title: Identification and characterization of two ankyrin-B isoforms in mammalian heart.
abstract: OBJECTIVE
  Excitation-contraction coupling in cardiomyocytes requires the proper targeting and retention of membrane proteins to unique domains by adaptor proteins like ankyrin-B. While ankyrin-B has been shown to interact with a variety of membrane and structural proteins located at different subcellular domains in cardiomyocytes, what regulates the specificity of ankyrin-B for particular interacting proteins remains elusive.
  
  
  RESULTS
  Here, we report the identification of two novel ankyrin-B isoforms AnkB-188 and AnkB-212 in human, rat, and mouse hearts. Novel cDNAs for both isoforms were isolated by long-range PCR of reverse-transcribed mRNA isolated from human ventricular tissue. The isoforms can be discriminated based on their function and subcellular distribution in cardiomyocytes. Heterologous overexpression of AnkB-188 increases sodium-calcium exchanger (NCX) membrane expression and current, while selective knockdown of AnkB-188 in cardiomyocytes reduces NCX expression and localization in addition to causing irregular contraction rhythms. Using an isoform-specific antibody, we demonstrate that the expression of AnkB-212 is restricted to striated muscles and is localized to the M-line of cardiomyocytes by interacting with obscurin. Selective knockdown of AnkB-212 significantly attenuates the expression of endogenous ankyrin-B at the M-line but does not disrupt NCX expression at transverse tubules in cardiomyocytes.
  
  
  CONCLUSIONS
  The identification and characterization of two functionally distinct ankyrin-B isoforms in heart provide compelling evidence that alternative splicing of the ANK2 gene regulates the fidelity of ankyrin-B interactions with proteins.
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, 6431 Fannin Street, MSE R331, Houston, TX 77030, USA.
authors.forename: Henry C
authors.initials: HC
authors.lastname: Wu
authors.affiliation: Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Gokay
authors.initials: G
authors.lastname: Yamankurt
authors.affiliation: Department of Anesthesiology, the Center for the Study of Itch, Washington University Pain Center, Washington University School of Medicine in St Louis, St Louis, MO 63110, USA.
authors.forename: JiaLie
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, 6431 Fannin Street, MSE R331, Houston, TX 77030, USA.
authors.forename: Janani
authors.initials: J
authors.lastname: Subramaniam
authors.affiliation: Department of Pediatrics, The University of Texas Medical School at Houston, Houston, TX 77030, USA.
authors.forename: Syed Shahrukh
authors.initials: SS
authors.lastname: Hashmi
authors.affiliation: Department of Anesthesiology, the Center for the Study of Itch, Washington University Pain Center, Washington University School of Medicine in St Louis, St Louis, MO 63110, USA.
authors.forename: Hongzhen
authors.initials: H
authors.lastname: Hu
authors.affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston, 6431 Fannin Street, MSE R331, Houston, TX 77030, USA shane.r.cunha@uth.tmc.edu.
authors.forename: Shane R
authors.initials: SR
authors.lastname: Cunha
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D017487:Ankyrins / Q000235:genetics*; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D019831:Sodium-Calcium Exchanger / Q000235:genetics / Q000378:metabolism
chemical_list: C498994:ANK2 protein, human; C498995:Ank2 protein, mouse; C432674:Ank2 protein, rat; D017487:Ankyrins; D020033:Protein Isoforms; D019831:Sodium-Calcium Exchanger
keywords: Alternative splicing; Ankyrin-B; Cardiomyocytes; Obscurin; Sodium–calcium exchanger