Characterization of pannexin1 and pannexin3 and their regulation by androgens in the male reproductive tract of the adult rat

Abstract

Pannexins (Panxs) are channel-forming proteins that have homology to the invertebrate gap junction proteins, the innexins. These proteins form membrane channels implicated in ATP release. To evaluate the role of Panxs in the male reproductive tract, we investigated the distribution and regulation of Panx1 and 3 in the testis, efferent ducts (ED), and epididymis of adult rats. In the testis, Panx1 localized to the basal compartment of the seminiferous epithelium, while Panx3 was expressed in Leydig cells. In the ED, both Panxs were expressed in the apical region of ciliated cells. In the epididymis, Panx1 was detected at the base of the epithelium, at times encompassing basal cells, while Panx3 was restricted to the apical plasma membrane of principal cells. Panx3 immunoreactions were high throughout the entire epididymis while Panx1 was high in all regions except the initial segment. Multiple transcripts for Panx1 were identified, and sequence analysis indicated that alternative splicing might account for them. Orchidectomy resulted in the expression of multiple immunoreactive Panx1 bands, and these appeared to be androgen-repressed throughout the epididymis. Panx3 levels in all epididymal regions were also androgen-repressed. Deglycosylation experiments indicated that some Panx1 species were due to glycosylation, but this did not account for all Panx1 immunoreactive species. In summary, Panxs expressed in the epididymis and regulated by both alternative splicing events and androgens. These proteins may play a role in ATP secretion into the epididymal lumen and basal extracellular spaces for functions involving sperm transport and maturation.

Pannexin1 and Pannexin3 Exhibit Distinct Localization Patterns in Human Skin Appendages and are Regulated during Keratinocyte Differentiation and Carcinogenesis

“…An alternative possibility is that since Panx3 is encoded by fi ve exons, this could allow for the possibility of splice variants leading to proteins of different sizes. However, unlike Panx1 (Baranova et al, 2004, Ma et al, 2009, Turmel et al, 2011, this has not yet been described for Panx3. Furthermore, as Panx3 is a glycoprotein, the degree of glycosylation or additional posttranslational modifi cations may account for its higher molecular weight.…”

Purinergic signalling in the reproductive system in health and disease

“…Since mutations of CFTR are a leading cause of infertility, the authors propose that defective ATP signalling in the epididymis might contribute to the dysfunction. It has been claimed that pannexins may play a role in ATP secretion into the epididymal lumen and basal extracellular spaces for functions involving sperm transport and maturation [405]. Evidence was presented that both ATP and NA act as cotransmitters in sympathetic nerves supplying the smooth muscle of the rat cauda epididymis involving P2X and α 1 -adrenoceptors, respectively [416].…”

The cellular life of pannexins

“…25 Exon 3 of rat Panx1 was also reported to be alternatively spliced in tissues of the male reproductive tract generating a shorter Panx1 isoform of ∼356 amino acids. 22 In this study, pannexin expression seemed to be regulated by testosterone. 22 Only one PANX2 splice variant was found to be the product of splicing resulting in an alternative start codon.…”

“…22 In this study, pannexin expression seemed to be regulated by testosterone. 22 Only one PANX2 splice variant was found to be the product of splicing resulting in an alternative start codon. This PANX2alt2 splice variant of only 509 amino acids has been proposed to play a regulatory role.…”

“…9 Glycosylation also plays a role in regulating the potential intermixing of pannexin family members into channels because the Gly2 glycosylation species of Panx1 appears incapable of being coimmunoprecipitated (coIP) with Panx2 when coexpressed in HEK293T cells. 9 Interestingly, the level of Panx1 glycosylation was reported to change in the male reproductive tract of rats in response to orchidectomy, 22 as well as after induction of hippocampal seizures by Co 2+ treatment in mouse brains. 30 All these phenomena suggests a role for the glycosylation state regulating pannexin function.…”