Life and Times of a Cellular Bleb

Biophys J. 2008 Mar 1;94(5):1836-53. doi: 10.1529/biophysj.107.113605. Epub 2007 Oct 5.

Abstract

Blebs are spherical cellular protrusions that occur in many physiological situations. Two distinct phases make up the life of a bleb, each of which have their own biology and physics: expansion, which lasts approximately 30 s, and retraction, which lasts approximately 2 min. We investigate these phases using optical microscopy and simple theoretical concepts, seeking information on blebbing itself, and on cytomechanics in general. We show that bleb nucleation depends on pressure, membrane-cortex adhesion energy, and membrane tension, and test this experimentally. Bleb growth occurs through a combination of bulk flow of lipids and delamination from the cell cortex via the formation and propagation of tears. In extreme cases, this can give rise to a traveling wave around the cell periphery, known as "circus movement." When growth stalls, an actin cortex reforms under the bleb membrane, and retraction starts, driven by myosin-II. Using flicker spectroscopy, we find that retracting blebs are fivefold more rigid than expanding blebs, an increase entirely explained by the properties of the newly formed cortical actin mesh. Finally, using artificially nucleated blebs as pressure sensors, we show that cells rounded up in mitosis possess a substantial intracellular pressure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Animals
  • Blister / etiology
  • Blister / metabolism*
  • Blister / pathology*
  • Cell Membrane / metabolism*
  • Cell Physiological Phenomena*
  • Cells, Cultured
  • Contractile Proteins / metabolism
  • Cytoskeleton / metabolism
  • Humans
  • Intracellular Fluid / metabolism
  • Microfilament Proteins / deficiency
  • Microfilament Proteins / metabolism*
  • Microscopy
  • Myosin Type II / metabolism

Substances

  • Actins
  • Contractile Proteins
  • Microfilament Proteins
  • Myosin Type II