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Biochemical Mechanism of FIT Proteins in Mediating Lipid Droplet Formation
Author(s) -
Gross David A.,
Zhan Chenyang,
Silver David L.
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.594.2
Subject(s) - endoplasmic reticulum , mutant , microbiology and biotechnology , function (biology) , lipid droplet , chemistry , transmembrane protein , biochemistry , biology , biophysics , gene , receptor
The process of lipid droplet (LD) formation is an evolutionarily conserved process among all eukaryotes and plays an important role in both cellular physiology and disease. Recently, our lab discovered F at storage‐ I nducing T rans m embrane proteins 1 & 2 (FIT1/FITM1 and FIT2/FITM2) as an evolutionarily‐conserved family of proteins involved in fat storage. These proteins have distinct tissue distributions, are both exclusively localized to the endoplasmic reticulum, mediate triglyceride (TAG)‐rich LD accumulation when overexpressed, but do not synthesize TAG. Our lab has shown that FIT proteins purified in detergent micelles directly bind to TAG with specificity and saturation binding kinetics in order to mediate LD formation. A FIT2 gain‐of‐function mutant that forms larger LDs, FLL(157–9)AAA, showed a significant increase in TAG binding, while FIT1 and a FIT2 partial loss‐of‐function mutant, N80A, displayed abrogated TAG binding, producing smaller LDs relative to wild‐type FIT2. Here, we present biochemical evidence supporting a unique two‐step mechanism for LD formation via FIT2. Attempts to reconstitute the activity of FIT proteins will also be presented. In summary, FIT proteins are the first transmembrane domain‐containing proteins shown to bind TAG, a function that is important for FIT‐mediated LD formation.