Ankyrin-based cardiac arrhythmias: a new class of channelopathies due to loss of cellular targeting.
OBJECTIVE
This review addresses a new mechanism for arrhythmia due to abnormal cellular localization of membrane ion channels and transporters. The focus is on ankyrins, a family of proteins that localize diverse membrane ion channels and transporters, and recent evidence that mutations affecting functions of ankyrins result in cardiac arrhythmia.


RESULTS
A loss-of-function mutation of ankyrin-B in humans and a null mutation in mice result in a dominantly-inherited fatal cardiac arrhythmia initially classified as type 4 long QT syndrome. Characterization of additional probands suggests ankyrin-B mutations cause a new cardiac arrhythmia syndrome associated with sinus node dysfunction that is distinct from long QT syndrome. Ankyrin-B mutation results in elevated calcium transients in cardiomyocytes accompanied by loss of cellular targeting of Na/K ATPase, Na/Ca exchanger, and InsP3 receptor (all ankyrin-binding proteins) to cardiomyocyte membrane domains. The principal voltage-gated Na channel in heart, Nav1.5, is directly associated with ankyrin-G, which is encoded by a distinct gene from ankyrin-B. Mutation of Nav1.5 causing loss of binding to ankyrin-G results in Brugada syndrome and loss of targeting of Nav1.5 to the cell surface of cardiomyocytes.


CONCLUSIONS
Ankyrin-B and ankyrin-G are recently recognized constituents of the heart that target diverse ion channels/pumps/transporters to physiologic sites of action in cardiomyocytes. Mutations of ankyrin-B cause a newly defined cardiac arrhythmia syndrome associated with abnormal calcium homeostasis in a mouse model. Ankyrin-G associates with the principal voltage-gated Na channel in the heart, and loss of this interaction due to mutation of Nav1.5 results in Brugada syndrome.
Mohler
Peter J
PJ
Department of Pathology, Vanderbilt University Medical Center, Nashville, TN 37232, USA. peter.j.mohler@vanderbilt.edu
Bennett
Vann
V
D000818:Animals; D017487:Ankyrins / Q000009:adverse effects*; D001145:Arrhythmias, Cardiac / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology
D017487:Ankyrins; D007473:Ion Channels