Selective effects of charge on G protein activation by FSH-receptor residues 551-555 and 650-653.
Two cytosolic regions of the rat testicular FSH receptor (FSHR), residues 533-555 and 645-653, have been identified as G protein-coupling domains. We localized the activity in these domains to their C-terminal sequences, residues 551-555 (KIAKR, net charge +3) and 650-653 (RKSH, net charge +3), and examined the effects of charge on G protein activation by the C-terminal peptides, using synthetic analogs containing additions, through alanine (A) linkages, of arginine (R, +), histidine (H, +) or both. RA-KIAKR (net charge +4) mimicked the effect of FSHR-(551-555) on guanine nucleotide exchange in rat testis membranes, but reduced its ability to inhibit FSH-stimulated estradiol biosynthesis in cultured rat Sertoli cells. Further increasing net charge by the addition of H (HARA-KIAKR, net charge +5) increased guanosine 5'-triphosphate (GTP) binding, but eliminated FSHR-(551-555) effects on FSH-stimulated steroidogenesis. HA-RKSH (net charge +4) significantly inhibited guanine nucleotide exchange in rat testis membranes, but stimulated basal and potentiated FSH-induced estradiol biosynthesis in cultured rat Sertoli cells. Addition of two H residues (HAHA-RKSH, net charge +5) restored GTP binding and further potentiated basal and FSH-stimulated steroidogenesis. These results suggest that positive charges in G protein-coupling domains of the FSHR play a role in modulating G protein activation and postbinding effects of FSH, such as steroidogenesis.
Grasso
P
P
Albany Medical College, NY, USA.
Deziel
M R
MR
Reichert
L E
LE
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D004563:Electrochemistry; D004958:Estradiol / Q000096:biosynthesis; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry* / Q000494:pharmacology; D017433:Protein Structure, Secondary; D051381:Rats; D017207:Rats, Sprague-Dawley; D011962:Receptors, FSH / Q000737:chemistry*; D012708:Sertoli Cells / Q000187:drug effects / Q000378:metabolism; D013329:Structure-Activity Relationship
D010446:Peptide Fragments; D011962:Receptors, FSH; D004958:Estradiol; D006160:Guanosine Triphosphate; D005640:Follicle Stimulating Hormone; D019204:GTP-Binding Proteins