Document Detail

Rab18 localizes to lipid droplets and induces their close apposition to the endoplasmic reticulum-derived membrane.
MedLine Citation:
PMID:  15914536     Owner:  NLM     Status:  MEDLINE    
Lipid droplets (LDs) are organelles that store neutral lipids, but their regulatory mechanism is not well understood. In the present study, we identified Rab18 as an LD component of HepG2 cells by proteomic analysis, and confirmed its localization by immunohistochemistry and western blotting. Wild-type and dominant-active Rab18 localized to LDs but the dominant-negative form did not. Endogenous Rab18 coexisted with adipocyte differentiation-related protein (ADRP) in LDs, but the labeling intensity of the two proteins showed clear reciprocity. Consistent with this observation, overexpression of Rab18 induced a decrease in the amounts of ADRP in LDs in HepG2 and BALB/c 3T3 cells. Furthermore, Rab18 overexpression caused close apposition of LDs to membrane cisternae connected to the rough ER. Two other procedures that decrease ADRP, i.e. RNA interference and brefeldin A treatment, induced the same morphological change, indicating that decrease in ADRP was the cause of the LD-ER apposition. In accordance with similar structures found between ER and other organelles, we propose that the ER membrane apposed to LDs should be named the LD-associated membrane, or LAM. The present results suggested that Rab18 regulates LAM formation, which is likely to be involved in mobilizing lipid esters stored in LDs.
Shintaro Ozeki; Jinglei Cheng; Kumi Tauchi-Sato; Naoya Hatano; Hisaaki Taniguchi; Toyoshi Fujimoto
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-05-24
Journal Detail:
Title:  Journal of cell science     Volume:  118     ISSN:  0021-9533     ISO Abbreviation:  J. Cell. Sci.     Publication Date:  2005 Jun 
Date Detail:
Created Date:  2005-06-09     Completed Date:  2005-10-27     Revised Date:  2011-10-18    
Medline Journal Info:
Nlm Unique ID:  0052457     Medline TA:  J Cell Sci     Country:  England    
Other Details:
Languages:  eng     Pagination:  2601-11     Citation Subset:  IM    
Department of Anatomy and Molecular Cell Biology, Graduate School of Medicine, Nagoya University, Showa, Japan.
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MeSH Terms
BALB 3T3 Cells
Down-Regulation / genetics
Endoplasmic Reticulum / chemistry,  metabolism*,  ultrastructure
Gene Expression
Intracellular Membranes / chemistry,  metabolism*,  ultrastructure
Lipid Metabolism*
Membrane Proteins / genetics,  metabolism
Protein Transport
Time Factors
Tumor Cells, Cultured
rab GTP-Binding Proteins / genetics,  metabolism*
Reg. No./Substance:
0/Membrane Proteins; 0/RAB18 protein, human; 0/Rab18 protein, mouse; 0/perilipin 2; EC 3.6.1.-/rab GTP-Binding Proteins

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