Identification of novel putative membrane proteins selectively expressed during adipose conversion of 3T3-L1 cells.
Fat tissue plays a critical role in the regulation of energy metabolism. Here we report the proteomic identification of a novel _fa_t tissue-specific _l_ow molecular weight _p_rotein (Falp) which responds to insulin. Falp is preferentially expressed in adipocytes but not in preadipocytes, as shown by two-dimensional gel electrophoresis. Northern blot analysis shows that the Falp gene is predominantly expressed in brown and white fat tissues, but not in any other tissues examined. Human homologs of mouse Falp are found to exist as two alternatively spliced isoforms, which share the same N-terminus but have different C-termini. Both human and mouse Falp contain a conserved putative transmembrane domain. Immunofluorescent analyses of 3T3-L1 adipocytes show that Falp protein strictly localizes at a compact perinuclear membrane compartment. Treatment of cells with insulin induces the redistribution of Falp into numerous discrete spotty structures spreading throughout the cytoplasm. Whereas the function of Falp is currently unclear, its tissue specific expression and the responsiveness to insulin suggest that Falp might be involved in a process specifically restricted to adipose tissue function, such as vesicular transport and protein secretion.
Xu
Aimin
A
The School of Biological Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand. a.xu@auckland.ac.nz
Choi
Kai-Luk
KL
Wang
Yu
Y
Permana
Paska A
PA
Xu
Lance Yi
LY
Bogardus
Clifton
C
Cooper
Garth J S
GJ
D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D019556:COS Cells; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D006801:Humans; D007150:Immunohistochemistry; D007328:Insulin / Q000494:pharmacology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution
D018076:DNA, Complementary; D007328:Insulin; D008565:Membrane Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; C458099:MRAP protein, human; C560868:MRAP protein, mouse