Abstract
The α 1 subunit of the L-type Ca2+ channel plays a dual role in skeletal muscle. It is essential both for L-type Ca2+ channel activity and for the functioning of the voltage-sensor structure that is situated in the triads as a key element for excitation-contraction coupling. This paper shows, with mouse muscle cells in primary culture, that indolizinsulphone SR33557 which has its binding site on the α 1 subunit blocks both L-type Ca2+ channel activity and contraction as the more classical 1,4-dihydropyridine blockers. However, unlike other Ca2+ channel blockers, it can pharmacologically discriminate between the two different roles of the α 1 subunit. SR33557 inhibition of both contractile and L-type Ca2+ channel activities is very voltage dependent and increases at depolarized potentials. Complete blockade of contraction was observed at low SR33557 concentrations (K 0.5=20 nM) and was associated with only minor L-type Ca2+ channel blockade (30%). The remaining and major part of the L-type Ca2+ channel activity (70%) was blocked at much higher SR33557 concentrations (K 0.5=0.6 μM). The results indicate that SR33557 has a much higher affinity for the α 1 subunit inserted into the voltage-sensor structure. They also suggest that the voltage-sensor structure, which probably includes most of the total T-tubule α 1 subunit, has intrinsic (but relatively small) Ca2+ channel activity. BayK8644, a L-type Ca2+ channel activator of the 1,4-dihydropyridine family, drastically increased contraction in parallel with an increase of the L-type Ca2+ current. SR33557 at low concentrations completely abolished contraction in BayK8644-treated myotubes while leaving a L-type Ca2+ current component larger than the normal L-type Ca2+ current observed in untreated control myotubes. SR33557 is the first reported molecule which can discriminate between the two functions of the α 1 subunit and eliminate contraction while leaving large L-type Ca2+ currents. For that reason it should become a potent tool for future studies of excitation-contraction coupling in skeletal muscle.
Similar content being viewed by others
References
Barrett JN, Barrett EF, Dribin LB (1981) Calcium-dependent slow potassium conductance in rat skeletal myotubes. Dev Biol 82:258–266
Campbell KP, Leung AT, Sharp AH (1988) The biochemistry and molecular biology of the dihydropyridine-sensitive calcium channel. Trends Neurosci 11: 425–430
Catterall WA (1991) Excitation-contraction coupling in vertebrate skelealmuscle: A tale of two calcium channels. Cell 64:871–874
Cognard C, Lazdunski M, Romey G (1986) Different types of Ca2+ channels in mammalian skeletal muscle cells in culture. Proc Natl Acad Sci USA 83:517–521
Cognard C, Romey G, Galizzi J-P, Fosset M, Lazdunski M (1986) Dihydropyridine-sensitive Ca2+ channels in mammalian skeletal muscle cells in culture: Electrophysiological properties and interactions with Ca2+ channel activator (BayK8644) and inhibitor (PN200-110). Proc Natl Acad Sci USA 83:1518–1522
Endo M (1977) Calcium release from the sarcoplasmic reticulum. Physiol Rev 57:70–108
Erdmann R, Lüttgau HCh (1989) The effect of the phenylal-kylamine D888 (devapamil) on force and Ca2+ current in isolated frog skeletal muscle fibres. J Physiol (Lond) 413:521–541
Hamill OP, Marty A, Neher E, Sakmann B, Sigworth FJ (1981) Improved patch-clamp techniques for high resolution current recording from cells and cell-free membrane patches. Pflügers Arch 391:85–100
Hosey M, Lazdunski M (1988) Calcium channels: molecular pharmacology, structure and regulation. J Membr Biol 104:81–105
Hugues M, Schmid H, Romey G, Duval D, Frelin C, Lazdunski M (1982) The Ca2+-dependent slow K+ conductance in cultured rat muscle cells: characterization with apamin. EMBO J 1:1039–1042
Ildefonse M, Jacquemond V, Rougier O, Renaud J-F, Fosset M, Lazdunski M (1985) Excitation-contraction coupling in skeletal muscle: evidence for a role of slow Ca2+ channels using Ca2+ activators. Biochem Biophys Res Commun 129:904–909
Koenig J, Bournaud R, Powell JA, Rieger F (1982) Appearance of contractile activity in muscular dysgenesis (mdg/mdg) mouse myotubes during coculture with normal spinal cord cells. Dev Biol 92:188–196
Lamb GD, Walsh T (1987) Calcium currents, charge movement and dihydropyridine binding in fast- and slow-twitch muscles of rat and rabbit. J Physiol (Lond) 393:595–617
Morad M, Nayler W, Kazda S, Schramm M (1988) The calcium channel: structure, function and implications. Springer, Berlin Heidelberg New York
Nokin P, Clinet M, Polster P, Beaufort P, Meysmans L, Gougat J, Chatelain P (1989) SR33557, a novel calcium antagonist: interaction with [3H](±)〈nitrendipine and [3H](-)desmethoxyverapamil binding sites in cerebral membranes. Naunyn-Schmiedebergs Arch Pharmacol 339:31–36
Nokin P, Clinet M, Beaufort L, Meysmans L, Laruel R, Chatelain P (1990) SR33557, a novel calcium entry blocker. II. Interactions with 1,4-dihydropyridine, phenylalkylamine and benzothiazepine binding sites in rat heart sarcolemmal membranes. J Pharmacol Exp Ther 255:600–617
Peres-Reyes E, Kim HS, Lacerda AE, Horne W, Wei X, Rampe D, Campbell KP, Brown AM, Birnbaumer L (1989) Induction of calcium currents by the expression of the α 1 subunit of the dihydropyridine receptor from skeletal muscle. Nature 340:233–236
Peres-Reyes E, Wei X, Castellano A, Birnbaumer L (1990) Molecular diversity of L-type calcium channels. Evidence for alternative splicing of the transcripts of three non-allelic genes. J Biol Chem 265:20430–20436
Rampe D, Triggle DJ (1990) New ligands for L-type Ca2+ channels. Trends Physiol Sci 11:112–115
Rios E, Pizarro G (1988) Voltage sensors and calcium channels of excitation-contraction coupling. News Physiol Sci 3:223–227
Romey G, Garcia L, Rieger F, Lazdunski M (1988) Targets for calcium channel blockers in mammalian skeletal muscle and their respective functions in excitation-contraction coupling. Biochem Biophys Res Commun 156:1324–1332
Romey G, Garcia L, Rieger F, Lazdunski M (1989) Ontogenesis and localization of Ca2+ channels in mammalian skeletal muscle in culture and role in excitation-contraction-coupling. Proc Natl Acad Sci USA 86:2933–2937
Schmid A, Romey G, Barhanin J, Lazdunski M (1989) SR33557, an indolizinsulfone blocker of Ca2+ channels: Identification of receptor sites and analysis of its mode of action. Mol Pharmacol 35:766–773
Tanabe T, Beam KG, Powel JA, Numa S (1988) Restoration of excitation-contraction coupling and slow calcium current in dysgenic muscle by dihydropyridine complementary DNA. Nature 336:134–139
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Bois, P., Romey, G. & Lazdunski, M. Indolizinsulphones. A class of blockers with dual but discriminative effects on L-type Ca2+ channel activity and excitation-contraction coupling in skeletal muscle. Pflügers Arch 419, 651–656 (1991). https://doi.org/10.1007/BF00370310
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00370310