Binding of protein phosphatase 2A to the L-type calcium channel Cav1.2 next to Ser1928, its main PKA site, is critical for Ser1928 dephosphorylation.
The cAMP-dependent protein kinase (PKA) controls a large number of cellular functions. One critical PKA substrate in the brain and heart is the L-type Ca(2+) channel Ca(v)1.2, the activity of which is upregulated by PKA. The main PKA phosphorylation site is serine 1928 in the central pore forming alpha(1)1.2 subunit of Ca(v)1.2. PKA is bound to Ca(v)1.2 within a macromolecular signaling complex consisting of the beta(2) adrenergic receptor, trimeric G(s) protein, and adenylyl cyclase for fast, localized, and hence specific signaling [Davare, M. A., Avdonin, V., Hall, D. D., Peden, E. M., Buret, A., Weinberg, R. J., Horne, M. C., Hoshi, T., and Hell, J. W. (2001) Science 293, 98-101]. Protein phosphatase 2A (PP2A) serves to effectively balance serine 1928 phosphorylation by PKA through its association with the Ca(v)1.2 complex [Davare, M. A., Horne, M. C., and Hell, J. W. (2000) J. Biol. Chem. 275, 39710-39717]. We now show that native PP2A holoenzymes, as well as the catalytic subunit itself, bind to alpha(1)1.2 immediately downstream of serine 1928. Of those holoenzymes, only heterotrimeric PP2A containing B' and B' ' subunits copurify with alpha(1)1.2. Preventing the binding of PP2A by truncating alpha(1)1.2 28 residues downstream of serine 1928 hampers its dephosphorylation in intact cells. Our results demonstrate for the first time that a stable interaction of PP2A with Ca(v)1.2 is required for effective reversal of PKA-mediated channel phosphorylation. Accordingly, PKA as well as PP2A are constitutively associated with Ca(v)1.2 for its proper regulation by phosphorylation and dephosphorylation of serine 1928.
Hall
Duane D
DD
Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242-1109, USA.
Feekes
Joel A
JA
Arachchige Don
Aruni S
AS
Shi
Mei
M
Hamid
Jawed
J
Chen
Lina
L
Strack
Stefan
S
Zamponi
Gerald W
GW
Horne
Mary C
MC
Hell
Johannes W
JW
D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D005786:Gene Expression Regulation; D010749:Phosphoprotein Phosphatases / Q000378:metabolism* / Q000494:pharmacology*; D010766:Phosphorylation; D011485:Protein Binding; D054648:Protein Phosphatase 2; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction
D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D011993:Recombinant Fusion Proteins; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2