Regulation of Lipoprotein Lipase by Protein Kinase Cα in 3T3-F442A Adipocytes

Ranganathan, Gouri; Song, Wei; Dean, Nicholas M.; Monia, Brett P.; Barger, Steven W.; Kern, Philip A.

doi:10.1074/jbc.m206917200

Cited by 21 publications

(15 citation statements)

References 44 publications

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“…The change in PKC α mRNA was accompanied by a 50 ± 10% decrease in PKC α protein as measured by Western blot analysis of cell lysates. Although there was no decrease in LPL mRNA expression in PKC α antisense-treated cells, LPL synthesis and protein expression were inhibited as demonstrated previously [11], and LPL activity was inhibited by 52 ± 12% (Figure 1). …”

Section: Resultssupporting

confidence: 83%

“…LPL is also translationally repressed following depletion of cellular PKC (protein kinase C), either through prolonged treatment with phorbol esters or through the use of antisense oligonucleotides to PKC α [11]. This PKC α -mediated inhibition of LPL translation also involved the 3′UTR of the LPL mRNA, although the precise nature of the RNA-binding protein is not known.…”

Section: Introductionmentioning

confidence: 99%

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Translational regulation of lipoprotein lipase in adipocytes: depletion of cellular protein kinase Cα activates binding of the C subunit of protein kinase A to the 3′-untranslated region of the lipoprotein lipase mRNA

Ünal

Pokrovskaya

Tripathi

et al. 2008

Biochemical Journal

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Adipose LPL (lipoprotein lipase) plays an important role in regulating plasma triacylglycerols and lipid metabolism. We have previously demonstrated that PKCα (protein kinase Cα) depletion inhibits LPL translation in 3T3-F442A adipocytes. Using in vitro translation experiments, the minimum essential region on the 3′UTR (3′-untranslated region) of LPL mRNA required for the inhibition of translation was identified as the proximal 39 nt. These results were confirmed by RNase protection analysis using cytoplasmic proteins isolated from the adipocytes treated with PKCα antisense oligomers and the LPL 3′UTR transcript (LPL 3′UTR nt: 1512–1640). The protein components involved in this RNA-binding interaction from PKCα depletion were passed through an affinity column containing a sequence of the LPL 3′UTR and, after Western blotting, the RNA-binding proteins were identified as the catalytic and the regulatory subunits of PKA (protein kinase A), Cα and RIIβ, and AKAP (A-kinase-anchoring protein) 121. This RNA inhibitory complex consisted of the same RNA-binding proteins that have been identified previously as mediators of LPL translational inhibition by PKA activation, suggesting that PKCα depletion inhibits LPL translation through PKA activation. In additional experiments, PKC depletion by prolonged PMA treatment or PKCα antisense oligomers resulted in an increase in PKA activity in 3T3-F442A adipocytes, comparable with PKA activation with adrenaline (epinephrine) treatment. These results demonstrate that LPL translational inhibition occurs through an RNA-binding complex involving PKA subunits and AKAP121, and this complex can be activated either through traditional PKA activation methods or through the depletion of PKCα.

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Section: Resultssupporting

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Translational regulation of lipoprotein lipase in adipocytes: depletion of cellular protein kinase Cα activates binding of the C subunit of protein kinase A to the 3′-untranslated region of the lipoprotein lipase mRNA

Ünal

Pokrovskaya

Tripathi

et al. 2008

Biochemical Journal

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“…It should be noted that other studies have also reported an important contribution of PKCs toward LPL secretion in macrophages and adipocytes. [37][38][39] Diabetes is known to activate a number of PKC isoforms. 40,41 We attempted to activate PKC by duplicating the plasma concentrations of glucose and FA observed after DZ, and study its influence on cardiac LPL.…”

Section: Kim Et Al Control Of Cardiac Lpl Secretion During Diabetes 257mentioning

confidence: 99%

Protein Kinase D Is a Key Regulator of Cardiomyocyte Lipoprotein Lipase Secretion After Diabetes

Kim¹,

Wang²,

Puthanveetil³

et al. 2008

Circulation Research

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Abstract-The diabetic heart switches to exclusively using fatty acid (FA) for energy supply and does so by multiple mechanisms including hydrolysis of lipoproteins by lipoprotein lipase (LPL) positioned at the vascular lumen. We determined the mechanism that leads to an increase in LPL after diabetes. Diazoxide (DZ), an agent that decreases insulin secretion and causes hyperglycemia, induced a substantial increase in LPL activity at the vascular lumen. This increase in LPL paralleled a robust phosphorylation of Hsp25, decreasing its association with PKC␦, allowing this protein kinase to phosphorylate and activate protein kinase D (PKD), an important kinase that regulates fission of vesicles from the golgi membrane. Rottlerin, a PKC␦ inhibitor, prevented PKD phosphorylation and the subsequent increase in LPL. Incubating control myocytes with high glucose and palmitic acid (GluϩPA) also increased the phosphorylation of Hsp25, PKC␦, and PKD in a pattern similar to that seen with diabetes, in addition to augmenting LPL activity. In myocytes in which PKD was silenced or a mutant form of PKC␦ was expressed, high GluϩPA were incapable of increasing LPL. Moreover, silencing of cardiomyocyte Hsp25 allowed phorbol 12-myristate 13-acetate to elicit a significant phosphorylation of PKC␦, an appreciable association between PKC␦ and PKD, and a vigorous activation of PKD. As these cells also demonstrated an additional increase in LPL, our data imply that after diabetes, PKD control of LPL requires dissociation of Hsp25 from PKC␦, association between PKC␦ and PKD, and vesicle fission. Results from this study could help in restricting cardiac LPL translocation, leading to strategies that overcome contractile dysfunction after diabetes. Key Words: heat shock protein Ⅲ protein kinase C Ⅲ hyperglycemia Ⅲ hyperlipidemia Ⅲ vesicles C ardiac muscle has a high demand for energy and uses multiple substrates, including fatty acid (FA), carbohydrate, amino acids, and ketones. 1 Among these substrates, carbohydrate and FA are the major sources from which the heart derives most of its energy. In a normal heart, whereas glucose and lactate account for approximately 30% of energy provided to the cardiac muscle, 70% of ATP generation is through FA oxidation. 2 FA delivery and utilization by the heart involves: (1) release from adipose tissue and transport to the heart after complexing with albumin, 3 (2) provision through breakdown of endogenous cardiac triglyceride (TG) stores, 4 (3) internalization of whole lipoproteins, 5 and (4) hydrolysis of circulating TG-rich lipoproteins to FA by lipoprotein lipase (LPL) positioned at the endothelial surface of the coronary lumen. 6 The molar concentration of FA bound to albumin is Ϸ10-fold less than that of FA in lipoprotein-TG, 7 and LPL-mediated hydrolysis of circulating TG-rich lipoproteins to FA is suggested to be the principal source of FA for cardiac utilization. 8 Coronary endothelial cells do not synthesize LPL. 9 In the heart, this enzyme is produced in cardiomyocytes and subsequently se...

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“…A recent report suggested that LPC contributes to the activation of a pro-inflammatory endothelial phenotype, an effect requiring inputs from protein kinase C (PKC) [94]. Interestingly, PKC has been implicated in the regulation of LPL in adipocytes [95] and macrophages [96]. Furthermore, in macrophages, leptin induced augmentation of LPL gene expression involved PKC activation [97].…”

Section: Lysophospholipidsmentioning

confidence: 96%

Cardiac lipoprotein lipase: Metabolic basis for diabetic heart disease

Pulinilkunnil¹,

Rodrigues²

2006

Cardiovascular Research

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The heart has a limited potential to synthesize fatty acid (FA), and, therefore, FA is supplied from several sources: lipolysis of endogenous cardiac triglyceride (TG) stores or from exogenous sources in the blood. Lipoprotein lipase (LPL), synthesized in cardiomyocytes, catalyzes the breakdown of the TG component of lipoproteins to provide FA to the heart. It is the vascular endothelial-bound LPL that determines the rate of plasma TG clearance, and, hence, it is also called heparin-releasable (HR) "functional" LPL. Functional LPL is regulated by numerous dietary and hormonal factors and is sensitive to pathophysiological alterations like those observed during diabetes. In this condition, absolute or relative lack of insulin impairs cardiac glucose transport and oxidation, resulting in FA becoming the preferred means of energy supply. To make available this increased requirement of the heart for FA, the diabetic heart upregulates its luminal LPL activity by posttranslational mechanisms. Chronically elevated cardiac LPL can result in abnormal FA supply and utilization by the heart tissue that could potentially initiate and sustain cardiac dysfunction during diabetes. As effective blood glucose control is difficult during diabetes, it is conceivable that a parallel increase in functional cardiac LPL activity may predispose people with diabetes to premature death from cardiac disease. By gaining more insight into the initial metabolic processes in the diabetic heart, we can attempt to piece together a part of the cascade of events leading to diabetic heart disease.

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Regulation of Lipoprotein Lipase by Protein Kinase Cα in 3T3-F442A Adipocytes

Cited by 21 publications

References 44 publications

Translational regulation of lipoprotein lipase in adipocytes: depletion of cellular protein kinase Cα activates binding of the C subunit of protein kinase A to the 3′-untranslated region of the lipoprotein lipase mRNA

Translational regulation of lipoprotein lipase in adipocytes: depletion of cellular protein kinase Cα activates binding of the C subunit of protein kinase A to the 3′-untranslated region of the lipoprotein lipase mRNA

Protein Kinase D Is a Key Regulator of Cardiomyocyte Lipoprotein Lipase Secretion After Diabetes

Cardiac lipoprotein lipase: Metabolic basis for diabetic heart disease

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