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Distinct stoichiometry of BK Ca channel tetramer phosphorylation specifies channel activation and inhibition by cAMP-dependent protein kinase

2004; National Academy of Sciences; Volume: 101; Issue: 32 Linguagem: Inglês

10.1073/pnas.0402590101

1091-6490

Lijun Tian, Lorraine S. Coghill, Heather McClafferty, Stephen H.-F. Macdonald, F. Antoni, Peter Ruth, Hans‐Guenther Knaus, Michael J. Shipston,

Nicotinic Acetylcholine Receptors Study

Large conductance voltage- and calcium-activated potassium (BK Ca ) channels are important signaling molecules that are regulated by multiple protein kinases and protein phosphatases at multiple sites. The pore-forming α-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 α-subunits, it is not known whether phosphorylation of all or single α-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 α-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 α-subunits is required for channel activation. In contrast, inhibition of BK Ca channel activity requires phosphorylation of only a single α-subunit at a splice insert (STREX)-specific PKA consensus site (S4 STREX ). Thus, distinct modes of BK Ca 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 BK Ca channels by reversible protein phosphorylation.