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Functional study of an aberrant splicing variant of the human luteinizing hormone (LH) receptor.

ABSTRACT: The luteinizing hormone receptor (LHR) is a member of a subfamily of G protein-coupled receptors that is characterized by its alternative splicing. In a previous study, we identified a splice site mutation of intron 6 (IVS6-3C>A) in a patient suffering from Leydig cell hypoplasia, which leads to aberrant splicing of LHR mRNA. In vitro expression analysis confirmed that this mutation results in the skipping of exon 7 in the mature mRNA of the LHR gene. In this study, we determined the impact of IVS6-3C>A on the RNA secondary structure and function of LHR-Del7. The three-dimensional structure of the leucine-rich repeats in LHR was predicted by molecular modeling. Radioactive ligand-binding assays verified that LHR-Del7 has no binding affinity for hCG. Furthermore, we detected negligible cAMP production in cells transfected with LHR-Del7. Cells co-expressing LHR-WT and LHR-Del7 were able to generate cAMP in response to hCG, but there was no significant difference between cells transfected with LHR-WT/vector and LHR-WT/LHR-Del7, although the variant was able to localize to cell surface, similar to wild-type receptor. These results indicated that LHR-Del7 does not have a dominant negative effect on LHR-WT cell surface expression, and although the pathological splicing variant LHR-Del7 was able to localize to cell membranes it failed to bind hCG and had no effect on wild-type LHR.

SUBMITTER: Han B

PROVIDER: S-EPMC3292396 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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Functional study of an aberrant splicing variant of the human luteinizing hormone (LH) receptor.

Han Bing B Wang Zhi-quan ZQ Xue Li-qiong LQ Ma Jun-hua JH Liu Wei W Liu Bing-li BL Wu Jia-jun JJ Pan Chun-ming CM Chen Xia X Zhao Shuang-xia SX Lu Ying-li YL Wu Wan-ling WL Qiao Jie J Song Huai-dong HD

Molecular human reproduction 20111014 3

The luteinizing hormone receptor (LHR) is a member of a subfamily of G protein-coupled receptors that is characterized by its alternative splicing. In a previous study, we identified a splice site mutation of intron 6 (IVS6-3C>A) in a patient suffering from Leydig cell hypoplasia, which leads to aberrant splicing of LHR mRNA. In vitro expression analysis confirmed that this mutation results in the skipping of exon 7 in the mature mRNA of the LHR gene. In this study, we determined the impact of I ...[more]

PMID: 22002533

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Project description:Luteinizing hormone (LH) is a pituitary heterodimeric glycoprotein essential in male and female reproduction. Its functional polymorphic variant (V-LH) is determined by two missense mutations (rs1800447, A/G, Trp8Arg; rs34349826, A/G, Ile15Thr) in the LH β-subunit encoding gene (LHB; 19q13.3; 1111 bp; 3 exons). Among women, V-LH has been associated with higher circulating LH and reduced fertility, but the knowledge of its effect on male reproductive parameters has been inconclusive. The objective of this study was to assess the effect of V-LH on hormonal, seminal and testicular parameters in the Baltic young men cohort (n = 986; age: 20.1 ± 2.1 years) and Estonian idiopathic infertility patients (n = 607; 35.1 ± 5.9 years). V-LH was detected by genotyping of the underlying DNA polymorphisms using PCR-RFLP combined with resequencing of a random subset of subjects. Genetic associations were tested using linear regression under additive model and results were combined in meta-analysis. No significant difference was detected between young men and infertility patients for the V-LH allele frequency (11.0 vs. 9.3%, respectively). V-LH was associated with higher serum LH in both, the young men cohort (p = 0.022, allelic effect = 0.26 IU/L) and the idiopathic infertility group (p = 0.008, effect = 0.59 IU/L). In meta-analysis, the statistical significance was enhanced (p = 0.0007, resistant to Bonferroni correction for multiple testing; effect = 0.33 IU/L). The detected significant association of V-LH with increased serum LH remained unchanged after additional adjustment for the SNPs previously demonstrated to affect LH levels (FSHB -211G/T, FSHR Asn680Ser, FSHR -29A/G). Additionally, a suggestive trend for association with reduced testicular volume was observed among young men, and with lower serum FSH among infertility patients. The V-LH carrier status did not affect sperm parameters and other circulating reproductive hormones. For the first time, we show a conclusive contribution of V-LH to the natural variance in male serum LH levels. Its downstream clinical consequences are still to be learned.

Project description:BACKGROUND:Luteinizing hormone secreted by the anterior pituitary gland regulates gonadal function. Luteinizing hormone secretion is regulated both by alterations in gonadotrope responsiveness to hypothalamic gonadotropin releasing hormone and by alterations in gonadotropin releasing hormone secretion. The mechanisms that determine gonadotrope responsiveness are unknown but may involve regulators of G protein signaling (RGSs). These proteins act by antagonizing or abbreviating interaction of Galpha proteins with effectors such as phospholipase Cbeta. Previously, we reported that gonadotropin releasing hormone-stimulated second messenger inositol trisphosphate production was inhibited when RGS3 and gonadotropin releasing hormone receptor cDNAs were co-transfected into the COS cell line. Here, we present evidence for RGS3 inhibition of gonadotropin releasing hormone-induced luteinizing hormone secretion from cultured rat pituitary cells. RESULTS:A truncated version of RGS3 (RGS3T = RGS3 314-519) inhibited gonadotropin releasing hormone-stimulated inositol trisphosphate production more potently than did RSG3 in gonadotropin releasing hormone receptor-bearing COS cells. An RSG3/glutathione-S-transferase fusion protein bound more 35S-Gqalpha than any other member of the G protein family tested. Adenoviral-mediated RGS3 gene transfer in pituitary gonadotropes inhibited gonadotropin releasing hormone-stimulated luteinizing hormone secretion in a dose-related fashion. Adeno-RGS3 also inhibited gonadotropin releasing hormone stimulated 3H-inositol phosphate accumulation, consistent with a molecular site of action at the Gqalpha protein. CONCLUSIONS:RGS3 inhibits gonadotropin releasing hormone-stimulated second messenger production (inositol trisphosphate) as well as luteinizing hormone secretion from rat pituitary gonadotropes apparently by binding and suppressing the transduction properties of Gqalpha protein function. A version of RGS3 that is amino-terminally truncated is even more potent than intact RGS3 at inhibiting gonadotropin releasing hormone-stimulated inositol trisphosphate production.

Dataset Information

Functional study of an aberrant splicing variant of the human luteinizing hormone (LH) receptor.

Publications

Functional study of an aberrant splicing variant of the human luteinizing hormone (LH) receptor.

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