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J Mol Endocrinol. 2015 Jun;54(3):193-204. doi: 10.1530/JME-14-0275. Epub 2015 Mar 19.

FSH receptor-specific residues L501 and I505 in extracellular loop 2 are essential for its function.

Author information

1
Division of Structural BiologyNational Institute for Research in Reproductive Health (Indian Council of Medical Research), Jehangir Merwanji Street, Parel, Mumbai 400 012, IndiaNational Institute for Research in Reproductive Health (Indian Council of Medical Research)ICMR Biomedical Informatics Centre, Jehangir Merwanji Street, Parel, Mumbai 400 012, India.
2
Division of Structural BiologyNational Institute for Research in Reproductive Health (Indian Council of Medical Research), Jehangir Merwanji Street, Parel, Mumbai 400 012, IndiaNational Institute for Research in Reproductive Health (Indian Council of Medical Research)ICMR Biomedical Informatics Centre, Jehangir Merwanji Street, Parel, Mumbai 400 012, India Division of Structural BiologyNational Institute for Research in Reproductive Health (Indian Council of Medical Research), Jehangir Merwanji Street, Parel, Mumbai 400 012, IndiaNational Institute for Research in Reproductive Health (Indian Council of Medical Research)ICMR Biomedical Informatics Centre, Jehangir Merwanji Street, Parel, Mumbai 400 012, India smitamahale@hotmail.com.

Abstract

The extracellular loop 2 (EL2) of FSH receptor (FSHR) plays a pivotal role in various events downstream of FSH stimulation. Because swapping the six FSHR-specific residues in EL2 (chimeric EL2M) with those from LH/choriogonadotropin receptor resulted in impaired internalization of FSH-FSHR complex and low FSH-induced cAMP production, six substitution mutants of EL2 were generated to ascertain the contribution of individual amino acids to the effects shown by chimeric EL2M. Results revealed that L(501)F mainly and I(505)V to a lesser extent contribute to the diminished receptor function in chimeric EL2M. HEK293 cells stably expressing WT and chimeric EL2M FSHR were generated to track the fate of the receptors post FSH induction. The chimeric EL2M FSHR stable clone showed weak internalization and cAMP response similar to transiently transfected cells. Furthermore, reduced FSH-induced ERK phosphorylation was also observed. The interaction of activated chimeric EL2M and L(501)F FSHR with β-arrestins was weak compared with WT FSHR, thus explaining the impaired internalization of chimeric EL2M and corroborating the indispensable role of EL2 in receptor function.

KEYWORDS:

FSH receptor; extracellular loop 2; internalization; signaling

PMID:
25791375
DOI:
10.1530/JME-14-0275
[Indexed for MEDLINE]

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