Analysis of Lipolytic Protein Trafficking and Interactions in Adipocytes

This work examined the colocalization, trafficking, and interactions of key proteins involved in lipolysis during brief cAMP-dependent protein kinase A (PKA) activation. Double label immunofluorescence analysis of 3T3-L1 adipocytes indicated that PKA activation increases the translocation of hormonesensitive lipase (HSL) to perilipin A (Plin)-containing droplets and increases the colocalization of adipose tissue triglyceride lipase (Atgl) with its coactivator, Abhd5. Imaging of live 3T3-L1 preadipocytes transfected with Aquorea victoria-based fluorescent reporters demonstrated that HSL rapidly and specifically translocates to lipid droplets (LDs) containing Plin, and that this translocation is partially dependent on Plin phosphorylation. HSL closely, if not directly, interacts with Plin, as indicated by fluorescence resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) experiments. In contrast, tagged Atgl did not support FRET or BiFC with Plin, although it did modestly translocate to LDs upon stimulation. Abhd5 strongly interacted with Plin in the basal state, as indicated by FRET and BiFC. PKA activation rapidly (within minutes) decreased FRET between Abhd5 and Plin, and this decrease depended upon Plin phosphorylation. Together, these results indicate that Plin mediates hormone-stimulated lipolysis via direct and indirect mechanisms. Plin indirectly controls Atgl activity by regulating accessibility to its coactivator, Abhd5. In contrast, Plin directly regulates the access of HSL to substrate via close, if not direct, interactions. The differential interactions of HSL and Atgl with Plin and Abhd5 also explain the findings that following stimulation, HSL and Atgl are differentially enriched at specific LDs. This work examined the colocalization, trafficking, and interactions of key proteins involved in lipolysis during brief cAMP-dependent protein kinase A (PKA) activation. Double label immunofluorescence analysis of 3T3-L1 adipocytes indicated that PKA activation increases the translocation of hormonesensitive lipase (HSL) to perilipin A (Plin)-containing droplets and increases the colocalization of adipose tissue triglyceride lipase (Atgl) with its coactivator, Abhd5. Imaging of live 3T3-L1 preadipocytes transfected with Aquorea victoria-based fluorescent reporters demonstrated that HSL rapidly and specifically translocates to lipid droplets (LDs) containing Plin, and that this translocation is partially dependent on Plin phosphorylation. HSL closely, if not directly, interacts with Plin, as indicated by fluorescence resonance energy transfer (FRET) and bimolecular fluorescence complementation (BiFC) experiments. In contrast, tagged Atgl did not support FRET or BiFC with Plin, although it did modestly translocate to LDs upon stimulation. Abhd5 strongly interacted with Plin in the basal state, as indicated by FRET and BiFC. PKA activation rapidly (within minutes) decreased FRET between Abhd5 and Plin, and this decrease depended upon Plin phosphorylation. Together, these results indicate that Plin mediates hormone-stimulated lipolysis via direct and indirect mechanisms. Plin indirectly controls Atgl activity by regulating accessibility to its coactivator, Abhd5. In contrast, Plin directly regulates the access of HSL to substrate via close, if not direct, interactions. The differential interactions of HSL and Atgl with Plin and Abhd5 also explain the findings that following stimulation, HSL and Atgl are differentially enriched at specific LDs. A central function of adipocytes is the storage and mobilization of energy in the form of triglyceride. A considerable amount is known about the enzymatic basis for lipogenesis and lipolysis; however, our understanding of how these processes are organized and regulated within cells is incomplete. Until recently, cellular triglyceride was considered to be stored in droplets lacking biological structure or organization. Growing evidence, however, suggests that lipid droplets are specialized, heterogeneous organelles that perform distinct roles in lipid biosynthesis, transport, and mobilization (1Brasaemle D.L. Dolios G. Shapiro L. Wang R. J. Biol. Chem. 2004; 279: 46835-46842Abstract Full Text Full Text PDF PubMed Scopus (639) Google Scholar, 2Liu P. Ying Y. Zhao Y. Mundy D.I. Zhu M. Anderson R.G. J. Biol. Chem. 2004; 279: 3787-3792Abstract Full Text Full Text PDF PubMed Scopus (439) Google Scholar, 3Wolins N.E. Brasaemle D.L. Bickel P.E. FEBS Lett. 2006; 580: 5484-5491Crossref PubMed Scopus (323) Google Scholar). A large number of proteins have been found to change their associations with lipid droplets in response to lipolytic stimulation. How these proteins are coordinated to control lipid storage and utilization remains largely unknown. It is well established that activation of cAMP-dependent kinase (PKA) 3The abbreviations used are: PKA, cAMP-dependent protein kinase; Atgl, adipose tissue triglyceride lipase; Abhd5, Abhydrolase domain containing 5; BiFC, bimolecular fluorescence complementation; FRET, fluorescence resonance energy transfer; HSL, hormone-sensitive lipase; IBMX, 1-methyl-3-isobutylxanthine; LD, lipid droplet; Plin, perilipin. is the major signaling mechanism by which hormones and neurotransmitters stimulate lipolysis in adipocytes (4Honnor R.C. Dhillon G.S. Londos C. J. Biol. Chem. 1985; 260: 15130-15138Abstract Full Text PDF PubMed Google Scholar, 5Honnor R.C. Dhillon G.S. Londos C. J. Biol. Chem. 1985; 260: 15122-15129Abstract Full Text PDF PubMed Google Scholar). Most work regarding hormone stimulated lipolysis has focused on perilipin (Plin), a protein that binds to the surface of certain lipid droplets (LDs), and hormone-sensitive lipase (HSL), which translocates to lipid during lipolytic activation. Plin is the major target for PKA-mediated phosphorylation in adipocytes (6Greenberg A.S. Egan J.J. Wek S.A. Garty N.B. Blanchette-Mackie E.J. Londos C. J. Biol. Chem. 1991; 266: 11341-11346Abstract Full Text PDF PubMed Google Scholar, 7Londos C. Brasaemle D.L. Schultz C.J. Adler-Wailes D.C. Levin D.M. Kimmel A.R. Rondinone C.M. Ann. N. Y. Acad. Sci. 1999; 892: 155-168Crossref PubMed Scopus (221) Google Scholar), appears to be essential for hormone-stimulated lipolysis (8Miyoshi H. Souza S.C. Zhang H.H. Strissel K.J. Christoffolete M.A. Kovsan J. Rudich A. Kraemer F.B. Bianco A.C. Obin M.S. Greenberg A.S. J. Biol. Chem. 2006; 281: 15837-15844Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar) and exerts both positive and negative effects on lipolytic rate (9Brasaemle D.L. Rubin B. Harten I.A. Gruia-Gray J. Kimmel A.R. Londos C. J. Biol. Chem. 2000; 275: 38486-38493Abstract Full Text Full Text PDF PubMed Scopus (370) Google Scholar, S.C. L. P. Wang Kraemer F.B. Obin M. Greenberg A.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Plin was as a that regulated access of to however, that Plin function as a that the of lipolytic proteins to a domain J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the and between Plin and proteins in the lipolytic during PKA activation PKA activation the translocation of HSL to which with the of stimulated lipolysis C. Brasaemle D.L. Schultz C.J. Adler-Wailes D.C. Levin D.M. Kimmel A.R. Rondinone C.M. Ann. N. Y. Acad. Sci. 1999; 892: 155-168Crossref PubMed Scopus (221) Google Scholar, D.L. Levin D.M. Adler-Wailes D.C. Londos C. 2000; PubMed Scopus Google Scholar). that Plin and HSL to PKA-mediated lipolysis J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, C. G. H. Kimmel A.R. Londos C. J. Biol. PubMed Scopus Google Scholar), and our work that HSL specifically translocates to a of LDs containing Plin J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). It is Plin and HSL directly, the on certain LDs and not or the on a that is with the of The of regulated lipolysis has with the of adipose triglyceride lipase (Atgl) J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar, R. G. G. R. M. A. G. A. R. 2004; PubMed Scopus Google Scholar) and that Abhd5, a protein A. C. A. Shapiro L. Dolios G. Wang R. Brasaemle D.L. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar), is a key of Atgl A. R. G. M. G. M. P. G. R. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). In to HSL, is known about and that Atgl a in basal and stimulated lipolysis R. G. G. R. M. A. G. A. R. 2004; PubMed Scopus Google Scholar, G. A. R. G. C. J. G. R. C. M. G. R. 2006; PubMed Scopus Google Scholar). it is not known Atgl translocates to lipid in response to PKA or if it is to specific LDs. Abhd5 is a of Atgl that binds to Plin with lipolytic to the of Abhd5 Plin A. C. A. Shapiro L. Dolios G. Wang R. Brasaemle D.L. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar). It is not known the of Abhd5 and Plin on a minutes) that is to the of or the of Abhd5 Plin is by Plin phosphorylation. these the that PKA phosphorylation of Plin Atgl indirectly its direct interactions with Abhd5. The strongly that lipolysis the trafficking, is known about and and during stimulated a of that for the the of lipolytic label of proteins and of fluorescence reporters in The results of these support the that Plin as a that at the of In protein indicate that Plin controls the of HSL with specific via close, if not direct, interactions. In contrast, Plin not directly with Plin is to control Atgl activity indirectly by rapidly Abhd5 in a dependent on Plin phosphorylation. of the differential of Atgl and HSL with Plin, these be to distinct following lipolytic activation. 3T3-L1 adipocytes by preadipocytes on cells in and with or IBMX, and for The was with with and for fluorescent 3T3-L1 preadipocytes on and in containing transfected at about or as by the was cells in with to to of lipid used in to colocalization of proteins in the by immunofluorescence the of A. P. L. C. J. PubMed Scopus Google Scholar). The key to this is the of of a the cells with containing and for for with the at or The with a for with The as for with the at or The and for with with for in and at of control in which of the was In of the fluorescent in the for HSL and Plin as J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). for Abhd5 a Brasaemle A. C. A. Shapiro L. Dolios G. Wang R. Brasaemle D.L. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar). for Atgl the to to the Atgl was in not and was by to Atgl H. Souza S.C. Zhang H.H. Kraemer F.B. Obin M.S. Greenberg A.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). was to the of Plin by Plin the of Plin lacking PKA was by a (8Miyoshi H. Souza S.C. Zhang H.H. Strissel K.J. Christoffolete M.A. Kovsan J. Rudich A. Kraemer F.B. Bianco A.C. Obin M.S. Greenberg A.S. J. Biol. Chem. 2006; 281: 15837-15844Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar) and for Plin to form was to the of HSL J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, M.A. Londos C. Kraemer F.B. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar), Atgl and Abhd5 the of Atgl and Abhd5 by J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar) or tissue by fluorescence complementation (BiFC) with of as by PubMed Scopus Google Scholar). The the HSL, Atgl, and Abhd5, the was on the the and of the to form is the protein for interactions. The the on its The was by a by and was the of the to form This the at the of Atgl was by and the of the was by the the of with the with controls and a a and a The following used for the indicated and FRET, and the control and was of adipocytes by a of between a and the containing The containing cells that the of the cells the This of large and LDs. at at the surface of the lipid live containing transfected 3T3-L1 cells in a containing containing and and with at cells of at a rate of in cells stimulated with a of and in to a of and and for Double and and to was with the to the The was and for of which to which for and of of this was to the translocation and colocalization of lipolytic proteins to cellular LDs. this the containing the of LDs was and fluorescence of in the and and on of the and The of colocalization was by the of translocation to LDs containing was by the of the and stimulation. was to the translocation analysis FRET was the G. B. B. J. Full Text Full Text PDF PubMed Scopus Google Scholar) and FRET the FRET of FRET to LDs containing the FRET the domain containing LDs was for the of and the FRET of was for for to the FRET for FRET for 3T3-L1 cells transfected with fluorescent a for cells and The of the FRET in was with transfected FRET at LDs containing and of the the FRET preadipocytes on and transfected with of the and with of to transfected for at in with in containing cells examined a by that was to cells by and cells as to the or of The rate of cellular was in colocalization and fluorescence by analysis of and by for BiFC was by Double of Plin, Atgl, HSL, and Abhd5 in 3T3-L1 the colocalization of lipolytic proteins in 3T3-L1 adipocytes basal and brief lipolytic with and immunofluorescence of adipocytes and the colocalization analysis of Plin was to LDs. In the surface of LDs and of the surface of droplets indicated and Plin Abhd5 was to lipid with Double label that Plin and Abhd5 proteins on as that these proteins directly A. C. A. Shapiro L. Dolios G. Wang R. Brasaemle D.L. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar, N. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar). In the state, HSL was largely Atgl was found in the and on lipid Double label immunofluorescence indicated that HSL was with Plin in of Atgl fluorescence with Atgl and Plin to be strongly in the basal Atgl and its Abhd5. brief with and IBMX, HSL was to and lipid it was with Plin basal HSL, did not the colocalization of Atgl and Atgl and Abhd5 following stimulation, with of the in colocalization on The colocalization of Atgl and Abhd5 at the was a decrease in the colocalization of Abhd5 with HSL and Atgl partially in the and on LDs stimulation, and did not the of by the differential colocalization with Plin and Abhd5, LDs differentially enriched with lipase stimulation. The results of label immunofluorescence are with the that HSL is specifically to LDs. It appears that the of Abhd5 with Plin, its with it appears that increases the translocation of HSL to droplets and the of Abhd5 and The colocalization of Atgl and Abhd5 at that or not Plin, and as a of the differential with Plin, Atgl, and HSL a distinct following stimulation. and of about on immunofluorescence on of cells at in colocalization strongly trafficking, it not about the or of protein or translocation in the of in these key a of fluorescent reporters for lipolytic protein and interactions in This not and of also of specific interactions the of FRET and BiFC. of to was largely and rapidly to containing LDs upon stimulation. in are of a 3T3-L1 and following of translocation is in stimulation, the of was to and to lipid droplets to and stimulation. In have not of lipid droplets during stimulation. of the fluorescence at the lipid droplets that translocation that within of and by The and of translocation was by by the fluorescence of and and stimulation. In the basal and and the of the was of HSL of stimulation, was at as in the in the and of indicated that translocation to LDs by and the colocalization to the of colocalization, the of was of the amount of that translocate to lipid the of was at and its was on LDs with J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). It was of to translocation in cells containing a of with and in is a containing and by with was strongly to LDs that a LDs if with rapidly to droplets containing in with translocation to LDs did not translocation of in the of Plin these indicate that HSL specifically translocates to Plin containing and that large which not Plin, are not by of on Plin is a major target for phosphorylation by PKA, and the of HSL translocation on Plin that PKA-mediated phosphorylation of Plin be This was examined by the translocation of to in which PKA phosphorylation to (8Miyoshi H. Souza S.C. Zhang H.H. Strissel K.J. Christoffolete M.A. Kovsan J. Rudich A. Kraemer F.B. Bianco A.C. Obin M.S. Greenberg A.S. J. Biol. Chem. 2006; 281: 15837-15844Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar). the translocation of to LDs The of translocation was the of as by the of was Plin for that HSL translocation is partially dependent on Plin phosphorylation. FRET between and of Plin of and to the interactions of the lipolytic FRET between the and if proteins are within the of or direct FEBS Lett. PubMed Scopus Google Scholar). The is of the of the and analysis of in protein interactions in the of in and partially basal these a FRET was found between the and a in the FRET that to the translocation of HSL to LDs indicated that translocation of to also the FRET FRET was to the translocation of the to did not the of FRET was FRET on Plin phosphorylation. of to or with the of Plin, cells Atgl largely of lipid droplets however, cells to form lipid droplets to that was not cells in is a with was on lipid droplets This colocalization was was the colocalization of HSL and Plin in the basal state, and the colocalization of HSL and Plin with translocation of to although the of the was that for The in fluorescence at LDs was however, did not the colocalization between the Atgl and Plin of the and that the of fluorescence on LDs that of Plin LDs that if did not support FRET to FRET between and in a on Plin was largely with on cellular LDs for did not change in the of or its colocalization with FRET of in interactions in the strongly FRET to that these proteins strongly in the the FRET within with a of of the also as a for FRET with In to Plin, was if not in the FRET the of with between and that and did not lipid in the or of Plin or FRET was in cells lacking cells be found that lipid droplets these Abhd5 and Atgl strongly at these lipid droplets as by cells Atgl and Abhd5 or lipid was to the effects of stimulation. BiFC between is a for protein interactions in Y. Full Text Full Text PDF PubMed Scopus Google Scholar). The is on the of of to form a fluorescent protein these are in by the of The is to FRET in that the of the proteins a that not of BiFC is that the reporters not in the of between the In to FRET, BiFC and are BiFC indicate protein interactions with to that of the proteins to or of did not a cellular the of BiFC, cells with to transfected and the of cells fluorescence BiFC was to BiFC at lipid droplets for positive of proteins the of with was the as it in transfected cells and the fluorescence was about positive the BiFC, did not BiFC with was of BiFC with This the of the BiFC and that to form BiFC is to the of the of BiFC between lipolytic proteins in 3T3-L1 with by of and are not in a with by of and are not BiFC also between and as by the colocalization and FRET In BiFC fluorescence was to lipid that the of Plin for lipid the of the BiFC fluorescence was also between and also with the translocation and FRET experiments. BiFC have HSL to lipid and it is in this that these BiFC to well lipid This to with Atgl lipid was and suggests that although BiFC HSL is to lipid the has In to HSL, Atgl did not form BiFC with of the BiFC used to interactions was of BiFC with not with the that Plin and Atgl not in BiFC was between and FRET, BiFC with lipid BiFC, the cells BiFC LDs that lipolytic BiFC between and results that Plin or form with a The Plin BiFC to be in that translocation of HSL at the between triglyceride and the however, and how this in cells remains Until recently, cellular triglyceride was considered to be stored in droplets lacking biological structure or however, that lipid droplets are specialized, heterogeneous organelles that perform distinct roles in lipid biosynthesis, and mobilization (1Brasaemle D.L. Dolios G. Shapiro L. Wang R. J. Biol. Chem. 2004; 279: 46835-46842Abstract Full Text Full Text PDF PubMed Scopus (639) Google Scholar, 2Liu P. Ying Y. Zhao Y. Mundy D.I. Zhu M. Anderson R.G. J. Biol. Chem. 2004; 279: 3787-3792Abstract Full Text Full Text PDF PubMed Scopus (439) Google Scholar, R.G. Biol. 2006; PubMed Scopus Google Scholar, M. R.G. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus (235) Google Scholar). is that hormone-stimulated lipolysis the interactions of and at lipid work established that lipolysis the translocation of HSL to LDs containing Plin C. Brasaemle D.L. Schultz C.J. Adler-Wailes D.C. Levin D.M. Kimmel A.R. Rondinone C.M. Ann. N. Y. Acad. Sci. 1999; 892: 155-168Crossref PubMed Scopus (221) Google Scholar, D.L. Levin D.M. Adler-Wailes D.C. Londos C. 2000; PubMed Scopus Google Scholar). Plin has been as a that by cellular N.E. Brasaemle D.L. Bickel P.E. FEBS Lett. 2006; 580: 5484-5491Crossref PubMed Scopus (323) Google Scholar, P. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar), have that Plin is as a that the of lipolytic proteins at LDs J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The work the and of lipolytic proteins by the of proteins basal and stimulated label by the of tagged reporters in cells and by interactions in cells with FRET and BiFC. of the of lipolytic proteins that the translocation of HSL to LDs. this of HSL translocation to lipid is well the work that HSL translocates specifically to droplets containing Plin, and that this direct of HSL with J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar) and the of Plin at is with and LDs with have and tagged proteins that HSL at droplets containing Plin stimulation. This for droplets as the Plin and HSL are in a stimulation. The translocation of HSL to LDs Plin and is partially dependent upon Plin phosphorylation in 3T3-L1 FRET and BiFC strongly indicate that HSL and Plin closely, if not directly, in and that this is rapidly by PKA activation. have been to interactions between HSL and Plin by or Londos C. Kraemer F.B. R.G. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar). In contrast, the that interactions at in In this have found that HSL interactions with Plin FRET, and at containing G. that lipid is essential in and is with that increases the to Plin and HSL in (8Miyoshi H. Souza S.C. Zhang H.H. Strissel K.J. Christoffolete M.A. Kovsan J. Rudich A. Kraemer F.B. Bianco A.C. Obin M.S. Greenberg A.S. J. Biol. Chem. 2006; 281: 15837-15844Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar). Plin has been as a that access of to stored triglyceride. The Plin not LDs in the state, Plin not LDs on to of HSL translocation Plin, HSL not translocate to droplets lacking Plin, HSL and Plin following stimulation, and Atgl is to LDs not support the that Plin as a lipase at the the support the that Plin as a that the lipolytic are with in adipocytes of Plin J. Anderson A. L. 2000; PubMed Scopus Google Scholar, C. Gruia-Gray J. D.L. C. Kimmel A.R. Londos C. Acad. Sci. A. PubMed Scopus Google Scholar), and for the that Plin and HSL lipolysis (8Miyoshi H. Souza S.C. Zhang H.H. Strissel K.J. Christoffolete M.A. Kovsan J. Rudich A. Kraemer F.B. Bianco A.C. Obin M.S. Greenberg A.S. J. Biol. Chem. 2006; 281: 15837-15844Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, C. G. H. Kimmel A.R. Londos C. J. Biol. PubMed Scopus Google Scholar). The that Plin as a for the PKA-mediated of lipolysis is by its interactions with Abhd5. Abhd5 was as a protein of function that directly interacted with Plin, and that PKA activation to its LDs A. C. A. Shapiro L. Dolios G. Wang R. Brasaemle D.L. J. Biol. Chem. 2004; 279: Full Text Full Text PDF PubMed Scopus Google Scholar). The function of Abhd5 was by which that Abhd5 is a of Atgl, a lipase A. R. G. M. G. M. P. G. R. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). label found that Abhd5 and Plin in decreased the colocalization between Plin and Abhd5, and the colocalization of Abhd5 with of the colocalization at LDs and lacking it is that of Abhd5 and Atgl are at our results that the in the of Abhd5 and Atgl that be to PKA activation largely at lacking The indicate that Plin as a for Abhd5 in the basal and a of the following PKA activation. This that Plin regulates the activity of Atgl indirectly by or Abhd5. In this the of Plin to Abhd5 to the well known of Plin to lipid (9Brasaemle D.L. Rubin B. Harten I.A. Gruia-Gray J. Kimmel A.R. Londos C. J. Biol. Chem. 2000; 275: 38486-38493Abstract Full Text Full Text PDF PubMed Scopus (370) Google Scholar). FRET analysis in cells demonstrated that rapidly the of Plin and Abhd5, and that this is dependent upon Plin phosphorylation. and the immunofluorescence support the of Atgl in Double label immunofluorescence that is considerable amount of Atgl is with LDs containing Plin and Abhd5 in the state, in to The of Abhd5 Plin of Atgl on droplets translocation It is also that of Atgl and Abhd5 that are following target In this it is that HSL and Atgl be partially to of differential interactions with HSL and Plin strongly interacted in BiFC and FRET Atgl and Plin did stimulation, HSL and Atgl be found differentially enriched on with HSL with and of Abhd5 and Atgl and Double label immunofluorescence indicate that PKA activation of Abhd5 to to the direct of Abhd5 with Atgl in by FRET and BiFC. have been to the Plin, Abhd5, and Atgl cells that Abhd5 and Atgl did not lipid for that of Plin or did not lipid it did to Atgl was in the of The for this is not it indicate that Abhd5 is to Plin it it is that at of triglyceride and transport, the of triglyceride in LDs that of these of for in upon the results and a for the of PKA regulated lipolysis in In this Plin is protein that regulates the of lipolytic in response to PKA activation. In the basal state, Plin and Abhd5 are Atgl is to LDs containing however, Atgl is to be its is by PKA activation to Plin which has Plin phosphorylation Abhd5 to Atgl on LDs with and PKA activation the translocation of HSL to in a that is partially dependent on Plin phosphorylation. Atgl and HSL to have enzymatic R. G. G. R. M. A. G. A. R. 2004; PubMed Scopus Google Scholar, R. G. A. R. PubMed Scopus Google Scholar), and the coordinated of these at LDs is essential for regulated to the that be for a of hormone stimulated LDs of and proteins (1Brasaemle D.L. Dolios G. Shapiro L. Wang R. J. Biol. Chem. 2004; 279: 46835-46842Abstract Full Text Full Text PDF PubMed Scopus (639) Google Scholar, 2Liu P. Ying Y. Zhao Y. Mundy D.I. Zhu M. Anderson R.G. J. Biol. Chem. 2004; 279: 3787-3792Abstract Full Text Full Text PDF PubMed Scopus (439) Google Scholar, R.G. Biol. 2006; PubMed Scopus Google Scholar) and the these proteins during and PKA activation remains largely The of as well as to protein and that this be in the analysis of lipolytic and for and and of for with