Molecular mechanism of calcium channel regulation in the fight-or-flight response.
During the fight-or-flight response, the sympathetic nervous system stimulates L-type calcium ion (Ca2+) currents conducted by Ca(V)1 channels through activation of β-adrenergic receptors, adenylyl cyclase, and phosphorylation by adenosine 3',5'-monophosphate-dependent protein kinase [also known as protein kinase A (PKA)], increasing contractility of skeletal and cardiac muscles. We reconstituted this regulation of cardiac Ca(V)1.2 channels in non-muscle cells by forming an autoinhibitory signaling complex composed of Ca(V)1.2Δ1800 (a form of the channel truncated at the in vivo site of proteolytic processing), its noncovalently associated distal carboxyl-terminal domain, the auxiliary α₂δ₁ and β(2b) subunits, and A-kinase anchoring protein 15 (AKAP15). A factor of 3.6 range of Ca(V)1.2 channel activity was observed from a minimum in the presence of protein kinase inhibitors to a maximum upon activation of adenylyl cyclase. Basal Ca(V)1.2 channel activity in unstimulated cells was regulated by phosphorylation of serine-1700 and threonine-1704, two residues located at the interface between the distal and the proximal carboxyl-terminal regulatory domains, whereas further stimulation of channel activity through the PKA signaling pathway only required phosphorylation of serine-1700. Our results define a conceptual framework for Ca(V)1.2 channel regulation and identify sites of phosphorylation that regulate channel activity.
Fuller
Matthew D
MD
Department of Pharmacology, University of Washington, Box 357280, Seattle, WA 98195-7280, USA.
Emrick
Michelle A
MA
Sadilek
Martin
M
Scheuer
Todd
T
Catterall
William A
WA
D054758:A Kinase Anchor Proteins / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005239:Fear; D008565:Membrane Proteins / Q000502:physiology; D008958:Models, Molecular; D010766:Phosphorylation; D015398:Signal Transduction; D013315:Stress, Psychological
D054758:A Kinase Anchor Proteins; C112596:AKAP7 protein, human; D020746:Calcium Channels, L-Type; C419385:L-type calcium channel alpha(1C); D008565:Membrane Proteins; D017868:Cyclic AMP-Dependent Protein Kinases