Proteomic Analysis of Proteins Associated with Lipid Droplets of Basal and Lipolytically Stimulated 3T3-L1 Adipocytes*

By D. Brasaemle, G. Dolios, L. Shapiro, Rong Wang. Journal of Biological Chemistry, 2004

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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.

Subfields: Biochemistry, Molecular Biology, Physiology

View Paper: https://www.semanticscholar.org/paper/7495f324a27e3d76fe3d15f950cb9fe86097456f

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Citations in the corpus

Regulation of lipolysis in adipocytes. (2007, neutral): “Presence of glucagon and glucagon-like peptide-1-(7-36)amide receptors in solubilized membranes of human adipose tissue.”
The multiple faces of caveolae (2007, background): “) under specific cellular conditions in cultured cells and in vivo”
PAT proteins, an ancient family of lipid droplet proteins that regulate cellular lipid stores (2009, background): “S3-12 also relocates to lipid droplets during lipolytic stimulation of adipocytes [4].”
Triglyceride metabolism in the liver (2017, neutral): “Several lipases are present in close association with LDs in adipocytes (30,66) (Fig.”
Lipid Droplets And Cellular Lipid Metabolism (2012, background): “Among ACSL proteins, ACSL3 and -4 are recruited to LDs specifically during lipolysis, and ACSL1 constitutively localizes there (62, 65).”
Triacylglycerol synthesis enzymes mediate lipid droplet growth by relocalizing from the ER to lipid droplets. (2013, result): “Consistent with previous findings, we found similar LD localization patterns for acyl-CoA synthetase enzymes (ACSL1 and ACSL3), which activate fatty acids and enable them to serve as substrates for TG synthesis enzymes (Figure 1C; Brasaemle et al., 2004; Fujimoto et al., 2007; Poppelreuther et al., ”