Differential expression and functional characterization of luteinizing hormone receptor splice variants in human luteal cells: implications for luteolysis.
The human LH receptor (LHR) plays a key role in luteal function and the establishment of pregnancy through its interaction with the gonadotropins LH and human chorionic gonadotropin. We previously identified four splice variants of the LHR in human luteinized granulosa cells (LGCs) and corpora lutea (CL). Real-time quantitative PCR revealed that expression of the full-length LHR (LHRa) and the most truncated form (LHRd) changed significantly in CL harvested at different stages of the ovarian cycle (P < 0.01, ANOVA). LHRa expression was reduced in the late luteal CL (P < 0.05). Conversely, an increase in LHRd expression was observed in the late luteal CL (P < 0.01). Chronic manipulation of human chorionic gonadotropin in LGC primary cultures supported the in vivo findings. LHRd encodes a protein lacking the transmembrane and carboxyl terminal domains. COS-7 cells expressing LHRd were unable to produce cAMP in response to LH stimulation. COS-7 cells coexpressing LHRd and LHRa also failed to generate cAMP in response to LH, suggesting that this truncated form has a negative effect on the signaling of LHRa. Immunofluorescence staining of LGC and COS-7 cells implied that there is a reduction in cell surface expression of LHRa when LHRd is present. Overall, these results imply expression of LHR splice variants is regulated in the human CL. Furthermore, during functional luteolysis a truncated variant could modulate the cell surface expression and activity of full-length LHR.
Dickinson
Rachel E
RE
Department of Reproductive and DevelopmentalSciences, Division of Obstetrics and Gynaecology, Centre for Reproductive Biology,The Queen's Medical Research Institute, Edinburgh, United Kingdom. r.dickinson@hrsu.mrc.ac.uk
Stewart
Alan J
AJ
Myers
Michelle
M
Millar
Robert P
RP
Duncan
W Colin
WC
D028341:Activins / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D006063:Chorionic Gonadotropin / Q000494:pharmacology; D003338:Corpus Luteum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism; D008184:Luteal Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D003341:Luteolysis / Q000235:genetics* / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011974:Receptors, LH / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction
D006063:Chorionic Gonadotropin; D020033:Protein Isoforms; D011974:Receptors, LH; C422405:activin A; D028341:Activins; D000242:Cyclic AMP; D006854:Hydrocortisone