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Modulation of CaV2.1 channels by Ca2+/calmodulin-dependent protein kinase II bound to the C-terminal domain.

ABSTRACT: Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is a key regulator of synaptic responses in the postsynaptic density, but understanding of its mechanisms of action in the presynaptic neuron is incomplete. Here we show that CaMKII constitutively associates with and modulates voltage-gated calcium (Ca(V))2.1 channels that conduct P/Q type Ca(2+) currents and initiate transmitter release. Both exogenous and brain-specific inhibitors of CaMKII accelerate voltage-dependent inactivation, cause a negative shift in the voltage dependence of inactivation, and reduce Ca(2+)-dependent facilitation of Ca(V)2.1 channels. The modulatory effects of CaMKII are reduced by a peptide that prevents binding to Ca(V)2.1 channels but not by a peptide that blocks catalytic activity, suggesting that binding rather than phosphorylation is responsible for modulation. Our results reveal a signaling complex formed by Ca(V)2.1 channels and CaMKII that regulates P/Q-type Ca(2+) current in neurons. We propose an "effector checkpoint" model for the control of Ca(2+) channel fitness for function that depends on association with CaMKII, SNARE proteins, and other effectors of Ca(2+) signals. This regulatory mechanism would be important in presynaptic nerve terminals, where Ca(V)2.1 channels initiate synaptic transmission and CaMKII has noncatalytic effects on presynaptic plasticity.

SUBMITTER: Jiang X

PROVIDER: S-EPMC2224214 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature

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Modulation of CaV2.1 channels by Ca2+/calmodulin-dependent protein kinase II bound to the C-terminal domain.

Jiang Xin X Lautermilch Nathan J NJ Watari Hirofumi H Westenbroek Ruth E RE Scheuer Todd T Catterall William A WA

Proceedings of the National Academy of Sciences of the United States of America 20071227 1

Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is a key regulator of synaptic responses in the postsynaptic density, but understanding of its mechanisms of action in the presynaptic neuron is incomplete. Here we show that CaMKII constitutively associates with and modulates voltage-gated calcium (Ca(V))2.1 channels that conduct P/Q type Ca(2+) currents and initiate transmitter release. Both exogenous and brain-specific inhibitors of CaMKII accelerate voltage-dependent inactivation, cause ...[more]

PMID: 18162541

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Project description:During the acquisition of memories, influx of Ca2+ into the postsynaptic spine through the pores of activated N-methyl-D-aspartate-type glutamate receptors triggers processes that change the strength of excitatory synapses. The pattern of Ca2+influx during the first few seconds of activity is interpreted within the Ca2+-dependent signaling network such that synaptic strength is eventually either potentiated or depressed. Many of the critical signaling enzymes that control synaptic plasticity,including Ca2+/calmodulin-dependent protein kinase II (CaMKII), are regulated by calmodulin, a small protein that can bindup to 4 Ca2+ ions. As a first step toward clarifying how the Ca2+-signaling network decides between potentiation or depression, we have created a kinetic model of the interactions of Ca2+, calmodulin, and CaMKII that represents our best understanding of the dynamics of these interactions under conditions that resemble those in a postsynaptic spine. We constrained parameters of the model from data in the literature, or from our own measurements, and then predicted time courses of activation and autophosphorylation of CaMKII under a variety of conditions. Simulations showed that species of calmodulin with fewer than four bound Ca2+ play a significant role in activation of CaMKII in the physiological regime,supporting the notion that processing of Ca2+ signals in a spine involves competition among target enzymes for binding to unsaturated species of CaM in an environment in which the concentration of Ca2+ is fluctuating rapidly. Indeed, we showed that dependence of activation on the frequency of Ca2+ transients arises from the kinetics of interaction of fluctuating Ca2+with calmodulin/CaMKII complexes. We used parameter sensitivity analysis to identify which parameters will be most beneficial to measure more carefully to improve the accuracy of predictions. This model provides a quantitative base from which to build more complex dynamic models of postsynaptic signal transduction during learning.

Project description:The Na+/H+ exchanger is a pH-regulatory protein that extrudes one H+ ion in exchange for one Na+ ion when intracellular pH declines. A number of studies have shown phorbol ester stimulation of activity in intact cells, leading to the idea that the exchanger is regulated by protein kinase C-mediated phosphorylation in vivo. cDNA encoding the protein has been cloned, and a recent model suggests a large internal cytoplasmic C-terminal domain that may be a site of regulation of the exchanger [Sardet, Franchi & Pouyssegur (1989) Cell 56, 271-280]. We examined this region of the protein using a rabbit cardiac Na+/H+ exchanger cDNA clone. cDNA of the Na+/H+ exchanger, coding for the C-terminal 178 amino acid residues, was cloned into the expression vector pEX-1 and expressed as a fusion protein with beta-galactosidase. The fusion protein reacted with an antibody produced against a synthetic peptide of the C-terminal 13 amino acid residues of the Na+/H+ exchanger, confirming the identity of the expressed protein. Control and experimental pEX-1-Na+/H+ exchanger protein was purified on a p-aminophenyl beta-D-thiogalactopyranoside-agarose column. Purified Ca2+/calmodulin-dependent protein kinase II readily phosphorylated the Na+/H+ exchanger protein in a Ca(2+)- and calmodulin-dependent manner in vitro, but this region of the protein was not a substrate for purified protein kinase C or for the catalytic subunit of cyclic AMP-dependent protein kinase. Control-expressed beta-galactosidase was phosphorylated to a maximal level of 0.77 +/- 0.17 mol of Pi/mol (mean +/- S.E.M., n = 6) whereas the fusion protein was phosphorylated to a maximal level of 4.09 +/- 0.39 mol of Pi/mol (n = 6), suggesting one site of phosphorylation in beta-galactosidase and three in the C-terminal domain of the Na+/H+ exchanger. Examination of the deduced amino acid sequence of this part of the exchanger reveals three consensus sequences for Ca2+/calmodulin-dependent protein kinase II. These results suggest that the exchanger may be directly regulated in vivo by calmodulin-dependent protein kinase II but not by protein kinase C or cyclic AMP-dependent protein kinase.

Dataset Information

Modulation of CaV2.1 channels by Ca2+/calmodulin-dependent protein kinase II bound to the C-terminal domain.

Publications

Modulation of CaV2.1 channels by Ca2+/calmodulin-dependent protein kinase II bound to the C-terminal domain.

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