Tags

Type your tag names separated by a space and hit enter

Voltage sensor movement and cAMP binding allosterically regulate an inherently voltage-independent closed-open transition in HCN channels.
J Gen Physiol. 2007 Feb; 129(2):175-88.JG

Abstract

The hyperpolarization-activated cyclic nucleotide-modulated cation (HCN) channels are regulated by both membrane voltage and the binding of cyclic nucleotides to a cytoplasmic, C-terminal cyclic nucleotide-binding domain (CNBD). Here we have addressed the mechanism of this dual regulation for HCN2 channels, which activate with slow kinetics that are strongly accelerated by cAMP, and HCN1 channels, which activate with rapid kinetics that are weakly enhanced by cAMP. Surprisingly, we find that the rate of opening of HCN2 approaches a maximal value with extreme hyperpolarization, indicating the presence of a voltage-independent kinetic step in the opening process that becomes rate limiting at very negative potentials. cAMP binding enhances the rate of this voltage-independent opening step. In contrast, the rate of opening of HCN1 is much greater than that of HCN2 and does not saturate with increasing hyperpolarization over the voltage range examined. Domain-swapping chimeras between HCN1 and HCN2 reveal that the S4-S6 transmembrane region largely determines the limiting rate in opening kinetics at negative voltages. Measurements of HCN2 tail current kinetics also reveal a voltage-independent closing step that becomes rate limiting at positive voltages; the rate of this closing step is decreased by cAMP. These results are consistent with a cyclic allosteric model in which a closed-open transition that is inherently voltage independent is subject to dual allosteric regulation by voltage sensor movement and cAMP binding. This mechanism accounts for several properties of HCN channel gating and has potentially important physiological implications.

Authors+Show Affiliations

Center for Neurobiology and Behavior, Columbia University, New York, NY 10032, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

17261842

Citation

Chen, Shan, et al. "Voltage Sensor Movement and cAMP Binding Allosterically Regulate an Inherently Voltage-independent Closed-open Transition in HCN Channels." The Journal of General Physiology, vol. 129, no. 2, 2007, pp. 175-88.
Chen S, Wang J, Zhou L, et al. Voltage sensor movement and cAMP binding allosterically regulate an inherently voltage-independent closed-open transition in HCN channels. J Gen Physiol. 2007;129(2):175-88.
Chen, S., Wang, J., Zhou, L., George, M. S., & Siegelbaum, S. A. (2007). Voltage sensor movement and cAMP binding allosterically regulate an inherently voltage-independent closed-open transition in HCN channels. The Journal of General Physiology, 129(2), 175-88.
Chen S, et al. Voltage Sensor Movement and cAMP Binding Allosterically Regulate an Inherently Voltage-independent Closed-open Transition in HCN Channels. J Gen Physiol. 2007;129(2):175-88. PubMed PMID: 17261842.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Voltage sensor movement and cAMP binding allosterically regulate an inherently voltage-independent closed-open transition in HCN channels. AU - Chen,Shan, AU - Wang,Jing, AU - Zhou,Lei, AU - George,Meena S, AU - Siegelbaum,Steven A, PY - 2007/1/31/pubmed PY - 2007/3/24/medline PY - 2007/1/31/entrez SP - 175 EP - 88 JF - The Journal of general physiology JO - J Gen Physiol VL - 129 IS - 2 N2 - The hyperpolarization-activated cyclic nucleotide-modulated cation (HCN) channels are regulated by both membrane voltage and the binding of cyclic nucleotides to a cytoplasmic, C-terminal cyclic nucleotide-binding domain (CNBD). Here we have addressed the mechanism of this dual regulation for HCN2 channels, which activate with slow kinetics that are strongly accelerated by cAMP, and HCN1 channels, which activate with rapid kinetics that are weakly enhanced by cAMP. Surprisingly, we find that the rate of opening of HCN2 approaches a maximal value with extreme hyperpolarization, indicating the presence of a voltage-independent kinetic step in the opening process that becomes rate limiting at very negative potentials. cAMP binding enhances the rate of this voltage-independent opening step. In contrast, the rate of opening of HCN1 is much greater than that of HCN2 and does not saturate with increasing hyperpolarization over the voltage range examined. Domain-swapping chimeras between HCN1 and HCN2 reveal that the S4-S6 transmembrane region largely determines the limiting rate in opening kinetics at negative voltages. Measurements of HCN2 tail current kinetics also reveal a voltage-independent closing step that becomes rate limiting at positive voltages; the rate of this closing step is decreased by cAMP. These results are consistent with a cyclic allosteric model in which a closed-open transition that is inherently voltage independent is subject to dual allosteric regulation by voltage sensor movement and cAMP binding. This mechanism accounts for several properties of HCN channel gating and has potentially important physiological implications. SN - 0022-1295 UR - https://www.unboundmedicine.com/medline/citation/17261842/Voltage_sensor_movement_and_cAMP_binding_allosterically_regulate_an_inherently_voltage_independent_closed_open_transition_in_HCN_channels_ L2 - https://rupress.org/jgp/article-lookup/doi/10.1085/jgp.200609585 DB - PRIME DP - Unbound Medicine ER -