Calcium-Mediated Dual-Mode Regulation of Cardiac Sodium Channel Gating

Biswas, Subrata; DiSilvestre, Deborah; Tian, Yanli; Halperin, Victoria L.; Tomaselli, Gordon F.

doi:10.1161/circresaha.108.193565

Cited by 40 publications

(72 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the absence of Ca 2+ , the apo-CaM C lobe binds to the IQ motif of neuronal (30,32,33) and cardiac isoforms (5,6,8,29,30,34). Introduced or inherited mutations to either EF hands or IQ motifs can abolish Ca 2+ -dependent effects on inactivation (6,7,11,28); however, the ability of the EF-hand region to bind Ca 2+ ions directly remains contentious (7,8,11,28,35). Importantly, it is not known how Ca 2+ or Ca 2+ /CaM interactions with the C-terminal EF-hand and IQ motifs are relayed to channel inactivation, but we (9) and others (10) Table S4. in Ca 2+ regulation, a possibility suggested previously (28).…”

Section: Discussionmentioning

confidence: 99%

“…Cytoplasmic Ca 2+ modulates the steady-state inactivation of voltage-gated sodium channels (6,7,11,28), an equilibrium relationship that provides a direct measure of channel availability at a given transmembrane potential (Fig. 3A).…”

Section: Diii-iv Linker Is the Physiological Endpoint For Camentioning

confidence: 99%

“…Consequently, their cytoplasmic levels oscillate between nanomolar and micromolar levels with each excitation-contraction cycle (2). Sodium channel steady-state inactivation, a process that controls channel availability at a given transmembrane potential, is modulated through interactions with Ca 2+ and calmodulin (CaM) (3)(4)(5)(6)(7)(8)(9)(10) can bind directly to the Na V "inactivation gate" (9, 10), a highly conserved ∼50-amino acid cytoplasmic linker connecting channel domains III and IV (DIII-IV linker) that contributes to the fastinactivated state of the channel (14)(15)(16). Thus, individual molecular players of Ca 2+ regulation have been identified but no crystallographic information is available detailing how the different Ca 2+ /CaM binding regions cooperate, and no consensus has been reached on how binding events in the C terminus of the channel are coupled to the conformational changes that underlie channel inactivation.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Crystallographic basis for calcium regulation of sodium channels

Sarhan

Tung²,

Petegem³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

124

140

View full text Add to dashboard Cite

Voltage-gated sodium channels underlie the rapid regenerative upstroke of action potentials and are modulated by cytoplasmic calcium ions through a poorly understood mechanism. We describe the 1.35 Å crystal structure of Ca 2+ -bound calmodulin (Ca 2+ /CaM) in complex with the inactivation gate (DIII-IV linker) of the cardiac sodium channel (Na V 1.5). The complex harbors the positions of five disease mutations involved with long Q-T type 3 and Brugada syndromes. In conjunction with isothermal titration calorimetry, we identify unique inactivation-gate mutations that enhance or diminish Ca 2+ /CaM binding, which, in turn, sensitize or abolish Ca 2+ regulation of full-length channels in electrophysiological experiments. Additional biochemical experiments support a model whereby a single Ca 2+ /CaM bridges the C-terminal IQ motif to the DIII-IV linker via individual N and C lobes, respectively. The data suggest that Ca 2+ /CaM destabilizes binding of the inactivation gate to its receptor, thus biasing inactivation toward more depolarized potentials.crystallography | patch-clamp electrophysiology | structural biology | cardiac arrhythmia V oltage-gated sodium channels (Na V s) support excitability in the cardiovascular and nervous systems, where they contribute to the rhythm and rate of action potentials. These large (∼220-kDa) transmembrane protein complexes are expressed at a high density in excitable cells, where they conduct large macroscopic inward sodium currents. These channels are exquisitely sensitive to subtle changes in the transmembrane potential, and modest alterations in channel gating can fine-tune or disorder electrical signaling at the organ and systemic level. The α-subunit of the channel contains cytoplasmic amino and carboxyl termini and is composed of four homologous transmembrane domains (DI-DIV) that are connected by intracellular linkers. Each domain contains voltage-sensing (S1-S4) and pore-forming (S5 and S6) domains that form the selectivity filter and putative activation gates. A crystal structure of a bacterial Na V was recently described (1) showing a similar overall fold compared with potassium channels. However, this bacterial variant is homotetrameric, and seems to lack a conserved fast-inactivation mechanism. As such, it has no homology with several relevant domains in mammalian Na V channels, and no crystal structure of any eukaryotic Na V region has yet been reported.Calcium ions (Ca 2+ ) are universal second messengers, and in the heart they form the electrochemical link between plasma membrane depolarization and myocyte contraction. Consequently, their cytoplasmic levels oscillate between nanomolar and micromolar levels with each excitation-contraction cycle (2). Sodium channel steady-state inactivation, a process that controls channel availability at a given transmembrane potential, is modulated through interactions with Ca 2+ and calmodulin (CaM) (3-10). The mechanistic details of Ca 2+ modulation of sodium channel inactivation are sparse, but the C-terminal region of the cha...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Diii-iv Linker Is the Physiological Endpoint For Camentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Crystallographic basis for calcium regulation of sodium channels

Sarhan

Tung²,

Petegem³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

124

140

View full text Add to dashboard Cite

show abstract

“…Here, even this small 5 mV change can exert a remarkable effect on the availability of sodium channels. There may be multiple Ca 2+ 73 They also proposed that CaM-driven regulation is of the cardiac sodium channel is negligible in wild-type channels at physiologically relevant Ca 2+ concentrations. The Ca 2+ /CaM complex forms a bridge between the IQ motif on the C-terminus and the DIII-IV linker region of the sodium channel.…”

Section: +mentioning

confidence: 99%

The late sodium current in heart failure: pathophysiology and clinical relevance

Horváth

Bers

2014

ESC Heart Failure

View full text Add to dashboard Cite

Large and growing body of data suggest that an increased late sodium current (I Na,late ) can have a significant pathophysiological role in heart failure and other heart diseases. The first goal of this article is to describe how I Na,late functions under physiological circumstances. The second goal is to show the wide range of cellular mechanisms that can increase I Na,late in cardiac disease, and also to describe how the up-regulated I Na,late contributes to the pathophysiology of heart failure. The final section of the article discusses the possible use of I Na,late -modifying drugs in heart failure, on the basis of experimental and preclinical data.

show abstract

“…Sodium channels take advantage of this dynamic environment by allowing Ca 2ϩ and calmodulin (CaM) to fine-tune channel availability by making more channels available for each action potential (6,11,12). Although the precise mechanistic details of this modulation remain speculative, the C-terminal region contains EF-hand like domains and an IQ motif that dynamically bind Ca 2ϩ and Ca 2ϩ /CaM, respectively, and mutations in these regions affect both calcium sensitivity and inactivation gating (6,11,(13)(14)(15)(16). Additionally, recent evidence suggests that CaM can bind directly to the DIII-DIV linker, a possibility that has been suggested previously in the context of an "inactivation complex" (14,17), therefore providing yet another pathway for Ca 2ϩ /CaM regulation of channel gating (18).…”

mentioning

confidence: 99%

A Double Tyrosine Motif in the Cardiac Sodium Channel Domain III-IV Linker Couples Calcium-dependent Calmodulin Binding to Inactivation Gating

Sarhan

Petegem

Ahern

2009

Journal of Biological Chemistry

View full text Add to dashboard Cite

Voltage-gated sodium channels maintain the electrical cadence and stability of neurons and muscle cells by selectively controlling the transmembrane passage of their namesake ion. The degree to which these channels contribute to cellular excitability can be managed therapeutically or fine-tuned by endogenous ligands. Intracellular calcium, for instance, modulates sodium channel inactivation, the process by which sodium conductance is negatively regulated. We explored the molecular basis for this effect by investigating the interaction between the ubiquitous calcium binding protein calmodulin (CaM) and the putative sodium channel inactivation gate composed of the cytosolic linker between homologous channel domains III and IV (DIII-IV). Experiments using isothermal titration calorimetry show that CaM binds to a novel double tyrosine motif in the center of the DIII-IV linker in a calcium-dependent manner, N-terminal to a region previously reported to be a CaM binding site. An alanine scan of aromatic residues in recombinant DIII-DIV linker peptides shows that whereas multiple side chains contribute to CaM binding, two tyrosines (Tyr 1494 and Tyr 1495 ) play a crucial role in binding the CaM C-lobe. The functional relevance of these observations was then ascertained through electrophysiological measurement of sodium channel inactivation gating in the presence and absence of calcium. Experiments on patch-clamped transfected tsA201 cells show that only the Y1494A mutation of the five sites tested renders sodium channel steady-state inactivation insensitive to cytosolic calcium. The results demonstrate that calcium-dependent calmodulin binding to the sodium channel inactivation gate double tyrosine motif is required for calcium regulation of the cardiac sodium channel.

show abstract

Calcium-Mediated Dual-Mode Regulation of Cardiac Sodium Channel Gating

Cited by 40 publications

References 20 publications

Crystallographic basis for calcium regulation of sodium channels

Crystallographic basis for calcium regulation of sodium channels

The late sodium current in heart failure: pathophysiology and clinical relevance

A Double Tyrosine Motif in the Cardiac Sodium Channel Domain III-IV Linker Couples Calcium-dependent Calmodulin Binding to Inactivation Gating

Contact Info

Product

Resources

About