scholarly journals p85α Gene Generates Three Isoforms of Regulatory Subunit for Phosphatidylinositol 3-Kinase (PI 3-Kinase), p50α, p55α, and p85α, with Different PI 3-Kinase Activity Elevating Responses to Insulin

1997 ◽  
Vol 272 (12) ◽  
pp. 7873-7882 ◽  
Author(s):  
Kouichi Inukai ◽  
Makoto Funaki ◽  
Takehide Ogihara ◽  
Hideki Katagiri ◽  
Akira Kanda ◽  
...  
Keyword(s):  
Kinase Activity ◽  
Regulatory Subunit ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

scholarly journals Phosphatidylinositol 3–Kinase Is Required for the Formation of Constitutive Transport Vesicles from the TGN

1997 ◽  
Vol 139 (2) ◽  
pp. 339-349 ◽  
Author(s):  
Steven M. Jones ◽  
Kathryn E. Howell
Keyword(s):  
Kinase Activity ◽  
Pi3 Kinase ◽  
Regulatory Subunit ◽  
Vesicle Formation ◽  
Phosphatidylinositol 3 Kinase ◽  
Response Curves ◽  
Direct Role ◽  
Lipid Kinase ◽  
Transport Vesicles ◽  
Phosphatidylinositol 3

An 85-kD cytosolic complex (p62cplx), consisting of a 62-kD phosphoprotein (p62) and a 25-kD GTPase, has been shown to be essential for the cell-free reconstitution of polymeric IgA receptor (pIgA-R)-containing exocytic transport vesicle formation from the TGN (Jones, S.M., J.R. Crosby, J. Salamero, and K.E. Howell. 1993. J. Cell Biol. 122:775–788). Here the p62cplx is identified as a regulatory subunit of a novel phosphatidylinositol 3–kinase (PI3-kinase). This p62cplx-associated PI3-kinase activity is stimulated by activation of the p62cplx-associated GTPase, and is specific for phosphatidylinositol (PI) as substrate, and is sensitive to wortmannin at micromolar concentrations. The direct role of this p62cplx-associated PI3-kinase activity in TGN-derived vesicle formation is indicated by the finding that both lipid kinase activity and the formation of pIgA-R–containing exocytic vesicles from the TGN are inhibited by wortmannin with similar dose-response curves and 50% inhibitory concentrations (3.5 μM). These findings indicate that phosphatidylinositol-3-phosphate (PI[3]P) is required for the formation of TGN-derived exocytic transport vesicles, and that the p62cplx-associated PI3-kinase and an activated GTPase are the essential molecules that drive production of this PI(3)P.

scholarly journals Regulation of the p85/p110 Phosphatidylinositol 3′-Kinase: Stabilization and Inhibition of the p110α Catalytic Subunit by the p85 Regulatory Subunit

1998 ◽  
Vol 18 (3) ◽  
pp. 1379-1387 ◽  
Author(s):  
Jinghua Yu ◽  
Yitao Zhang ◽  
James McIlroy ◽  
Tamara Rordorf-Nikolic ◽  
George A. Orr ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Kinase Activity ◽  
Thermal Inactivation ◽  
Insect Cells ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Phosphatidylinositol 3 Kinase ◽  
Lipid Kinase ◽  
Phosphatidylinositol 3

ABSTRACT We propose a novel model for the regulation of the p85/p110α phosphatidylinositol 3′-kinase. In insect cells, the p110α catalytic subunit is active as a monomer but its activity is decreased by coexpression with the p85 regulatory subunit. Similarly, the lipid kinase activity of recombinant glutathione S-transferase (GST)-p110α is reduced by 65 to 85% upon in vitro reconstitution with p85. Incubation of p110α/p85 dimers with phosphotyrosyl peptides restored activity, but only to the level of monomeric p110α. These data show that the binding of phosphoproteins to the SH2 domains of p85 activates the p85/p110α dimers by inducing a transition from an inhibited to a disinhibited state. In contrast, monomeric p110 had little activity in HEK 293T cells, and its activity was increased 15- to 20-fold by coexpression with p85. However, this apparent requirement for p85 was eliminated by the addition of a bulky tag to the N terminus of p110α or by the growth of the HEK 293T cells at 30°C. These nonspecific interventions mimicked the effects of p85 on p110α, suggesting that the regulatory subunit acts by stabilizing the overall conformation of the catalytic subunit rather than by inducing a specific activated conformation. This stabilization was directly demonstrated in metabolically labeled HEK 293T cells, in which p85 increased the half-life of p110. Furthermore, p85 protected p110 from thermal inactivation in vitro. Importantly, when we examined the effect of p85 on GST-p110α in mammalian cells at 30°C, culture conditions that stabilize the catalytic subunit and that are similar to the conditions used for insect cells, we found that p85 inhibited p110α. Thus, we have experimentally distinguished two effects of p85 on p110α: conformational stabilization of the catalytic subunit and inhibition of its lipid kinase activity. Our data reconcile the apparent conflict between previous studies of insect versus mammalian cells and show that p110α is both stabilized and inhibited by dimerization with p85.

Association with Longevity of Phosphatidylinositol 3-Kinase Regulatory Subunit 1 Gene Variants Stems from Protection against Mortality Risk in Men with Cardiovascular Disease

Gerontology ◽  
2021 ◽  
pp. 1-9
Author(s):  
Timothy A. Donlon ◽  
Randi Chen ◽  
Kamal H. Masaki ◽  
Bradley J. Willcox ◽  
Brian J. Morris
Keyword(s):  
Cardiovascular Disease ◽  
Life Span ◽  
Mortality Risk ◽  
Regulatory Subunit ◽  
Phosphatidylinositol 3 Kinase ◽  
Survival Curves ◽  
Genotypic Effect ◽  
Hazard Ratios ◽  
Phosphatidylinositol 3

<b><i>Introduction:</i></b> Genetic variation in the phosphatidylinositol 3-kinase reregulatory subunit 1 gene (<i>PIK3R1</i>) is associated with longevity. <b><i>Objective:</i></b> The aim of the study was to determine whether cardiovascular disease (CVD) affects this association. <b><i>Methods:</i></b> We performed a longitudinal study of longevity-associated <i>PIK3R1</i> single-nucleotide polymorphism <i>rs7709243</i> genotype by CVD status in 3,584 elderly American men of Japanese ancestry. <b><i>Results:</i></b> At baseline (1991–1993), 2,254 subjects had CVD and 1,314 did not. The follow-up until Dec 31, 2019 found that overall, men with a CVD had higher mortality than men without a CVD (<i>p</i> = 1.7 × 10<sup>−5</sup>). However, survival curves of CVD subjects differed according to <i>PIK3R1</i> genotype. Those with longevity-associated <i>PIK3R1 TT</i>/<i>CC</i> had survival curves similar to those of subjects without a CVD (<i>p</i> = 0.11 for <i>TT</i>/<i>CC</i>, and <i>p</i> = 0.054 for <i>TC</i>), whereas survival curves for CVD subjects with the <i>CT</i> genotype were significantly attenuated compared with survival curves of subjects without a CVD (<i>p</i> = 0.0000012 compared with <i>TT</i>/<i>CC</i>, and <i>p</i> = 0.0000028 compared with <i>TC</i>). Men without CVD showed no association of longevity-associated genotype with life span (<i>p</i> = 0.58). Compared to subjects without any CVD, hazard ratios for mortality risk were 1.26 (95% CI, 1.14–1.39; <i>p</i> = 0.0000043) for <i>CT</i> subject with CVD and 1.07 (95% CI 0.99–1.17; <i>p</i> = 0.097) for <i>CC</i>/<i>TT</i> subjects with CVD. There was no genotypic effect on life span for 1,007 subjects with diabetes and 486 with cancer. <b><i>Conclusion:</i></b> Our study provides novel insights into the basis for <i>PIK3R1</i> as a longevity gene. We suggest that the <i>PIK3R1</i> longevity genotype attenuates mortality risk in at-risk individuals by protection against cellular stress caused by CVD.

scholarly journals Inhibition of phosphatidylinositol 3-kinase activity by association with 14-3-3 proteins in T cells.

1995 ◽  
Vol 92 (22) ◽  
pp. 10142-10146 ◽  
Author(s):  
N. Bonnefoy-Berard ◽  
Y. C. Liu ◽  
M. von Willebrand ◽  
A. Sung ◽  
C. Elly ◽  
...  
Keyword(s):  
T Cells ◽  
Kinase Activity ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

Phosphatidylinositol 3-kinase activation is mediated by high-affinity interactions between distinct domains within the p110 and p85 subunits

1994 ◽  
Vol 14 (1) ◽  
pp. 42-49
Author(s):  
K H Holt ◽  
L Olson ◽  
W S Moye-Rowley ◽  
J E Pessin
Keyword(s):  
Gene Fusion ◽  
Kinase Activity ◽  
Expression System ◽  
Sh2 Domain ◽  
Full Length ◽  
Transactivation Domain ◽  
Phosphatidylinositol 3 Kinase ◽  
Sh2 Domains ◽  
Amino Terminal ◽  
Phosphatidylinositol 3

Domains of interaction between the p85 and p110 subunits of phosphatidylinositol 3-kinase (PI 3-kinase) were studied with the yeast two-hybrid expression system. A gene fusion between the GAL4 transactivation domain and p85 activated transcription from a GAL1-lacZ reporter gene when complemented with a gene fusion between the GAL4 DNA binding domain and p110. To define subdomains responsible for this interaction, a series of p85 deletion mutants were analyzed. A 192-amino-acid inter-SH2 (IS) fragment (residues 429 to 621) was the smallest determinant identified that specifically associated with p110. In analogous experiments, the subdomain within p110 responsible for interaction with p85 was localized to an EcoRI fragment encoding the amino-terminal 127 residues. Expression of these two subdomains [p85(IS) with p110RI] resulted in 100-fold greater reporter activity than that obtained with full-length p85 and p110. Although the p85(IS) domain conferred a strong interaction with the p110 catalytic subunit, this region was not sufficient to impart phosphotyrosine peptide stimulation of PI 3-kinase activity. In contrast, coexpression of the p110 subunit with full-length p85 or with constructs containing the IS sequences flanked by both SH2 domains of p85 [p85(n/cSH2)] or either of the individual SH2 domains [p85(nSH2+IS) or p85(IS+cSH2)] resulted in PI 3-kinase activity that was activated by a phosphotyrosine peptide. These data suggest that phosphotyrosine peptide binding to either SH2 domain generates an intramolecular signal propagated through the IS region to allosterically activate p110.

scholarly journals Association of phosphatidylinositol 3-kinase with the insulin receptor: compartmentation in rat liver

2000 ◽  
Vol 279 (2) ◽  
pp. E266-E274 ◽  
Author(s):  
Paul G. Drake ◽  
Alejandro Balbis ◽  
Jiong Wu ◽  
John J. M. Bergeron ◽  
Barry I. Posner
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Insulin Receptor ◽  
Rat Liver ◽  
Intracellular Signaling ◽  
Kinase Activity ◽  
Glycogen Synthase ◽  
Metabolic Effects ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

Phosphatidylinositol 3-kinase (PI 3-kinase) plays an important role in a variety of hormone and growth factor-mediated intracellular signaling cascades and has been implicated in the regulation of a number of metabolic effects of insulin, including glucose transport and glycogen synthase activation. In the present study we have examined 1) the association of PI 3-kinase with the insulin receptor kinase (IRK) in rat liver and 2) the subcellular distribution of PI 3-kinase-IRK interaction. Insulin treatment promoted a rapid and pronounced recruitment of PI 3-kinase to IRKs located at the plasma membrane, whereas no increase in association with endosomal IRKs was observed. In contrast to IRS-1-associated PI 3-kinase activity, association of PI 3-kinase with the plasma membrane IRK did not augment the specific activity of the lipid kinase. With use of the selective PI 3-kinase inhibitor wortmannin, our data suggest that the cell surface IRK β-subunit is not a substrate for the serine kinase activity of PI 3-kinase. The functional significance for the insulin-stimulated selective recruitment of PI 3-kinase to cell surface IRKs remains to be elucidated.

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