The β1 subunit but not the β2 subunit colocalizes with the human heart NA+ channel (hH1) already within the endoplasmic reticulum

T. Zimmer, C. Biskup, C. Bollensdorff, K. Benndorf

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    36 Citations (Scopus)


    Voltage-dependent Na+ channels are hetero-multimers consisting of a pore-forming α subunit and accessory β subunits. In order to provide more insight into the trafficking and assembly of the cardiac Na+ channel complex, we investigated the subcellular localization of the Na+ channel β1 and β2 subunits, both in the absence and presence of the human heart Na+ channel (hH1). We fused spectrally distinct variants of the green fluorescent protein (GFP) to hH1 and to the β1 and β2 subunit, and expressed the optically labeled β subunits separately or in combination with hH1 in HEK293 cells. In contrast to the predominant localization of hH1 channels within the endoplasmic reticulum (ER), both β subunits were clearly targeted to the plasma membrane when expressing their cDNAs alone. Upon coexpression of the α subunit, the β1 subunit was efficiently retained within the ER and found to be colocalized with hH1. In contrast to this, hH1 and the β2 subunit were not colocalized, i.e., they were detected mainly within the ER and the plasma membrane, respectively. These results indicate that hH1 and the β2 subunit are transported separately to the plasma membrane whereas the hH1/β1 complex occurs already within the ER, which possibly facilitates trafficking of the channel complex to the plasma membrane.

    Original languageEnglish
    Pages (from-to)13-21
    Number of pages9
    JournalJournal of Membrane Biology
    Issue number1
    Publication statusPublished - 1 Mar 2002



    • Green fluorescent protein (GFP)
    • Human heart Na channel (hH1)
    • Na channel trafficking
    • Nachannel β
    • Subunit assembly
    • Subunits

    ASJC Scopus subject areas

    • Biophysics
    • Physiology
    • Cell Biology

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