Cytosolic lipid droplets are unique among cellular organelles. These essential structures, found in nearly all eukaryotic cells, serve several functions besides fat storage, including serving as a depot for hormones and signaling molecules, providing phospholipid precursors for other organelles, innate immunity, and as a platform for assembly of pathogens. Unlike other organelles, droplets contain a single phospholipid leaflet which surrounds their hydrophobic cores. Despite the fact that they are the basis of both obesity, which affects two thirds of Americans, and lipodystrophy, an often fatal disease caused by the inability to properly store fat, there is still sketchy knowledge of their assembly. Recent progress has shown that, while droplets can form spontaneously, a few proteins and lipids are involved in regulating this process and ensuring that fully functional droplets are produced. While these components have been identified, much is unknown about their functions. This proposal seeks to test hypotheses regarding the mechanism of action of Pet10p (a yeast perilipin), seipin, and Scs3p (a Fit2 protein), and to gain molecular insight into how they function together. A driving hypothesis is that Pet10p collaborates in trans (i.e., at the bud rather than at the ER/droplet junction) with seipin, Scs3p, and diacylglycerol to promote and regulate droplet assembly.
In Aim 1, focusing on Pet10p, the multiple phenotypes in PET10-deletion cells with be matched with specific domains to probe function. The basis of the stabilizing effect of Pet10p on droplets will be elucidated, and whether the same activity is responsible for its role in droplet formation will be determined. The focus of Aim 2 will be a deeper understanding the function of seipin, including mapping function to structure, control of targeting proteins to droplets, and its role in vectorial budding of droplets. Studies to elucidate structure from cryo-EM images will also be initiated.
Aim 3 will focus on the collaboration of seipin, Pet10p and Scs3p on early steps of droplet budding. Whether seipin attracts Pet10p through seipin?s amino terminal will be determined, and the role of Pet10p and Scs3p on budding will be studied. The order of arrival at the nascent structure will be probed. Overall, the proposed research will elucidate important functions of the droplet assembly factors, and, for the first time, study how they interact.

Public Health Relevance

Contact PD/PI: Goodman, Joel Project Narrative This proposal seel(s to uncover basic mechanisms of lipid droplet assembly. As lipid droplets storefat,theyarethebasisofenergystorageinthebody. Understandinghowfatis.stored,an essential function of nearly all cells, will fill in important gaps to our understanding of obesity, in which too much fat is stored, and lipodystrophy, in which cells lack the ability to properly store this energy-rich product.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM084210-10
Application #
9748530
Study Section
Membrane Biology and Protein Processing Study Section (MBPP)
Program Officer
Maas, Stefan
Project Start
2008-05-01
Project End
2022-05-31
Budget Start
2019-06-01
Budget End
2020-05-31
Support Year
10
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Texas Sw Medical Center Dallas
Department
Pharmacology
Type
Schools of Medicine
DUNS #
800771545
City
Dallas
State
TX
Country
United States
Zip Code
75390
Henne, W Mike; Reese, Michael L; Goodman, Joel M (2018) The assembly of lipid droplets and their roles in challenged cells. EMBO J 37:
Gao, Qiang; Binns, Derk D; Kinch, Lisa N et al. (2017) Pet10p is a yeast perilipin that stabilizes lipid droplets and promotes their assembly. J Cell Biol 216:3199-3217
Chen, Xiao; Goodman, Joel M (2017) The collaborative work of droplet assembly. Biochim Biophys Acta Mol Cell Biol Lipids 1862:1205-1211
Cai, Yingqi; Goodman, Joel M; Pyc, Michal et al. (2015) Arabidopsis SEIPIN Proteins Modulate Triacylglycerol Accumulation and Influence Lipid Droplet Proliferation. Plant Cell 27:2616-36
Hashemi, Hayaa F; Goodman, Joel M (2015) The life cycle of lipid droplets. Curr Opin Cell Biol 33:119-24
Cartwright, Bethany R; Binns, Derk D; Hilton, Christopher L et al. (2015) Seipin performs dissectible functions in promoting lipid droplet biogenesis and regulating droplet morphology. Mol Biol Cell 26:726-39
Gao, Qiang; Goodman, Joel M (2015) The lipid droplet-a well-connected organelle. Front Cell Dev Biol 3:49
Han, Sungwon; Binns, Derk D; Chang, Yu-Fang et al. (2015) Dissecting seipin function: the localized accumulation of phosphatidic acid at ER/LD junctions in the absence of seipin is suppressed by Sei1p(?Nterm) only in combination with Ldb16p. BMC Cell Biol 16:29
Han, Sungwon; Bahmanyar, Shirin; Zhang, Peixiang et al. (2012) Nuclear envelope phosphatase 1-regulatory subunit 1 (formerly TMEM188) is the metazoan Spo7p ortholog and functions in the lipin activation pathway. J Biol Chem 287:3123-37
Cartwright, Bethany R; Goodman, Joel M (2012) Seipin: from human disease to molecular mechanism. J Lipid Res 53:1042-55

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