Phosphatidylinositol 3-kinase: Structure and expression of the 110 kd catalytic subunit

Hiles, Ian D.; Otsu, Masayuki; Volinia, Stefano; Fry, Michael; Gout, Ivan; Dhand, Ritu; Panayotou, George; Ruiz-Larrea, Fernanda; Thompson, Andrew R.; Totty, Nicholas F.; Hsuan, J. Justin; Courtneidge, Sara A.; Parker, Peter J.; Waterfield, Michael D.

doi:10.1016/0092-8674(92)90166-a

Cited by 659 publications

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“…Subclass IA PI 3-kinase enzymes are heterodimers composed of a catalytic subunit of 110 kDa and an adapter regulatory p85 subunit (Hiles et al, 1992;Hu et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Lower Phosphoinositide 3-Kinase (PI 3-kinase) Activity and Differential Expression Levels of Selective Catalytic and Regulatory PI 3-Kinase Subunit Isoforms in Prefrontal Cortex and Hippocampus of Suicide Subjects

Dwivedi

Rizavi

Teppen

et al. 2007

Neuropsychopharmacol

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Phosphoinositide 3 (PI 3)-kinase is one of the key signaling enzymes that participates in a myriad of physiological functions in brain and is utilized by neurotrophins to mediate neuronal plasticity, cell survival, and inhibition of apoptosis for several neuronal subtypes. Our recent demonstration that expression of neurotrophic factors and activation of the receptor tyrosine kinase B are significantly altered in postmortem brain of suicide subjects led us to examine whether suicide brain is associated with alterations in PI 3-kinase signaling. In prefrontal cortex (PFC), hippocampus, and cerebellum of suicide (n ¼ 28) and nonpsychiatric control (n ¼ 21) subjects we examined catalytic activation of PI 3-kinase, and mRNA and protein levels of regulatory (p85a, p85b) and catalytic (p110a, p110b) subunits of PI 3-kinase. It was observed that the catalytic activity of PI 3-kinase was significantly reduced in PFC and hippocampus of suicide subjects compared with nonpsychiatric control subjects. Competitive PCR analysis revealed significantly reduced mRNA expression of p85b and p110a and increased expression of p85a subunit isoforms in PFC and hippocampus of suicide subjects. Alterations in these catalytic and regulatory subunits were accompanied by changes in their respective protein levels. These changes were not present in cerebellum of suicide subjects. Also, these changes were present in all suicide subjects irrespective of psychiatric diagnosis. Our findings of reduced activation and altered expression of specific PI 3-kinase regulatory and catalytic subunit isoforms demonstrate abnormalities in this signaling pathway in postmortem brain of suicide subjects and suggest possible involvement of aberrant PI 3-kinase signaling in the pathogenic mechanisms of suicide.

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“…Subclass IA PI 3-kinase enzymes are heterodimers composed of a catalytic subunit of 110 kDa and an adapter regulatory p85 subunit (Hiles et al, 1992;Hu et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Lower Phosphoinositide 3-Kinase (PI 3-kinase) Activity and Differential Expression Levels of Selective Catalytic and Regulatory PI 3-Kinase Subunit Isoforms in Prefrontal Cortex and Hippocampus of Suicide Subjects

Dwivedi

Rizavi

Teppen

et al. 2007

Neuropsychopharmacol

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confidence: 99%

“…Receptor-regulated forms of PI 3-kinase appear to prefer to phosphorylate phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P 2 ) in vivo (3-5). The product of this reaction, phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P 3 ), is a candidate second messenger that regulates a variety of cellular responses to growth factors perhaps through the activation of serine/threonine protein kinases such as Akt/PKB and/or certain protein kinase C isoforms and small GTP-binding proteins such as Rac 1 (6 -10).The first form of PI 3-kinase to be purified and cloned was identified as a heterodimer composed of a 110-kDa catalytic subunit with a tightly bound regulatory subunit of 85 kDa (11)(12)(13)(14). The p85 subunit possesses a number of regions with homology to recognized signaling proteins.…”

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confidence: 99%

“…Binding of the SH2 domains to phosphotyrosine residues within the sequence context, YMXM, which occurs in a wide range of activated growth factor receptors and adaptor proteins, causes the translocation and activation of the catalytic subunit (2, 15-16). More recently, a number of distinct p85 and p110 subunit isoforms have been identified (11,14,17), but the functional significance of this heterogeneity is not yet clear (18).Heterotrimeric G-protein-regulated forms of PI 3-kinase have also been identified following the observations that activation of G-protein-coupled receptors in neutrophils and platelets caused a rapid accumulation of PtdIns(3,4,[5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Stephens et al (22) partially purified a G-protein ␤␥ subunit (G␤␥)-responsive PI 3-kinase from a myeloid cell line (U937).…”

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confidence: 99%

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Purification and Characterization of Gβγ-responsive Phosphoinositide 3-Kinases from Pig Platelet Cytosol

Tang

Downes

1997

Journal of Biological Chemistry

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A G-protein ␤␥ subunit (G␤␥)-responsive phosphoinositide 3-kinase (PI 3-kinase) was purified approximately 5000-fold from pig platelet cytosol. The enzyme was purified by polyethylene glycol precipitation of the cytosol followed by column chromatography on Q-Sepharose fast flow, gel filtration, heparin-Sepharose, and hydroxyapatite. The major G␤␥-responsive PI 3-kinase is distinct from p85 containing PI 3-kinase as the activities can be distinguished chromatographically and immunologically and is related to p110␥ as it crossreacts with anti-p110␥-specific antibodies. The p110␥-related PI 3-kinase cannot be activated by G-protein ␣ i/o subunits, and it has an apparent native molecular mass of 210 kDa. The p110␥-related PI 3-kinase phosphorylates phosphatidylinositol (PtdIns), phosphatidylinositol 4-phosphate (PtdIns4P), and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P 2 ). The apparent K m values for ATP were found to be 25 M with PtdIns, 44 M with PtdIns4P, and 37 M with PtdIns(4,5)P 2 as the substrate. G␤␥ subunits did not alter the K m of the enzyme for ATP; however, V max increased 2-fold with PtdIns as substrate, 3.5-fold with PtdIns4P, and 10-fold with PtdIns(4,5)P 2 . Under basal conditions the apparent K m values for lipid substrates were 64, 10, and 15 M for PtdIns, PtdIns4P, and PtdIns(4,5)P 2 , respectively. In the presence of G␤␥ subunits the dependence of PI 3-kinase activity on the concentrations of lipid substrates became complex with the highest level of stimulation occurring at high substrate concentration, suggesting that the binding of G␤␥ and lipid substrate (particularly PtdIns(4,5)P 2 ) may be mutually cooperative. Wortmannin and LY294002 inhibit the G␤␥-responsive PI 3-kinase activity with IC 50 values of 10 nM and 2 M, respectively. Unlike the p85 containing PI 3-kinase in platelets, the p110␥-related PI 3-kinase is not associated with a PtdIns(3,4,5)P 3 specific 5-phosphatase.The p85-associated PI 3-kinase was not activated by G␤␥ alone but could be synergistically activated by G␤␥ and phosphotyrosyl platelet-derived growth factor receptor peptides. This may represent a form of coincidence detection through which the effects of tyrosine kinase and G-protein-linked receptors might be coordinated.Phosphoinositide 3-kinases (PI 3-kinases, 1 EC 2.7.1.137) phosphorylate the D-3 position of the inositol ring in inositol phospholipids and were originally identified through their association with viral oncoproteins and activated tyrosine kinases (1, 2). Receptor-regulated forms of PI 3-kinase appear to prefer to phosphorylate phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P 2 ) in vivo (3-5). The product of this reaction, phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P 3 ), is a candidate second messenger that regulates a variety of cellular responses to growth factors perhaps through the activation of serine/threonine protein kinases such as Akt/PKB and/or certain protein kinase C isoforms and small GTP-binding proteins such as Rac 1 (6 -10).The first form of PI 3-kinase to be...

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“…Active PI3K is a heterodimer composed of an 85-kDa regulatory subunit and a 110-kDa catalytic P13K ASSOCIATION 7409 subunit (6,21). Association between P13K and the PDGFR is mediated by SH2 domains within the 85-kDa subunit of P13K (22,26,31) and is dependent upon autophosphorylation of tyrosine residues within the kinase insert domain of the PDGFR (11,22,25,31).…”

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confidence: 99%

The SH3 domain of p56lck is involved in binding to phosphatidylinositol 3'-kinase from T lymphocytes.

Vogel

Fujita

1993

Mol. Cell. Biol.

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Many of the Src-like tyrosine kinases are thought to participate in multiprotein complexes that modulate transmembrane signalling through tyrosine phosphorylation. We have used in vitro binding studies employing bacterially expressed glutathione S-transferase-p561k fusion proteins and cell extracts to map regions on p56kk that are involved in binding to phosphatidylinositol 3'-kinase (P13K). Deletions within the SH3 domain of pS6kk abolished binding of P13K activity from T-cell lysates, whereas deletion of the SH2 domain caused only a slight reduction in the level of P13K activity bound to p56kk sequences. The binding of P13K from T-cell extracts to p56kk was not blocked by antiphosphotyrosine antibodies, but p56-kkbound P13K activity was sensitive to phosphatase treatment. The SH3 domain of p56kk also bound the majority of P13K activity from uninfected chicken embryo fibroblasts. However, a drastically different binding specificity was observed with use of extracts of Rous sarcoma virus v-src-transformed cells, in which the majority of P13K activity bound to the SH2 domain of p56k in a phosphotyrosine-dependent manner. These results suggest that are two modes of PI3K binding to p56kk, and presumably to other Src-like tyrosine kinases. In one mode, PI3K from T cells or uninfected chicken embryo fibroblasts binds predominantly to the SH3 domain of p56kk. In the other mode, involving P13K from Rous sarcoma virus-transformed cells, binding is largely phosphotyrosine dependent and requires the SH2 domain of pS6kk.The Ick gene is a member of the src family of genes, which encode a series of eight closely related protein tyrosine kinases (for a review, see reference 23?. The product of the ick gene is a 56-kDa protein (p561 ) that is expressed predominantly in cells of the lymphoid lineage, primarily T lymphocytes and lymphoid tumor cell lines (28, 30, 37).Expression of p56" has also been observed in human carcinomas of the lung and colon (50).Members of the Src family of tyrosine kinases are characterized by an NH2-terminal unique region followed by three regions that contain different degrees of homology among all members of the family (23, 42). In p561ck, Src homology region 3 (SH3) extends from amino acids 56 to 114. The SH2 domain includes amino acids 115 to 221 and the SH1, or catalytic, domain comprises most of the remainder of the C-terminal half of the protein. Recent evidence indicates that the SH2 region of Src-like kinases functions as a protein association domain that is important in the formation of multienzyme complexes that regulate signal transduction through tyrosine phosphorylation (5, 27).Several proteins have been reported to form complexes with pS6lc in T lymphocytes. The NH2-terminal unique region of p56"kk has been shown to associate with the C-terminal region of two T-cell transmembrane glycoproteins, CD4 and CD8 (3,39,40,45,48). The accessory role of CD4 and CD8 in T-cell signalling has led to the suggestion that p56"'" may participate in antigen-stimulated signal transduction events (18,36)....

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Phosphatidylinositol 3-kinase: Structure and expression of the 110 kd catalytic subunit

Cited by 659 publications

References 58 publications

Lower Phosphoinositide 3-Kinase (PI 3-kinase) Activity and Differential Expression Levels of Selective Catalytic and Regulatory PI 3-Kinase Subunit Isoforms in Prefrontal Cortex and Hippocampus of Suicide Subjects

Lower Phosphoinositide 3-Kinase (PI 3-kinase) Activity and Differential Expression Levels of Selective Catalytic and Regulatory PI 3-Kinase Subunit Isoforms in Prefrontal Cortex and Hippocampus of Suicide Subjects

Purification and Characterization of Gβγ-responsive Phosphoinositide 3-Kinases from Pig Platelet Cytosol

The SH3 domain of p56lck is involved in binding to phosphatidylinositol 3'-kinase from T lymphocytes.

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