Insulin stimulates the release of a subset of GPI-anchored proteins in a G-protein independent manner.
The glycosyl-phosphatidylinositol anchored protein, membrane dipeptidase (EC 3.4.13.19) is released from the surface of 3T3-L1 adipocytes in response to insulin treatment through the action of a phospholipase C. The present study investigates the role of guanine-nucleotide binding proteins (G-proteins) in this process. Treatment of permeabilized 3T3-L1 adipocytes with GTPgammaS did not cause release of membrane dipeptidase into the medium, while GDPbetaS did not inhibit the insulin-stimulated release of membrane dipeptidase. Other activators of G-proteins, including the tetradecapeptide mastoparan, pertussis toxin and AlF3, also caused no significant release of membrane dipeptidase from the surface of the 3T3-L1 adipocytes. From these observations it is concluded that G-proteins are not involved in the insulin-stimulated release of membrane dipeptidase. Although X-Pro aminopeptidase (EC 3.4.11.9) is GPI-anchored in 3T3-L1 adipocytes as shown by digestion with bacterial phosphatidylinositol-specific phospholipase C, it was not released upon insulin treatment of the cells, indicating that only a subset of the GPI-anchored proteins are susceptible to insulin-stimulated release.
Movahedi
S
S
School of Biochemistry and Molecular Biology, University of Leeds, UK.
Pang
S
S
Hooper
N M
NM
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000201:enzymology / Q000648:ultrastructure; D000469:Alkaline Phosphatase / Q000378:metabolism*; D017607:Aluminum Compounds / Q000494:pharmacology; D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D004150:Dipeptidases / Q000378:metabolism*; D005459:Fluorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins; D051379:Mice; D010455:Peptides; D037342:Pertussis Toxin; D010738:Type C Phospholipases / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D014862:Wasp Venoms / Q000494:pharmacology
D017607:Aluminum Compounds; D017261:Glycosylphosphatidylinositols; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D010566:Virulence Factors, Bordetella; D014862:Wasp Venoms; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C037500:mastoparan; D037342:Pertussis Toxin; D000469:Alkaline Phosphatase; D010738:Type C Phospholipases; D000626:Aminopeptidases; C022750:X-Pro aminopeptidase; D004150:Dipeptidases; C038937:dipeptidase; D019204:GTP-Binding Proteins; D005459:Fluorides; C032311:aluminum fluoride