Abstract
Adipophilin (ADPH), a prominent protein component of lipid storage droplets (LSDs), is postulated to be necessary for the formation and cellular function of these structures. The presence of significant sequence similarities within an approximately 100 amino acid region of the N-terminal portions of ADPH and related LSD binding proteins, perilipin and TIP47, has implicated this region, known as the "PAT" domain, in LSD targeting. Here we investigate the role of the PAT domain in targeting ADPH to LSDs by expressing this region, as well as selected N- and C-terminal truncations of mouse ADPH in COS7 cells as epitope-tagged fusion proteins. Our studies show that truncations lacking either the PAT domain or the C-terminal half of ADPH both correctly targeted LSDs and increased the LSD content of transfected cells. Neither the PAT domain nor the C-terminal half of ADPH appeared to target LSDs or affect the LSD number. Instead, targeting fragments encompassed a putative alpha-helical region between amino acids 189 and 205, implicating this region in both LSD targeting and regulation of LSD formation.
Highlights
Adipophilin (ADPH), a prominent protein component of lipid storage droplets (LSDs), is postulated to be necessary for the formation and cellular function of these structures
ADPH[1–220]-vesicular stomatitis virus (VSV) begins at the N-terminus of ADPH and encompasses both the PAT domain and the major ␣-helical region predicted by Chou-Fasman analysis
Our studies show that intact, full-length ADPH is not required for LSD targeting
Summary
Adipophilin (ADPH), a prominent protein component of lipid storage droplets (LSDs), is postulated to be necessary for the formation and cellular function of these structures. N- and C-terminal truncations of mouse ADPH that encompassed a putative ␣-helical region between amino acids 189 and 205 targeted LSDs and increased LSD number in transfected cells. These findings demonstrate that the LSD-targeting and lipid droplet-accumulation functions of ADPH do not require the full-length protein and raise the possibility that a discrete structural region of ADPH possessing ␣-helical properties is responsible for both LSD association and regulation of LSD formation and, potentially, metabolism
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