Postlipolytic insulin-dependent remodeling of micro lipid droplets in adipocytes

Despite the lipolysis-lipogenesis cycle being a fundamental process in adipocyte biology, very little is known about the morphological changes that occur during this process. The remodeling of lipid droplets to form micro lipid droplets (mLDs) is a striking feature of lipolysis in adipocytes, but once lipolysis ceases, the cell must regain its basal morphology. We characterized mLD formation in cultured adipocytes, and in primary adipocytes isolated from mouse epididymal fat pads, in response to acute activation of lipolysis. Using real-time quantitative imaging and electron tomography, we show that formation of mLDs in cultured adipocytes occurs throughout the cell to increase total LD surface area by ~30% but does not involve detectable fission from large LDs. Peripheral mLDs are monolayered structures with a neutral lipid core and are sites of active lipolysis. Electron tomography reveals preferential association of mLDs with the endoplasmic reticulum. Treatment with insulin and fatty acids results in the reformation of macroLDs and return to the basal state. Insulin-dependent reformation of large LDs involves two distinct processes: microtubule-dependent homotypic fusion of mLDs and expansion of individual mLDs. We identify a physiologically important role for LD fusion that is involved in a reversible lipolytic cycle in adipocytes.     

Fat-specific Protein 27 Undergoes Ubiquitin-dependent Degradation Regulated by Triacylglycerol Synthesis and Lipid Droplet Formation

The fat-specific protein 27 (Fsp27), a protein localized to lipid droplets (LDs), plays an important role in controlling lipid storage and mitochondrial activity in adipocytes. Fsp27-null mice display increased energy expenditure and are resistant to high fat diet-induced obesity and diabetes. However, little is known about how the Fsp27 protein is regulated. Here, we show that Fsp27 stability is controlled by the ubiquitin-dependent proteasomal degradation pathway in adipocytes. The ubiquitination of Fsp27 is regulated by three lysine residues located in the C-terminal region. Substitution of these lysine residues with alanines greatly increased Fsp27 stability and enhanced lipid storage in adipocytes. Furthermore, Fsp27 was stabilized and rapidly accumulated following treatment with β-agonists that induce lipolysis and fatty acid re-esterification in adipocytes. More importantly, Fsp27 stabilization was dependent on triacylglycerol synthesis and LD formation, because knockdown of diacylglycerol acyltransferase in adipocytes significantly reduced Fsp27 accumulation in adipocytes. Finally, we observed that increased Fsp27 during β-agonist treatment preferentially associated with LDs. Taken together, our data revealed that Fsp27 can be stabilized by free fatty acid availability, triacylglycerol synthesis, and LD formation. The stabilization of Fsp27 when free fatty acids are abundant further enhances lipid storage, providing positive feedback to regulate lipid storage in adipocytes.     

Lipid droplet-organelle interactions; sharing the fats

Lipid droplets (LDs) are key cellular organelles involved in lipid storage and mobilisation. While the major signalling cascades and many of the regulators of lipolysis have been identified, the cellular interactions involved in lipid mobilisation and release remain largely undefined. In non-adipocytes, LDs are small, mobile and interact with other cellular compartments. In contrast, adipocytes primarily contain very large, immotile LDs. The striking morphological differences between LDs in adipocytes and non-adipocytes suggest that key differences must exist in the manner in which LDs in different cell types interact with other organelles. Recent studies have highlighted the complexity of LD interactions, which can be both homotypic, with each other, and heterotypic, with other organelles. The molecules involved in these interactions are also now emerging, including Rab proteins, key regulators of membrane traffic, and caveolin, an integral membrane protein providing a functional link between the cell surface and LDs. Here we summarise recent insights into the cell biology of the LD particularly focussing on the homotypic and heterotypic interactions in both adipocytes and non-adipocytes. We speculate that these interactions may involve inter-organelle membrane contact sites or a hemi-fusion type mechanism to facilitate lipid transfer.     

Dynamics of protein and polar lipid recruitment during lipid droplet assembly in Chlamydomonas reinhardtii

In plants, neutral lipids are frequently synthesized and stored in seed tissues, where the assembly of lipid droplets (LDs) coincides with the accumulation of triacylglycerols (TAGs). In addition, photosynthetic, vegetative cells can form cytosolic LDs and much less information is known about the makeup and biogenesis of these LDs. Here we focus on Chlamydomonas reinhardtii as a reference model for LDs in a photosynthetic cell, because in this unicellular green alga LD dynamics can be readily manipulated by nitrogen availability. Nitrogen deprivation leads to cellular quiescence during which cell divisions cease and TAGs accumulate. The major lipid droplet protein (MLDP) forms a proteinaceous coat surrounding mature LDs. Reducing the amount of MLDP affects LD size and number, TAG breakdown and timely progression out of cellular quiescence following nitrogen resupply. Depending on nitrogen availability, MLDP recruits different proteins to LDs, tubulins in particular. Conversely, depolymerization of microtubules drastically alters the association of MLDP with LDs. LDs also contain select chloroplast envelope membrane proteins hinting at an origin of LDs, at least in part, from chloroplast membranes. Moreover, LD surface lipids are rich in de novo synthesized fatty acids, and are mainly composed of galactolipids which are typical components of chloroplast membranes. The composition of the LD membrane is altered in the absence of MLDP. Collectively, our results suggest a mechanism for LD formation in C. reinhardtii involving chloroplast envelope membranes by which specific proteins are recruited to LDs and a specialized polar lipid monolayer surrounding the LD is formed.     

Quantitative electron microscopy shows uniform incorporation of triglycerides into existing lipid droplets

The lipid droplet (LD) is an organelle with a lipid ester core and a surface phospholipid monolayer. The mechanism of LD biogenesis is not well understood. The present study aimed to elucidate the LD growth process, for which we developed a new electron microscopic method that quantifies the proportion of existing and newly synthesized triglycerides in individual LDs. Our method takes advantage of the reactivity of unsaturated fatty acids and osmium tetroxide, which imparts LDs an electron density that reflects fatty acid composition. With this method, existing triglyceride-rich LDs in 3Y1 fibroblasts were observed to incorporate newly synthesized triglycerides at a highly uniform rate. This uniformity and its persistence even after microtubules were depolymerized suggest that triglycerides in fibroblasts are synthesized in the local vicinity of individual LDs and then incorporated. In contrast, LDs in 3T3-L1 adipocytes showed heterogeneity in the rate at which lipid esters were incorporated, indicating different mechanisms of LD growth in fibroblasts and adipocytes.     

Decoration of myocellular lipid droplets with perilipins as a marker for in vivo lipid droplet dynamics: A super-resolution microscopy study in trained athletes and insulin resistant individuals

In many different cell types neutral lipids can be stored in lipid droplets (LDs). Nowadays, LDs are viewed as dynamic organelles, which store and release fatty acids depending on energy demand (LD dynamics). Proteins like perilipin 2 (PLIN2) and PLIN5 decorate the LD membrane and are determinants of LD lipolysis and fat oxidation, thus affecting LD dynamics. Trained athletes and type 2 diabetes (T2D) patients both have high levels of intramyocellular lipid (IMCL). While IMCL content scales negatively with insulin resistance, athletes are highly insulin sensitive in contrast to T2D patients, the so-called athlete's paradox. Differences in LD dynamics may be an underlying factor explaining the athlete's paradox. We aimed to quantify PLIN2 and PLIN5 content at individual LDs as a reflection of the ability to switch between fatty acid release and storage depending on energy demand. Thus, we developed a novel fluorescent super-resolution microscopy approach and found that PLIN2 protein abundance at the LD surface was higher in T2D patients than in athletes. Localization of adipocyte triglyceride lipase (ATGL) to the LD surface was lower in LDs abundantly decorated with PLIN2. While PLIN5 abundance at the LD surface was similar in athletes and T2D patients, we have observed previously that the number of PLIN5 decorated LDs was higher in athletes, indicating more LDs in close association with mitochondria. Thus, in athletes interaction of LDs with mitochondria was more pronounced and LDs have the protein machinery to be more dynamic, while in T2D patients the LD pool is more inert. This observation contributes to our understanding of the athlete's paradox.     

Lipid droplet autophagy in the yeast Saccharomyces cerevisiae

Cytosolic lipid droplets (LDs) are ubiquitous organelles in prokaryotes and eukaryotes that play a key role in cellular and organismal lipid homeostasis. Triacylglycerols (TAGs) and steryl esters, which are stored in LDs, are typically mobilized in growing cells or upon hormonal stimulation by LD-associated lipases and steryl ester hydrolases. Here we show that in the yeast Saccharomyces cerevisiae, LDs can also be turned over in vacuoles/lysosomes by a process that morphologically resembles microautophagy. A distinct set of proteins involved in LD autophagy is identified, which includes the core autophagic machinery but not Atg11 or Atg20. Thus LD autophagy is distinct from endoplasmic reticulum–autophagy, pexophagy, or mitophagy, despite the close association between these organelles. Atg15 is responsible for TAG breakdown in vacuoles and is required to support growth when de novo fatty acid synthesis is compromised. Furthermore, none of the core autophagy proteins, including Atg1 and Atg8, is required for LD formation in yeast.     

Adipose triglyceride lipase regulates basal lipolysis and lipid droplet size in adipocytes

In adipocytes, lipid droplet (LD) size reflects a balance of triglyceride synthesis (lipogenesis) and hydrolysis (lipolysis). Perilipin A (Peri A) is the most abundant phosphoprotein on the surface of adipocyte LDs and has a crucial role in lipid storage and lipolysis. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) are the major rate-determining enzymes for lipolysis in adipocytes. Each of these proteins (Peri A, ATGL, and HSL) has been demonstrated to regulate lipid storage and release in the adipocyte. However, in the absence of protein kinase A (PKA) stimulation (basal state), the lipases (ATGL and HSL) are located mainly in the cytoplasm, and their contribution to basal rates of lipolysis and influence on LD size are poorly understood. In this study, we utilize an adenoviral system to knockdown or overexpress ATGL and HSL in an engineered model system of adipocytes in the presence or absence of Peri A. We are able to demonstrate in our experimental model system that in the basal state, LD size, triglyceride storage, and fatty acid release are mainly influenced by the expression of ATGL. These results demonstrate for the first time the relative contributions of ATGL, HSL, and Peri A on determination of LD size in the absence of PKA stimulation.     

Shrinking and development of lipid droplets in adipocytes during catecholamine-induced lipolysis

Time-lapse observation of adipocytes during catecholamine-induced lipolysis clearly shows that shrinking of existing lipid droplets (LDs) occurs in some adipocytes and that small LDs are newly developed in almost all cells. Immunofluorescence imaging reveals that activation and localization of hormone-sensitive lipase (HSL) on the surface of LDs, which are required for conferring maximal lipolysis, are necessary for the shrinking of the LDs. However, not all adipocytes in which phosphorylated HSL is localized on LDs exhibit shrinking of LDs. The simultaneous shrinking and development of LDs yield apparent fragmentation and dispersion of LDs in adipocytes stimulated with catecholamine.     

Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes

The spatiotemporal dynamics of triglyceride (TG) storage in unilocular adipocytes are not well understood. Here we applied ex vivo technology to study trafficking and metabolism of fluorescent fatty acids in adipose tissue explants. Live imaging revealed multiple cytoplasmic nodules surrounding the large central lipid droplet (cLD) of unilocular adipocytes. Each cytoplasmic nodule harbors a series of closely associated cellular organelles, including micro–lipid droplets (mLDs), mitochondria, and the endoplasmic reticulum. Exogenously added free fatty acids are rapidly adsorbed by mLDs and concurrently get esterified to TG. This process is greatly accelerated by insulin. mLDs transfer their content to the cLD, serving as intermediates that mediate packaging of newly synthesized TG in the large interior of a unilocular adipocyte. This study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy.     

Fsp27 promotes lipid droplet growth by lipid exchange and transfer at lipid droplet contact sites

Lipid droplets (LDs) are dynamic cellular organelles that control many biological processes. However, molecular components determining LD growth are poorly understood. Genetic analysis has indicated that Fsp27, an LD-associated protein, is important in controlling LD size and lipid storage in adipocytes. In this paper, we demonstrate that Fsp27 is focally enriched at the LD-LD contacting site (LDCS). Photobleaching revealed the occurrence of lipid exchange between contacted LDs in wild-type adipocytes and Fsp27-overexpressing cells but not Fsp27-deficient adipocytes. Furthermore, live-cell imaging revealed a unique Fsp27-mediated LD growth process involving a directional net lipid transfer from the smaller to larger LDs at LDCSs, which is in accordance with the biophysical analysis of the internal pressure difference between the contacting LD pair. Thus, we have uncovered a novel molecular mechanism of LD growth mediated by Fsp27.     

CIDE family proteins control lipid homeostasis and the development of metabolic diseases

Dysregulation of lipid homeostasis leads to the development of metabolic disorders including obesity, diabetes, cardiovascular disease and cancer. Lipid droplets (LDs) are subcellular organelles vital in the maintenance of lipid homeostasis by coordinating lipid synthesis, lipid storage, lipid secretion and lipolysis. Under fed condition, free fatty acids (FFAs) are remodeled and esterified into neutral lipids by lipogenesis and stored in the LDs. The lipid storage capacity of LDs is controlled by its growth via local lipid synthesis or by LD fusion. During fasting, neutral lipids are hydrolyzed by lipolysis, released as FFAs and secreted to meet energy demand. C ell death‐i nducing D NA fragmentation factor alpha (DFFA)‐like e ffector (CIDE) family proteins composed of Cidea, Cideb and Cidec/Fsp27 are ER‐ and LD‐associated proteins and have emerged as important regulators of lipid homeostasis. Notably, when localized on the LDs, CIDE proteins enrich at the LD‐LD contact sites (LDCSs) and control LD fusion and growth. Here, we summarize these recent advances made on the role of CIDE proteins in the regulation of lipid metabolism with a particular focus on the molecular mechanisms underlying CIDE‐mediated LD fusion and growth.     

Quantitative Mapping of Triacylglycerol Chain Length and Saturation Using Broadband CARS Microscopy

Lipid droplets (LDs), present in many cell types, are highly dynamic organelles that store neutral lipids, primarily triacylglycerols (TAGs). With the discovery of new LD functions (e.g., in immune response, protein clearage, and occurrence with disease), new methods to study LD chemical composition in situ are necessary. We present an approach for in situ, quantitative TAG analysis using label-free, coherent Raman microscopy that allows deciphering LD TAG composition in different biochemically complex samples with submicrometer spatial resolution. Employing a set of standard TAGs, we generate a spectral training matrix capturing the variation caused in Raman-like spectra by TAG backbone, chain length, and number of double bonds per chain, as well as the presence of proteins or other diluting molecules. Comparing our fitting approach to gas chromatography measurements for mixtures of standard TAGs and food oils, we find the root mean-square error for the prediction of TAG chemistry to be 0.69 CH₂ and 0.15 #C=C. When progressing to more complex samples such as oil emulsions and LDs in various eukaryotic cells, we find good agreement with bulk gas chromatography measurements. For differentiated adipocytes, we find a significant increase in the number of double bonds in small LDs (below 2 μm in diameter) compared to large LDs (above 2 μm in diameter). Coupled with a relatively limited sample preparation requirement, this approach should enable rapid and accurate TAG LD analysis for a variety of cell biology and technological applications.     

Unique regulation of adipose triglyceride lipase (ATGL) by perilipin 5, a lipid droplet-associated protein

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, [(32)P]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 [(32)P]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.     

Comparing lipid remodeling of brown adipose tissue,white adipose tissue,and liver after one-week high fat diet intervention with quantitative Raman microscopy

Brown adipose tissue (BAT) consists of highly metabolically active adipocytes that catabolize nutrients to produce heat. Playing an active role in triacylglycerol (TAG) clearance, research has shown that dietary fatty acids can modulate the TAG chemistry deposition in BAT after weeks-long dietary intervention, similar to what has been shown in white adipose tissue (WAT). Our objective was to compare the influence of sustained, nonchronic dietary intervention (a 1-week interval) on WAT and interscapular BAT lipid metabolism and deposition in situ. We use quantitative, label-free chemical microscopy to show that 1 week of high fat diet (HFD) intervention results in dramatically larger lipid droplet (LD) growth in BAT (and liver) compared to LD growth in inguinal WAT (IWAT). Moreover, BAT showed lipid remodeling as increased unsaturated TAGs in LDs, resembling the dietary lipid composition, while WAT (and liver) did not show lipid remodeling on this time scale. Concurrently, expression of genes involved in lipid metabolism, particularly desaturases, was reduced in BAT and liver from HFD-fed mice after 1 week. Our data show that BAT lipid chemistry remodels exceptionally fast to dietary lipid intervention compared WAT, which further points towards a role in TAG clearance.     

Molecular speciation and dynamics of oxidized triacylglycerols in lipid droplets: Mass spectrometry and coarse-grained simulations

Lipid droplets (LDs) are ubiquitous and physiologically active organelles regulating storage and mobilization of lipids in response to metabolic demands. Among the constituent LD neutral lipids, such as triacylglycerols, cholesterol esters, and free fatty acids, oxidizable polyunsaturated molecular species may be quite abundant, yet the structural and functional roles of their oxidation products have not been studied. Our previous work documented the presence of these peroxidized species in LDs. Assuming that hydrophilic oxygen-containing functionalities may markedly change the hydrophobic/hydrophilic molecular balance, here we utilized computational modeling to test the hypothesis that lipid peroxidation causes redistribution of lipids between the highly hydrophobic core and the polar surface (phospho)lipid monolayer—the area enriched with integrated enzymatic machinery. Using quantitative liquid chromatography/mass spectrometry, we characterized molecular speciation of oxTAGs in LDs of dendritic cells in cancer and hypoxic trophoblasts cells as two cellular models associated with dyslipidemia. Among the many types of oxidized lipids identified, we found that oxidatively truncated forms and hydroxyl derivatives of TAGs were the prevailing oxidized lipid species in LDs in both cell types. Using coarse-grained molecular dynamics (CG-MD) simulations we established that lipid oxidation changed their partitioning whereby oxidized lipids migrated into the outer monolayer of the LD, where they can affect essential metabolic pathways and undergo conversions, possibly leading to the formation of oxygenated lipid mediators.     

Regulated localization of Rab18 to lipid droplets: effects of lipolytic stimulation and inhibition of lipid droplet catabolism

Rab GTPases are crucial regulators of membrane traffic. Here we have examined a possible association of Rab proteins with lipid droplets (LDs), neutral lipid-containing organelles surrounded by a phospholipid monolayer, also known as lipid bodies, which have been traditionally considered relatively inert storage organelles. Although we found close apposition between LDs and endosomal compartments labeled by expressed Rab5, Rab7, or Rab11 constructs, there was no detectable labeling of the LD surface itself by these Rab proteins. In contrast, GFP-Rab18 localized to LDs and immunoelectron microscopy showed direct association with the monolayer surface. Green fluorescent protein (GFP)-Rab18-labeled LDs underwent oscillatory movements in a localized area as well as sporadic, rapid, saltatory movements both in the periphery of the cell and toward the perinuclear region. In both adipocytes and non-adipocyte cell lines Rab18 localized to a subset of LDs. To gain insights into this specific localization, Rab18 was co-expressed with Cav3DGV, a truncation mutant of caveolin-3 shown to inhibit the catabolism and motility of lipid droplets. GFP-Rab18 and mRFP-Cav3DGV labeled mutually exclusive subpopulations of LDs. Moreover, in 3T3-L1 adipocytes, stimulation of lipolysis increased the localization of Rab18 to LDs, an effect reversed by beta-adrenergic antagonists. These results show that a Rab protein localizes directly to the monolayer surface of LDs. In addition, association with the LD surface was increased following stimulation of lipolysis and inhibited by a caveolin mutant suggesting that recruitment of Rab18 is regulated by the metabolic state of individual LDs.     

CGI-58 facilitates lipolysis on lipid droplets but is not involved in the vesiculation of lipid droplets caused by hormonal stimulation

A lipid droplet (LD)-associated protein, perilipin, is a critical regulator of lipolysis in adipocytes. We previously showed that Comparative Gene Identification-58 (CGI-58), a product of the causal gene of Chanarin-Dorfman syndrome, interacts with perilipin on LDs. In this study, we investigated the function of CGI-58 using RNA interference. Notably, CGI-58 knockdown caused an abnormal accumulation of LDs in both 3T3-L1 preadipocytes and Hepa1 hepatoma cells. CGI-58 knockdown did not influence the differentiation of 3T3-L1 adipocytes but reduced the activity of both basal and cAMP-dependent protein kinase-stimulated lipolysis. In vitro studies showed that CGI-58 itself does not have lipase/esterase activity, but it enhanced the activity of adipose triglyceride lipase. Upon lipolytic stimulation, endogenous CGI-58 was rapidly dispersed from LDs into the cytosol along with small particulate structures. This shift in localization depends on the phosphorylation of perilipin, because phosphorylated perilipin lost the ability to bind CGI-58. During lipolytic activation, LDs in adipocytes vesiculate into micro-LDs. Using coherent anti-Stokes Raman scattering microscopy, we pursued the formation of micro-LDs in single cells, which seemed to occur in cytoplasmic regions distant from the large central LDs. CGI-58 is not required for this process. Thus, CGI-58 facilitates lipolysis in cooperation with perilipin and other factors, including lipases.     

Quantitative live-cell PALM reveals nanoscopic Faa4 redistributions and dynamics on lipid droplets during metabolic transitions of yeast

Lipid droplets (LDs) are dynamic organelles for lipid storage and homeostasis. Cells respond to metabolic changes by regulating the spatial distribution of LDs and enzymes required for LD growth and turnover. The small size of LDs precludes the observation of their associated enzyme densities and dynamics with conventional fluorescence microscopy. Here we employ quantitative photo-activated localization microscopy to study the density of the fatty acid (FA) activating enzyme Faa4 on LDs in live yeast cells with single-molecule sensitivity and 30 nm resolution. During the log phase LDs colocalize with the endoplasmic reticulum (ER) where their emergence and expansion are mediated by the highest observed Faa4 densities. During transition to the stationary phase, LDs with a ∼2-fold increased surface area translocate to the vacuolar surface and lumen and exhibit a ∼2.5-fold increase in Faa4 density. The increased Faa4 density on LDs further suggests its role in LD expansion, is caused by its ∼5-fold increased expression level, and is specific to exogenous FA chain-lengths. When lipolysis is induced by refreshed medium, Faa4 shuttles through ER- and lipophagy to the vacuole, where it may activate FAs for membrane expansion and degrade Faa4 to reset its cellular abundance to levels in the log phase.     

SREBP Activation by Antipsychotic- and Antidepressant-Drugs in Cultured Human Liver Cells: Relevance for Metabolic Side-Effects?

Despite the critical roles of intracellular lipid droplets (LDs) in lipid storage and metabolism, little is known about the molecular mechanisms of their functions. Several protein components associated with the surface of LDs have been identified. A major one is perilipin in adipocytes and steroidogenic cells, whereas ADRP in most other cell types. They are loosely grouped as a small protein family sharing a common N-terminal motif, called the PAT domain. Perilipin regulates the breakdown of triacylglycerol in LDs via its phosphorylation. ADRP is characterized as a fatty acid binding protein and involved in lipid uptake and LD formation. For examining the functions of perilipin and ADRP at the molecular level, we performed yeast two-hybrid screening in this study, to find their functional partners. We identified CGI-58, a product of the causal gene of Chanarin-Dorfman syndrome (CDS), as an interactor for both perilipin and ADRP. Specific interaction between CGI-58 and perilipin was confirmed in a GST-pulldown assay and supported by fluorescence microscopic analyses. We further demonstrated that CGI-58 is principally located at the surface of LDs in 3T3-L1 cells, together with perilipin, and its expression is upregulated upon stimulation for adipocyte differentiation. Other than CGI-58, we also identified in yeast two-hybrid screening HSP86 and D52 tumor proteins as binding partners of perilipin, and IRG-47 of ADRP. These factors might be cooperated with perilipin and ADRP, and hence involved in membrane dynamics of LDs as well as the regulation of lipolysis on the surface of LDs.