Abstract
During the development of mammalian muscle the γ-subunit of the nicotinic acetylcholine receptor (AChR) is replaced by the ɛ-subunit to produce well-defined alterations in the conductance and gating of the channel. To gain a better unterstanding of the functional role of the γ and ɛ-subunits, we have studied the properties of an AChR channel lacking these subunits. The AChR expressed in Xenopus oocytes injected with the bovine α-, β and δ-subunit-specific mRNAs (referred to as αβδ-AChR) is unusual in that its channel opens spontaneously at a high frequency in the absence of agonist. From a comparison of the αβδ-AChR with complete receptors containing either the γ or ɛ-subunit, we conclude that the γ and ɛ-subunits influence most channel properties, including agonist binding, and are especially important for stabilizing the closed state of the unliganded receptor channel. The αβδ-AChR can form when a complete set of four subunit-specific mRNAs is injected. The ease with which it is assembled raises the possibility that the αβδ- AChR contributes to some of the variations in receptor properties that occur during development.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Brehm P, Henderson L (1988) Regulation of acetylcholine receptor channel function during development of skeletal muscle. Dev Biol 129: 1–11
Brehm P, Kullberg R, Moody-Corbett F (1984) Properties of nonjunctional acetylcholine receptor channels in innervated muscle of Xenopus laevis. J Physiol (Lond) 350: 631–648
Gu Y, Hall Z (1988) Immunological evidence for a change in subunits of the actylcholine receptor in developing and denervated rat muscle. Neuron 1: 117–125
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
Imoto K, Busch C, Sakmann B, Mishina M, Konno T, Nakai J, Bujo H, Mori Y, Fukuda K, Numa S (1988) Rings of negatively charged amino acids determine the acetylcholine receptor channel conductance. Nature 335: 645–648
Jackson MB (1984) Spontaneous openings of the acetylcholine receptor channel. Proc Natl Acad Sci USA 81: 3901–3904
Jackson MB (1986) Kinetics of unliganded acetylcholine receptor channel gating. Biophys J 49: 663–672
Jackson MB (1988) Dependence of acetylcholine receptor channel kinetics on agonist concentration in cultured mouse muscle fibres. J Physiol (Lond) 397: 555–583
Karlin A (1980) Molecular properties of nicotinic acetylcholine receptors. In: Cotman CW, Poste G, Nicolson GL (eds) Cell Surface Reviews, vol 6, North Holland, Amsterdam, pp 191–260
Kurosaki T, Fukuda K, Konno T, Mori Y, Tanaka K, Mishina M, Numa S (1987) Functional properties of nicotinic acetylcholine receptor subunits expressed in various combinations. FEBS Lett 214: 253–258
Methfessel C, Witzemann V, Takahashi T, Mishina M, Numa S, Sakmann B (1986) Patch clamp measurements on Xenopus laevis oocytes: currents through endogenous channels and implanted acetylcholine receptor and sodium channels. Pflügers Arch 407: 577–588
Mishina M, Kurosaki T, Tobimatsu T, Morimoto Y, Noda M, Yamamoto T, Terao M, Lindstrom J, Takahashi T, Kuno M, Numa S (1984) Expression of functional acetylcholine receptor from cloned cDNAs. Nature 307: 604–608
Mishina M, Tobimatsu T, Imoto K, Tanaka K, Fujita Y, Fukuda K, Kurasaki M, Takahashi H, Morimoto Y, Hirose T, Inayama S, Takahashi T, Kuno M, Numa S (1985) Location of functional regions of acetylcholine receptor α-subunit by site-directed mutagenesis. Nature 313: 364–369
Mishina M, Takai T, Imoto K, Noda M, Takahashi T, Numa S, Methfessel C, Sakmann B (1986) Molecular distinction between fetal and adult forms of muscle acetylcholine receptor. Nature 321: 406–411
Monod J, Wyman J, Changeux JP (1965) On the nature of allosteric transitions: a plausible model. J Mol Biol 12: 88–112
Moss SJ, Beeson DMW, Jackson JF, Darlison MG, Barnard EA (1987) Differential expression of nicotinic acetylcholine receptor genes in innervated and denervated chicken muscle. EMBO J 6: 3917–3921
Mulrine NK, Ogden DC (1988) The equilibrium open probability of nicotinic ion channels at the rat skeletal neuromuscular junction in vitro. J Physiol (Lond) 401: 95P
Neubig RR, Boyd ND, Cohen JB (1982) Conformations of Torpedo acetylcholine receptor associated with ion transport and desensitization. Biochemistry 21: 3460–3467
Numa S (1986) Evolution of ionic channels. Chem Scripta 26B: 173–178
Sakmann B, Methfessel C, Mishina M, Takahashi T, Takai T, Kurasaki M, Fukuda K, Numa S (1985) Role of acetylcholine receptor subunits in gating of the channel. Nature 318: 538–543
Steinbach JH (1989) Structural and functional diversity in vertebrate skeletal muscle nicotinic acetylcholine receptors. Anno Rev Physiology 51: 353–365
White MM, Mayne KM, Lester HA, Davidson N (1985) Mouse-Torpedo hybrid acetylcholine receptors: functional homology does not equal sequence homology. Proc Natl Acad Sci USA 82: 4852–4856
Witzemann V, Barg, B, Nishikawa Y, Sakmann B, Numa, S (1987) Differential regulation of muscle acetylcholine recepor γ- and ɛ- subunit mRNAs. FEBS Lett 223: 104–112
Witzemann V, Barg B, Criado M, Stein E, Sakmann B (1989) Developmental regulation of five subunit specific mRNAs encoding acetylcholine receptor subtypes in rat muscle. FEBS Lett 242: 419–424
Yoshii K, Yu L, Mayne KM, Davidson N, Lester H (1987) Equilibrium properties of mouse-Torpedo acetylcholine receptor hybrids expressed in Xenopus oocytes. J Gen Physiol 90: 553–573
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Jackson, M.B., Imoto, K., Mishina, M. et al. Spontaneous and agonist-induced openings of an acetylcholine receptor channel composed of bovine muscle α-, β and δ-subunits. Pflugers Arch. 417, 129–135 (1990). https://doi.org/10.1007/BF00370689
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00370689