Androgen induces olfactory expression of prostaglandin E₂ receptor Ep1 in the burrow-living fish Bostrychus sinensis

It is well documented that androgens modify olfactory processing in vertebrates. In fish, several lines of evidence indicate that androgens increase olfactory sensitivity to prostaglandin pheromone, but the molecular mechanism is still unclear. Our previous studies showed that prostaglandin E₂ (PGE₂) is a sex pheromone in the burrowing-living fish Chinese black sleeper (Bostrychus sinensis) and that the PGE₂ receptor 1 (Ep1) in the olfactory rosette is a candidate receptor for sensing sex pheromone PGE₂. In the present study, we found that testosterone (T) and 11-ketotestosterone (11-KT) exhibited stimulatory effects on the expression of ep1 in the olfactory rosette in vivo and ex vivo. Moreover, the androgen receptor (Ar) agonist R1881 had similar effects to 11-KT on the expression of ep1 ex vivo, suggesting the up-regulatory effect is mediated by Ar. The amount of arα transcripts (˜1500 copies/100 ng total RNA) was greater than that of arβ (˜300 copies/100 ng total RNA) in the olfactory rosette, and the expression levels of arα increased with spermatogenesis and peaked at late meiosis stage. Moreover, activated Arα but not Arβ transactivated a 2k bp ep1 promoter in HEK293T cell, and some OSNs exhibited co-localization of arα mRNA and Ep1 protein signals. Taken together, our results suggest that Arα, but not Arβ, plays a crucial role in mediating the androgen-induced up-regulation of ep1 expression in B. sinensis. The present study is the first to shed light on the molecular mechanisms whereby androgens enhance responsiveness to prostaglandin sex pheromones in teleosts.