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The human heart and rat brain IIA Na+ channels interact with different molecular regions of the beta1 subunit - PubMed

The human heart and rat brain IIA Na+ channels interact with different molecular regions of the beta1 subunit

Thomas Zimmer et al. J Gen Physiol. 2002 Dec.

Abstract

The alpha subunit of voltage-gated Na(+) channels of brain, skeletal muscle, and cardiomyocytes is functionally modulated by the accessory beta(1), but not the beta(2) subunit. In the present study, we used beta(1)/beta(2) chimeras to identify molecular regions within the beta(1) subunit that are responsible for both the increase of the current density and the acceleration of recovery from inactivation of the human heart Na(+) channel (hH1). The channels were expressed in Xenopus oocytes. As a control, we coexpressed the beta(1)/beta(2) chimeras with rat brain IIA channels. In agreement with previous studies, the beta(1) extracellular domain sufficed to modulate IIA channel function. In contrast to this, the extracellular domain of the beta(1) subunit alone was ineffective to modulate hH1. Instead, the putative membrane anchor plus either the intracellular or the extracellular domain of the beta(1) subunit was required. An exchange of the beta(1) membrane anchor by the corresponding beta(2) subunit region almost completely abolished the effects of the beta(1) subunit on hH1, suggesting that the beta(1) membrane anchor plays a crucial role for the modulation of the cardiac Na(+) channel isoform. It is concluded that the beta(1) subunit modulates the cardiac and the neuronal channel isoforms by different molecular interactions: hH1 channels via the membrane anchor plus additional intracellular or extracellular regions, and IIA channels via the extracellular region only.

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Figures

F<sc>igure</sc> 1. — **Figure 1.**
Modulation of hH1 and IIA Na⁺ channels by the β₁ subunit. (A) Representative current traces for hH1 and hH1/β₁ channels at the test potentials −10 and −30 mV. The τ_h values of hH1 versus hH1/β₁ channels were statistically indistinguishable (−30 mV: τ_h = 2.21 ± 0.18 for hH1, τ_h = 2.01 ± 0.43 for hH1/β₁ [P = 0.64]; −10 mV: τ_h = 1.25 ± 0.07 for hH1, τ_h = 1.12 ± 0.08 for hH1/β₁ [P = 0.23]). Number of experiments: n = 11 for hH1, n = 6 for hH1/β₁. Calibration bars = 4 ms, at −30 mV: 0.25 μA for hH1, 0.62 μA for hH1/β₁; at −10 mV: 0.45 μA for hH1, 1.06 μA for hH1/β₁. (B) Effect of the β₁ subunit on the hH1 peak current amplitude in *Xenopus* oocytes (*P < 0.001). Currents were measured 3 d after injection at the test potential of −25 mV. Measurements were performed in seven different batches of oocytes. Data from a single batch of oocytes were normalized with respect to the mean current of hH1-injected oocytes (n = 63 for hH1, n = 50 for hH1/β₁, and n = 52 for hH1/β₂). (C) Time course of recovery from inactivation of hH1 channels. The respective voltage protocol is shown in the inset (n = 32 for hH1, n = 38 for hH1/β₁, and n = 21 for hH1/β₂). (D) Effect of the β₁ subunit on the inactivation time course of rat brain IIA Na⁺ currents. The Na⁺ currents were elicited by a test pulse to −10 mV, and normalized with respect to the peak current. Calibration bars = 5 ms, 0.9 μA for IIA, 0.8 μA for IIA/β₁, and 0.7 μA for IIA/β₂. Statistically, the inactivation time constant τ_h was not different for IIA and IIA/β₂ channels at the applied test pulses (unpublished data). (E) Effect of the β₁ subunit on the IIA peak current amplitude (*P < 0.001). Currents were measured 3 d after injection at the test potential of −10 mV (n = 13 for IIA, n = 13 for IIA/β₁ and n = 13 for IIA/β₂). (F) Time course of recovery from inactivation of IIA channels. Currents were elicited by the same voltage protocol as indicated in C, except that a test pulse to −10 mV was used (n = 7 for IIA, n = 7 for IIA/β₁ and n = 6 for IIA/β₂). Bars indicate SEM.

F<sc>igure</sc> 2. — **Figure 2.**
Structure of the chimeras between the Na⁺ channel β₁ and β₂ subunits used in this study. The corresponding terminal amino acids of the β₁ (white boxes) and β₂ (gray boxes) subunit regions are indicated. The assumed topology of both subunits in the plasma membrane is shown below the cartoons of the chimeras.

F<sc>igure</sc> 3. — **Figure 3.**
Modulatory effect of chimeras β₁₂₂ and β₂₁₁ on hH1 and IIA channels. (A) Schematic representation of the domain structures of both chimeras. (B) Relative current amplitudes (test pulse to −25 mV; *P < 0.001; n = 55 for hH1, n = 37 for hH1/β₁, n = 38 for hH1/β₁₂₂, and n = 50 for hH1/β₂₁₁). (C) Time course of recovery from inactivation of hH1 channels (n = 7 for hH1, n = 6 for hH1/β₁, n = 5 for hH1/β₁₂₂, and n = 6 for hH1/β₂₁₁). (D) Effect of β₁₂₂ on the inactivation time course of rat brain IIA Na⁺ currents (test pulse: −10 mV). Calibration bars = 5 ms, 0.25 μA for IIA, 0.52 μA for IIA/β₁, 0.27 μA for IIA/β₁₂₂, and 0.21 μA for IIA/β₂₁₁. (E) Effect of β₁₂₂ on the IIA peak current amplitude (test pulse to −10 mV; *P < 0.001; n = 19 for IIA, n = 13 for IIA/β₁, n = 19 for IIA/β₁₂₂, and n = 17 for IIA/β₂₁₁). (F) Time course of recovery from inactivation of IIA channels. For voltage protocol, see legend to Fig. 1 (n = 13 for IIA, n = 12 for IIA/β₁ and n = 12 for IIA/β₁₂₂, and n = 12 for IIA/β₂₁₁). Bars indicate SEM.

F<sc>igure</sc> 4. — **Figure 4.**
Coexpression of chimeras β₁₂₁ and β₂₂₁ with hH1 and IIA channels. (A) Schematic representation of the domain structures of both chimeras. (B) Relative current amplitudes (test pulse to −25 mV; *P < 0.001; n = 29 for hH1, n = 17 for hH1/β₁, n = 28 for hH1/β₁₂₁, and n = 21 for hH1/β₂₂₁). (C) Time course of recovery from inactivation of hH1 channels (n = 21 for hH1, n = 17 for hH1/β₁, n = 12 for hH1/β₁₂₁, and n = 19 for hH1/β₂₂₁). (D) Effect of β₁₂₁ on the time course of inactivation of rat brain IIA Na⁺ currents (test pulse to −10 mV). Calibration bars = 5 ms, 0.93 μA for IIA, 0.90 μA for IIA/β₁, 0.62 μA for IIA/β₁₂₁, and 0.90 μA for IIA/β₂₂₁. (E) Effect of β₁₂₁ and β₂₂₁ on the IIA peak current amplitude (test pulse to −10 mV; *P < 0.001; n = 15 for IIA, n = 9 for IIA/β₁, n = 12 for IIA/β₁₂₁, and n = 19 for IIA/β₂₂₁). (F) Time course of recovery from inactivation of IIA channels (n = 13 for IIA, n = 9 for IIA/β₁ and n = 5 for IIA/β₁₂₁, and n = 13 for IIA/β₂₂₁). Bars indicate SEM.

F<sc>igure</sc> 5. — **Figure 5.**
Coexpression of chimera β₂₁₂ and β_21Δ with hH1 channels. (A) Schematic representation of the domain structure of β₂₁₂ and β_21Δ. (B) Relative current amplitudes (test pulse to −25 mV; *P < 0.001; n = 17 for hH1, n = 10 for hH1/β₁, n = 21 for hH1/β₂₁₂, and n = 11 for β_21Δ). (C) Time course of recovery from inactivation of hH1 channels (n = 10 for hH1, n = 4 for hH1/β₁, n = 11 for hH1/β₂₁₂, and n = 7 for β_21Δ). Bars indicate SEM.

F<sc>igure</sc> 6. — **Figure 6.**
Coexpression of β_11Δ and β_12Δ with hH1 and IIA channels. (A) Schematic representation of the domain structures of both deletion variants. (B) Relative current amplitudes (test pulse to −25 mV; *P < 0.001; n = 38 for hH1, n = 38 for hH1/β₁, n = 30 for hH1/β_11Δ, and n = 23 for hH1/β_12Δ). (C) Time course of recovery from inactivation of hH1 channels (n = 23 for hH1, n = 21 for hH1/β₁, n = 19 for hH1/β_11Δ, and n = 20 for hH1/β_12Δ). (D) Effect of β_11Δ and β_12Δ on the inactivation time course of rat brain IIA Na⁺ currents (test pulse to −10 mV). Calibration bars = 5 ms, 0.92 μA for IIA, 0.76 μA for IIA/β₁, 0.80 μA for IIA/β_11Δ, and 0.28 μA for IIA/β_12Δ. (E) Effect of β_11Δ and β_12Δ on the IIA peak current amplitude (test pulse to −10 mV; *P < 0.001; n = 16 for IIA, n = 14 for IIA/β₁, n = 21 for IIA/β_11Δ, and n = 9 for IIA/β_12Δ). (F) Time course of recovery from inactivation of IIA channels (n = 13 for IIA, n = 13 for IIA/β₁, n = 16 for IIA/β_11Δ, and n = 10 for IIA/β_12Δ). Bars indicate SEM.

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References

1. Auld, V.J., A.L. Goldin, D.S. Krafte, J. Marshall, J.M. Dunn, W.A. Catterall, H.A. Lester, N. Davidson, and R.J. Dunn. 1988. A rat brain Na+ channel α subunit with novel gating properties. Neuron. 1:449–461. - PubMed
1. Catterall, W.A. 1992. Cellular and molecular biology of voltage-gated sodium channels. Physiol. Rev. 72:S15–S48. - PubMed
1. Chauhan, V.S., S. Tuvia, M. Buhusi, V. Bennett, and A.O. Grant. 2000. Abnormal cardiac Na+ channel properties and QT heart rate adaptation in neonatal ankyrinB knockout mice. Circ. Res. 86:441–447. - PubMed
1. Chen, C., and S.C. Cannon. 1995. Modulation of Na+ channel inactivation by the β1 subunit: a deletion analysis. Pflugers Arch. 431:186–195. - PubMed
1. Gellens, M.E., A.L. George, L. Chen, M. Chahine, R. Horn, R.L. Barchi, and R.G. Kallen. 1992. Primary structure and functional expression of the human cardiac tetrodotoxin-insensitive voltage-dependent sodium channel. Proc. Natl. Acad. Sci. USA. 89:554–558. - PMC - PubMed

The human heart and rat brain IIA Na+ channels interact with different molecular regions of the beta1 subunit - PubMed