Weibel-Palade body

In physiology, Weibel-Palade bodies are organelles in the endothelial cells, the cells which make up the endothelium, the exceedingly thin cell sheet which lines all blood vessels, and the heart. They are named after the two scientists who first described them in 1964. They play a dual role in blood coagulation hemostasis and inflammation.

Constituents

There are two major constituents of Weibel-Palade bodies. One is von Willebrand factor (vWF), a multimeric protein involved in blood coagulation [cite journal |author=Wagner DD, Olmsted JB, Marder VJ |title=Immunolocalization of von Willebrand protein in Weibel-Palade bodies of human endothelial cells |journal=J. Cell Biol. |volume=95 |issue=1 |pages=355–60 |year=1982 |month=October |pmid=6754744 |pmc=2112360 |url=http://www.jcb.org/cgi/reprint/95/1/355 | format=PDF |doi=10.1083/jcb.95.1.355] . The second is P-selectin [cite journal |author=Bonfanti R, Furie BC, Furie B, Wagner DD |title=PADGEM (GMP140) is a component of Weibel-Palade bodies of human endothelial cells |journal=Blood |volume=73 |issue=5 |pages=1109–12 |year=1989 |month=April |pmid=2467701 |url=http://bloodjournal.hematologylibrary.org/cgi/reprint/73/5/1109 | format=PDF] [cite journal |author=McEver RP, Beckstead JH, Moore KL, Marshall-Carlson L, Bainton DF |title=GMP-140, a platelet alpha-granule membrane protein, is also synthesized by vascular endothelial cells and is localized in Weibel-Palade bodies |journal=J. Clin. Invest. |volume=84 |issue=1 |pages=92–9 |year=1989 |month=July |pmid=2472431 |pmc=303957 |doi=10.1172/JCI114175] , which binds to passing immune cells (leukocytes). This allows the fast moving leukocytes in the blood to bind to the cells lining the blood vessels and slow down in a series of steps called the leukocyte adhesion cascade. Subsequently, leukocytes transmigrate across the endothelium and enter the surrounding tissue where they can migrate to the site of infection.

Additional Weibel-Palade body components are the chemokines Interleukin-8 and eotaxin-3, endothelin-1, angiopoietin-2, osteoprotegerin, the tetraspanin CD63/lamp3 and α-1,3-fucosyltransferase VI.

Clinical significance

The importance of Weibel-Palade bodies are highlighted by some human disease mutations. Mutations within vWF are the usual cause of the most common inherited bleeding disorder, von Willebrand disease. VWD has an estimated prevalence in some human populations of up to 1%, and is most often characterized by prolonged and variable mucocutaneous bleeding. Type III von Willebrand Disease is a severe bleeding disorder, not unlike severe hemophilia type A or B. VWF acts in primary hemostasis to recruit platelets at a site of injury, and is also important in secondary hemostasis, acting as a chaperone for coagulation factor VIII (FVIII).

Production

Multimeric vWF is assembled in the Golgi apparatus from vWF dimers. The Golgi then buds off vesicles, covered in a lipid bilayer, which consist almost exclusively of vWF. The only parallel organelle in physiology is the "alpha" granule of platelets, which also contains vWF. Weibel-Palade bodies are the main source of vWF, though, and α-granules probably play a minor role.

History

Weibel-Palade bodies were initially described by the Swiss anatomist Ewald R. Weibel and the Romanian physiologist George Emil Palade in 1964. [cite journal |author=Weibel ER, Palade GE |title=New cytoplasmic components in arterial endothelia |journal=J. Cell Biol. |volume=23 |issue= |pages=101–12 |year=1964 |month=October |pmid=14228505 |pmc=2106503 |doi=10.1083/jcb.23.1.101] Prof. Palade was to win the Nobel Prize in Physiology or Medicine in 1974 for his work on the function of organelles in cells.

References

ee also

* Endothelium
* Von Willebrand factor
* Platelet

External links

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