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Alternative splicing converts the G‐protein coupled follitropin receptor gene into a growth factor type I receptor: Implications for pleiotropic actions of the hormone
Author(s) -
Sairam M.R.,
Jiang L.G.,
Yarney T.A.,
Khan H.
Publication year - 1997
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199712)48:4<471::aid-mrd7>3.0.co;2-n
Subject(s) - biology , follicle stimulating hormone receptor , alternative splicing , receptor , complementary dna , microbiology and biotechnology , 5 ht5a receptor , transmembrane domain , transmembrane protein , hek 293 cells , exon , gene , genetics , follicle stimulating hormone , endocrinology , hormone , luteinizing hormone
Pituitary follitropin (FSH) has pleiotropic actions on gonads, but it is not certain if all these events are mediated by a single receptor. A single gene for the FSH receptor undergoes extensive alternate splicing generating multiple transcripts, and several of these have been cloned and characterized from the sheep testis. In this study we have investigated the expression in HEK (human embryonic kidney) 293 cells of a cloned cDNA encoding the first eight exons of the FSH receptor along with a carboxyterminal extension that contributed a hypothetical single transmembrane domain. This cDNA, which lacked the conventional seven transmembrane motif of the full‐length 695 residue wild‐type receptor protein, was also efficiently expressed on the cell surface and exhibited high affinity and specificity for FSH binding. LH did not compete for FSH binding indicating that these structures contained all the motifs necessary for specific hormone recognition. Following hormone binding and affinity crosslinking the deduced Mr of the expressed receptor was compatible with dimer formation. The expression of these altered FSH receptors on the cell surface was confirmed by immunohistochemistry, which revealed punctate labeling in a pattern comparable to that shown by cells transfected by wild‐type receptor cDNA. Addition of FSH stimulated 3 H‐thymidine incorporation in trasfected cells in a biphasic manner. By performing RT‐PCR we could show that similar altered receptor transcripts were present in both the ovary and testis. Our results reveal for the first time that the seven transmembrane structure of FSH‐receptor is not absolutely necessary for cell surface expression and hormone binding provided other compensating motifs are present in the protein structure for membrane insertion. Some of these features are typical of growth factor receptors. Our investigations also demonstrate that alternate splicing of the FSH receptor gene provides a mechanism for creating receptor diversity and suggest that multiple receptors could be involved in regulation of hormone action. Mol. Reprod. Dev. 48:471–479, 1997. © 1997 Wiley‐Liss, Inc.