Jd. Malhotra et al., Characterization of sodium channel alpha- and beta-subunits in rat and mouse cardiac myocytes, CIRCULATION, 103(9), 2001, pp. 1303-1310
Citations number
30
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cardiovascular & Respiratory Systems","Cardiovascular & Hematology Research
Background-Sodium channels isolated from mammalian brain are composed of al
pha-, beta (1)-, and beta (2)-subunits. The composition of sodium channels
in cardiac muscle, however, has not been defined, and disagreement exists o
ver which beta -subunits are expressed in the myocytes. Some investigators
have demonstrated beta (1) expression in heart. Others have not detected an
y 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.
Methods and Results-The goal of this study was to define the subunit compos
ition of cardiac sodium channels in myocytes. We show that cardiac sodium c
hannels are composed of alpha-, beta (1)-, and beta (2)-subunits, Nav1.5 an
d Nav1.1 are expressed in myocytes and are associated with beta (1)- and be
ta (2)-subunits. Immunocytochemical localization of Nav1.1, beta (1), and b
eta (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 b
eta (2) in transfected cells resulted in no detectable changes in sodium cu
rrent.
Conclusions-Cardiac sodium channels are composed of alpha- (Nav1.1 or Nav1.
5), beta (1)-, and beta (2)-subunits. Although beta (1)-subunits modulate c
ardiac sodium channel current, beta (2)-subunit function in heart may be li
mited to cell adhesion.