Abstract
We have reported phosphorylations of the basolateral membrane (BLM) proteins by membrane-bound A-kinase (PKA) by effect of cAMP in rat parotid gland (PG) acinar cells (Kurihara K et al. Am. J. Physiol. 279, C1516-1527, 2000). In the present study, we examined the distribution and function of PKA/A-kinase anchoring protein (AKAP) complex, in order to elucidate the regulation of Na/K-ATPase by phosphorylation among three major salivary glands, i.e., submandibular gland (SMG), sublingual gland (SLG), and PG. Both AKAP-150 protein and its mRNA were clearly detected in the PG, but not detected in SMG and SLG. Membrane-bound form of the RII regulatory subunit, an index for the amount of membrane-anchored PKA holo-enzyme, was substantially present in membranes from PG, but less detectable in those from SMG and SLG. AKAP-150 in PG acinar cells was co-immunoprecipitated with RII regulatory subunit by an anti-RII antiserum, suggesting that AKAP-150 is indeed functional in anchoring RII molecules in vivo. Thus, the AKAP-150/PKA complex is expressed and functions specifically in PG. Furthermore, Na/K-ATPase in the PG was phosphorylated by membrane-anchored endogenous PKA triggered by the addition of cAMP, but those in the SMG and SLG membranes were not. The regulation of Na/K-ATPase by phosphorylation associated to AKAP-anchored PKA is a characteristic rather specific for PG among the three major salivary glands. [Jpn J Physiol 54 Suppl:S89 (2004)]
