title: Insulin stimulates the acute release of adipsin from 3T3-L1 adipocytes.
abstract: The release of adipsin, a serine proteinase with complement factor D activity, from 3T3-L1 adipocytes was measured by quantitative immunoblotting. This protein is secreted constitutively from 3T3-L1 adipocytes, and there is a 2-fold increase in the amount of adipsin released from cells treated with insulin for 1 to 10 min. Longer exposure to insulin had no further effect on the rate of adipsin release. Adipsin does not appear to be anchored by a glycosylphosphatidylinositol moiety, since adipsin which was been released with Triton X-114 from an intracellular membrane fraction partitions into the aqueous phase. Using a previously described procedure for the isolation of vesicles containing the insulin-responsive intracellular glucose transporters (GT vesicles), we show here that these GT vesicles contain an insulin-responsive pool of adipsin. Thus, insulin stimulates the secretion of a soluble protein, adipsin, as well as translocation to the plasma membrane of integral membrane proteins, including the glucose transporter, the transferrin receptors, and the insulin-like growth factor II receptor.
authors.affiliation: Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03756.
authors.forename: K
authors.initials: K
authors.lastname: Kitagawa
authors.forename: B S
authors.initials: BS
authors.lastname: Rosen
authors.forename: B M
authors.initials: BM
authors.lastname: Spiegelman
authors.forename: G E
authors.initials: GE
authors.lastname: Lienhard
authors.forename: L I
authors.initials: LI
authors.lastname: Tanner
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D002451:Cell Compartmentation / Q000187:drug effects; D002460:Cell Line; D011416:Complement Factor D; D007328:Insulin / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D051379:Mice; D008970:Molecular Weight; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D012636:Secretory Rate / Q000187:drug effects; D012697:Serine Endopeptidases; D012995:Solubility
chemical_list: D007328:Insulin; D009004:Monosaccharide Transport Proteins; D012697:Serine Endopeptidases; D011416:Complement Factor D; C493491:complement factor D, mouse