scholarly journals Fyn Regulates Adipogenesis by Promoting PIKE-A/STAT5a Interaction

2013 ◽  
Vol 33 (9) ◽  
pp. 1797-1808 ◽  
Author(s):  
Margaret Chui Ling Tse ◽  
Xia Liu ◽  
Seran Yang ◽  
Keqiang Ye ◽  
Chi Bun Chan
Keyword(s):  
Kinase Activity ◽  
Adipocyte Differentiation ◽  
Multiple Roles ◽  
Signal Transducer ◽  
Functional Interaction ◽  
Cellular Processes ◽  
Activity Inhibition ◽  
Phosphoinositide 3 Kinase ◽  
Adipogenic Transcription Factor

Fyn is a tyrosine kinase with multiple roles in a variety of cellular processes. Here we report that Fyn is a new kinase involved in adipocyte differentiation. Elevated Fyn protein is detected specifically in the adipocytes of obese mice. Moreover, Fyn expression increases progressively in 3T3-L1 cells during in vitro adipogenesis, which correlates with its kinase activity. Inhibition of Fyn by either genetic or pharmacological manipulation restrains the 3T3-L1 preadipocytes from fully differentiating into mature adipocytes. Mechanistically, Fyn regulates the activity of the adipogenic transcription factor signal transducer and activator of transcription 5a (STAT5a) through enhancing its interaction with the GTPase phosphoinositide 3-kinase enhancer A (PIKE-A). The STAT5a activity is therefore reduced in Fyn - or PIKE -ablated adipose tissues, leading to diminished expression of adipogenic markers and adipocyte differentiation. Our data thus demonstrate a novel functional interaction between Fyn, PIKE-A, and STAT5a in mediating adipogenesis.

scholarly journals Inhibitory Odorant Signaling in Mammalian Olfactory Receptor Neurons

2010 ◽  
Vol 103 (2) ◽  
pp. 1114-1122 ◽  
Author(s):  
Kirill Ukhanov ◽  
Elizabeth A. Corey ◽  
Daniela Brunert ◽  
Katharina Klasen ◽  
Barry W. Ache
Keyword(s):  
Olfactory Receptor ◽  
Olfactory Receptor Neurons ◽  
Electrophysiological Response ◽  
Cellular Processes ◽  
Receptor Neurons ◽  
Phosphoinositide 3 Kinase ◽  
Mixture Suppression ◽  
G Protein Coupled ◽  
Kinetics Of

Odorants inhibit as well as excite olfactory receptor neurons (ORNs) in many species of animals. Cyclic nucleotide-dependent activation of canonical mammalian ORNs is well established but it is still unclear how odorants inhibit these cells. Here we further implicate phosphoinositide-3-kinase (PI3K), an indispensable element of PI signaling in many cellular processes, in olfactory transduction in rodent ORNs. We show that odorants rapidly and transiently activate PI3K in the olfactory cilia and in the olfactory epithelium in vitro. We implicate known G-protein–coupled isoforms of PI3K and show that they modulate not only the magnitude but also the onset kinetics of the electrophysiological response of ORNs to complex odorants. Finally, we show that the ability of a single odorant to inhibit another can be PI3K dependent. Our collective results provide compelling support for the idea that PI3K-dependent signaling mediates inhibitory odorant input to mammalian ORNs and at least in part contributes to the mixture suppression typically seen in the response of ORNs to complex natural odorants.

scholarly journals The Class II Phosphoinositide 3-Kinase C2β Is Not Essential for Epidermal Differentiation

2005 ◽  
Vol 25 (24) ◽  
pp. 11122-11130 ◽  
Author(s):  
Kazutoshi Harada ◽  
Amy B. Truong ◽  
Ti Cai ◽  
Paul A. Khavari
Keyword(s):  
Class Ii ◽  
Epidermal Cells ◽  
Epidermal Differentiation ◽  
Class I ◽  
Differentiation Markers ◽  
Cellular Processes ◽  
Targeted Gene Deletion ◽  
Epidermal Growth ◽  
Phosphoinositide 3 Kinase

ABSTRACT Phosphoinositide 3-kinases (PI3Ks) regulate an array of cellular processes and are comprised of three classes. Class I PI3Ks include the well-studied agonist-sensitive p110 isoforms; however, the functions of class II and III PI3Ks are less well characterized. Of the three class II PI3Ks, C2α and C2β are widely expressed in many tissues, including the epidermis, while C2γ is confined to the liver. In contrast to the class I PI3K p110α, which is expressed throughout the epidermis, C2β was found to be localized in suprabasal cells, suggesting a potential role for C2β in epidermal differentiation. Overexpressing C2β in epidermal cells in vitro induced differentiation markers. To study a role for C2β in tissue, we generated transgenic mice overexpressing C2β in both suprabasal and basal epidermal layers. These mice lacked epidermal abnormalities. Mice deficient in C2β were then generated by targeted gene deletion. C2β knockout mice were viable and fertile and displayed normal epidermal growth, differentiation, barrier function, and wound healing. To exclude compensation by C2α, RNA interference was then used to knock down both C2α and C2β in epidermal cells simultaneously. Induction of differentiation markers was unaffected in the absence of C2α and C2β. These findings indicate that class II PI3Ks are not essential for epidermal differentiation.

Early phosphoinositide 3-kinase activity is required for late activation of protein kinase Cε in platelet-derived-growth-factor-stimulated cells: evidence for signalling across a large temporal gap

2001 ◽  
Vol 358 (2) ◽  
pp. 281-285 ◽  
Author(s):  
Egle BALCIUNAITE ◽  
Andrius KAZLAUSKAS
Keyword(s):  
Protein Kinase ◽  
Kinase Activity ◽  
Recent Observation ◽  
Time Interval ◽  
Long Time ◽  
Subsequent Activation ◽  
Phase Interval ◽  
Phosphoinositide 3 Kinase

At least two signalling systems have the potential to contribute to the activation of protein kinase C (PKC) family members such as PKC∊. One of these is phosphoinositide 3-kinase (PI 3-kinase), whose lipid products activate PKC∊ in vitro and in living cells. The recent observation that there are multiple waves of PI 3-kinase and PKC∊ activity within the G0-to-S phase interval provides a new opportunity to investigate the relationship between these two signalling enzymes in vivo. We have assessed the relative importance of the early and late waves of PI 3-kinase activity for the corresponding waves of PKC∊ activity. Blocking the first phase of PI 3-kinase activity inhibited both early and late activation of PKC∊. In contrast, the second wave of PI 3-kinase activity was dispensable for late activation of PKC∊. These findings suggested that early PI 3-kinase activation induced a stable change in PKC∊, which predisposed it to subsequent activation by lipid cofactors. Indeed, partial proteolysis of PKC∊ indicated that early activation of PI 3-kinase led to a conformation change in PKC∊ that persisted as the activity of PKC∊ cycled. We propose a two-step hypothesis for the activation of PKC∊ in vivo. One step is stable and depends on PI 3-kinase, whereas the other is transient and may depend on the availability of lipid cofactors. Finally, these studies reveal that PI 3-kinase and PKC∊ are capable of communicating over a relatively long time interval and begin to elucidate the mechanism.

scholarly journals A tightly associated serine/threonine protein kinase regulates phosphoinositide 3-kinase activity.

1993 ◽  
Vol 13 (3) ◽  
pp. 1657-1665 ◽  
Author(s):  
C L Carpenter ◽  
K R Auger ◽  
B C Duckworth ◽  
W M Hou ◽  
B Schaffhausen ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Phosphatase ◽  
Kinase Activity ◽  
Protein Phosphatase 2A ◽  
T Antigen ◽  
Serine Kinase ◽  
Phosphatase 2A ◽  
Phosphoinositide 3 Kinase

We identified a serine/threonine protein kinase that is associated with and phosphorylates phosphoinositide 3-kinase (PtdIns 3-kinase). The serine kinase phosphorylates both the 85- and 110-kDa subunits of PtdIns 3-kinase and purifies with it from rat liver and immunoprecipitates with antibodies raised to the 85-kDa subunit. Tryptic phosphopeptide maps indicate that p85 from polyomavirus middle T-transformed cells is phosphorylated in vivo at three sites phosphorylated in vitro by the associated serine kinase. The 85-kDa subunit of PtdIns 3-kinase is phosphorylated in vitro on serine at a stoichiometry of approximately 1 mol of phosphate per mol of p85. This phosphorylation results in a three- to sevenfold decrease in PtdIns 3-kinase activity. Dephosphorylation with protein phosphatase 2A reverses the inhibition. This suggests that the association of protein phosphatase 2A with middle T antigen may function to activate PtdIns 3-kinase.

Physiological roles of PKB/Akt isoforms in development and disease

2007 ◽  
Vol 35 (2) ◽  
pp. 231-235 ◽  
Author(s):  
B. Dummler ◽  
B.A. Hemmings
Keyword(s):  
Protein Kinase ◽  
Mammalian Cells ◽  
Adipocyte Differentiation ◽  
Protein Kinase B ◽  
Signal Transducer ◽  
Akt Isoforms ◽  
Tumour Development ◽  
Glucose Homoeostasis ◽  
Signalling Cascades ◽  
Phosphoinositide 3 Kinase

PKB (protein kinase B, also known as Akt) is a serine/threonine protein kinase that is important in various signalling cascades and acts as a major signal transducer downstream of activated phosphoinositide 3-kinase. There are three closely related isoforms of PKB in mammalian cells, PKBα (Akt1), PKBβ (Akt2) and PKBγ (Akt3), and this review discusses recent advances in our understanding of the functions of these isoforms in the regulation of adipocyte differentiation, glucose homoeostasis and tumour development.

scholarly journals The PRK2 kinase is a potential effector target of both Rho and Rac GTPases and regulates actin cytoskeletal organization.

1997 ◽  
Vol 17 (4) ◽  
pp. 2247-2256 ◽  
Author(s):  
S Vincent ◽  
J Settleman
Keyword(s):  
Protein Kinases ◽  
Kinase Activity ◽  
Rho Kinase ◽  
Close Relative ◽  
Rho Proteins ◽  
Cellular Processes ◽  
Rac Gtpases ◽  
Downstream Effector ◽  
Rho Family Gtpases

The Ras-related Rho family GTPases mediate signal transduction pathways that regulate a variety of cellular processes. Like Ras, the Rho proteins (which include Rho, Rac, and CDC42) interact directly with protein kinases, which are likely to serve as downstream effector targets of the activated GTPase. Activated RhoA has recently been reported to interact directly with several protein kinases, p120 PKN, p150 ROK alpha and -beta, p160 ROCK, and p164 Rho kinase. Here, we describe the purification of a novel Rho-associated kinase, p140, which appears to be the major Rho-associated kinase activity in most tissues. Peptide microsequencing revealed that p140 is probably identical to the previously reported PRK2 kinase, a close relative of PKN. However, unlike the previously described Rho-binding kinases, which are Rho specific, p140 associates with Rac as well as Rho. Moreover, the interaction of p140 with Rho in vitro is nucleotide independent, whereas the interaction with Rac is completely GTP dependent. The association of p140 with either GTPase promotes kinase activity substantially, and expression of a kinase-deficient form of p140 in microinjected fibroblasts disrupts actin stress fibers. These results indicate that p140 may be a shared kinase target of both Rho and Rac GTPases that mediates their effects on rearrangements of the actin cytoskeleton.

scholarly journals Evidence for modification of protein phosphorylation by cytokinins

1972 ◽  
Vol 130 (4) ◽  
pp. 901-911 ◽  
Author(s):  
R. K. Ralph ◽  
P. J. A. McCombs ◽  
G. Tener ◽  
S. J. Wojcik
Keyword(s):  
Protein Phosphorylation ◽  
Chinese Cabbage ◽  
Kinase Activity ◽  
Protein Kinase Activity ◽  
Secondary Phloem ◽  
Phloem Tissue ◽  
Cyclic Monophosphate ◽  
Cellular Processes ◽  
Ylacetic Acid

Kinetin stimulated phosphorylation of protein in floated Chinese-cabbage leaf discs, but inhibited protein phosphorylation in nuclei+chloroplast extracts from Chinese-cabbage or tobacco leaves. Kinetin also inhibited protein phosphorylation in isolated tobacco nuclei or nuclei from carrot secondary-phloem tissue. Purified Chinese-cabbage leaf ribosomes exhibited protein kinase activity which was inhibited by kinetin and zeatin. The ribosome-associated kinase responded to kinetin and zeatin differently from that associated with nuclei+chloroplast preparations. Protein phosphorylation in vitro was not affected by adenosine 3′:5′-cyclic monophosphate, indol-3-ylacetic acid or gibberellic acid. It was only inhibited by N9-unsubstituted purines, among which the known cytokinins were the most effective inhibitors. The results are discussed in relation to possible similarities between the effects of cytokinins in plant tissues and the effects of adenosine 3′:5′-cyclic monophosphate in animal tissues. Both compounds appear to modify the activity of protein kinases and both affect many different cellular processes.

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.

NH2 terminus of serum and glucocorticoid-regulated kinase 1 binds to phosphoinositides and is essential for isoform-specific physiological functions

2007 ◽  
Vol 292 (6) ◽  
pp. F1741-F1750 ◽  
Author(s):  
Alan C. Pao ◽  
James A. McCormick ◽  
Hongyan Li ◽  
John Siu ◽  
Cedric Govaerts ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Kinase Activity ◽  
Regulatory Protein ◽  
Forkhead Transcription Factor ◽  
Cellular Processes ◽  
Cellular Compartments ◽  
Stimulation Of

Serum and glucocorticoid regulated kinase 1 (SGK1) has been identified as a key regulatory protein that controls a diverse set of cellular processes including sodium (Na+) homeostasis, osmoregulation, cell survival, and cell proliferation. Two other SGK isoforms, SGK2 and SGK3, have been identified, which differ most markedly from SGK1 in their NH2-terminal domains. We found that SGK1 and SGK3 are potent stimulators of epithelial Na+ channel (ENaC)-dependent Na+ transport, while SGK2, which has a short NH2 terminus, is a weak stimulator of ENaC. Further characterization of the role of the SGK1 NH2 terminus revealed that its deletion does not affect in vitro kinase activity but profoundly limits the ability of SGK1 either to stimulate ENaC-dependent Na+ transport or inhibit Forkhead-dependent gene transcription. The NH2 terminus of SGK1, which shares sequence homology with the phosphoinositide 3-phosphate [PI( 3 )P] binding domain of SGK3, binds phosphoinositides in protein lipid overlay assays, interacting specifically with PI( 3 )P, PI( 4 )P, and PI( 5 )P, but not with PI( 3 , 4 , 5 )P3. Moreover, a point mutation that reduces phosphoinositide binding to the NH2 terminus also reduces SGK1 effects on Na+ transport and Forkhead activity. These data suggest that the NH2 terminus, although not required for PI 3-kinase-dependent modulation of SGK1 catalytic activity, is required for multiple SGK1 functions, including stimulation of ENaC and inhibition of the proapoptotic Forkhead transcription factor. Together, these observations support the idea that the NH2-terminal domain acts downstream of PI 3-kinase-dependent activation to target the kinase to specific cellular compartments and/or substrates, possibly through its interactions with a subset of phosphoinositides.

scholarly journals Regulation of Phosphoinositide 3-Kinase by Its Intrinsic Serine Kinase Activity In Vivo

2004 ◽  
Vol 24 (3) ◽  
pp. 966-975 ◽  
Author(s):  
Lazaros C. Foukas ◽  
Caroline A. Beeton ◽  
Jorgen Jensen ◽  
Wayne A. Phillips ◽  
Peter R. Shepherd
Keyword(s):  
Growth Factor ◽  
Kinase Activity ◽  
Catalytic Subunit ◽  
Protein Kinase Activity ◽  
Growth Factor Signaling ◽  
Serine Kinase ◽  
Lipid Kinase ◽  
Phosphoinositide 3 Kinase

ABSTRACT One potentially important mechanism for regulating class Ia phosphoinositide 3-kinase (PI 3-kinase) activity is autophosphorylation of the p85α adapter subunit on Ser608 by the intrinsic protein kinase activity of the p110 catalytic subunit, as this downregulates the lipid kinase activity in vitro. Here we investigate whether this phosphorylation can occur in vivo. We find that p110α phosphorylates p85α Ser608 in vivo with significant stoichiometry. However, p110β is far less efficient at phosphorylating p85α Ser608, identifying a potential difference in the mechanisms by which these two isoforms are regulated. The p85α Ser608 phosphorylation was increased by treatment with insulin, platelet-derived growth factor, and the phosphatase inhibitor okadaic acid. The functional effects of this phosphorylation are highlighted by mutation of Ser608, which results in reduced lipid kinase activity and reduced association of the p110α catalytic subunit with p85α. The importance of this phosphorylation was further highlighted by the finding that autophosphorylation on Ser608 was impaired, while lipid kinase activity was increased, in a p85α mutant recently discovered in human tumors. These results provide the first evidence that phosphorylation of Ser608 plays a role as a shutoff switch in growth factor signaling and contributes to the differences in functional properties of different PI 3-kinase isoforms in vivo.

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