title: Central core disease mutations R4892W, I4897T and G4898E in the ryanodine receptor isoform 1 reduce the Ca2+ sensitivity and amplitude of Ca2+-dependent Ca2+ release.
abstract: Three CCD (central core disease) mutants, R4892W (Arg4892-->), I4897T and G4898E, in the pore region of the skeletal-muscle Ca2+-release channel RyR1 (ryanodine receptor 1) were characterized using a newly developed assay that monitored Ca2+ release in the presence of Ca2+ uptake in microsomes isolated from HEK-293 cells (human embryonic kidney 293 cells), co-expressing each of the three mutants together with SERCA1a (sarcoplasmic/endoplasmic-reticulum Ca2+-ATPase 1a). Both Ca2+ sensitivity and peak amplitude of Ca2+ release were either absent from or sharply decreased in homotetrameric mutants. Co-expression of wild-type RyR1 with mutant RyR1 (heterotetrameric mutants) restored Ca2+ sensitivity partially, in the ratio 1:2, or fully, in the ratio 1:1. Peak amplitude was restored only partially in the ratio 1:2 or 1:1. Reduced amplitude was not correlated with maximum Ca2+ loading or the amount of expressed RyR1 protein. High-affinity [3H]ryanodine binding and caffeine-induced Ca2+ release were also absent from the three homotetrameric mutants. These results indicate that decreased Ca2+ sensitivity is one of the serious defects in these three excitation-contraction uncoupling CCD mutations. In CCD skeletal muscles, where a mixture of wild-type and mutant RyR1 is expressed, these defects are expected to decrease Ca2+-induced Ca2+ release, as well as orthograde Ca2+ release, in response to transverse tubular membrane depolarization.
authors.affiliation: Banting and Best Department of Medical Research, Charles H. Best Institute, University of Toronto, 112 College St., Toronto, ON, Canada M5G 1L6.
authors.forename: Guo Guang
authors.initials: GG
authors.lastname: Du
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Khanna
authors.forename: Xinghua
authors.initials: X
authors.lastname: Guo
authors.forename: David H
authors.initials: DH
authors.lastname: MacLennan
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001120:Arginine / Q000235:genetics; D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D002127:Calcium Isotopes / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000096:biosynthesis; D002460:Cell Line; D018698:Glutamic Acid / Q000235:genetics; D005998:Glycine / Q000235:genetics; D006801:Humans; D007532:Isoleucine / Q000378:metabolism; D007668:Kidney / Q000737:chemistry / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D008861:Microsomes / Q000737:chemistry / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense / Q000235:genetics*; D020512:Myopathy, Central Core / Q000235:genetics*; D010070:Oxalates / Q000378:metabolism; D010783:Photometry / Q000379:methods; D020033:Protein Isoforms / Q000235:genetics; D019837:Ryanodine Receptor Calcium Release Channel / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D013912:Threonine / Q000235:genetics; D014364:Tryptophan / Q000235:genetics
chemical_list: D002127:Calcium Isotopes; D010070:Oxalates; D020033:Protein Isoforms; D019837:Ryanodine Receptor Calcium Release Channel; D007532:Isoleucine; D013912:Threonine; D018698:Glutamic Acid; D014364:Tryptophan; D000255:Adenosine Triphosphate; D001120:Arginine; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium; D005998:Glycine