A Splice Variant of the Human Luteinizing Hormone (LH) Receptor Modulates the Expression of Wild-Type Human LH Receptor

Abstract

We previously reported a splice variant form of human LH receptor [hLHR(exon 9)] that lacks exon 9, coding the N-terminal extracellular region close to the first transmembrane domain. Several recent studies suggest that G protein-coupled receptors are able to form dimerization or oligomerization of the receptor, suggesting an intermolecular interaction between hLHR(exon 9) and the wild-type LH receptor (hLHR). The aim of this study, using coimmunoprecipitation, is to examine whether hLHR forms an association with hLHR(exon 9). An interaction between hLHR(exon 9) with the immature band (68 kDa) of hLHR and not with the mature band (85 kDa) was seen. When hLHR and hLHR(exon 9) were coexpressed, the density of hLHR expression was significantly reduced, compared with hLHR expressed alone. The human chorionic gonadotropin-stimulated cAMP accumulation in the cells expressing hLHR(exon 9) was also impaired, compared with the cells expressing hLHR. In this study, we demonstrated that hLHR is capable of forming receptor complexes. Our findings may expand the possibility of a splice variant of hLHR specifically modulating the functional property of the wild-type hLHR.

Luteinizing Hormone Receptor Ectodomain Splice Variant Misroutes the Full-Length Receptor into a Subcompartment of the Endoplasmic Reticulum

“…In the present study we demonstrate that the common splice variant comprising a large portion of the N-terminal extracellular domain of the receptor can regulate expression of the full-length receptor in a heterologous expression system in mammalian cells. Similar findings have been reported in the past for a few other GPCRs (Grosse et al, 1997;Karpa et al, 2000;Sarmiento et al, 2004) and recently also for another LHR variant (Nakamura et al, 2004). Thus, regulation of GPCRs by their corresponding splice variants may be a more common phenomenon than has been anticipated.…”

“…It can be hypothesized that misrouting of the full-length receptor might be a consequence of its interaction with the variant. In agreement with this possibility, Nakamura et al (2004) have shown that the human LHR splice variant lacking exon 9 interacts with and can alter expression of the full-length LHR as well as that of another glycoprotein hormone receptor, the follicle-stimulating hormone receptor (Yamashita et al, 2005). Furthermore, the recently reported crystal structure of the truncated follicle-stimulating hormone receptor ectodomain and its cognate hormone reveal that the ectodomain is able to dimerize in the absence of the C-terminal half of the protein (Fan and Hendrickson, 2005).…”

“…A few splice variants and ER-retained mutant forms of GPCRs have been shown to interfere with normal processing and transport of the corresponding wild-type receptors (Benkirane et al, 1997;Grosse et al, 1997;Karpa et al, 2000;Brothers et al, 2004;Kaykas et al, 2004;Nakamura et al, 2004;Sarmiento et al, 2004). Thus, we next investigated whether the LHRvariant that was apparently sequestered by the ER quality control components might have an effect on the biogenesis of the full-length receptor.…”

“…Cell surface expression of GPCRs has also been found to be modulated by their corresponding splice variants and naturally occurring mutant forms. They appear to function in a dominant negative manner and hinder cell surface expression of the corresponding wild-type receptors, most likely through association in the ER (Benkirane et al, 1997;Grosse et al, 1997;Karpa et al, 2000;Brothers et al, 2004;Kaykas et al, 2004;Nakamura et al, 2004;Sarmiento et al, 2004).The LHR is a GPCR that recognizes glycoprotein hormones LH and chorionic gonadotropin (CG) that are secreted by the pituitary gland and placenta, respectively. These hormones are the major regulators of reproductive-related endocrine functions and steroidogenesis (Pierce and Parsons, 1981).…”

Molecular determinants of a competent bovine corpus luteum: first- vs final-wave dominant follicles

“…The variants reported include a complete deletion of exon 10 and/ or partial deletion of exon 11, and there is also a loss of exon 3 in bovine granulosa cells (Nogueira et al 2007). In humans, a splice variant lacking exon 10 produces a protein capable of binding hCG, but not LH (Müller et al 2003) and, in keeping with a further human splice variant lacking exon 9, can form complexes with other LHCGR isoforms to reduce overall receptor expression and cAMP accumulation (Nakamura et al 2004, Ndiaye et al 2005, Minegishi et al 2007. Primer design in this study (Table 1) allowed us to confirm the expression of LHCGR transcripts lacking exons 3 and 9; however, we were unable to detect transcripts lacking exon 10 in any of the somatic (i.e.…”