4nvp
Structure of the cyclic nucleotide-binding domain of HCN4 channel complexed with 7-CH-cAMP
Structural highlights
DiseaseHCN4_HUMAN Sick sinus syndrome;Brugada syndrome. Sick sinus syndrome 2 (SSS2) [MIM:163800: The term 'sick sinus syndrome' encompasses a variety of conditions caused by sinus node dysfunction. The most common clinical manifestations are syncope, presyncope, dizziness, and fatigue. Electrocardiogram typically shows sinus bradycardia, sinus arrest, and/or sinoatrial block. Episodes of atrial tachycardias coexisting with sinus bradycardia ('tachycardia-bradycardia syndrome') are also common in this disorder. SSS occurs most often in the elderly associated with underlying heart disease or previous cardiac surgery, but can also occur in the fetus, infant, or child without heart disease or other contributing factors. SSS2 onset is in utero or at birth. Note=The disease is caused by mutations affecting the gene represented in this entry.[1] [2] Brugada syndrome 8 (BRGDA8) [MIM:613123: A tachyarrhythmia characterized by right bundle branch block and ST segment elevation on an electrocardiogram (ECG). It can cause the ventricles to beat so fast that the blood is prevented from circulating efficiently in the body. When this situation occurs, the individual will faint and may die in a few minutes if the heart is not reset. Note=The disease is caused by mutations affecting the gene represented in this entry.[3] FunctionHCN4_HUMAN Hyperpolarization-activated ion channel with very slow activation and inactivation exhibiting weak selectivity for potassium over sodium ions. May contribute to the native pacemaker currents in heart (If) and in neurons (Ih). Activated by cAMP. May mediate responses to sour stimuli.[4] [5] Publication Abstract from PubMedHyperpolarization-activated cyclic nucleotide-gated (HCN) channels play a central role in the regulation of cardiac and neuronal firing rate, and these channels can be dually activated by membrane hyperpolarization and by binding of cyclic nucleotides. cAMP has been shown to directly bind HCN channels and modulate their activity. Despite this, while there are selective inhibitors that block the activation potential of the HCN channels, regulation by cAMP analogs has not been well investigated. A comprehensive screen of 47 cyclic nucleotides with modifications in the nucleobase, ribose moiety, and cyclic phosphate was tested on the three isoforms HCN1, HCN2, and HCN4. 7-CH-cAMP was identified to be a high affinity binder for HCN channels and crosschecked for its ability to act on other cAMP receptor proteins. While 7-CH-cAMP is a general activator for cAMP- and cGMP-dependent protein kinases as well as for the guanine nucleotide exchange factors Epac1 and Epac2, it displays the highest affinity to HCN channels. The molecular basis of the high affinity was investigated by determining the crystal structure of 7-CH-cAMP in complex with the cyclic nucleotide binding domain of HCN4. Electrophysiological studies demonstrate a strong activation potential of 7-CH-cAMP for the HCN4 channel in vivo. So, this makes 7-CH-cAMP a promising activator of the HCN channels in vitro whose functionality can be translated in living cells. Cyclic Nucleotide Mapping of Hyperpolarization-Activated Cyclic Nucleotide-Gated (HCN) Channels.,Moller S, Alfieri A, Bertinetti D, Aquila M, Schwede F, Lolicato M, Rehmann H, Moroni A, Herberg FW ACS Chem Biol. 2014 May 16;9(5):1128-37. doi: 10.1021/cb400904s. Epub 2014 Mar 7. PMID:24605759[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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