title: Vesicularization of the endoplasmic reticulum is a fast response to plasma membrane injury.
abstract: The endoplasmic reticulum of most cell types mainly consists of an extensive network of narrow sheets and tubules. It is well known that an excessive increase of the cytosolic Ca(2+) concentration induces a slow but extensive swelling of the endoplasmic reticulum into a vesicular morphology. We observed that a similar extensive transition to a vesicular morphology may also occur independently of a change of cytosolic Ca(2+) and that the change may occur at a time scale of seconds. Exposure of various types of cultured cells to saponin selectively permeabilized the plasma membrane and resulted in a rapid swelling of the endoplasmic reticulum even before a loss of permeability barrier was detectable with a low-molecular mass dye. The structural alteration was reversible provided the exposure to saponin was not too long. Mechanical damage of the plasma membrane resulted in a large-scale transition of the endoplasmic reticulum from a tubular to a vesicular morphology within seconds, also in Ca(2+)-depleted cells. The rapid onset of the phenomenon suggests that it could perform a physiological function. Various mechanisms are discussed whereby endoplasmic reticulum vesicularization could assist in protection against cytosolic Ca(2+) overload in cellular stress situations like plasma membrane injury.
authors.affiliation: Laboratory of Cellular Transport Systems, Department of Molecular Cell Biology, KULeuven, Campus Gasthuisberg O/N1, Bus 802, B3000 Leuven, Belgium. Luc.Raeymaekers@med.kuleuven.be
authors.forename: Luc
authors.initials: L
authors.lastname: Raeymaekers
authors.forename: Els
authors.initials: E
authors.lastname: Larivière
mesh_terms: D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000648:ultrastructure*; D002463:Cell Membrane Permeability; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000648:ultrastructure*; D006801:Humans; D012503:Saponins / Q000494:pharmacology; D013314:Stress, Mechanical
chemical_list: D012503:Saponins; D002118:Calcium