A βIV-spectrin/CaMKII signaling complex is essential for membrane excitability in mice

Department of Internal Medicine, Division of Cardiovascular Medicine, University of Iowa Carver College of Medicine, Iowa City, Iowa 52242, USA.
The Journal of clinical investigation (Impact Factor: 13.22). 09/2010; 120(10):3508-19. DOI: 10.1172/JCI43621
Source: PubMed


Ion channel function is fundamental to the existence of life. In metazoans, the coordinate activities of voltage-gated Na(+) channels underlie cellular excitability and control neuronal communication, cardiac excitation-contraction coupling, and skeletal muscle function. However, despite decades of research and linkage of Na(+) channel dysfunction with arrhythmia, epilepsy, and myotonia, little progress has been made toward understanding the fundamental processes that regulate this family of proteins. Here, we have identified β(IV)-spectrin as a multifunctional regulatory platform for Na(+) channels in mice. We found that β(IV)-spectrin targeted critical structural and regulatory proteins to excitable membranes in the heart and brain. Animal models harboring mutant β(IV)-spectrin alleles displayed aberrant cellular excitability and whole animal physiology. Moreover, we identified a regulatory mechanism for Na(+) channels, via direct phosphorylation by β(IV)-spectrin-targeted calcium/calmodulin-dependent kinase II (CaMKII). Collectively, our data define an unexpected but indispensable molecular platform that determines membrane excitability in the mouse heart and brain.


Available from: Matthew Rasband, Sep 03, 2014
  • Source
    • "Calmodulin-dependent kinase (CaMKII), a serine/threonine kinase with diverse regulatory functions in ion transporter function, transcription, and cell death, is targeted to the AIS through interaction with the CaMKII-binding motif of β-IV-spectrin. A C-terminal truncation of β-IV-spectrin resulted in aberrant targeting of CaMKII, while localization of ankyrin-G and spectrin at the AIS was normal (59). Cyclin-dependent kinase (Cdk)-dependent phosphorylation of the Kv2β subunit inhibits the interaction of Kv2β with microtubule proteins. "
    [Show abstract] [Hide abstract]
    ABSTRACT: The progress of developing effective interventions against psychiatric disorders has been limited due to a lack of understanding of the underlying cellular and functional mechanisms. Recent research findings focused on exploring novel causes of psychiatric disorders have highlighted the importance of the axonal initial segment (AIS), a highly specialized neuronal structure critical for spike initiation of the action potential. In particular, the role of voltage-gated sodium channels, and their interactions with other protein partners in a tightly regulated macromolecular complex has been emphasized as a key component in the regulation of neuronal excitability. Deficits and excesses of excitability have been linked to the pathogenesis of brain disorders. Identification of the factors and regulatory pathways involved in proper AIS function, or its disruption, can lead to the development of novel interventions that target these mechanistic interactions, increasing treatment efficacy while reducing deleterious off-target effects for psychiatric disorders.
    Frontiers in Psychiatry 08/2014; 5:109. DOI:10.3389/fpsyt.2014.00109
  • Source
    • "CaMKII is an established regulator of the myocardial Na+ current (INa), and simultaneously potentiates late INa (INaL) while decreasing channel availability (Herren et al., 2013). While the specific phosphorylations required for these effects remain debated, available evidence suggests that either or both Ser-571 and Ser-516 may be key sites (Hund et al., 2010; Ashpole et al., 2012; Koval et al., 2012; Herren et al., 2013), and it is generally agreed that the I-II intracellular linker is the critical phosphoregulatory domain. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Calcium/calmodulin-dependent protein kinase II (CaMKII) activity has been shown to contribute to arrhythmogenesis in a remarkably broad range of cardiac pathologies. Several of these involve significant structural and electrophysiologic remodeling, whereas others are due to specific channelopathies, and are not typically associated with arrhythmogenic changes to protein expression or cellular and tissue structure. The ability of CaMKII to contribute to arrhythmia across such a broad range of phenotypes suggests one of two interpretations regarding the role of CaMKII in cardiac arrhythmia: (1) some CaMKII-dependent mechanism is a common driver of arrhythmia irrespective of the specific etiology of the disease, or (2) these different etiologies expose different mechanisms by which CaMKII is capable of promoting arrhythmia. In this review, we dissect the available mechanistic evidence to explore these two possibilities and discuss how the various molecular actions of CaMKII promote arrhythmia in different pathophysiologic contexts.
    Frontiers in Pharmacology 05/2014; 5:110. DOI:10.3389/fphar.2014.00110 · 3.80 Impact Factor
  • Source
    • "The following commercially available antibodies were used: rabbit polyclonal Cx43 (Invitrogen, 1∶250) and mouse monoclonal Cx43 (BD Transduction Laboratories, 1∶200), rabbit polyclonal and mouse monoclonal N-cadherin (both Sigma-Aldrich, 1∶800), mouse monoclonal α-actinin (Sigma-Aldrich, 1∶1000), mouse monoclonal desmoplakin (AbD Serotec, 1∶2000), mouse monoclonal plakoglobin (Sigma-Aldrich, 1∶1000), mouse monoclonal plakophilin-2 (Progen, 1∶1000) and rabbit polyclonal Zona Occludens-1 (ZO-1, Invitrogen, 1∶50). A custom, affinity-purified rabbit anti-human Nav1.5 antibody (1∶100) was produced at the Ohio State University, USA [10], [11]. The secondary antibodies donkey anti-mouse DyLight (Dyl, 1∶250), donkey anti-mouse fluorescein (FITC, 1∶100), donkey anti-rabbit TexasRed (TX, 1∶100) and goat anti-rabbit (FITC, 1∶250) were purchased from Jackson Laboratories. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In cardiac muscle, the intercalated disk (ID) at the longitudinal cell-edges of cardiomyocytes provides as a macromolecular infrastructure that integrates mechanical and electrical coupling within the heart. Pathophysiological disturbance in composition of this complex is well known to trigger cardiac arrhythmias and pump failure. The mechanisms underlying assembly of this important cellular domain in human heart is currently unknown. We collected 18 specimens from individuals that died from non-cardiovascular causes. Age of the specimens ranged from a gestational age of 15 weeks through 11 years postnatal. Immunohistochemical labeling was performed against proteins comprising desmosomes, adherens junctions, the cardiac sodium channel and gap junctions to visualize spatiotemporal alterations in subcellular location of the proteins. Changes in spatiotemporal localization of the adherens junction proteins (N-cadherin and ZO-1) and desmosomal proteins (plakoglobin, desmoplakin and plakophilin-2) were identical in all subsequent ages studied. After an initial period of diffuse and lateral labelling, all proteins were fully localized in the ID at approximately 1 year after birth. Nav1.5 that composes the cardiac sodium channel and the gap junction protein Cx43 follow a similar pattern but their arrival in the ID is detected at (much) later stages (two years for Nav1.5 and seven years for Cx43, respectively). Our data on developmental maturation of the ID in human heart indicate that generation of the mechanical junctions at the ID precedes that of the electrical junctions with a significant difference in time. In addition arrival of the electrical junctions (Nav1.5 and Cx43) is not uniform since sodium channels localize much earlier than gap junction channels.
    PLoS ONE 04/2014; 9(4):e94722. DOI:10.1371/journal.pone.0094722 · 3.23 Impact Factor
Show more