Bleb (cell biology)

In cell biology, a bleb is a bulge, or protrusion of the plasma membrane of a cell, human bioparticulate or abscess with an internal environment similar to that of a simple cell, characterized by a spherical, bulky morphology.[1][1] It is characterized by the decoupling of the cytoskeleton from the plasma membrane, degrading the internal structure of the cell, allowing the flexibility required to allow the cell to separate into individual bulges, or pockets of the intercellular matrix.[1] Most commonly, blebs are seen in apoptosis (programmed cell death), but are also seen in other non-apoptotic functions. Blebbing or zeiosis is the formation of blebs.

The process of apoptosis, with blebbing shown in the middle illustration

Formation

Bleb growth is driven by intracellular pressure generated in the cytoplasm when the actin cortex undergoes actomyosin contractions,[2] leading to the eventual break up into several billion pieces because the pressure is different than the exterior surface of the growth anatomical presence. The disruption of the membrane-actin cortex interactions[1] are dependent on the activity of myosin-ATPase[3]

Bleb formation can be initiated in two ways: 1) through local rupture of the cortex or 2) through local detachment of the cortex from the plasma membrane.[4] This generates a weak spot through which the cytoplasm flows, leading to the expansion of the bulge of membrane by increasing the surface area through tearing of the membrane from the cortex, during which time, actin levels decrease.[2] The cytoplasmic flow is driven by hydrostatic pressure inside the cell.[5][6]

Physiological function

Apoptotic function

Blebbing is one of the defined features of apoptosis.[3] During apoptosis (programmed cell death), the cell's cytoskeleton breaks up and causes the membrane to bulge outward.[7] These bulges may separate from the cell, taking a portion of cytoplasm with them, to become known as apoptotic bodies. Phagocytic cells eventually consume these fragments and the components are recycled.

Nonapoptotic functions

Blebbing also has important functions in other cellular processes, including cell locomotion, cell division, and physical or chemical stresses. Blebs have been seen in cultured cells in certain stages of the cell cycle. These blebs are used for cell locomotion in embryogenesis.[8] The types of blebs vary greatly, including variations in bleb growth rates, size, contents, and actin content. It also plays an important role in all five varieties of necrosis, a generally detrimental process. However, cell organelles do not spread into necrotic blebs.

Inhibition

In 2004, a chemical known as blebbistatin was shown to inhibit the formation of blebs. This agent was discovered in a screen for small molecule inhibitors of nonmuscle myosin IIA and was shown to lower the affinity of myosin with actin,[9][10][11] thus altering the contractile forces that impinge on the cytoskeleton-membrane interface.

Notes

  1. 1 2 3 4 Fackler OT, Grosse R (Jun 2008). "Cell motility through plasma membrane blebbing". J Cell Biol. 181 (6): 879–84. doi:10.1083/jcb.200802081. PMC 2426937. PMID 18541702.
  2. 1 2 Charras, G. T. (January 8, 2008). "A short history of blebbing". Journal of Microscopy 231 (3): 466 in 466–478. doi:10.1111/j.1365-2818.2008.02059.x. PMID 18755002.
  3. 1 2 Wickman, G. R.; Julian, L.; Mardilovich, K.; Schumacher, S.; Munro, J.; Rath, N.; Zander, S. Al; Mleczak, A.; Sumpton, D. (2013-10-01). "Blebs produced by actin–myosin contraction during apoptosis release damage-associated molecular pattern proteins before secondary necrosis occurs". Cell Death & Differentiation 20 (10): 1293–1305. doi:10.1038/cdd.2013.69. ISSN 1350-9047. PMC 3770329. PMID 23787996.
  4. ↑ Charras, G; Paluch, E (Sep 2008). "Blebs lead the way: how to migrate without lamellipodia.". Nature reviews. Molecular cell biology 9 (9): 730–6. doi:10.1038/nrm2453. PMID 18628785.
  5. ↑ Charras, GT; Yarrow, JC; Horton, MA; Mahadevan, L; Mitchison, TJ (May 19, 2005). "Non-equilibration of hydrostatic pressure in blebbing cells.". Nature 435 (7040): 365–9. Bibcode:2005Natur.435..365C. doi:10.1038/nature03550. PMID 15902261.
  6. ↑ Tinevez, JY; Schulze, U; Salbreux, G; Roensch, J; Joanny, JF; Paluch, E (Nov 3, 2009). "Role of cortical tension in bleb growth.". Proceedings of the National Academy of Sciences of the United States of America 106 (44): 18581–6. Bibcode:2009PNAS..10618581T. doi:10.1073/pnas.0903353106. PMID 19846787.
  7. ↑ Vermeulen K, Van Bockstaele DR, Berneman ZN (Oct 2005). "Apoptosis: mechanisms and relevance in cancer". Ann Hematol. 84 (10): 627–39. doi:10.1007/s00277-005-1065-x. PMID 16041532.
  8. ↑ Barros, L. F.; Kanaseki, T.; Sabirov, R.; Morishima, S.; Castro, J.; Bittner, C. X.; Maeno, E.; Ando-Akatsuka, Y.; Okada, Y. (2003-01-01). "Apoptotic and necrotic blebs in epithelial cells display similar neck diameters but different kinase dependency". Cell Death & Differentiation 10 (6): 687–697. doi:10.1038/sj.cdd.4401236. ISSN 1350-9047.
  9. ↑ Straight AF,Cheung A, Limouze J, Chen I, Westwood NJ, Sellers JR, and Mitchison TJ (March 2003). "Dissecting temporal and Spatial control of cytokinesis with a myosin II inhibitor". Science 299 (5613): 1743–47. Bibcode:2003Sci...299.1743S. doi:10.1126/science.1081412. PMID 12637748.
  10. ↑ Kovács M, Tóth J, Hetényi C, Málnási-Csizmadia A, Sellers JR (Aug 2004). "Mechanism of blebbistatin inhibition of myosin II". J Biol Chem. 279 (34): 35557–63. doi:10.1074/jbc.M405319200. PMID 15205456.
  11. ↑ Limouze J, Straight AF, Mitchison T, Sellers JR (2004). "Specificity of blebbistatin, an inhibitor of myosin II". J Muscle Res Cell Motil. 25 (4–5): 337–41. doi:10.1007/s10974-004-6060-7. PMID 15548862.

References

External links

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