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Constantine Londos - One of the best experts on this subject based on the ideXlab platform.
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Unique Regulation of Adipose Triglyceride Lipase (ATGL) by Perilipin 5, a Lipid Droplet-associated Protein
The Journal of biological chemistry, 2011Co-Authors: Hong Wang, Knut Tomas Dalen, Constantine Londos, Tomohiro Yamaguchi, Mark A Rizzo, Jun Liu, Ming Bell, Urmilla Sreenevasan, Rosalind A. ColemanAbstract:Lipolysis is a critical metabolic pathway contributing to energy homeostasis through degradation of triacylglycerides stored in lipid droplets (LDs), releasing fatty acids. Neutral lipid lipases act at the oil/water interface. In mammalian cells, LD surfaces are coated with one or more members of the Perilipin protein family, which serve important functions in regulating lipolysis. We investigated mechanisms by which three Perilipin proteins control lipolysis by adipocyte triglyceride lipase (ATGL), a key lipase in adipocytes and non-adipose cells. Using a cell culture model, we examined interactions of ATGL and its co-lipase CGI-58 with Perilipin 1 (Perilipin A), Perilipin 2 (adipose differentiation-related protein), and Perilipin 5 (LSDP5) using multiple techniques as follows: anisotropy Forster resonance energy transfer, co-immunoprecipitation, [32P]orthophosphate radiolabeling, and measurement of lipolysis. The results show that ATGL interacts with CGI-58 and Perilipin 5; the latter is selectively expressed in oxidative tissues. Both proteins independently recruited ATGL to the LD surface, but with opposite effects; interaction of ATGL with CGI-58 increased lipolysis, whereas interaction of ATGL with Perilipin 5 decreased lipolysis. In contrast, neither Perilipin 1 nor 2 interacted directly with ATGL. Activation of protein kinase A (PKA) increased [32P]orthophosphate incorporation into Perilipin 5 by 2-fold, whereas neither ATGL nor CGI-58 was labeled under the incubation conditions. Cells expressing both ectopic Perilipin 5 and ATGL showed a 3-fold increase in lipolysis following activation of PKA. Our studies establish Perilipin 5 as a novel ATGL partner and provide evidence that the protein composition of Perilipins at the LD surface regulates lipolytic activity of ATGL.
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activation of hormone sensitive lipase requires two steps protein phosphorylation and binding to the pat 1 domain of lipid droplet coat proteins
Journal of Biological Chemistry, 2009Co-Authors: Hong Wang, Amy Marcinkiewicz, Knut Tomas Dalen, Heidi Dorward, Deanna L Russell, Dawei Gong, Constantine Londos, Tomohiro Yamaguchi, Cecilia Holm, Mark A RizzoAbstract:Lipolysis is an important metabolic pathway controlling energy homeostasis through degradation of triglycerides stored in lipid droplets and release of fatty acids. Lipid droplets of mammalian cells are coated with one or more members of the PAT protein family, which serve important functions in regulating lipolysis. In this study, we investigate the mechanisms by which PAT family members, Perilipin A, adipose differentiation-related protein (ADFP), and LSDP5, control lipolysis catalyzed by hormone-sensitive lipase (HSL), a major lipase in adipocytes and several non-adipose cells. We applied fluorescence microscopic tools to analyze proteins in situ in cultured Chinese hamster ovary cells using fluorescence recovery after photobleaching and anisotropy Forster resonance energy transfer. Fluorescence recovery after photobleaching data show that ADFP and LSDP5 exchange between lipid droplet and cytoplasmic pools, whereas Perilipin A does not. Differences in protein mobility do not correlate with PAT protein-mediated control of lipolysis catalyzed by HSL or endogenous lipases. Forster resonance energy transfer and co-immunoprecipitation experiments reveal that each of the three PAT proteins bind HSL through interaction of the lipase with amino acids within the highly conserved amino-terminal PAT-1 domain. ADFP and LSDP5 bind HSL under basal conditions, whereas phosphorylation of serine residues within three amino-terminal protein kinase A consensus sequences of Perilipin A is required for HSL binding and maximal lipolysis. Finally, protein kinase A-mediated phosphorylation of HSL increases lipolysis in cells expressing ADFP or LSDP5; in contrast, phosphorylation of Perilipin A exerts the major control over HSL-mediated lipolysis when Perilipin is the main lipid droplet protein.
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degradation of Perilipin is mediated through ubiquitination proteasome pathway
Biochimica et Biophysica Acta, 2006Co-Authors: Carole Sztalryd, Constantine LondosAbstract:Perilipin protein coats the surface of intracellular lipid droplets and plays fundamental roles in lipid droplet formation and triacylglycerol hydrolysis. Perilipin is transcriptionally regulated through peroxisome proliferator-activated receptor and post-translationally stabilized by stored intracellular neutral lipids. In this study, we show that Perilipin protein accumulates in transfected Chinese hamster ovary cells cultured in the presence of fatty acids but in turn is destabilized when lipid precursors for triacylglycerol synthesis are removed from culture serum. Adding fatty acids in the culture medium prevents the degradation of Perilipin. Moreover, specific proteasome inhibitors, MG132, lactacystin, and ALLN, block the degradation, whereas inhibitors of other proteases are ineffective. Pulse-chase experiments confirm that Perilipin is degraded through proteasome, a process that is inhibited by MG132 or ALLN and blunted by the addition of oleic acid. We have detected the co-immunoprecipitation of Perilipin and ubiquitin, thus confirming that Perilipin is conjugated to poly-ubiquitin and targeted for proteasomal degradation. Treatment with MG132 increases the expression of Perilipin associated with lipid droplets as well as modestly throughout the cytosol. We conclude that the degradation of Perilipin is mediated through an ubiquitination-proteasome pathway, which suggests another mode for the post-translational regulation of Perilipin.
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the central role of Perilipin a in lipid metabolism and adipocyte lipolysis
Iubmb Life, 2004Co-Authors: John T Tansey, Carole Sztalryd, Alan R Kimmel, Erica M Hlavin, Constantine LondosAbstract:The related disorders of obesity and diabetes are increasing to epidemic proportions. The role of neutral lipid storage and hydrolysis, and hence the adipocyte, is central to understanding this phenomenon. The adipocyte holds the major source of stored energy in the body in the form of triacylglycerols (TAG). It has been known for over 35 years that the breakdown of TAG and release of free (unesterified) fatty acids and glycerol from fat tissue can be regulated by a cAMP-mediated process. However, beyond the initial signaling cascade, the mechanistic details of this lipolytic reaction have remained unclear. Work in recent years has revealed that both hormone-sensitive lipase (HSL), generally thought to be the rate-limiting enzyme, and Perilipin, a lipid droplet surface protein, are required for optimal lipid storage and fatty acid release. There are multiple Perilipin proteins encoded by mRNA splice variants of a single Perilipin gene. The Perilipin proteins are polyphosphorylated by protein kinase A and phosphorylation is necessary for translocation of HSL to the lipid droplet and enhanced lipolysis. Hence, the surface of the lipid storage droplet has emerged as a central site of regulation of lipolysis. This review will focus on adipocyte lipolysis with emphasis on hormone signal transduction, lipolytic enzymes, the lipid storage droplet, and fatty acid release from the adipocyte. IUBMB Life, 56: 379-385, 2004
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the central role of Perilipin a in lipid metabolism and adipocyte lipolysis
Iubmb Life, 2004Co-Authors: John T Tansey, Carole Sztalryd, Alan R Kimmel, Erica M Hlavin, Constantine LondosAbstract:The related disorders of obesity and diabetes are increasing to epidemic proportions. The role of neutral lipid storage and hydrolysis, and hence the adipocyte, is central to understanding this phenomenon. The adipocyte holds the major source of stored energy in the body in the form of triacylglycerols (TAG). It has been known for over 35 years that the breakdown of TAG and release of free (unesterified) fatty acids and glycerol from fat tissue can be regulated by a cAMP-mediated process. However, beyond the initial signaling cascade, the mechanistic details of this lipolytic reaction have remained unclear. Work in recent years has revealed that both hormone-sensitive lipase (HSL), generally thought to be the rate-limiting enzyme, and Perilipin, a lipid droplet surface protein, are required for optimal lipid storage and fatty acid release. There are multiple Perilipin proteins encoded by mRNA splice variants of a single Perilipin gene. The Perilipin proteins are polyphosphorylated by protein kinase A and phosphorylation is necessary for translocation of HSL to the lipid droplet and enhanced lipolysis. Hence, the surface of the lipid storage droplet has emerged as a central site of regulation of lipolysis. This review will focus on adipocyte lipolysis with emphasis on hormone signal transduction, lipolytic enzymes, the lipid storage droplet, and fatty acid release from the adipocyte.
Dawn L Brasaemle - One of the best experts on this subject based on the ideXlab platform.
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Perilipin a and the control of triacylglycerol metabolism
Molecular and Cellular Biochemistry, 2009Co-Authors: Dawn L Brasaemle, Vidya Subramanian, Anne Garcia, Amy Marcinkiewicz, Alexis RothenbergAbstract:Perilipin A is the most abundant protein associated with the lipid droplets of adipocytes and functions to control both basal and stimulated lipolysis. Under basal or fed conditions, Perilipin A shields stored triacylglycerols from cytosolic lipases, thus promoting triacylglycerol storage. When catecholamines bind to cell surface receptors to initiate signals that activate cAMP-dependent protein kinase (PKA), phosphorylated Perilipin A facilitates maximal lipolysis. Mutagenesis studies have revealed that central sequences of moderately hydrophobic amino acids are required to target nascent Perilipin A to lipid droplets and provide an anchor into the hydrophobic environment of lipid droplets. Sequences of amino acids in the unique carboxyl terminus of Perilipin A and those in amino terminal sequences flanking the first hydrophobic stretch are required for the barrier function of Perilipin A in promoting triacylglycerol storage. Site-directed mutagenesis studies of serine residues within six PKA consensus sites of Perilipin A reveal functions for phosphorylation of at least three of the sites. Phosphorylation of one or more of the serines within three amino terminal PKA sites is required to facilitate hormone-sensitive lipase access to lipid substrates. Phosphorylation of serines within two carboxyl terminal sites is also required for maximal lipolysis. Phosphorylation of serine 492 (site 5) triggers a massive remodeling of lipid droplets, whereby large peri-nuclear lipid droplets fragment into myriad lipid micro-droplets that scatter throughout the cytoplasm. We hypothesize that Perilipin A binds accessory proteins to provide assistance in carrying out these functions.
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Thematic review series: adipocyte biology. The Perilipin family of structural lipid droplet proteins: stabilization of lipid droplets and control of lipolysis.
Journal of lipid research, 2007Co-Authors: Dawn L BrasaemleAbstract: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 hormone-sensitive 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 adipocyte.
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the phosphorylation of serine 492 of Perilipin a directs lipid droplet fragmentation and dispersion
Journal of Biological Chemistry, 2006Co-Authors: Amy Marcinkiewicz, Anne Garcia, Denise Gauthier, Dawn L BrasaemleAbstract:Perilipin A is a key regulator of triacylglycerol storage and hydrolysis in adipocytes; phosphorylation of Perilipin A by protein kinase A facilitates maximal lipolysis. Chronic stimulation of lipolysis in 3T3-L1 adipocytes causes large perinuclear lipid droplets to fragment into myriad dispersed Perilipin A-covered microlipid droplets. In cultured fibroblasts stably expressing ectopic Perilipin A, clustered lipid droplets disperse throughout the cytoplasm upon incubation of the cells with forskolin and isobutylmethylxanthine (IBMX) to elevate levels of cAMP and activate protein kinase A, mirroring events observed in adipocytes. Furthermore, diethylum-belliferyl phosphate inhibits stimulated lipolysis but not the dispersion of lipid droplets, suggesting that products of lipolysis are not required for this remodeling process. We hypothesized that protein kinase A-mediated phosphorylation of Perilipin A triggers the remodeling of lipid droplets. The mutation of serine 492 of Perilipin A to alanine prevented the dispersion of clustered lipid droplets in fibroblasts stably expressing the mutated Perilipin upon incubation with forskolin and IBMX. In contrast, the substitution of serines 81, 222, 276, or 433 with alanine, either singly or in combinations, did not affect the protein kinase A-mediated remodeling of lipid droplets. Interestingly, substitution of serines 433, 492, and 517 of Perilipin A with glutamic acid residues blocked the dispersion of clustered lipid droplets in cells incubated with forskolin and IBMX, indicating that the addition of a negative charge does not mimic a phosphate group. We conclude that protein kinase A-mediated phosphorylation of serine 492 of Perilipin A drives the fragmentation and dispersion of lipid droplets.
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proteomic analysis of proteins associated with lipid droplets of basal and lipolytically stimulated 3t3 l1 adipocytes
Journal of Biological Chemistry, 2004Co-Authors: Dawn L Brasaemle, Lawrence Shapiro, Georgia Dolios, Rong WangAbstract:Abstract Adipocytes hold the body's major energy reserve as triacylglycerols packaged in large lipid droplets. Perilipins, the most abundant proteins on these lipid droplets, play a critical role in facilitating both triacylglycerol storage and hydrolysis. The stimulation of lipolysis by β-adrenergic agonists triggers rapid phosphorylation of Perilipin and translocation of hormone-sensitive lipase to the surfaces of lipid droplets and more gradual fragmentation and dispersion of micro-lipid droplets. Because few lipid droplet-associated proteins have been identified in adipocytes, we isolated lipid droplets from basal and lipolytically stimulated 3T3-L1 adipocytes and identified the component proteins by mass spectrometry. Structural proteins identified in both preparations include Perilipin, S3-12, vimentin, and TIP47; in contrast, adipophilin, caveolin-1, and tubulin selectively localized to droplets in lipolytically stimulated cells. Lipid metabolic enzymes identified in both preparations include hormone-sensitive lipase, lanosterol synthase, NAD(P)-dependent steroid dehydrogenase-like protein, acyl-CoA synthetase, long chain family member (ACSL) 1, and CGI-58. 17-β-Hydroxysteroid dehydrogenase, type 7, was identified only in basal preparations, whereas ACSL3 and 4 and two short-chain reductase/dehydrogenases were identified on droplets from lipolytically stimulated cells. Additionally, both preparations contained FSP27, ribophorin I, EHD2, diaphorase I, and ancient ubiquitous protein. Basal preparations contained CGI-49, whereas lipid droplets from lipolytically stimulated cells contained several Rab GTPases and tumor protein D54. A close association of mitochondria with lipid droplets was suggested by the identification of pyruvate carboxylase, prohibitin, and a subunit of ATP synthase in the preparations. Thus, adipocyte lipid droplets contain specific structural proteins as well as lipid metabolic enzymes; the structural reorganization of lipid droplets in response to the hormonal stimulation of lipolysis is accompanied by increases in the relative mass of several proteins and the recruitment of additional proteins.
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hydrophobic sequences target and anchor Perilipin a to lipid droplets
Journal of Lipid Research, 2004Co-Authors: Vidya Subramanian, Anne Garcia, Anna Sekowski, Dawn L BrasaemleAbstract:Perilipins regulate triacylglycerol storage and hydrolysis in adipocytes. The central 25% of the Perilipin A sequence, including three hydrophobic sequences (H1, H2, and H3) and an acidic region, targets and anchors Perilipins to lipid droplets. Thus, we hypothesized that H1, H2, and H3 are targeting and anchoring motifs. We now show that deletion of any single hydrophobic sequence or combinations of H1 and H3 or H2 and H3 does not prevent targeting of the mutated Perilipin to lipid droplets. In contrast, mutated Perilipin lacking H1 and H2 showed reduced targeting, whereas Perilipin lacking H1, H2, and H3 targeted poorly to lipid droplets; thus, H3 is a weak targeting signal and either H1 or H2 is required for optimal targeting. Complete elimination of Perilipin targeting was observed only when all three hydrophobic sequences were deleted in combination with either the acidic region or N-terminal sequences predicted to form amphipathic beta-strands. Unlike intact Perilipin A, mutated Perilipin lacking either H1 and H2 or H1, H2, and H3 was released from lipid droplets after alkaline carbonate treatment, suggesting that these forms are loosely associated with lipid droplets. The three hydrophobic sequences play a major role in targeting and anchoring Perilipins to lipid droplets.
Alan R Kimmel - One of the best experts on this subject based on the ideXlab platform.
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the Perilipins major cytosolic lipid droplet associated proteins and their roles in cellular lipid storage mobilization and systemic homeostasis
Annual Review of Nutrition, 2016Co-Authors: Alan R Kimmel, Carole SztalrydAbstract:The discovery by Dr. Constantine Londos of Perilipin 1, the major scaffold protein at the surface of cytosolic lipid droplets in adipocytes, marked a fundamental conceptual change in the understanding of lipolytic regulation. Focus then shifted from the enzymatic activation of lipases to substrate accessibility, mediated by Perilipin-dependent protein sequestration and recruitment. Consequently, the lipid droplet became recognized as a unique, metabolically active cellular organelle and its surface as the active site for novel protein-protein interactions. A new area of investigation emerged, centered on lipid droplets' biology and their role in energy homeostasis. The Perilipin family is of ancient origin and has expanded to include five mammalian genes and a growing list of evolutionarily conserved members. Universally, the Perilipins modulate cellular lipid storage. This review provides a summary that connects the Perilipins to both cellular and whole-body homeostasis.
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Perilipins lipid droplet coat proteins adapted for tissue specific energy storage and utilization and lipid cytoprotection
Biochimie, 2014Co-Authors: Carole Sztalryd, Alan R KimmelAbstract:Cytosolic lipid storage droplets are primary functional organelles that regulate cellular lipid metabolism and homeostasis. Paradoxically, excess lipid stores are linked to both adaptive (fasting and chronic exercise) and mal-adaptive (obesity and related health complications) conditions. Thus, collective metabolic and physiological processes must balance lipid storage and utilization with prevention of lipocytotoxicity and compounding tissue dysfunctions, urging the need to further define the connection of mammalian lipid droplet function and lipid homeostasis. The Perilipins are a multi-protein family that targets lipid droplet surfaces and regulates lipid storage and hydrolysis. Study of Perilipin functions has provided insight into the physiological roles of cytosolic lipid droplets and their relationship with obesity-related pathologies. Here, we review the current knowledge of the multiple Perilipin proteins in regulating tissue-specific lipid droplets and associations with tissue and systemic energetics.
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Perilipin is present in islets of langerhans and protects against lipotoxicity when overexpressed in the beta cell line ins 1
Endocrinology, 2009Co-Authors: Jorgen Borg, Guoheng Xu, Cecilia Klint, Nils Wierup, Kristoffer Strom, Sara Larsson, F Sundler, R Lupi, Piero Marchetti, Alan R KimmelAbstract:Lipids have been shown to play a dual role in pancreatic β-cells: a lipid-derived signal appears to be necessary for glucose-stimulated insulin secretion, whereas lipid accumulation causes impaired insulin secretion and apoptosis. The ability of the protein Perilipin to regulate lipolysis prompted an investigation of the presence of Perilipin in the islets of Langerhans. In this study evidence is presented for Perilipin expression in rat, mouse, and human islets of Langerhans as well as the rat clonal β-cell line INS-1. In rat and mouse islets, Perilipin was verified to be present in β-cells. To examine whether the development of lipotoxicity could be prevented by manipulating the conditions for lipid storage in the β-cell, INS-1 cells with adenoviral-mediated overexpression of Perilipin were exposed to lipotoxic conditions for 72 h. In cells exposed to palmitate, Perilipin overexpression caused increased accumulation of triacylglycerols and decreased lipolysis compared with control cells. Whereas glucose-stimulated insulin secretion was retained after palmitate exposure in cells overexpressing Perilipin, it was completely abolished in control β-cells. Thus, overexpression of Perilipin appears to confer protection against the development of β-cell dysfunction after prolonged exposure to palmitate by promoting lipid storage and limiting lipolysis.
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structure of a lipid droplet protein the pat family member tip47
Structure, 2004Co-Authors: Sabrina J Hickenbottom, Alan R Kimmel, Constantine Londos, James H HurleyAbstract:Abstract The p erilipin/ A DRP/ T IP47 (PAT) proteins localize to the surface of intracellular neutral lipid droplets. Perilipin is essential for lipid storage and hormone regulated lipolysis in adipocytes, and Perilipin null mice exhibit a dramatic reduction in adipocyte lipid stores. A significant fraction of the ∼200 amino acid N-terminal region of the PAT proteins consists of 11-mer helical repeats that are also found in apolipoproteins and other lipid-associated proteins. The C-terminal 60% of TIP47, a representative PAT protein, comprises a monomeric and independently folded unit. The crystal structure of the C-terminal portion of TIP47 was determined and refined at 2.8 A resolution. The structure consists of an α/β domain of novel topology and a four-helix bundle resembling the LDL receptor binding domain of apolipoprotein E. The structure suggests an analogy between PAT proteins and apolipoproteins in which helical repeats interact with lipid while the ordered C-terminal region is involved in protein:protein interactions.
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the central role of Perilipin a in lipid metabolism and adipocyte lipolysis
Iubmb Life, 2004Co-Authors: John T Tansey, Carole Sztalryd, Alan R Kimmel, Erica M Hlavin, Constantine LondosAbstract:The related disorders of obesity and diabetes are increasing to epidemic proportions. The role of neutral lipid storage and hydrolysis, and hence the adipocyte, is central to understanding this phenomenon. The adipocyte holds the major source of stored energy in the body in the form of triacylglycerols (TAG). It has been known for over 35 years that the breakdown of TAG and release of free (unesterified) fatty acids and glycerol from fat tissue can be regulated by a cAMP-mediated process. However, beyond the initial signaling cascade, the mechanistic details of this lipolytic reaction have remained unclear. Work in recent years has revealed that both hormone-sensitive lipase (HSL), generally thought to be the rate-limiting enzyme, and Perilipin, a lipid droplet surface protein, are required for optimal lipid storage and fatty acid release. There are multiple Perilipin proteins encoded by mRNA splice variants of a single Perilipin gene. The Perilipin proteins are polyphosphorylated by protein kinase A and phosphorylation is necessary for translocation of HSL to the lipid droplet and enhanced lipolysis. Hence, the surface of the lipid storage droplet has emerged as a central site of regulation of lipolysis. This review will focus on adipocyte lipolysis with emphasis on hormone signal transduction, lipolytic enzymes, the lipid storage droplet, and fatty acid release from the adipocyte. IUBMB Life, 56: 379-385, 2004
Andrew S Greenberg - One of the best experts on this subject based on the ideXlab platform.
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regulation of adipocyte lipolysis by degradation of the Perilipin protein nelfinavir enhances lysosome mediated Perilipin proteolysis
Journal of Biological Chemistry, 2007Co-Authors: Julia Kovsan, Sandra C Souza, Andrew S Greenberg, Ronit Benromano, Assaf RudichAbstract:A decrease in the lipid droplet-associated protein Perilipin may constitute a mechanism for enhanced adipocyte lipolysis under nonstimulated (basal) conditions, and increased basal lipolysis has been linked to whole body metabolic dysregulation. Here we investigated whether the lipolytic actions of the human immunodeficiency virus protease inhibitor, nelfinavir, are mediated by decreased Perilipin protein content and studied the mechanisms by which it occurs. Time course analysis revealed that the decrease in Perilipin protein content preceded the increase in lipolysis. A causative relationship was suggested by demonstrating that nelfinavir potently increased lipolysis in adipocytes derived from mouse embryonal fibroblasts expressing Perilipin but not in mouse embryonal fibroblast adipocytes devoid of Perilipin and that adenoviral mediated overexpression of Perilipin in 3T3-L1 adipocytes blocked the lipolytic actions of nelfinavir. Nelfinavir did not alter mRNA content of Perilipin but rather decreased Perilipin proteins t((1/2)) from >70 to 12 h. Protein degradation of Perilipin in both control and nelfinavir-treated adipocytes could be prevented by inhibiting lysosomal proteolysis using leupeptin or NH(4)Cl but not by the proteasome inhibitor MG-132. We propose that proteolysis of Perilipin involving the lysosomal protein degradation machinery may constitute a novel mechanism for enhancing adipocyte lipolysis.
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dynamics of lipid droplet associated proteins during hormonally stimulated lipolysis in engineered adipocytes stabilization and lipid droplet binding of adipocyte differentiation related protein adipophilin
Molecular Endocrinology, 2006Co-Authors: Danielle N Gross, Sandra C Souza, Andrew S Greenberg, Hideaki Miyoshi, Hui Hong Zhang, Martin S Obin, Toshio Hosaka, Elizabeth C Pino, Paul F PilchAbstract:In mature adipocytes, triglyceride is stored within lipid droplets, which are coated with the protein Perilipin, which functions to regulate lipolysis by controlling lipase access to the droplet in a hormone-regulatable fashion. Adipocyte differentiation-related protein (ADRP) is a widely expressed lipid droplet binding protein that is coexpressed with Perilipin in differentiating fat cells but is minimally present in fully differentiated cultured adipocytes. We find that fibroblasts ectopically expressing C/EBPalpha (NIH-C/EBPalpha cells) differentiate into mature adipocytes that simultaneously express Perilipin and ADRP. In response to isoproterenol, Perilipin is hyperphosphorylated, lipolysis is enhanced, and subsequently, ADRP expression increases coincident with it surrounding intracellular lipid droplets. In the absence of lipolytic stimulation, inhibition of proteasomal activity with MG-132 increased ADRP levels to those of cells treated with 10 mum isoproterenol, but ADRP does not surround the lipid droplet in the absence of lipolytic stimulation. We overexpressed a Perilipin A construct in NIH-C/EBPalpha cells where the six serine residues known to be phosphorylated by protein kinase A were changed to alanine (Peri A Delta1-6). These cells show no increase in ADRP expression in response to isoproterenol. We propose that ADRP can replace Perilipin on existing lipid droplets or those newly formed as a result of fatty acid reesterification, under dynamic conditions of hormonally stimulated lipolysis, thus preserving lipid droplet morphology/structure.
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obese subjects carrying the 11482g a polymorphism at the Perilipin locus are resistant to weight loss after dietary energy restriction
The Journal of Clinical Endocrinology and Metabolism, 2005Co-Authors: Dolores Corella, Andrew S Greenberg, Jose V Sorli, D Godoy, Olga Portoles, Oscar Coltell, Jose M. OrdovasAbstract:Context: Dietary treatment of obesity could be improved if predictive information about the individual’s genetic response to diet was available. Adipose tissue has been the focus of efforts to identify candidate genes. Perilipin is a major protein found in adipocytes, and Perilipin knockout mice are lean and resistant to diet-induced obesity. Objective: The objective of the study was to examine the association of several polymorphisms at the Perilipin (PLIN) locus with obesity and weight reduction in response to a low-energy diet in obese patients. Design: This study was a 1-yr randomized (depending on the PLIN genotype) trial with three follow-up evaluations. Setting: The study was conducted at a university research center. Subjects: One hundred fifty obese patients (body mass index, 42 ± 8 kg/m2) at baseline and 48 patients who completed the dietary follow-up treatment for weight loss participated in the study. Interventions: Subjects completed a 1-yr low-energy diet. Main Outcomes Measurements: Body we...
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lipase selective functional domains of Perilipin a differentially regulate constitutive and protein kinase a stimulated lipolysis
Journal of Biological Chemistry, 2003Co-Authors: Hui H Zhang, Sandra C Souza, Fredric B Kraemer, Martin S Obin, Kizito V Muliro, Andrew S GreenbergAbstract:Perilipin (Peri) A is a lipid droplet-associated phosphoprotein that acts dually as a suppressor of basal (constitutive) lipolysis and as an enhancer of cyclic AMP-dependent protein kinase (PKA)-stimulated lipolysis by both hormone-sensitive lipase (HSL) and non-HSL(s). To identify domains of Peri A that mediate these multiple actions, we introduced adenoviruses expressing truncated or mutated Peri A and HSL into NIH 3T3 fibroblasts lacking endogenous Perilipins and HSL but overexpressing acyl-CoA synthetase 1 and fatty acid transporter 1. We identified two lipase-selective functional domains: 1) Peri A (amino acids 1-300), which inhibits basal lipolysis and promotes PKA-stimulated lipolysis by HSL, and 2) Peri A (amino acids 301-517), which inhibits basal lipolysis by non-HSL and promotes PKA-stimulated lipolysis by both HSL and non-HSL. PKA site mutagenesis revealed that PKA-stimulated lipolysis by HSL requires phosphorylation of one or more sites within Peri 1-300 (Ser81, Ser222, and Ser276). PKA-stimulated lipolysis by non-HSL additionally requires phosphorylation of one or more PKA sites within Peri 301-517 (Ser433, Ser492, and Ser517). Peri 301-517 promoted PKA-stimulated lipolysis by HSL yet did not block HSL-mediated basal lipolysis, indicating that an additional region(s) within Peri 301-517 promotes hormone-stimulated lipolysis by HSL. These results suggest a model of Peri A function in which 1) lipase-specific "barrier" domains block basal lipolysis by HSL and non-HSL, 2) differential PKA site phosphorylation allows PKA-stimulated lipolysis by HSL and non-HSL, respectively, and 3) additional domains within Peri A further facilitate PKA-stimulated lipolysis, again with lipase selectivity.
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Perilipin expression in human adipose tissues effects of severe obesity gender and depot
Obesity Research, 2003Co-Authors: Yanxin Wang, Andrew S Greenberg, Sean Sullivan, Maria E Trujillo, Mijeong Lee, Stephen H Schneider, Robert E Brolin, You Hou Kang, Yaron Werber, Susan K FriedAbstract:Objective: Perilipins are phosphoproteins that are localized to the surface of triacylglycerol droplets within adipocytes where they regulate the rate of lipolysis. We sought to determine the effects of severe obesity and depot [omental (Om) vs. subcutaneous (Sc)] on Perilipin expression in the adipose tissue of individuals. Research Methods and Procedures: Samples of Om and Sc adipose tissues obtained at surgery from severely obese subjects and fat aspirations from nonobese subjects were analyzed for Perilipin protein and mRNA levels by Northern and Western analysis. Results: Perilipin A (periA) was the major Perilipin expressed in adipose tissues. periA mRNA relative abundance was significantly lower in Sc adipose tissue from severely obese compared to that from nonobese subjects. Western blotting of adipose tissue extracts showed that periA protein levels expressed relative to tissue protein or fat cell surface area were significantly lower (∼ −40%) in abdominal Sc adipose tissue from severely obese compared to that from nonobese subjects. However, the calculated mass of Perilipin per fat cell did not differ between the two groups. Perilipin mRNA levels were higher in Sc compared to Om adipose tissue from obese individuals (p < 0.025; n = 26; 17 women, 9 men); however, periA protein levels did not differ. In addition, Perilipin protein, but not mRNA, levels were higher in Sc adipose tissue from obese men than from women (p < 0.025). Discussion: Variations in Perilipin expression may contribute to the higher basal lipolytic rates observed in obese compared to nonobese individuals and in obese women compared to obese men.
Carole Sztalryd - One of the best experts on this subject based on the ideXlab platform.
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The Perilipin family of lipid droplet proteins: Gatekeepers of intracellular lipolysis.
Biochimica et biophysica acta. Molecular and cell biology of lipids, 2017Co-Authors: Carole SztalrydAbstract:Lipid droplets in chordates are decorated by two or more members of the Perilipin family of lipid droplet surface proteins. The Perilipins sequester lipids by protecting lipid droplets from lipase action. Their relative expression and protective nature is adapted to the balance of lipid storage and utilization in specific cells. Most cells of the body have tiny lipid droplets with Perilipins 2 and 3 at the surfaces, whereas specialized fat-storing cells with larger lipid droplets also express Perilipins 1, 4, and/or 5. Perilipins 1, 2, and 5 modulate lipolysis by controlling the access of lipases and co-factors of lipases to substrate lipids stored within lipid droplets. Although Perilipin 2 is relatively permissive to lipolysis, Perilipins 1 and 5 have distinct control mechanisms that are altered by phosphorylation. Here we evaluate recent progress toward understanding functions of the Perilipins with a focus on their role in regulating lipolysis and autophagy. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.
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the Perilipins major cytosolic lipid droplet associated proteins and their roles in cellular lipid storage mobilization and systemic homeostasis
Annual Review of Nutrition, 2016Co-Authors: Alan R Kimmel, Carole SztalrydAbstract:The discovery by Dr. Constantine Londos of Perilipin 1, the major scaffold protein at the surface of cytosolic lipid droplets in adipocytes, marked a fundamental conceptual change in the understanding of lipolytic regulation. Focus then shifted from the enzymatic activation of lipases to substrate accessibility, mediated by Perilipin-dependent protein sequestration and recruitment. Consequently, the lipid droplet became recognized as a unique, metabolically active cellular organelle and its surface as the active site for novel protein-protein interactions. A new area of investigation emerged, centered on lipid droplets' biology and their role in energy homeostasis. The Perilipin family is of ancient origin and has expanded to include five mammalian genes and a growing list of evolutionarily conserved members. Universally, the Perilipins modulate cellular lipid storage. This review provides a summary that connects the Perilipins to both cellular and whole-body homeostasis.
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Perilipins lipid droplet coat proteins adapted for tissue specific energy storage and utilization and lipid cytoprotection
Biochimie, 2014Co-Authors: Carole Sztalryd, Alan R KimmelAbstract:Cytosolic lipid storage droplets are primary functional organelles that regulate cellular lipid metabolism and homeostasis. Paradoxically, excess lipid stores are linked to both adaptive (fasting and chronic exercise) and mal-adaptive (obesity and related health complications) conditions. Thus, collective metabolic and physiological processes must balance lipid storage and utilization with prevention of lipocytotoxicity and compounding tissue dysfunctions, urging the need to further define the connection of mammalian lipid droplet function and lipid homeostasis. The Perilipins are a multi-protein family that targets lipid droplet surfaces and regulates lipid storage and hydrolysis. Study of Perilipin functions has provided insight into the physiological roles of cytosolic lipid droplets and their relationship with obesity-related pathologies. Here, we review the current knowledge of the multiple Perilipin proteins in regulating tissue-specific lipid droplets and associations with tissue and systemic energetics.
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Perilipin 5 a lipid droplet associated protein provides physical and metabolic linkage to mitochondria
Journal of Lipid Research, 2011Co-Authors: Hong Wang, Dawei Gong, Urmilla Sreenivasan, Andrew Saladino, Brian M Polster, Linda M Lund, William C Stanley, Carole SztalrydAbstract:Maintaining cellular lipid homeostasis is crucial to oxidative tissues, and it becomes compromised in obesity. Lipid droplets (LD) play a central role in lipid homeostasis by mediating fatty acid (FA) storage in the form of triglyceride, thereby lowering intracellular levels of lipids that mediate cellular lipotoxicity. LDs and mitochondria have interconnected functions, and anecdotal evidence suggests they physically interact. However, the mechanisms of interaction have not been identified. Perilipins are LD-scaffolding proteins and potential candidates to play a role in their interaction with mitochondria. We examined the contribution of LD Perilipin composition to the physical and metabolic interactions between LD and mitochondria using multiple techniques: confocal imaging, electron microscopy (EM), and lipid storage and utilization measurements. Using neonatal cardiomyocytes, reconstituted cell culture models, and rodent heart tissues, we found that Perilipin 5 (Plin5) recruits mitochondria to the LD surface through a C-terminal region. Compared with control cells, Plin5-expressing cells show decreased LD hydrolysis, decreased palmitate β-oxidation, and increased palmitate incorporation into triglycerides in basal conditions, whereas in stimulated conditions, LD hydrolysis inhibition is lifted and FA released for β-oxidation. These results suggest that Plin5 regulates oxidative LD hydrolysis and controls local FA flux to protect mitochondria against excessive exposure to FA during physiological stress.
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oxidative tissue Perilipin 5 links storage with the furnace
Trends in Endocrinology and Metabolism, 2011Co-Authors: Hong Wang, Carole SztalrydAbstract:Cellular energy homeostasis is a crucial function of oxidative tissues and is altered in obesity, a continuously rising health problem. Lipid droplets (LD) are thought to play a central role in lipid homeostasis by mediating the transient storage of fatty acids in the form of triglyceride, while preventing high levels of toxic lipid intermediates or oxidized lipids that mediate cellular lipotoxicity. Members of the Perilipin protein family coating LD surfaces have been found to serve important regulatory and structural functions crucial to the regulation of lipid stores. This review examines the results of studies on one of the newest members of the Perilipin family, Perilipin 5, which has emerged as a putative key player in LD function in oxidative tissues.