The II-III loop of the skeletal muscle dihydropyridine receptor is responsible for the Bi-directional coupling with the ryanodine receptor

J Biol Chem. 1999 Jul 30;274(31):21913-9. doi: 10.1074/jbc.274.31.21913.

Abstract

The dihydropyridine receptor (DHPR) in the skeletal muscle plasmalemma functions as both voltage-gated Ca(2+) channel and voltage sensor for excitation-contraction (EC) coupling. As voltage sensor, the DHPR regulates intracellular Ca(2+) release via the skeletal isoform of the ryanodine receptor (RyR-1). Interaction with RyR-1 also feeds back to increase the Ca(2+) current mediated by the DHPR. To identify regions of the DHPR important for receiving this signal from RyR-1, we expressed in dysgenic myotubes a chimera (SkLC) having skeletal (Sk) DHPR sequence except for a cardiac (C) II-III loop (L). Tagging with green fluorescent protein (GFP) enabled identification of expressing myotubes. Dysgenic myotubes expressing GFP-SkLC or SkLC lacked EC coupling and had very small Ca(2+) currents. Introducing a short skeletal segment (alpha(1S) residues 720-765) into the cardiac II-III loop (replacing alpha(1C) residues 851-896) of GFP-SkLC restored both EC coupling and Ca(2+) current densities like those of the wild type skeletal DHPR. This 46-amino acid stretch of skeletal sequence was recently shown to be capable of transferring strong, skeletal-type EC coupling to an otherwise cardiac DHPR (Nakai, J., Tanabe, T., Konno, T., Adams, B., and Beam, K.G. (1998) J. Biol. Chem. 273, 24983-24986). Thus, this segment of the skeletal II-III loop contains a motif required for both skeletal-type EC coupling and RyR-1-mediated enhancement of Ca(2+) current.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Animals, Newborn
  • Calcium Channels / chemistry*
  • Calcium Channels / genetics
  • Calcium Channels / physiology*
  • Calcium Channels, L-Type
  • Cells, Cultured
  • Green Fluorescent Proteins
  • Heart / physiology
  • Luminescent Proteins / genetics
  • Membrane Potentials
  • Mice
  • Mice, Mutant Strains
  • Molecular Sequence Data
  • Muscle, Skeletal / cytology
  • Muscle, Skeletal / physiology*
  • Muscle, Skeletal / physiopathology
  • Patch-Clamp Techniques
  • Protein Structure, Secondary
  • Receptor Cross-Talk / physiology*
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / metabolism
  • Restriction Mapping
  • Ryanodine Receptor Calcium Release Channel / genetics
  • Ryanodine Receptor Calcium Release Channel / physiology*
  • Signal Transduction

Substances

  • Calcium Channels
  • Calcium Channels, L-Type
  • Luminescent Proteins
  • Recombinant Fusion Proteins
  • Ryanodine Receptor Calcium Release Channel
  • Green Fluorescent Proteins