. We suggest that the phosphatidylinositol 3-kinase p85 alpha/p110 alpha complex is a downstream effector of Ras.
Metabolism (metabolic pathways involving proteins which contain this domain)

Structure (3D structures containing this domain)

Links (links to other resources describing this domain)
INTERPRO IPR003113

PDB code	Main view	Title
2rd0		Structure of a human p110alpha/p85alpha complex
2v1y		Structure of a phosphoinositide 3-kinase alpha adaptor- binding domain (abd) in a complex with the ish2 domain from p85 alpha
3hhm		Crystal structure of p110alpha h1047r mutant in complex with nish2 of p85alpha and the drug wortmannin
3hiz		Crystal structure of p110alpha h1047r mutant in complex with nish2 of p85alpha

PI3K_p85B

3D Structures of PI3K_p85B domains in PDB