Vault (organelle)

Major Vault Protein repeat

Structure of the Vault complex from rat liver.[1]
Identifiers
Symbol Vault
Pfam PF01505
InterPro IPR002499
PROSITE PDOC51224

The vault or vault cytoplasmic ribonucleoprotein is a eukaryotic organelle whose function is not fully understood. Discovered and successfully isolated by cell biologist Nancy Kedersha and biochemist Leonard Rome of the UCLA School of Medicine in the 1980s, vaults are cytoplasmic organelles which under an electron microscope resemble the arches of a cathedral vault, with 39-fold symmetry.[1] They are present in many types of eukaryotic cells and appear to be highly conserved amongst eukaryotes.[2] Vaults become part of lipid rafts where they may play a role fighting pathogens.[3]

Morphology

Vaults are large ribonucleoprotein particles. About 3 times the size of a ribosome and weighing approximately 13 MDa, they are found in many diverse eukaryotic cells. They measure 34 nm by 60 nm from a negative stain, 26 nm by 49 nm from cryo-electron microscopy, and 35 nm by 59 nm from STEM.[4] The vaults consist primarily of proteins, making it difficult to stain with conventional techniques. The protein structure consists of many major vault proteins (MVP) bound to one of the two minor vault proteins. Two large complexes of several MVP's and a minor vault protein close together to form the barrel-like vault organelle. They also contain small vault RNAs (vRNAs, also known as vtRNAs) of 86–141 bases within.[5]

Function

Despite not being fully elucidated, vaults have been associated with the nuclear pore complexes and their octagonal shape appears to support this.[6] It has been concluded that the vault's function is the transportation of molecules, such as mRNA, from the nucleus to parts of the cytoplasm.[7] It is also thought that vaults play a role in protein synthesis.[8]

Association with cancer

In the late 1990s, researchers found that vaults (especially the MVP) were over-expressed in cancer patients who were diagnosed with multidrug resistance, that is the resistance against many chemotherapy treatments.[9] Although this does not prove that increased number of vaults led to drug resistance, it does hint at some sort of involvement. This has potential in discovering the mechanisms behind drug-resistance in tumor cells and improving anticancer drugs.[10]

Evolutionary conservation

Vaults have been identified in mammals, amphibians, avians and Dictyostelium discoideum.[2] The Vault model used by the Pfam database identifies homologues in Paramecium tetraurelia, Kinetoplastida, many vertebrates, a cnidarian (starlet sea anemone), molluscs, Trichoplax adhaerens, flatworms, Echinococcus granulosus and Choanoflagellate.[11]

Although vaults have been observed in many eukaryotic species, a few species do not appear to have the protein. These include:[12]

These four species are model organisms for plants, nematodes, animal genetics and fungi respectively. Despite these exceptions, the high degree of similarity of vaults in organisms that do have them implies some sort of evolutionary importance.[2]

See also

External links

References

  1. 1 2 Tanaka H, Kato K, Yamashita E, et al. (January 2009). "The structure of rat liver vault at 3.5 angstrom resolution". Science 323 (5912): 384–8. doi:10.1126/science.1164975. PMID 19150846.
  2. 1 2 3 Kedersha NL, Miquel MC, Bittner D, Rome LH (1990). "Vaults. II. Ribonucleoprotein structures are highly conserved among higher and lower eukaryotes.". J Cell Biol 110 (4): 895–901. doi:10.1083/jcb.110.4.895. PMC 2116106. PMID 1691193.
  3. ↑ Tanaka H, Kato K, Yamashita E, et al. (January 2009). "The structure of rat liver vault at 3.5 angstrom resolution". Science 323 (5912): 384–8. doi:10.1126/science.1164975. PMID 19150846.
  4. ↑ Kedersha N. L., Heuser J. E., Chugani D. C., Rome L. H. (1991). "Vaults. III. Vault ribonucleoprotein particles open into flower-like structures with octagonal symmetry". J. Cell Biol 112 (2): 225–235. doi:10.1083/jcb.112.2.225. PMC 2288824. PMID 1988458.
  5. ↑ van Zon A, Mossink MH, Scheper RJ, Sonneveld P, Wiemer EA (September 2003). "The vault complex". Cell. Mol. Life Sci. 60 (9): 1828–37. doi:10.1007/s00018-003-3030-y. PMID 14523546.
  6. ↑ Unwin P. N. T., Milligan R. A. (1982). "A large particle associated with the perimeter of the nuclear pore complex". J. Cell Biol 93 (1): 63–75. doi:10.1083/jcb.93.1.63. PMC 2112107. PMID 7068761.
  7. ↑ Chugani DC, Rome LH, Kedersha NL (September 1993). "Evidence that vault ribonucleoprotein particles localize to the nuclear pore complex". J. Cell. Sci. 106: 23–9. PMID 8270627.
  8. ↑ Cannon, Joseph N.; Stanfield, Cindy L; Niles, Mary Jane; Germann, William J (2007). Principles of human physiology (3rd ed.). San Francisco: Pearson/Benjamin Cummings. p. 41. ISBN 978-0-8053-8286-0.
  9. ↑ Mossink MH, van Zon A, Scheper RJ, Sonneveld P, Wiemer EA (October 2003). "Vaults: a ribonucleoprotein particle involved in drug resistance?". Oncogene 22 (47): 7458–67. doi:10.1038/sj.onc.1206947. PMID 14576851.
  10. ↑ Kickhoefer VA, Vasu SK, Rome LH (May 1996). "Vaults are the answer, what is the question?". Trends Cell Biol. 6 (5): 174–8. doi:10.1016/0962-8924(96)10014-3. PMID 15157468.
  11. ↑ http://pfam.sanger.ac.uk/family/PF01505 Major Vault Protein repeat Pfam family
  12. ↑ Rome L, Kedersha N, Chugani D (1991). "Unlocking vaults: organelles in search of a function.". Trends Cell Biol 1 (2-3): 47–50. doi:10.1016/0962-8924(91)90088-Q. PMID 14731565.
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