We propose to study the function and modulation of ion channels in muscle with the long term goal of understanding their role in muscle membrane excitability and in the process of excitation-contraction coupling. In order to study ion channel properties we will use electrophysiological (voltage-and patch-clamp), and biochemical approaches, including reconstitution in planar lipid bilayers as well as in liposomes. Surface and transverse tubule membranes from frog and rat muscle will be isolated in order to study Na+ and Ca2+ -activated K+ channels in planar bilayers. To compare with the bilayer studies, Na+ channels will be also characterized in cut muscle fibers from the frog. Sarcoplasmic reticulum membranes will be isolated to investigate the properties of native Ca2+ release channels. This membrane preparation will be also used to purify the Ca2+ channels which will be incorporated into vesicles and planar bilayers. Their properties will be compared with those of the channels present in native membranes. All the above-mentioned channels will be studied regarding their selectivity, gating, as well as their pharmacological and regulation profile. The purified calcium channel macromolecule will be characterized in terms of ryanodine and InsP3 binding. The characteristics of Ca2+ release from sarcoplasmic reticulum membranes will be studied in vesicles and skinned muscle fibers. Lipid kinases involved in the metabolism of phosphoinositides and the phospholipase C present in the transverse tubule membrane will be characterized. Phosphoinositide metabolism will be investigated in skinned frog muscle livers. Ca2+ -activated K+ channels and other conductances regulated by extracellular transmitters and intracellular modulators will be studied in Drosophila larval muscle, using both wild and mutant types of this fly. The use of Drosophila larval muscle will allow us to gain a deeper understanding of the molecular basis of ion channel modulation in muscle cells.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM035981-05
Application #
3289528
Study Section
Physiology Study Section (PHY)
Project Start
1986-05-01
Project End
1992-04-30
Budget Start
1990-05-01
Budget End
1991-04-30
Support Year
5
Fiscal Year
1990
Total Cost
Indirect Cost
Name
Center of Scientific Studies of Santiago
Department
Type
DUNS #
City
Santiago
State
Country
Chile
Zip Code
Vergara, C; Ramirez, B; Behrens, M I (1993) Colchicine alters apamin receptors, electrical activity, and skeletal muscle relaxation. Muscle Nerve 16:935-40
Naranjo, D; Latorre, R (1993) Ion conduction in substates of the batrachotoxin-modified Na+ channel from toad skeletal muscle. Biophys J 64:1038-50
Caviedes, P; Olivares, E; Salas, K et al. (1993) Calcium fluxes, ion currents and dihydropyridine receptors in a new immortal cell line from rat heart muscle. J Mol Cell Cardiol 25:829-45
Delgado, R; Latorre, R; Labarca, P (1992) K(+)-channel blockers restore synaptic plasticity in the neuromuscular junction of dunce, a Drosophila learning and memory mutant. Proc Biol Sci 250:181-5
Toro, L; Stefani, E; Latorre, R (1992) Internal blockade of a Ca(2+)-activated K+ channel by Shaker B inactivating ""ball"" peptide. Neuron 9:237-45
Labarca, P; Latorre, R (1992) Insertion of ion channels into planar lipid bilayers by vesicle fusion. Methods Enzymol 207:447-63
Behrens, M I; Vergara, C (1992) Increase of apamin receptors in skeletal muscle induced by colchicine: possible role in myotonia. Am J Physiol 263:C794-802
Correa, A M; Bezanilla, F; Latorre, R (1992) Gating kinetics of batrachotoxin-modified Na+ channels in the squid giant axon. Voltage and temperature effects. Biophys J 61:1332-52
Caviedes, R; Liberona, J L; Hidalgo, J et al. (1992) A human skeletal muscle cell line obtained from an adult donor. Biochim Biophys Acta 1134:247-55
Correa, A M; Latorre, R; Bezanilla, F (1991) Ion permeation in normal and batrachotoxin-modified Na+ channels in the squid giant axon. J Gen Physiol 97:605-25

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