scholarly journals Differential regulation of class IA phosphoinositide 3-kinase catalytic subunits p110α and β by protease-activated receptor 2 and β-arrestins

2007 ◽  
Vol 408 (2) ◽  
pp. 221-230 ◽  
Author(s):  
Ping Wang ◽  
Puneet Kumar ◽  
Chang Wang ◽  
Kathryn A. DeFea
Keyword(s):  
G Protein ◽  
Small Gtpase ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Catalytic Subunits ◽  
Pi3k Activity ◽  
Phosphoinositide 3 Kinase ◽  
Protease Activated Receptor 2

PAR-2 (protease-activated receptor 2) is a GPCR (G-protein-coupled receptor) that can elicit both G-protein-dependent and -independent signals. We have shown previously that PAR-2 simultaneously promotes Gαq/Ca2+-dependent activation and β-arrestin-1-dependent inhibition of class IA PI3K (phosphoinositide 3-kinase), and we sought to characterize further the role of β-arrestins in the regulation of PI3K activity. Whereas the ability of β-arrestin-1 to inhibit p110α (PI3K catalytic subunit α) has been demonstrated, the role of β-arrestin-2 in PI3K regulation and possible differences in the regulation of the two catalytic subunits (p110α and p110β) associated with p85α (PI3K regulatory subunit) have not been examined. In the present study we have demonstrated that: (i) PAR-2 increases p110α- and p110β-associated lipid kinase activities, and both p110α and p110β are inhibited by over-expression of either β-arrestin-1 or -2; (ii) both β-arrestin-1 and -2 directly inhibit the p110α catalytic subunit in vitro, whereas only β-arrestin-2 directly inhibited p110β; (iii) examination of upstream pathways revealed that PAR-2-induced PI3K activity required the small GTPase Cdc (cell-division cycle)42, but not tyrosine phosphorylation of p85; and (iv) β-arrestins inhibit PAR-2-induced Cdc42 activation. Taken together, these results indicated that β-arrestins could inhibit PAR-2-stimulated PI3K activity, both directly and through interference with upstream pathways, and that the two β-arrestins differ in their ability to inhibit the p110α and p110β catalytic subunits. These results are particularly important in light of the growing interest in PAR-2 as a pharmacological target, as commonly used biochemical assays that monitor G-protein coupling would not screen for β-arrestin-dependent signalling events.

scholarly journals Interaction of Ras with phosphoinositide 3-kinase γ

1997 ◽  
Vol 326 (3) ◽  
pp. 891-895 ◽  
Author(s):  
Ignacio RUBIO ◽  
Pablo RODRIGUEZ-VICIANA ◽  
Julian DOWNWARD ◽  
Reinhard WETZKER
Keyword(s):  
Binding Site ◽  
G Proteins ◽  
Terminal Region ◽  
Regulatory Subunit ◽  
Heterotrimeric G Proteins ◽  
Modest Increase ◽  
Pi3k Activity ◽  
Phosphoinositide 3 Kinase ◽  
Stimulation Of

Phosphoinositide 3-kinase γ (PI3Kγ) can be activated in vitro by both α and βγ subunits of heterotrimeric G-proteins and does not interact with p85, the regulatory subunit of PI3Kα. Here we demonstrate the binding of Ras to PI3Kγ in vitro. An N-terminal region of PI3Kγ was identified as a binding site for Ras. After co-expression with PI3Kγ in COS-7 cells, Ras induced only a modest increase in PI3K activity compared with the stimulation of PI3Kα by Ras in the same cells.

scholarly journals The Role of Protein Phosphatase 2A Catalytic Subunit Cα in Embryogenesis: Evidence from Sequence Analysis and Localization Studies

1999 ◽  
Vol 380 (9) ◽  
pp. 1117-1120 ◽  
Author(s):  
Jürgen Götz ◽  
Wilfried Kues
Keyword(s):  
Protein Phosphatase ◽  
Genomic Organization ◽  
Protein Phosphatase 2A ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Catalytic Subunits ◽  
Regulatory Subunits ◽  
Phosphatase 2A ◽  
The Brain

AbstractProtein phosphatase 2A (PP2A) constitutes one of the major families of protein serine/threonine phosphatases found in all eukaryotic cells. PP2A holoenzymes are composed of a catalytic subunit complexed with a structural regulatory subunit of 65 kDa. These core subunits associate with regulatory subunits of various sizes to form different heterotrimers which have been purified and evaluated with regard to substrate specificity. In fully differentiated tissues PP2A expression levels are highest in the brain, however, relatively little is known about expression in the developing embryo.In order to determine the composition of PP2A catalytic subunits in the mouse, cDNAs were cloned and the genomic organization of PP2A Cα was determined.By a gene targeting approach in the mouse, we have previously shown that the absence of the major catalytic subunit of PP2A, Cα, resulted in embryonic lethality around embryonic day E6.5. No mesoderm was formed which implied that PP2A plays a crucial role in gastrulation.Here, we extended our studies and analyzed wildtype embryos for Cα expression at subsequent stages of development. After gastrulation is completed, we find high expression of Cα restricted to the neural folds, which suggests that PP2A plays an additional pivotal role in neurulation.

The tyrosine phosphatase CD148 interacts with the p85 regulatory subunit of phosphoinositide 3-kinase

2008 ◽  
Vol 413 (1) ◽  
pp. 193-200 ◽  
Author(s):  
Nobuo Tsuboi ◽  
Tadahiko Utsunomiya ◽  
Richard L. Roberts ◽  
Hideyuki Ito ◽  
Keiko Takahashi ◽  
...  
Keyword(s):  
Tyrosine Phosphatase ◽  
Growth Factor Receptor ◽  
Regulatory Subunit ◽  
Mutant Form ◽  
Dependent Manner ◽  
Screening Assay ◽  
Intact Cells ◽  
Pi3k Activity ◽  
Phosphoinositide 3 Kinase

CD148 is a transmembrane tyrosine phosphatase that has been implicated in the regulation of cell growth and transformation. However, the signalling mechanisms of CD148 are incompletely understood. To identify the specific intracellular molecules involved in CD148 signalling, we carried out a modified yeast two-hybrid screening assay. Using the substrate-trapping mutant form of CD148 (CD148 D/A) as bait, we recovered the p85 regulatory subunit of PI3K (phosphoinositide 3-kinase). CD148 D/A, but not catalytically active CD148, interacted with p85 in a phosphorylation-dependent manner in vitro and in intact cells. Growth factor receptor and PI3K activity were also trapped by CD148 D/A via p85 from pervanadate-treated cell lysates. CD148 prominently and specifically dephosphorylated p85 in vitro. Co-expression of CD148 reduced p85 phosphorylation induced by active Src, and attenuated the increases in PI3K activity, yet CD148 did not alter the basal PI3K activity. Finally, CD148 knock-down by siRNA (short interfering RNA) increased PI3K activity on serum stimulation. Taken together, these results demonstrate that CD148 may interact with and dephosphorylate p85 when it is phosphorylated and modulate the magnitude of PI3K activity.

scholarly journals Biochemical and transcription analysis of acetohydroxyacid synthase isoforms in Mycobacterium tuberculosis identifies these enzymes as potential targets for drug development

Microbiology ◽  
2011 ◽  
Vol 157 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Vinayak Singh ◽  
Deepak Chandra ◽  
Brahm S. Srivastava ◽  
Ranjana Srivastava
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Drug Development ◽  
De Novo ◽  
Ex Vivo ◽  
Regulatory Subunit ◽  
Acetohydroxyacid Synthase ◽  
Transcription Analysis ◽  
Catalytic Subunits

Acetohydroxyacid synthase (AHAS) is a biosynthetic enzyme essential for de novo synthesis of branched-chain amino acids. The genome sequence of Mycobacterium tuberculosis revealed genes encoding four catalytic subunits, ilvB1 (Rv3003c), ilvB2 (Rv3470c), ilvG (Rv1820) and ilvX (Rv3509c), and one regulatory subunit, ilvN (Rv3002c), of AHAS. All these genes were found to be expressed in M. tuberculosis growing in vitro. Each AHAS subunit gene was cloned and expressed in Escherichia coli. AHAS activity of IlvB1 and IlvG was found in cell-free lysates and with recombinant purified proteins. Kinetic studies with purified IlvG revealed positive cooperativity towards substrate and cofactors. To understand the role of the catalytic subunits in the biology of M. tuberculosis, expression of AHAS genes was analysed in different physiological conditions. ilvB1, ilvB2 and ilvG were differentially expressed. The role of ilvB1 in persistence is known, but the upregulation of ilvB2 and ilvG in extended stationary phase, ex vivo, and in acid stress and hypoxic environments, suggests the relevance of AHAS enzymes in the metabolism and survival of M. tuberculosis by functioning as catabolic AHAS. These enzymes are therefore potential targets for drug development.

The p101 subunit of PI3Kγ restores activation by Gβ mutants deficient in stimulating p110γ

2012 ◽  
Vol 441 (3) ◽  
pp. 851-858 ◽  
Author(s):  
Aliaksei Shymanets ◽  
Mohammad R. Ahmadian ◽  
Katja T. Kössmeier ◽  
Reinhard Wetzker ◽  
Christian Harteneck ◽  
...  
Keyword(s):  
Protein Kinase ◽  
G Protein ◽  
Crucial Role ◽  
Kinase Activity ◽  
Lipid Vesicles ◽  
Lipid Kinase ◽  
Dimeric Protein ◽  
Phosphoinositide 3 Kinase

G-protein-regulated PI3Kγ (phosphoinositide 3-kinase γ) plays a crucial role in inflammatory and allergic processes. PI3Kγ, a dimeric protein formed by the non-catalytic p101 and catalytic p110γ subunits, is stimulated by receptor-released Gβγ complexes. We have demonstrated previously that Gβγ stimulates both monomeric p110γ and dimeric p110γ/p101 lipid kinase activity in vitro. In order to identify the Gβ residues responsible for the Gβγ–PI3Kγ interaction, we examined Gβ1 mutants for their ability to stimulate lipid and protein kinase activities and to recruit PI3Kγ to lipid vesicles. Our findings revealed different interaction profiles of Gβ residues interacting with p110γ or p110γ/p101. Moreover, p101 was able to rescue the stimulatory activity of Gβ1 mutants incapable of modulating monomeric p110γ. In addition to the known adaptor function of p101, in the present paper we show a novel regulatory role of p101 in the activation of PI3Kγ.

The p110δ subunit of phosphoinositide 3-kinase is required for the lipopolysaccharide response of mouse B cells

2004 ◽  
Vol 32 (5) ◽  
pp. 789-791 ◽  
Author(s):  
B.J. Hebeis ◽  
E. Vigorito ◽  
M. Turner
Keyword(s):  
B Cells ◽  
Adaptive Immune System ◽  
Nuclear Factor Κb ◽  
Catalytic Subunit ◽  
Regulatory Subunit ◽  
Activation Markers ◽  
Kinase Activation ◽  
Extracellular Signal ◽  
Phosphoinositide 3 Kinase

PI3K (phosphoinositide 3-kinase) IA family members contain a regulatory subunit and a catalytic subunit. The p110δ catalytic subunit is expressed predominantly in haematopoietic cells. There, among other functions, it regulates antigen receptor-mediated responses. Using mice deficient in the p110δ subunit of PI3K, we investigated the role of this subunit in LPS (lipopolysaccharide)-induced B cell responses, which are mediated by Toll-like receptor 4 and RP105. After injection of DNP-LPS (where DNP stands for 2,4-dinitrophenol), p110δ−/− mice produced reduced levels of DNP-specific IgM and IgG when compared with wild-type mice. In vitro, the proliferation and up-regulation of surface activation markers such as CD86 and CD25 induced by LPS and an antibody against RP105 were decreased. We analysed the activation state of key components of the LPS pathway in B cells to determine whether there was a defect in signalling in p110δ−/− B cells. They showed normal extracellular-signal-regulated kinase phosphorylation, but anti-RP105-induced protein kinase B, IκB (inhibitor of nuclear factor κB) and c-Jun N-terminal kinase activation was severely reduced. This demonstrates that the p110δ subunit of PI3K is involved in the LPS response in B cells and may represent a link between the innate and the adaptive immune system.

scholarly journals PI3Kβ—A Versatile Transducer for GPCR, RTK, and Small GTPase Signaling

Endocrinology ◽  
2019 ◽  
Vol 160 (3) ◽  
pp. 536-555 ◽  
Author(s):  
Anne R Bresnick ◽  
Jonathan M Backer
Keyword(s):  
G Proteins ◽  
Tyrosine Kinases ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Catalytic Subunits ◽  
Regulatory Subunits ◽  
Phosphoinositide 3 Kinase ◽  
G Protein Coupled

AbstractThe phosphoinositide 3-kinase (PI3K) family includes eight distinct catalytic subunits and seven regulatory subunits. Only two PI3Ks are directly regulated downstream from G protein–coupled receptors (GPCRs): the class I enzymes PI3Kβ and PI3Kγ. Both enzymes produce phosphatidylinositol 3,4,5-trisposphate in vivo and are regulated by both heterotrimeric G proteins and small GTPases from the Ras or Rho families. However, PI3Kβ is also regulated by direct interactions with receptor tyrosine kinases (RTKs) and their tyrosine phosphorylated substrates, and similar to the class II and III PI3Ks, it binds activated Rab5. The unusually complex regulation of PI3Kβ by small and trimeric G proteins and RTKs leads to a rich landscape of signaling responses at the cellular and organismic levels. This review focuses first on the regulation of PI3Kβ activity in vitro and in cells, and then summarizes the biology of PI3Kβ signaling in distinct tissues and in human disease.

scholarly journals PRKAR2A deficiency protects mice from experimental colitis by increasing IFN-stimulated gene expression and modulating the intestinal microbiota

2021 ◽  
Author(s):  
Lumin Wei ◽  
Rongjing Zhang ◽  
Jinzhao Zhang ◽  
Juanjuan Li ◽  
Deping Kong ◽  
...  
Keyword(s):  
Experimental Colitis ◽  
Regulatory Subunit ◽  
Protective Effects ◽  
Intestinal Epithelial ◽  
Catalytic Subunits ◽  
Regulatory Subunits ◽  
Pka Regulatory Subunit ◽  
Cross Fostering ◽  
Specific Deletion

AbstractProtein kinase A (PKA) plays an important role in regulating inflammation via its catalytic subunits. Recently, PKA regulatory subunits have been reported to directly modulate some signaling pathways and alleviate inflammation. However, the role of PKA regulatory subunits in colonic inflammation remains unclear. Therefore, we conducted this study to investigate the role of the PKA regulatory subunit PRKAR2A in colitis. We observed that PRKAR2A deficiency protected mice from dextran sulfate sodium (DSS)-induced experimental colitis. Our experiments revealed that the intestinal epithelial cell-specific deletion of Prkar2a contributed to this protection. Mechanistically, the loss of PRKAR2A in Prkar2a−/− mice resulted in an increased IFN-stimulated gene (ISG) expression and altered gut microbiota. Inhibition of ISGs partially reversed the protective effects against DSS-induced colitis in Prkar2a−/− mice. Antibiotic treatment and cross-fostering experiments demonstrated that the protection against DSS-induced colitis in Prkar2a−/− mice was largely dependent on the gut microflora. Altogether, our work demonstrates a previously unidentified function of PRKAR2A in promoting DSS-induced colitis.

scholarly journals Hyperglycaemia up-regulates placental growth factor (PlGF) expression and secretion in endothelial cells via suppression of PI3 kinase-Akt signalling and activation of FOXO1

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Samir Sissaoui ◽  
Stuart Egginton ◽  
Ling Ting ◽  
Asif Ahmed ◽  
Peter W. Hewett
Keyword(s):  
Endothelial Cells ◽  
Growth Factor ◽  
Endothelial Dysfunction ◽  
Akt Activation ◽  
Forkhead Box ◽  
Pi3k Activity ◽  
Binding Sequence

AbstractPlacenta growth factor (PlGF) is a pro-inflammatory angiogenic mediator that promotes many pathologies including diabetic complications and atherosclerosis. Widespread endothelial dysfunction precedes the onset of these conditions. As very little is known of the mechanism(s) controlling PlGF expression in pathology we investigated the role of hyperglycaemia in the regulation of PlGF production in endothelial cells. Hyperglycaemia stimulated PlGF secretion in cultured primary endothelial cells, which was suppressed by IGF-1-mediated PI3K/Akt activation. Inhibition of PI3K activity resulted in significant PlGF mRNA up-regulation and protein secretion. Similarly, loss or inhibition of Akt activity significantly increased basal PlGF expression and prevented any further PlGF secretion in hyperglycaemia. Conversely, constitutive Akt activation blocked PlGF secretion irrespective of upstream PI3K activity demonstrating that Akt is a central regulator of PlGF expression. Knock-down of the Forkhead box O-1 (FOXO1) transcription factor, which is negatively regulated by Akt, suppressed both basal and hyperglycaemia-induced PlGF secretion, whilst FOXO1 gain-of-function up-regulated PlGF in vitro and in vivo. FOXO1 association to a FOXO binding sequence identified in the PlGF promoter also increased in hyperglycaemia. This study identifies the PI3K/Akt/FOXO1 signalling axis as a key regulator of PlGF expression and unifying pathway by which PlGF may contribute to common disorders characterised by endothelial dysfunction, providing a target for therapy.

scholarly journals Signaling Pathways Regulating TC21-induced Tumorigenesis

2007 ◽  
Vol 282 (38) ◽  
pp. 27713-27720 ◽  
Author(s):  
Mete Erdogan ◽  
Ambra Pozzi ◽  
Neil Bhowmick ◽  
Harold L Moses ◽  
Roy Zent
Keyword(s):  
P38 Mapk ◽  
Cancer Progression ◽  
Transforming Growth Factor ◽  
Cellular Transformation ◽  
Tumor Formation ◽  
Transformed Cells ◽  
Growth Inhibitory ◽  
Phosphoinositide 3 Kinase

TC21(R-Ras2), a Ras-related GTPase with transforming potential similar to H-, K- and N-Ras, is implicated in the pathogenesis of human cancers. Transforming growth factor β (TGF-β), a cytokine that plays a significant role in modulating tumorigenesis, normally prevents uncontrolled cell proliferation but paradoxically induces proliferation in H-Ras-transformed cancer cells. Although TC21 activates some pathways that mediate cellular transformation by the classical Ras proteins, the mechanisms through which TC21 induces tumor formation and how TGF-β regulates TC21 transformed cells is not known. To better understand the role of TC21 in cancer progression, we overexpressed an activated G23V mutant of TC21 in a nontumorigenic murine mammary epithelial (EpH4) cell line. Mutant TC21-expressing cells were significantly more oncogenic than cells expressing activated G12V H-Ras both in vivo and in vitro. TC21-induced transformation and proliferation required activation of p38 MAPK, mTOR (the mammalian target of rapamycin), and phosphoinositide 3-kinase but not Akt/PKB. Transformation by TC21 rendered EpH4 cells insensitive to the growth inhibitory effects of TGF-β, and the soft agar growth of these cells was increased upon TGF-β stimulation. Despite losing responsiveness to TGF-β-mediated growth inhibition, both Smad-dependent and independent pathways remained intact in TC21-transformed cells. Thus, overexpression of active TC21 in EpH4 cells induces tumorigenicity through the phosphoinositide 3-kinase, p38 MAPK, and mTOR pathways, and these cells lose their sensitivity to the normal growth inhibitory role of TGF-β.

Sign in / Sign up

Export Citation Format

Share Document