Role of third intracellular loop of galanin receptor type 1 in signal transduction.
To determine the domains essential for G-protein coupling of the human galanin receptor type 1 (GalR1), we have used both GalR1 mutants and synthetic receptor-derived peptides in(125)I-galanin and [(35)S]-GTPgammaS binding studies. Replacement of potential phosphorylation sites by Leu in the third intracellular loop (IC3) of GalR1 did not affect K(D)values for the receptor. Peptides derived form the IC3 loop, and especially the N-terminal part of it were able to increase the rate of [(35)S]-GTPgammaS binding to the trimeric Gialpha1beta1gamma2, but not to Gsalphabeta1gamma2, whereas the peptides corresponding to the IC1 and IC2 loops had no such effect. IC3 loop peptides also inhibited the binding of(125)I-galanin to GalR1 in membranes from Rin m5F cells. Our results suggest that the IC3 loop of GalR1, especially its N-terminal part, defines the coupling of the receptor to the Gialpha1beta1gamma2 protein and consequently, to the signal transduction cascade.
Rezaei
K
K
Department of Neurochemistry and Neurotoxicology, Stockholm University, Stockholm, S-10691, Sweden.
Saar
K
K
Soomets
U
U
Valkna
A
A
Näsman
J
J
Zorko
M
M
Akerman
K
K
Schroeder
T
T
Bartfai
T
T
Langel
U
U
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D019004:Galanin / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007930:Leucine; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D010766:Phosphorylation; D017433:Protein Structure, Secondary; D044091:Receptor, Galanin, Type 1; D044088:Receptors, Galanin; D018013:Receptors, Neuropeptide / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D018411:Spodoptera; D014162:Transfection
D010446:Peptide Fragments; D044091:Receptor, Galanin, Type 1; D044088:Receptors, Galanin; D018013:Receptors, Neuropeptide; D011994:Recombinant Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019004:Galanin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D007930:Leucine