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  • Title: Identification and characterization of two ankyrin-B isoforms in mammalian heart.
    Author: Wu HC, Yamankurt G, Luo J, Subramaniam J, Hashmi SS, Hu H, Cunha SR.
    Journal: Cardiovasc Res; 2015 Sep 01; 107(4):466-77. PubMed ID: 26109584.
    Abstract:
    AIMS: 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. METHODS AND 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. CONCLUSION: 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.
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