β Subunit heterogeneity of L-type Ca2+ channels in smooth muscle tissues

2000 
Abstract Various β subunit isoforms stabilize different gating properties of voltage-gated L-type Ca 2+ channels. We therefore investigated the expression of Ca 2+ channel β subunit isoforms in different smooth muscle types on the protein level by immunoblotting and immunoprecipitation employing β subunit-selective sequence-directed antibodies. From the four known β subunit isoforms only β2 and β3 were detected in porcine uterus, bovine trachea and bovine aorta membranes. Multiple immunoreactive β2 bands were detected in a tissue-selective manner indicating structural heterogeneity of β2. Immunoprecipitation of (+)-[ 3 H]isradipine-prelabeled channels revealed that β2 and β3 participate in Ca 2+ channel formation in uterus and trachea, and β3 in aortic smooth muscle. We conclude that β2 and β3 subunits form L-type Ca 2+ channels in smooth muscle tissues. This subunit heterogeneity may be important to fine-tune channel function.
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