A novel nonsense mutation of the glucocorticoid receptor gene causing glucocorticoid resistance with infertility.

Abstract

Purpose: Chrousos syndrome is a rare disease mainly caused by inactivated mutations in the NR3C1 gene, which encodes the human glucocorticoid receptor (GR). We reported a male patient of Chrousos syndrome, who had a novel nonsense mutation (c.1839T > A, p. Tyr613Ter) in NR3C1 and presented with oligospermic and infertility but without other typical clinical manifestation. The aim of this study is to explore the molecular mechanisms that cause the unique clinical manifestations in this patient.

Methods: Mutant plasmids were transfected to HEK293T and HeLa cells to evaluate glucocorticoid sensitivity and GR expression. Proteomic and further cellular experiments were used to illustrate the mechanism of GR expression change induced by mutation.

Results: The mutation causes the deletion of the ligand-binding region of the GR (GR Y613*). Compared with GR wild type (GR WT), GR Y613* had a decreased affinity with dexamethasone, reduced nuclear translocation and decreased transactivation of the glucocorticoid response gene mouse mammary tumor virus promoter. GR Y613* caused decreased protein but unchanged gene expression. E3 ligase STUB1 was identified to regulate ubiquitin-proteasome degradation of GR Y613*. Compared with other human tissues and cell types, expression of STUB1 in testis and Sertoli cells was low.

Conclusions: GR Y613* causes reduced sensitivity to glucocorticoids. STUB1 promotes ubiquitination and degradation of GR Y613*. Low expression of STUB1 in human testis compared with other tissue might cause accumulation of GR Y613*, as a potential explanation of the infertility of Chrousos syndrome.