Catenins in the rat epididymis: their expression and regulation in adulthood and during postnatal development

Tight and adhering junctions are important in maintaining the integrity of the epididymal epithelium and formation of the blood epididymal barrier, which are crucial for sperm maturation and storage. The composition of the catenin-adhering junctional family of proteins and their relationship with tight junctions remain to be established in the epididymis. In the normal adult rat epididymis, immunostaining for three anticatenin antibodies (alpha, beta-, and p120ctn) was noted along the lateral plasma membranes (LPM) between adjacent epithelial cells. Although alpha-catenin and beta-catenin were maximally expressed in the corpus and cauda epididymis, p120 expression was intense and similar in all epididymal regions. Bilateral orchidectomy of adult rats indicated that the expression of p120 at the LPM was not altered compared with that in control animals. On the other hand, staining at the LPM for alpha- and beta-catenin was markedly reduced, concomitant with an increased cytoplasmic reaction in each epididymal region. As the staining pattern for alpha- and beta-catenin returned to that seen in control animals after testosterone supplementation, it is suggested that their localization and targeting to the LPM are regulated by androgens. This is confirmed by postnatal studies in which maximal expression at the LPM for each catenin occurs by d 49, when androgen levels are adult-like. Immunolocalization of zona occludens-1 along with immunoprecipitation of epididymal homogenates of the initial segment/caput region of the epididymis revealed that zona occludens-1 is an integral part of the adhering junctional complex in young rats and coprecipitates with beta-catenin at the level of the apical tight junctions.