Distribution of the endoplasmic reticulum and its relationship with the sarcoplasmic reticulum in skeletal myofibers

Exp Cell Res. 2003 Sep 10;289(1):47-57. doi: 10.1016/s0014-4827(03)00231-3.


We have analyzed the distribution of the endoplasmic reticulum (ER) within isolated rat skeletal muscle flexor digitorum brevis myofibers. Studies with confocal microscopy indicated that the resident ER proteins displayed a perinuclear and cross-striated distribution that extended over the I band areas. Interestingly, two discrete distribution patterns were observed when different receptor or viral marker proteins were blocked in the ER. Accordingly, the vesicular stomatitis virus G protein that lost its efficient export through the Golgi apparatus during myogenesis preferentially marked the A-I junctional areas. The proteins that retained their Golgi processing after myogenesis, on the contrary, concentrated around the myonuclei and over the Z lines. Furthermore, the ER exit site marker sec23 located to Z lines but not to A-I junctions. To analyze the ultrastructural organization of the ER, we infected myofibers with recombinant virus expressing KDEL-tagged peroxidase that is translocated into the ER. With transmission electron microscopy, peroxidase activity was found in perinuclear and Z line-flanking tubular structures, but also within the terminal cisternae of the sarcoplasmic reticulum. The translocon-associated protein exhibited a similar localization. Taken together, the terminal cisternae contained unevenly distributed rough ER structures apparently lacking the export function. The exporting ER comprised perinuclear and Z line-flanking structures.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Compartmentation / physiology
  • Endoplasmic Reticulum / metabolism
  • Endoplasmic Reticulum / ultrastructure*
  • Female
  • Fluorescent Antibody Technique
  • Golgi Apparatus / metabolism
  • Golgi Apparatus / ultrastructure
  • Membrane Glycoproteins / metabolism
  • Microscopy, Electron
  • Muscle Fibers, Skeletal / metabolism
  • Muscle Fibers, Skeletal / ultrastructure*
  • Muscle, Skeletal / metabolism
  • Muscle, Skeletal / ultrastructure*
  • Protein Folding
  • Protein Transport / physiology*
  • Proteins / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Fusion Proteins / metabolism
  • Sarcoplasmic Reticulum / metabolism
  • Sarcoplasmic Reticulum / ultrastructure*
  • Vesicular Transport Proteins
  • Viral Envelope Proteins / metabolism


  • G protein, vesicular stomatitis virus
  • Membrane Glycoproteins
  • Proteins
  • Recombinant Fusion Proteins
  • Sec23a protein, rat
  • Vesicular Transport Proteins
  • Viral Envelope Proteins