Insulin stimulates the release of the glycosyl phosphatidylinositol-anchored membrane dipeptidase from 3T3-L1 adipocytes through the action of a phospholipase C.
Membrane dipeptidase (MDP; EC 3.4.13.19) enzymic activity that was inhibited by cilastatin has been detected on the surface of 3T3-L1 cells. On differentiation of the cells from fibroblasts to adipocytes the activity of MDP increased 12-fold. Immunoelectrophoretic blot analysis indicated that on adipogenesis the increase in the amount of MDP preceded the appearance of GLUT-4. MDP on 3T3-L1 adipocytes was anchored in the bilayer by a glycosyl phosphatidylinositol (GPI) moiety as evidenced by its release into the medium in a hydrophilic form on treatment of the cells with bacterial phosphatidylinositol-specific phospholipase C and the appearance of the inositol 1,2-cyclic monophosphate cross-reacting determinant. Incubation of 3T3-L1 adipocytes with either insulin or the sulphonylurea glimepiride led to a rapid concentration- and time-dependent release of MDP from the cell surface. The hydrophilic form of MDP released from the cells on stimulation with insulin was recognized by antibodies against the inositol 1,2-cyclic monophosphate cross-reacting determinant, indicating that it had been generated by cleavage of its GPI anchor through the action of a phospholipase C.
Movahedi
S
S
Department of Biochemistry and Molecular Biology, University of Leeds, U.K.
Hooper
N M
NM
D016475:3T3 Cells; D017667:Adipocytes / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology*; D000818:Animals; D004150:Dipeptidases / Q000096:biosynthesis / Q000187:drug effects / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000737:chemistry / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry; D051379:Mice; D013453:Sulfonylurea Compounds / Q000494:pharmacology; D010738:Type C Phospholipases / Q000187:drug effects / Q000378:metabolism*
D017261:Glycosylphosphatidylinositols; D007328:Insulin; D008565:Membrane Proteins; D013453:Sulfonylurea Compounds; C057619:glimepiride; D010738:Type C Phospholipases; D004150:Dipeptidases; C038937:dipeptidase