Abstract: Multiple sites on the α1 and β subunits of purified skeletal muscle calcium channels are phosphorylated by cyclic AMP‐dependent protein kinase, resulting in three different tryptic phosphopeptides derived from each subunit. Phosphoprotein phosphatases dephosphorylated these sites selectively. Phosphoprotein phosphatase 1 (PP1) and phosphoprotein phosphatase 2A (PP2A) dephosphorylated both α1 and β subunits at similar rates, whereas calcineurin dephosphorylated β subunits preferentially. PP1 dephosphorylated phosphopeptides 1 and 2 of the α1 subunit more rapidly than phosphopeptide 3. In contrast, PP2A dephosphorylated phosphopeptide 3 of the α1 subunit preferentially. All three phosphoprotein phosphatases preferentially dephosphorylated phosphopeptide 1 of the β subunit and dephosphorylated phosphopeptides 2 and 3 more slowly. Mn2+ increased the rate and extent of dephosphorylation of all sites by calcineurin so that >80% dephosphorylation of both α1 and β sub‐units was obtained. The results demonstrate selective dephosphorylation of different phosphorylation sites on the α1 and β subunits of skeletal muscle calcium channels by the three principal serine/threonine phosphoprotein phosphatases.
|Original language||English (US)|
|Number of pages||7|
|Journal||Journal of neurochemistry|
|State||Published - Oct 1993|
All Science Journal Classification (ASJC) codes
- Cellular and Molecular Neuroscience