Mannose 6-phosphate/insulin-like growth factor II receptor fails to interact with G-proteins. Analysis of mutant cytoplasmic receptor domains.
The binding of insulin-like growth factor II (IGF II) to the mannose 6-phosphate (M6P)/IGF II receptor has previously been reported to induce the activation of trimeric G(i)2 proteins by functional coupling to a 14-amino acid region within the cytoplasmic receptor domain (Nishimoto, I., Murayama, Y., Katada, T., Ui, M., and Ogata, E. (1989) J. Biol. Chem. 264, 14029-14038). In the present study, we examined further the potential functional coupling of G-proteins with the human M6P/IGF II receptor and mutant receptors lacking the proposed G-protein activator sequence. IGF II treatment of mouse L-cells expressing either wild type or mutant M6P/IGF II receptors failed to attenuate the pertussis toxin-catalyzed modification of a 40-kDa protein or enhance GTPase activity. In broken L-cell membranes expressing wild type or mutant M6P/IGF II receptors, 30 nM IGF II also failed to affect the pertussis toxin substrate activity. By using phospholipid vesicles reconstituted with human wild type or mutant M6P/IGF II receptors and pertussis toxin-sensitive G-proteins, no stimulation of GTP gamma S binding to or GTPase activity of G(i)2, G(o)1, or G(i)/G(o) mixtures were observed in response to 1 microM IGF II. Furthermore, in vesicles containing purified wild type M6P/IGF II receptors and monomeric G alpha o1 or G alpha i2 and beta gamma dimers no effects of IGF II on GTP gamma S binding could be detected. However, when vesicles reconstituted with M6P/IGF II receptors and G(i)2 proteins were incubated with 100 microM mastoparan GTP gamma S binding was stimulated and GTPase activity was increased significantly. These results indicate that the human M6P/IGF II receptor neither interacts with G-proteins in mouse L-cell membranes nor is coupled to G(i)2 proteins in phospholipid vesicles. This study suggests strongly that the M6P/IGF II receptor does not function in transmembrane signaling in response to IGF II.
Körner
C
C
Institut für Biochemie II, Georg-August-Universität Göttingen, Federal Republic of Germany.
Nürnberg
B
B
Uhde
M
M
Braulke
T
T
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D002384:Catalysis; D003593:Cytoplasm / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007739:L Cells / Q000378:metabolism; D008360:Mannosephosphates / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D037342:Pertussis Toxin; D010743:Phospholipids / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000235:genetics / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000378:metabolism
D008360:Mannosephosphates; D010743:Phospholipids; D017527:Receptor, IGF Type 2; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; C027693:mannose-6-phosphate; D007335:Insulin-Like Growth Factor II; D037342:Pertussis Toxin; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins