Aquaporin-4 as a molecular partner of cystic fibrosis transmembrane conductance regulator in rat Sertoli cells

Sertoli cells (SCs) form the blood–testis barrier (BTB) that controls the microenvironment where the germ cells develop. The cystic fibrosis transmembrane conductance regulator (CFTR) plays an essential role to male fertility and it was recently suggested that it may promote water transport. Interestingly, Aquaporin-4 (AQP4) is widely expressed in blood barriers, but was never identified in SCs. Herein we hypothesized that SCs express CFTR and AQP4 and that they can physically interact. Primary SCs cultures from 20-day-old rats were maintained and CFTR and AQP4 mRNA and protein expression was assessed by RT-PCR and Western blot, respectively. The possible physical interaction between CFTR and AQP4 was studied by co-immunoprecipitation. We were able to confirm the presence of CFTR at mRNA and protein level in cultured rat SCs. AQP4 mRNA analysis showed that cultured rat SCs express the transcript variant c of AQP4, which was followed by immunodetection of the correspondent protein. The co-immunoprecipitation experiments showed a direct interaction between AQP4 and CFTR in cultured rat SCs. Our results suggest that CFTR physically interacts with AQP4 in rat SCs evidencing a possible mechanism by which CFTR can control water transport through BTB. The full enlightenment of this particular relation between CFTR and AQP4 may point towards possible therapeutic targets to counteract male subfertility/infertility in men with Cystic Fibrosis and mutations in CFTR gene, which are known to impair spermatogenesis due to defective water transport.