Heat shock affects trafficking of DAX-1 by inducing its rapid and reversible cytoplasmic localization

Heat stress upregulates aromatases expression through nuclear DAX-1 deficiency in R2C Leydig tumor cells

An appropriate balance between testicular testosterone and estradiol is required for spermatogenesis. Excess estradiol is often identified in the semen and serum of infertile men; however, the mechanisms behind this observation remain unclear. This study indicates the relationship between heat stress and aromatase synthesis in Leydig cells. We used R2C rat Leydig tumor cells, which can synthesize both testosterone and estradiol. Aromatase transcription was regulated by the PⅡ promoter with or without heat stress. Heat stress at 40 °C increased aromatase expression and decreased testosterone to estradiol ratio and nuclear DAX-1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1), which is a suppressor of steroidogenic factor 1 (SF-1). Leptomycin B and KPT-185, a nuclear export inhibitor, prevented nuclear DAX-1 deficiency induced by heat stress and inhibited aromatase transcription. These results indicate that heat stress interferes with DAX-1-SF-1 interaction and induces SF-1-dependent aromatase transcription.

Nuclear Import of a Secreted "Candidatus Liberibacter asiaticus" Protein is Temperature Dependent and Contributes to Pathogenicity in Nicotiana benthamiana

“Candidatus Liberibacter asiaticus” (CLas), one of the causal agents of citrus Huanglongbing (HLB), secretes proteins with functions that are largely unknown. In this study, we demonstrated that CLIBASIA_00460, one of the CLas-encoded Sec-dependent presecretory proteins, might contribute to the phytopathogenicity of CLas. CLIBASIA_00460 was conserved in CLas strains and expressed at a significantly higher level in citrus than in Asian citrus psyllid. Agrobacteria-mediated transient expression in Nicotiana benthamiana epidermal cells showed that the mature CLIBASIA_00460 (m460) without the putative Sec-dependent signal peptide was localized in multiple cellular compartments including nucleus at 25°C, but that nuclear accumulation was greatly decreased as the temperature rose to 32°C. When overexpressed via a Potato virus X (PVX)-based expression vector in N. benthamiana, m460 induced no local symptoms, but tiny necrotic spots were scattered on the systemic leaves. However, NLS-m460, which contains the SV40 nuclear localization sequence (NLS) at the N-terminus to promote nuclear import of m460, caused chlorosis and necrosis in the local leaves and severe necrosis in the systemic leaves. Taken together, these data suggest that CLIBASIA_00460 represented a novel virulence factor of CLas, and that nuclear localization of this protein was temperature dependent and positively correlated with its pathogenicity in planta.

Role of Orphan Nuclear Receptor DAX-1/NR0B1 in Development, Physiology, and Disease

DAX-1/NR0B1 is an unusual orphan receptor that has a pivotal role in the development and function of steroidogenic tissues and of the reproductive axis. Recent studies have also indicated that this transcription factor has an important function in stem cell biology and in several types of cancer. Here I critically review the most important findings on the role of DAX-1 in development, physiology, and disease of endocrine tissues since the cloning of its gene twenty years ago.

Targeting DAX-1 in embryonic stem cells and cancer

IMPORTANCE OF THE FIELD

DAX-1 (NR0B1) is an unusual orphan nuclear receptor whose function is essential for the development of the human adrenal cortex and onset of puberty. Recent data have implicated this transcription factor also in embryonic stem cell and cancer biology.

AREAS COVERED IN THIS REVIEW

The role of DAX-1 in the regulation of development and function of the adrenal cortex, reproductive axis, embryonic stem cells and a few types of cancer.

WHAT THE READER WILL GAIN

Here we review the past and present milestones in DAX-1 research and try to provide hints about the development and fields of application of DAX-1-targeted drugs in the future.

TAKE HOME MESSAGE

The unusual structure and restricted expression pattern of DAX-1 may offer unique opportunities for drug discovery.