A transgenic myogenic cell line lacking ryanodine receptor protein for homologous expression studies: Reconstitution of Ry1R protein and function

R. A. Moore, H. Nguyen, J. Galceran, Isaac N Pessah, P. D. Allen

Research output: Contribution to journalArticle

59 Scopus citations

Abstract

CCS embryonic stem (ES) cells possessing two mutant alleles (ry1r- /ry1r-) for the skeletal muscle ryanodine receptor (RyR) have been produced and injected subcutaneously into severely compromised immunodeficient mice to produce teratocarcinomas in which Ry1R expression is absent. Several primary fibroblast cell lines were isolated and subcloned from one of these tumors that contain the knockout mutation in both alleles and exhibit a doubling time of 18-24 h, are not contact growth inhibited, do not exhibit drastic morphological change upon serum reduction, and possess the normal complement of chromosomes. Four of these fibroblast clones were infected with a retrovirus containing the cDNA encoding myoD and a puromycin selection marker. Several (1-2 μg/ml) puromycin-resisrant subclones from each initial cell line were expanded and examined for their ability to express myoD and to form multinucleated myotubes that express desmin and myosin upon removal of mitogens. One of these clones (1B5 cells) was selected on this basis for further study. These cells, upon withdrawal of mitogens for 5-7 d, were shown by Western blot analysis to express key triadic proteins, including skeletal triadin, calsequestrin, FK506-binding protein, 12 kD, sarco(endo)plasmic reticulum calcium-ATPasel, and dihydropyridine receptors. Neither RyR isoform protein, Ry1R (skeletal), Ry2R (cardiac), nor Ry3R (brain), were detected in differentiated 1B5 cells. Measurements of intracellular Ca2+ by ratio fluorescence imaging of fura-2-1oaded cells revealed that differentiated 1B5 cells exhibited no responses to K+ (40 mM) depolarization, ryanodine (50- 500 μM), or caffeine (20-100 mM). Transient transfection of the 1 B5 cells with the full-length rabbit Ry1 R cDNA restored the expected responses to K+ depolarization, caffeine, and ryanodine. Depolarization-induced Ca2+ release was independent of extracellular Ca2+, consistent with skeletal- type excitation-contraction coupling. Wild-type Ry1R expressed in 1 B5 cells were reconstituted into bilayer lipid membranes and found to be indistinguishable from channels reconstituted from rabbit sarcoplasmic reticulum with respect to unitary conductance, open dwell times, and responses to ryanodine and ruthenium red. The 1 B5 cell line provides a powerful and easily managed homologous expression system in which to study how Ry1 R structure relates to function.

Original languageEnglish (US)
Pages (from-to)843-851
Number of pages9
JournalJournal of Cell Biology
Volume140
Issue number4
DOIs
StatePublished - Feb 23 1998

ASJC Scopus subject areas

  • Cell Biology

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