Characterization of Sodium Channel α- and β-Subunits in Rat and Mouse Cardiac Myocytes
2001; Lippincott Williams & Wilkins; Volume: 103; Issue: 9 Linguagem: Inglês
10.1161/01.cir.103.9.1303
ISSN1524-4539
AutoresJyoti Malhotra, Chunling Chen, Ilaria Rivolta, Hugues Abriel, Ricky Malhotra, Laura N. Mattei, Frank C. Brosius, Robert S. Kass, Lori L. Isom,
Tópico(s)Neuroscience and Neuropharmacology Research
ResumoSodium channels isolated from mammalian brain are composed of alpha-, beta(1)-, and beta(2)-subunits. The composition of sodium channels in cardiac muscle, however, has not been defined, and disagreement exists over which beta-subunits are expressed in the myocytes. Some investigators have demonstrated beta(1) expression in heart. Others have not detected any auxiliary subunits. On the basis of Northern blot analysis of total RNA, beta(2) expression has been thought to be exclusive to neurons and absent from cardiac muscle.The goal of this study was to define the subunit composition of cardiac sodium channels in myocytes. We show that cardiac sodium channels are composed of alpha-, beta(1)-, and beta(2)-subunits. Nav1.5 and Nav1.1 are expressed in myocytes and are associated with beta(1)- and beta(2)-subunits. Immunocytochemical localization of Nav1.1, beta(1), and beta(2) in adult heart sections showed that these subunits are expressed at the Z lines, as shown previously for Nav1.5. Coexpression of Nav1.5 with beta(2) in transfected cells resulted in no detectable changes in sodium current.Cardiac sodium channels are composed of alpha- (Nav1.1 or Nav1.5), beta(1)-, and beta(2)-subunits. Although beta(1)-subunits modulate cardiac sodium channel current, beta(2)-subunit function in heart may be limited to cell adhesion.
Referência(s)