Protein kinase C inhibitors block insulin and PMA-stimulated hexose transport in isolated rat adipocytes and BC3H-1 myocytes

Standaert, Mary L.; Buckley, Donna J.; Ishizuka, Tatsuo; Hoffman, Joanne M.; Cooper, Denise R.; Pollet, Robert J.; Farese, Robert V.

doi:10.1016/0026-0495(90)90090-y

Cited by 45 publications

(24 citation statements)

References 49 publications

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“…PKC was initially shown to play a role in glucose transport in primary rat adipocytes (43,57). Overexpression of PKC-␦ in 3T3-L1 adipocytes enhanced both basal and insulin-induced glucose transport (61).…”

Section: Discussionmentioning

confidence: 99%

Increased glucose uptake promotes oxidative stress and PKC-δ activation in adipocytes of obese, insulin-resistant mice

Talior

Yarkoni²,

Bashan³

et al. 2003

American Journal of Physiology-Endocrinology and Metabolism

161

130

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Increased oxidative stress is believed to be one of the mechanisms responsible for hyperglycemia-induced tissue damage and diabetic complications. In these studies, we undertook to characterize glucose uptake and oxidative stress in adipocytes of type 2 diabetic animals and to determine whether these promote the activation of PKC-δ. The adipocytes used were isolated either from C57Bl/6J mice that were raised on a high-fat diet (HF) and developed obesity and insulin resistance or from control animals. Basal glucose uptake significantly increased (8-fold) in HF adipocytes, and this was accompanied with upregulation of GLUT1 expression levels. Insulin-induced glucose uptake was inhibited in HF adipocytes and GLUT4 content reduced by 20% in these adipocytes. Reactive oxygen species (ROS) increased twofold in HF adipocytes compared with control adipocytes and were largely reduced with decreased glucose concentrations. At zero glucose, ROS levels were reduced to the normal levels seen in control adipocytes. The activity of PKC-δ increased twofold in HF adipocytes compared with control adipocytes and was further activated by H2O2. Moreover, PKC-δ activity was inhibited in HF adipocytes either by glucose deprivation or by treatment with the antioxidant N-acetyl-l-cysteine. In summary, we propose that increased glucose intake in HF adipocytes increases oxidative stress, which in turn promotes the activation of PKC-δ. These consequential events may be responsible, at least in part, for development of HF diet-induced insulin resistance in the fat tissue.

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Section: Discussionmentioning

confidence: 99%

Increased glucose uptake promotes oxidative stress and PKC-δ activation in adipocytes of obese, insulin-resistant mice

Talior

Yarkoni²,

Bashan³

et al. 2003

American Journal of Physiology-Endocrinology and Metabolism

161

130

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“…Evidence has accumulated to show that direct PKC activation by phorbol esters or DAG leads to the stimulation of glucose transport in adipocytes [30,50,51] and skeletal muscle [35±37], and GLUT4 translocation to the cell surface in adipocytes [30,51,52]. Insulin [38,53] and muscle contraction [54,55] have been reported to activate the PKC pathway. Furthermore, PKC activation through stimulation with phorbol esters increases glucose transport [35±37].…”

Section: Discussionmentioning

confidence: 99%

Changes in glucose transport and protein kinase Cβ 2 in rat skeletal muscle induced by hyperglycaemia

et al. 1999

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Skeletal muscle is quantitatively the most important tissue involved in maintaining glucose homeostasis, accounting for about 80 % of glucose disposal after a glucose infusion or ingestion [1]. Glucose transport is the rate-limiting step for glucose metabolism in insulin sensitive tissues [2,3]. In skeletal muscle, glucose transport is mediated by a process involving the translocation of glucose transporters (GLUT), namely GLUT4, from an intracellular site to the plasma membrane [4,5]. Glucose transporter 4 translocation Diabetologia (1999) Abstract Aims/hypothesis. We have previously reported that hyperglycaemia activates glucose transport in skeletal muscle by a Ca 2+ -dependent pathway, which is distinct from the insulin-signalling pathway. The aim of this study was to explain the signalling mechanism by which hyperglycaemia autoregulates glucose transport in skeletal muscle. Methods. Isolated rat soleus muscle was incubated in the presence of various concentrations of glucose or 3-O-methylglucose and protein kinase C and phospholipase C inhibitors. Glucose transport activity, cell surface glucose transporter 1 and glucose transporter 4 content and protein kinase C translocation was determined. Results. High concentrations of 3-O-methylglucose led to a concentration-dependent increase in [ 3 H]-3-O-methylglucose transport in soleus muscle. Dantrolene, an inhibitor of Ca 2+ released from the sarcoplasmic reticulum, decreased the V max and the K m of the concentration-response curve. Protein kinase C inhibitors (H-7 and GF109203X) inhibited the stimulatory effect of high glucose concentrations on hexose transport, whereas glucose transport stimulated by insulin was unchanged. Incubation of muscle with glucose (25 mmol/l) and 3-O-methylglucose (25 mmol/l) led to a three fold gain in protein kinase Cb 2 in the total membrane fraction, whereas membrane content of protein kinase Ca, b 1 , d, e and q were unchanged. A short-term increase in the extracellular glucose concentration did not change cell surface recruitment of glucose transporter 1 or glucose transporter 4, as assessed by exofacial photolabelling with [ 3 H]-ATB-BMPA bis-mannose. Conclusion/interpretation. Protein kinase Cb 2 is involved in a glucose-sensitive, Ca 2+ -dependent signalling pathway, which is possibly involved in the regulation of glucose transport in skeletal muscle. This glucose-dependent increase in 3-0-methylglucose transport is independent of glucose transporter 4 and glucose transporter 1 translocation to the plasma membrane and may involve modifications of cell surface glucose transporter activity. [Diabetologia (1999

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“…Certain evidence (8,15,16) suggests that a protein kinase distal to PI 3-kinase (8, 17) may be required for insulin effects on GLUT 4 translocation and glucose transport. Insulin effects on these processes are sensitive to PKC inhibitors but, in general, the required concentrations of these inhibitors (8,15,16) have exceeded those required to inhibit conventional and novel DAG-sensitive PKCs.…”

Section: Resultsmentioning

confidence: 99%

Protein Kinase C-ζ as a Downstream Effector of Phosphatidylinositol 3-Kinase during Insulin Stimulation in Rat Adipocytes

Standaert

Galloway

Karnam

et al. 1997

Journal of Biological Chemistry

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423

399

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Insulin provoked rapid increases in enzyme activity of immunoprecipitable protein kinase C-(PKC-) in rat adipocytes. Concomitantly, insulin provoked increases in 32 P labeling of PKC-both in intact adipocytes and during in vitro assay of immunoprecipitated PKC-; the latter probably reflected autophosphorylation, as it was inhibited by the PKC-pseudosubstrate. Insulin-induced activation of immunoprecipitable PKC-was inhibited by LY294002 and wortmannin; this suggested dependence upon phosphatidylinositol (PI) 3-kinase. Accordingly, activation of PI 3-kinase by a pYXXM-containing peptide in vitro resulted in a wortmannin-inhibitable increase in immunoprecipitable PKC-enzyme activity. Also, PI-3,4-(PO 4 ) 2 , PI-3,4,5-(PO 4 ) 3 , and PI-4,5-(PO 4 ) 2 directly stimulated enzyme activity and autophosphoralytion in control PKC-immunoprecipitates to levels observed in insulin-treated PKC-immunoprecipitates. In studies of glucose transport, inhibition of immunoprecipitated PKC-enzyme activity in vitro by both the PKC-pseudosubstrate and RO 31-8220 correlated well with inhibition of insulin-stimulated glucose transport in intact adipocytes. Also, in adipocytes transiently expressing hemagglutinin antigentagged GLUT4, co-transfection of wild-type or constitutive PKC-stimulated hemagglutinin antigen-GLUT4 translocation, whereas dominant-negative PKC-partially inhibited it. Our findings suggest that insulin activates PKC-through PI 3-kinase, and PKC-may act as a downstream effector of PI 3-kinase and contribute to the activation of GLUT4 translocation.The atypical protein kinase C (PKC), 1 PKC-, is ubiquitously expressed, but little is known about its activation or actions. This ignorance partly derives from the fact that PKC-is not activated by membrane-associated diacylglycerol (DAG) or phorbol esters, generally does not translocate appreciably from cytosol to membrane when activated, and is not depleted by prolonged phorbol ester treatment. Consequently, methods used to evaluate DAG-sensitive conventional (␣, ␤, and ␥) and novel (␦, ⑀, , and ) PKCs are not relevant to PKC-and other DAG-insensitive, atypical PKCs. Although not activated by DAG, PKC-is activated in vitro by phosphatidylserine and polyphosphoinositides, including D3-PO 4 derivatives of phosphatidylinositol (PI) (1, 2). Because of its activation by polyphosphoinositides, PKC-has been suspected to operate downstream of PI 3-kinase; however, direct experimental evidence for this suspicion is lacking, particularly in intact cells. Since insulin increases total polyphosphoinositide levels (3-6), probably largely through PI 3-kinase activation (7), we examined the possibility that insulin activates PKC-by a PI 3-kinasedependent mechanism. To this end, we assayed immunoprecipitable PKC-(a) following treatment of intact adipocytes with insulin in the presence and absence of PI 3-kinase inhibitors; (b) following PI 3-kinase activation in vitro by a pYXXMcontaining peptide; and (c) in response to polyphosphoinositides added directly to the assay of PKC-in vitro. Also...

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Protein kinase C inhibitors block insulin and PMA-stimulated hexose transport in isolated rat adipocytes and BC3H-1 myocytes

Cited by 45 publications

References 49 publications

Increased glucose uptake promotes oxidative stress and PKC-δ activation in adipocytes of obese, insulin-resistant mice

Increased glucose uptake promotes oxidative stress and PKC-δ activation in adipocytes of obese, insulin-resistant mice

Changes in glucose transport and protein kinase Cβ 2 in rat skeletal muscle induced by hyperglycaemia

Protein Kinase C-ζ as a Downstream Effector of Phosphatidylinositol 3-Kinase during Insulin Stimulation in Rat Adipocytes

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