Background: Rat coagulating gland epithelial cells export proteins by an apocrine secretion mode within membrane blebs arising from the apical plasma membrane. Using a pan-PMCA antibody, we have recently shown the plasma membrane Ca(2+)-ATPase (PMCA) being part of the apical plasma membrane of epithelial cells and incorporated into the aposomal membrane. The mRNA of PMCA isoforms 1 and 4 respectively, have been detected by RT-PCR in rat coagulating gland.
Methods: In order to identify which PMCA isoform is integrated into aposomes during apocrine secretion and whether or not PMCA export is influenced by androgens RT-PCR, in situ hybridization, Western blotting, and immunofluorescence experiments were performed.
Results: PMCA1b is the isoform which is expressed and located in the apical plasma membrane of coagulating gland epithelial cells and is integrated into the aposomal membrane. In contrast, PMCA4 mRNA and protein are restricted to the stroma. Androgen deprivation by castration within 14 days leads to an accumulation of PMCA1b in coagulating gland epithelium, while aposomes are not detected anymore.
Conclusions: We showed for the first time that PMCA isoform 1b is released via aposomes of the epithelial cells of the rat coagulating gland and that the localization of PMCA1b in the epithelial cells is influenced by androgens.
(c) 2008 Wiley-Liss, Inc.