β-Adrenergic Receptor Stimulates L-Type Calcium Current in Adult Smooth Muscle Cells

Abstract

The hormonal regulation of L-type calcium current was investigated in freshly isolated tracheal smooth muscle cells using the whole-cell configuration of the patch-clamp technique. Isoproterenol stimulated the L-type calcium current 2.6-fold through β-adrenoceptors. Dialysis of these cells with cyclic AMP, cyclic AMP analogues or the catalytic sub-unit of cyclic AMP kinase had no effect on basal or isoproterenol-stimulated calcium current. The calcium current was stimulated and inhibited by dialysis of the cells with GTPγS and GDPβS, respectively. Evidently, in some smooth muscle cells the β-adrenoceptor couples directly to L-type calcium channels via a G protein.

Receptor for catecholamines responding to catechol which potentiates voltage‐dependent calcium current in single cells from guinea‐pig taenia caeci

“…This result is similar to that of Ohya et al (1987) who found that cyclic AMP did not potentiate ICa in cells from the longitudinal smooth muscle of rabbit jejunums in contrast to results in pig coronary artery smooth muscle where forskolin potentiated ICa (Fukumitsu et al, 1990). We have also found that potentiation of ICa in guinea-pig taenia cells did not appear to be mediated by a G-protein, contrary to results obtained in tracheal smooth muscle by Welling et al (1991; or to be mediated by activation of protein kinase C which has been implicated in the increase in ha produced by muscarinic and and other receptor activation in amphibian gastric smooth muscle cells (Vivaudou et al, 1988). I Author for correspondence.…”

“…studied in single cells by electrophysiological techniques (Welling et al, 1991;. However, the action of Iso in raising intracellular calcium activity is not confined to single, enzymedigested, cells as it has been observed in strips of tracheal smooth muscle (Takuwa et al, 1988).…”

Cardiac L-type Calcium Channel β-Subunits Expressed in Human Heart Have Differential Effects on Single Channel Characteristics

“…This is not unexpected, because N-terminal interaction sequences remain despite the premature translational stop, which results in loss of the principal ␤-subunit interaction domain and, furthermore, of potential phosphorylation sites for protein kinase C and the casein kinase II (30). Also, such structural features may alter interaction with G-proteins (35,36). ␤ 3trunc expression may actually compete with other isoforms and thus reduce single channel activity in native heteromultimeric complexes, but channels behaving in such a manner were not detected in native failing human myocytes (5,29,37).…”

A potential site of functional modulation by protein kinase A in the cardiac Ca2+ channel α1C subunit

“…It is unclear why the smooth muscle L-type Ca 2+ currents are not enhanced by PKA [35][36][37][38]. It may be hypothesized, by analogy with oocytes and CHO cells, that in smooth muscle cells the channel is fully phosphorylated; another possibility is that a majority of the channels contain a truncated cqc subunit that, due a posttranslational modification, loses a part of its C-terminus including the residue analogous to S1928.…”