期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2004
卷号：101
期号：32
页码：11897-11902
DOI：10.1073/pnas.0402590101
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Large conductance voltage- and calcium-activated potassium (BKCa) channels are important signaling molecules that are regulated by multiple protein kinases and protein phosphatases at multiple sites. The pore-forming {alpha}-subunits, derived from a single gene that undergoes extensive alternative pre-mRNA splicing, assemble as tetramers. Although consensus phosphorylation sites have been identified within the C-terminal domain of {alpha}-subunits, it is not known whether phosphorylation of all or single {alpha}-subunits within the tetramer is required for functional regulation of the channel. Here, we have exploited a strategy to study single-ion channels in which both the {alpha}-subunit splice-variant composition is defined and the number of consensus phosphorylation sites available within each tetramer is known. We have used this approach to demonstrate that cAMP-dependent protein kinase (PKA) phosphorylation of the conserved C-terminal PKA consensus site (S899) in all four {alpha}-subunits is required for channel activation. In contrast, inhibition of BKCa channel activity requires phosphorylation of only a single {alpha}-subunit at a splice insert (STREX)-specific PKA consensus site (S4STREX). Thus, distinct modes of BKCa channel regulation by PKA phosphorylation exist: an "all-or-nothing" rule for activation and a "single-subunit" rule for inhibition. This essentially digital regulation has important implications for the combinatorial and conditional regulation of BKCa channels by reversible protein phosphorylation.
