Regulation of adipose tissue lipolysis: phosphorylation of hormone‐sensitive lipase in intact rat adipocytes

Belfrage, Per; Fredrikson, Gudrun; Nilsson, Nils Östen; Strålfors, Peter

doi:10.1016/0014-5793(80)80775-7

Cited by 80 publications

(58 citation statements)

References 12 publications

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“…This enzyme, partially purified from rat (23,24) and chicken (25) adipose tissue, is phosphorylated/activated by cAMP-dependent protein kinase and dephosphorylated/deactivated by phosphoprotein phosphatases of various origins (34). Hormone-sensitive lipase has not been isolated or characterized from tissues other than adipose tissue [the adrenal is the only exception to date (26,27)] and thus provides a unique marker for this cell type.…”

Section: Discussionmentioning

confidence: 99%

“…The increase in levels ofthese enzymes and receptors, together with the accumulation ofstored triglycerides, strongly supports the conclusion of Green and coworkers that the 3T3-L1 cell can serve as a model for studies ofadipose tissue metabolism. However, thus far there is no evidence for the expression of the most characteristic and functionally important enzyme of adipose tissue-hormone-sensitive lipase, the neutral lipase activated by cyclic AMP (cAMP)-dependent protein kinase that controls rates of lipid mobilization (20)(21)(22)(23)(24)(25). This enzyme appears to be unique to the adipocyte.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hormone-sensitive lipase in differentiated 3T3-L1 cells and its activation by cyclic AMP-dependent protein kinase.

Kawamura¹,

Jensen²,

Wancewicz³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

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Differentiation of 3T3-L1 fibroblasts to adipo- 3T3-L1 fibroblasts, a subclone of Swiss mouse embryo 3T3 fibroblasts isolated by , are capable of differentiating into adipocyte-like cells engorged with cytoplasmic lipid droplets. The differentiation can be accelerated by treating 3T3-Ll fibroblasts with serum (4), insulin (2), biotin (5), or 1-methyl-3-isobutylxanthine (MIX) (6). Rubin et al. (7) found the combination of MIX and dexamethasone (DEX) to be highly effective. The accumulation oftriglyceride is accompanied by a marked increase in the specific activities of several enzymes involved in fatty acid synthesis and triglyceride synthesis (2, 5, 7-10). There is also an increase in lipoprotein lipase which allows the cells to utilize efficiently the fatty acids from lipoproteins in the medium (11-15). The differentiated 3T3-Ll cells acquire hormone receptors for insulin (7,(16)(17)(18), l3-adrenergic agonists, and adrenocorticotropic hormone (corticotropin) (19). The increase in levels ofthese enzymes and receptors, together with the accumulation ofstored triglycerides, strongly supports the conclusion of Green and coworkers that the 3T3-L1 cell can serve as a model for studies ofadipose tissue metabolism. However, thus far there is no evidence for the expression of the most characteristic and functionally important enzyme of adipose tissue-hormone-sensitive lipase, the neutral lipase activated by cyclic AMP (cAMP)-dependent protein kinase that controls rates of lipid mobilization (20)(21)(22)(23)(24)(25). This enzyme appears to be unique to the adipocyte. The only other tissue in which it has been reported is the adrenal (26, 27). Attempts in this laboratory to demonstrate it in rat heart, skeletal muscle, and liver under various conditions have been negative (unpublished results). Severson (28) reported negative results in rat heart. It has been shown that treatment with dibutyryl cAMP and epinephrine over a period of 2 weeks reduces the accumulation of lipid in 3T3-L1 cells (1), suggesting the presence of a hormone-sensitive lipase. However, the observed reduction in lipid accumulation could be due to inhibition ofthe biosynthesis offatty acid and triglyceride.The studies reported here demonstrate a striking increase (19-fold) in neutral triglyceride lipase during differentiation. Concurrently, basal rate of glycerol release increased by more than 1 order ofmagnitude and glycerol release was further stimulated 3-fold by isoproterenol. Finally, the neutral triglyceride lipase activity in differentiated cells was increased 2-fold by treatment with cAMP-dependent protein kinase. MATERIALS AND METHODSMaterials. Labeled triolein, diolein, and monoolein (containing [1-'4C]oleic acid distributed randomly among the acylated positions) and cholesteryl [1-'4C]oleate were purchased from Rosechem (Los Angeles, CA). Dulbecco's modified Eagle's medium, fetal calf serum, penicillin, and streptomycin were obtained from Irvine Scientific (Santa Ana, CA). MIX was from Aldrich, isoproterenol hydrochloride was from Br...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hormone-sensitive lipase in differentiated 3T3-L1 cells and its activation by cyclic AMP-dependent protein kinase.

Kawamura¹,

Jensen²,

Wancewicz³

et al. 1981

Proc. Natl. Acad. Sci. U.S.A.

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“…To date, dephosphorylation following exposure of cells to insulin has only been demonstrated directly in intact cells for fat cell triacylglycerol lipase (in the presence of noradrenaline) [ 127,128] and for fat cell pyruvate dehydrogenase [67]. We would like to suggest that the phosphorylation of the protein of subunit Mr 22,000 observed in insulin treated fat cells may turn out to play an important role in initiating the dephosphorylation of some cytoplasmic enzymes.…”

Section: Activation Of a Cyclic Nucleotide Independent Protein Kinasementioning

confidence: 94%

“…Detection of changes in the phosphorylation of a phosphoprotein (subunit Mr 85,000) which is most probably triacylglycerol lipase has been achieved by Belfrage and colleagues [127,128]. Due to the high specific activity of this enzyme, its concentration in fat cells is very low compared with many other phosphoproteins.…”

Section: Effects Of Insulin On Specific Protein Phosphorylation In Inmentioning

confidence: 99%

A partial view of the mechanism of insulin action

1981

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Insulin was discovered 60 years ago [1]; since then its structure has been determined by the pioneer work of Sanger [2] and by Hodgkin, Blundell and colleagues [3]. Moreover the principle effects of insulin on carbohydrate, fat and protein metabolism have been well recognised, at least ingeneral terms, for some 20 years [4][5][6][7], yet, we do not have a satisfactory description at the molecular level of how this hormone brings about its wide range of effects on target cells. This is certainly not due to any lack of attention to the problem by research workers. The literature on this subject is vast and, in the absence of any generally acceptable hypothesis, it also tends to be rather confused and certainly conflicting. Since it is quite unrealistic to survey the whole field, we make no apology for concentrating on certain aspects in this article.Insulin has both long and short term effects on the metabolism of its target cells. The long term effects involve changes in both general and specific protein synthesis and breakdown, while short term effects are those brought about solely through changes in the activity of pre-existing enzymes and membrane transporters. To a large extent, we will neglect all aspects of long term regulation including protein synthesis and amino acid metabolism. In fact, advances in these areas have been delayed by the lack of satisfactory preparations suitable for probing the mechanisms involved in the specific induction and repression of enzymes by insulin in vitro. This situation will probably change rapidly as a number of such preparations have been reported recently. Particularly promising are the 3T3-L1 preadipocyte cell line [8,9] and also the maintenance liver cell cultures from young rats in which glucokinase activity has been shown to be rapidly induced on exposure to insulin in the presence of glucose [10].In the rest of this review we will concentrate on those studies concerned with short term effects of insulin on carbohydrate and fat metabolism in the cells of liver, muscle and, particularly, adipose tissue. All these cells have specific insulin receptors on the outward face of the plasma membrane but we will not be considering the nature of these receptors nor their interaction with insulin nor the mechanisms which may govern the number of insulin receptors. These aspects have all been well covered in other recent reviews [11][12][13]. We shall address ourselves to the problem of the process or processes whereby alterations in the level of occupancy of the plasma membrane insulinreceptors lead to a wide range of intracellular changes. The assumption will be made that neither the whole insulin molecule nor part of it needsto enter the cells of its target tissue to bring about the effects of insulin. There seems little doubt that insulin bound to its receptor can be "internalized" into liver and probably other cells [14, 15], however, the process appears to be too slow to represent the means whereby insulin could bring about its short term effects. On the other hand, antibo...

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“…[83][84][85][86]. Hormone-sensitive lipase was identified as a substrate for PKA; phosphorylation of the protein modestly activates lipase activity (78,(87)(88)(89)(90)(91)(92). However, the observed 2-fold increase of in vitro lipase activity after the phosphorylation of hormone-sensitive lipase does not explain the 50-to 100-fold increase in lipolysis after activation of the b-adrenergic receptor-mediated signaling pathway in intact adipocytes (86).…”

Section: Cytosolic Lipases Hydrolyze Neutral Lipids Stored In Lipid Dmentioning

confidence: 99%

Thematic review series: Adipocyte Biology. The perilipin family of structural lipid droplet proteins: stabilization of lipid droplets and control of lipolysis

Brasaemle

2007

Journal of Lipid Research

881

784

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The majority of eukaryotic cells synthesize neutral lipids and package them into cytosolic lipid droplets. In vertebrates, triacylglycerol-rich lipid droplets of adipocytes provide a major energy storage depot for the body, whereas cholesteryl ester-rich droplets of many other cells provide building materials for local membrane synthesis and repair. These lipid droplets are coated with one or more of five members of the perilipin family of proteins: adipophilin, TIP47, OXPAT/MLDP, S3-12, and perilipin. Members of this family share varying levels of sequence similarity, lipid droplet association, and functions in stabilizing lipid droplets. The most highly studied member of the family, perilipin, is the most abundant protein on the surfaces of adipocyte lipid droplets, and the major substrate for cAMP-dependent protein kinase [protein kinase A (PKA)] in lipolytically stimulated adipocytes. Perilipin serves important functions in the regulation of basal and hormonally stimulated lipolysis. Under basal conditions, perilipin restricts the access of cytosolic lipases to lipid droplets and thus promotes triacylglycerol storage. In times of energy deficit, perilipin is phosphorylated by PKA and facilitates maximal lipolysis by hormonesensitive lipase and adipose triglyceride lipase. A model is discussed whereby perilipin serves as a dynamic scaffold to coordinate the access of enzymes to the lipid droplet in a manner that is responsive to the metabolic status of the adi- The ability to synthesize sterol esters or triacylglycerols and store these neutral lipids in cytoplasmic lipid droplets is a universal property of eukaryotes from yeast to humans. Although the presence of lipid droplets in cells and tissues had been noted in early observations of stained histological sections, the elucidation of the functions and composition of lipid droplets is a relatively recent development. Early hypotheses that lipid droplets provide a homeostatic mechanism to regulate intracellular lipid levels date back to studies in the 1970s in the laboratory of Michael S. Brown and Joseph L. Goldstein showing the esterification of cholesterol derived from the receptor-mediated uptake of low density lipoproteins and the depletion of cholesteryl ester stores after the withdrawal of lipoproteins from the culture medium of cells (1-3). Despite early speculation that cytosolic lipid droplets provide an important source of cholesterol for the maintenance, repair, and synthesis of membranes, very few studies throughout the 1970s and 1980s addressed the formation or dissolution of lipid droplets.The first hint that proteins coat the cytosolic surfaces of intracellular lipid droplets and play critical roles in regulating neutral lipid metabolism emerged with the discovery of perilipins on adipocyte lipid droplets in the laboratory of Constantine Londos in 1991 (4). Since the identification of perilipins, four additional lipid droplet proteins with sequence similarity to perilipins have been described in vertebrates, with two additional famil...

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Regulation of adipose tissue lipolysis: phosphorylation of hormone‐sensitive lipase in intact rat adipocytes

Cited by 80 publications

References 12 publications

Hormone-sensitive lipase in differentiated 3T3-L1 cells and its activation by cyclic AMP-dependent protein kinase.

Hormone-sensitive lipase in differentiated 3T3-L1 cells and its activation by cyclic AMP-dependent protein kinase.

A partial view of the mechanism of insulin action

Thematic review series: Adipocyte Biology. The perilipin family of structural lipid droplet proteins: stabilization of lipid droplets and control of lipolysis

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