Activation of the skeletal muscle calcium release channel by a cytoplasmic loop of the dihydropyridine receptor.
Expression studies with skeletal and cardiac muscle cDNAs have suggested that the putative cytoplasmic loop region of the dihydropyridine receptor (DHPR) alpha 1 subunit between transmembrane repeats II and III (DCL) is a major determinant of the type of excitation-contraction coupling (skeletal or cardiac) in rescued dysgenic muscle cells (Tanabe, T., Beam, K. G., Adams, B. A., Niidome, T., and Numa, S. (1990) Nature 346, 567-569). In this study, the possibility of a direct functional interaction with the sarcoplasmic reticulum ryanodine receptor/Ca2+ release channel has been tested by expressing the DCLs of the mammalian skeletal and cardiac muscle DHPR alpha 1 subunit in Escherichia coli. The purified peptides activated the skeletal muscle ryanodine receptor/Ca2+ release channel in single channel and [3H]ryanodine binding measurements, by increasing channel open probability and the affinity of [3H]ryanodine binding, respectively. The two peptides did not activate the cardiac muscle Ca2+ release channel. Other proteins (polylysine, serum albumin) also increased [3H]ryanodine binding and Ca2+ release channel activity, but their activation mechanisms were distinguishable from DCLs. These results show that the II-III cytoplasmic loop of the skeletal and cardiac DHPR alpha 1 subunit functionally interacts with the skeletal, but not cardiac, muscle Ca2+ release channel. Furthermore, our studies suggest that in addition to the DHPR, the sarcoplasmic reticulum Ca2+ release channel may determine the type of E-C coupling that exists in muscle.
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Department of Biochemistry, University of North Carolina, Chapel Hill 27599-7260.
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Meissner
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D000595:Amino Acid Sequence; D000818:Animals; D015220:Calcium Channels / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000378:metabolism; D004285:Dogs; D004926:Escherichia coli; D007700:Kinetics; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism; D012433:Ryanodine / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D015220:Calcium Channels; D009124:Muscle Proteins; D011994:Recombinant Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine