Active Relocation of Chromatin and Endoplasmic Reticulum Into Blebs in Late Apoptotic Cells

J Cell Sci. 2005 Sep 1;118(Pt 17):4059-71. doi: 10.1242/jcs.02529.


Plasma membrane blebbing is a defining characteristic of apoptosis, but its significance is not understood. Using live-cell imaging we have identified two phases of apoptotic blebbing. The early phase is restricted to adherent cells, and is prevented by the Rho-activated kinase inhibitor Y27632. The late phase is partially resistant to Y27632, and generates morphologically distinct membrane protrusions that are likely precursors to apoptotic bodies. Late blebbing is observed in all apoptotic cells tested. It occurs at a fixed period before phosphatidyl serine exposure, indicating that it is a universal and important feature of apoptosis. Late blebs contain a cortical layer of endoplasmic reticulum that often surrounds condensed chromatin, while other organelles are excluded. The appearance in some apoptotic cells of partially formed sheets of endoplasmic reticulum suggest that these cortical layers are newly formed by the remodelling of the endoplasmic reticulum of interphase cells. Formation of endoplasmic reticulum and chromatin-containing blebs requires both actin and microtubules, and is prevented by the caspase-6 inhibitor zVEID.fmk.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Amides / metabolism
  • Animals
  • Apoptosis / physiology*
  • Biomarkers / metabolism
  • Caspase 6
  • Caspase Inhibitors
  • Cell Adhesion
  • Cell Line
  • Cell Membrane / metabolism*
  • Cell Membrane / ultrastructure
  • Chromatin / metabolism*
  • Chromatin / ultrastructure*
  • Cytoskeleton / metabolism
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum / ultrastructure*
  • Enzyme Inhibitors / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Microtubules / metabolism
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Pyridines / metabolism
  • rho-Associated Kinases


  • Actins
  • Amides
  • Biomarkers
  • Caspase Inhibitors
  • Chromatin
  • Enzyme Inhibitors
  • Intracellular Signaling Peptides and Proteins
  • Pyridines
  • Y 27632
  • Protein-Serine-Threonine Kinases
  • rho-Associated Kinases
  • CASP6 protein, human
  • Caspase 6