Extracellular loop 2 in the FSH receptor is crucial for ligand mediated receptor activation.
The present study aims to determine the role of the specific residues of the extracellular loops (ELs) of the FSH receptor (FSHR) in hormone binding and receptor activation. By substituting the sequences of each of the ELs of human FSHR with those of the luteinizing hormone/choriogonadotropin receptor (LH/CGR), we generated three mutant constructs where the three ELs were individually replaced. A fourth construct had all the three substituted ELs. The receptor expression and hormone binding ability of the mutants were comparable to that of the wild type. Hormone-induced signaling and internalization were lower in the EL2 substitution mutant (EL2M). In this mutant, the EL2 of FSHR was substituted with the corresponding loop of LH/CGR. Interestingly, homology modeling revealed a change in the orientation of EL2 in the mutant receptor. Thus, disruption of EL2 affected overall receptor function, suggesting the role of FSHR specific residues of the loop in ligand mediated signaling.
Division of Structural Biology, National Institute for Research in Reproductive Health (Indian Council of Medical Research), Parel, Mumbai 400 012, India.
Madhavi
M
Dupakuntla
Bhakti
B
Pathak
Binita Sur
BS
Roy
Smita D
SD
Mahale
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000075368:Anoctamins; D018118:Chloride Channels; D000242:Cyclic AMP / Q000378:metabolism; D005640:Follicle Stimulating Hormone / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D059748:Proteolysis; D011962:Receptors, FSH / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011974:Receptors, LH / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D040681:Structural Homology, Protein
C575623:Ano2 protein, rat; D000075368:Anoctamins; D018118:Chloride Channels; D008024:Ligands; D011962:Receptors, FSH; D011974:Receptors, LH; D011993:Recombinant Fusion Proteins; D005640:Follicle Stimulating Hormone; D000242:Cyclic AMP