CD14
Cluster of differentiation 14 also known as CD14 is a human gene.[1][2]
The protein encoded by this gene is a component of the innate immune system. CD14 exists in two forms. Either it is anchored into the membrane by a glycosylphosphatidylinositol tail (mCD14) or it appears in a soluble form (sCD14). Soluble CD14 either appears after shedding of mCD14 (48 kDa) or is directly secreted from intracellular vesicles (56 kDa).[3]
CD14 takes its name from its inclusion in the cluster of differentiation group of cell surface marker proteins.
CD14 was the first described pattern recognition receptor.
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[edit] Function
CD14 acts as a co-receptor (along with the Toll-like receptor TLR 4 and MD-2) for the detection of bacterial lipopolysaccharide (LPS).[4][5] CD14 can bind LPS only in the presence of lipopolysaccharide-binding protein (LBP). Although LPS is considered its main ligand, CD14 also recognizes other pathogen-associated molecular patterns.
[edit] Tissue distribution
CD14 is expressed mainly by macrophages and (at 10 times lesser extent) by neutrophil granulocytes. It is also expressed by dendritic cells. A soluble form sCD14 is secreted by the liver and monocytes and is sufficient in low concentrations to confer LPS-responsiveness to cells that otherwise do not express CD14. sCD14 is also present in human milk, where it is believed to regulate microbial growth in the infant gut.
[edit] Differentiation
CD14+ cells are monocytes that can differentiate into a host of different cells. (A '+' sign refers to the presence of the CD14 protein on a cell. )
One type of cell is the dendritic cell, where differentiation is encouraged by cytokines. Examples of cytokines that will cause dendritic cell differentiation includes GM-CSF and IL-4.
[edit] Interactions
CD14 has been shown to interact with Lipopolysaccharide-binding protein.[6][7]
[edit] References
- ^ Setoguchi M, Nasu N, Yoshida S, Higuchi Y, Akizuki S, Yamamoto S (July 1989). "Mouse and human CD14 (myeloid cell-specific leucine-rich glycoprotein) primary structure deduced from cDNA clones". Biochim. Biophys. Acta 1008 (2): 213–22. doi:10.1016/0167-4781(80)90012-3. PMID 2472171.
- ^ Simmons DL, Tan S, Tenen DG, Nicholson-Weller A, Seed B (1 January 1989). "Monocyte antigen CD14 is a phospholipid anchored membrane protein". Blood 73 (1): 284–9. PMID 2462937. http://www.bloodjournal.org/cgi/pmidlookup?view=long&pmid=2462937.
- ^ Kirkland TN, Viriyakosol S (1998). "Structure-function analysis of soluble and membrane-bound CD14". Prog. Clin. Biol. Res. 397: 79–87. PMID 9575549.
- ^ Kitchens RL (2000). "Role of CD14 in cellular recognition of bacterial lipopolysaccharides". Chem. Immunol.. Chemical Immunology and Allergy 74: 61–82. doi:10.1159/000058750. ISBN 3-8055-6917-3. PMID 10608082.
- ^ Tapping RI, Tobias PS (2000). "Soluble CD14-mediated cellular responses to lipopolysaccharide". Chem. Immunol.. Chemical Immunology and Allergy 74: 108–21. doi:10.1159/000058751. ISBN 3-8055-6917-3. PMID 10608084.
- ^ Thomas, Celestine J; Kapoor Mili, Sharma Shilpi, Bausinger Huguette, Zyilan Umit, Lipsker Dan, Hanau Daniel, Surolia Avadhesha (Nov. 2002). "Evidence of a trimolecular complex involving LPS, LPS binding protein and soluble CD14 as an effector of LPS response". FEBS Lett. (Netherlands) 531 (2): 184–8. doi:10.1016/S0014-5793(02)03499-3. ISSN 0014-5793. PMID 12417309.
- ^ Yu, B; Wright S D (1995). "LPS-dependent interaction of Mac-2-binding protein with immobilized CD14". J. Inflamm. (UNITED STATES) 45 (2): 115–25. ISSN 1078-7852. PMID 7583357.
[edit] External links
[edit] Further reading
- Todd RF, Petty HR (1997). "Beta 2 (CD11/CD18) integrins can serve as signaling partners for other leukocyte receptors". J. Lab. Clin. Med. 129 (5): 492–8. doi:10.1016/S0022-2143(97)90003-2. PMID 9142045.
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