Bleb (cell biology)

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In cell biology, a bleb is an irregular bulge in the plasma membrane of a cell, caused by localized decoupling of the cytoskeleton from the plasma membrane.[1] Blebbing or zeiosis is the formation of blebs.

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

Physiological functions[edit]

During apoptosis (programmed cell death), the cell's cytoskeleton breaks up and causes the membrane to bulge outward.[2] 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.

Blebbing also has important functions in other cellular processes, including cell locomotion, cell division, and physical or chemical stresses. The types of blebs vary greatly, including variations in bleb growth rates, size, contents, and actin content.

Prokaryotic gram-negative microbes also reveal membrane blebbing as a physiogical process and it has been a news to cell biologists.[3] Physiological significance of membrane blebbing in gram negative microbes was first realized, when virulent Salmonella microbes were seen to produce numerous periplasmic protrusions (later referred to as invasosomes, virulence organelles and finally as periplasmic organelles) while closely encountering animal host ileal epithelial cell microvilli in vivo, under transmission electron microscope.[4] A structural model of microbial bleb or periplasmic organelle has been proposed as expanded area containing a periplasmic bulge above bacterial inner membrane and peptidoglycan layer, externally bounded by lipopolysaccharide-rich bacterial outer membrane, and considered to be riveted at the base of the bulge with few Type3 secretory needle complex like rivet complexes.[5] These periplasmic organelles were then shown to represent a preparative stage for release of bacterial outer membrane bounded nano-sized vesicles (outer membrane vesicles, OMVs), suggested to translocate bacterial signals to host/target cells, as a new mode of membrane vesicle trafficking at the host-pathogen interface, for many purposes, including invasion of host.[6]

Pharmacology[edit]

A chemical known as blebbistatin was shown, in 2004, 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,[7][8][9] thus altering the contractile forces that impinge on the cytoskeleton-membrane interface.

Notes[edit]

  1. ^ 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. ^ 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. 
  3. ^ YashRoy R.C. (1999) Exocytosis in prokaryotes and its role in Salmonella invasion.ICAR NEWS - A Science and Technology Newsletter October 1999, vol. 5(4), page 18. https://www.researchgate.net/publication/230822402_'Exocytosis_in_prokaryotes'_and_its_role_in_Salmonella_invasion?ev=prf_pub
  4. ^ YashRoy R.C. (1992) Salmonella 3,10:r:- surface interaction with intestinal epithelial microvilli. Indian Journal of Animal Sciences vol. 62(60, pp. 502-504. https://www.researchgate.net/publication/230817080_Salmonella_310r_surface_interactions_with_intestinal_epithelial_microvilli?ev=prf_pub
  5. ^ YashRoy R.C. (2003) Eucaryotic cell intoxication by Gram-negative pathogens: A novel bacterial outermembrane-bound nanovesicular exocytosis model for Type-III secretion system. Toxicology International vol. 10(1), pp. 1-9. https://www.researchgate.net/publication/230793514_Eukaryotic_cell_intoxication_by_Gram-negative_pathogens_A_novel_bacterial_outermembrane-bound_nanovesicular_exocytosis_model_for_Type-III_secretion_system._Toxicology_International_vol._10_No._1_pages_1-9_year_2003?ev=prf_pub
  6. ^ YashRoy R.C. (1993) Electron microscope studies of surface pili and vesicles of Salmonella 3,10:r:- organisms. Indian Journal of Animal Sciences vol. 66(2), pp. 97-102. https://www.researchgate.net/publication/230817087_Electron_microscope_studies_of_surface_pilli_and_vesicles_of_Salmonella_310r-_organisms?ev=prf_pub
  7. ^ 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. 
  8. ^ 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. 
  9. ^ 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[edit]

External links[edit]

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