Biology:Eosinophil cationic protein

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Short description: Mammalian protein found in Homo sapiens


A representation of the 3D structure of the protein myoglobin showing turquoise α-helices.
Generic protein structure example

Eosinophil cationic protein (ECP) also known as ribonuclease 3 is a basic protein located in the eosinophil primary matrix.[1] In humans, the eosinophil cationic protein is encoded by the RNASE3 gene.[2]

ECP is released during degranulation of eosinophils. This protein is related to inflammation and asthma because in these cases, there are increased levels of ECP in the body. There are three glycosolated forms of ECP and consequently ECP has a range of molecular weights from 18-22 kDa.[3]

Function

Eosinophil cationic protein and the sequence related eosinophil-derived neurotoxin (RNASE2) are both members of the Ribonuclease A superfamily. Both proteins possess neurotoxic, helmintho-toxic, and ribonucleo-lytic activities. Eosinophil cationic protein is localized to the granule matrix of the eosinophil.[4]

Ribonuclease activity and cytotoxicity

The ribonuclease activity of ECP is not essential for cytotoxicity.[5]

When the two known ribonuclease active-site residues are modified to non-functional counterparts (Lysine at position 38 to Arginine and Histidine at position 128 to Aspartate)[6] and compared to the wild-type ECP, the mutated ECP retains its cytotoxicity but no longer has its ribonuclease activity. The experiment confirmed that converting the two amino acids to non-functional counterparts did inhibit ECP’s ribonuclease activity. However, ECP retained its anti-parasitic activity. Also, it did not change the production and transportation of ECP in bacteria.

ECP is a potent cytotoxic protein capable of killing cells of guinea pig tracheal epithelium,[7] mammalian leukemia,[8] epidermis carcinoma,[7] and breast carcinoma,[9] as well as non-mammalian cells such as parasites, bacteria, and viruses.[10]

Mature ECP is cytotoxic to human bronchial epithelial (BEAS-2B) cells by specific binding to cell surface heparan sulfate proteoglycans (HSPGs) followed by endocytosis.[11]

ECP-induced apoptosis

Role of rECP in TNF-α apoptosis signaling. rECP increases BEAS-2B cells TNF-α production and release. The release of TNF-α binding to TNF receptor results in receptor internalization and activates caspase-8. Caspase-8-induced apoptosis can either trigger mitochondrial response or directly cause PARP activation by caspase-3. However, rECP-induced apoptosis shows no effects on mitochondrial responses. Accordingly, we suggest that rECP induces mitochondria-independent apoptosis.[12]

Studies show that ECP, along with other RNases including EDN, had been reported to induce apoptosis in cells. A latest study indicated that ECP caused cytotoxicity in HL-60 and HeLa cells via caspase-3 like activity.[13] Accordingly, cytotoxic RNases play an important role in cell death. However, the mechanism of ECP-induced apoptosis is still not fully verified. Recent studies have shown that eosinophils can induce epithelial cell death via apoptosis and necrosis.[14]

ECP triggers apoptosis by caspase-8 activation through mitochondria-independent pathway.[12] Increases in chromatin condensation, sub-G1 population, PARP cleavage, and DNA fragmentation indicate that ECP induces apoptosis in human bronchial epithelial (BEAS-2B) cells.[12]

Clinical significance

Eosinophil granulocytes appear in large numbers in inflammation sites and in response to certain parasitic infections. These cytoplasmic granules contain positively charged proteins that characterize the cells. ECP is one of the four highly basic proteins that enter the surrounding tissues when activated eosinophils degranulate. Although circulating ECP levels can vary widely among patients, some studies show that serum ECP measurements are useful in monitoring many active inflammatory diseases.[15] ECP concentrations in plasma and other body fluids increase during inflammatory reactions marked by activated eosinophils.[16]

Serum ECP levels are also a useful, objective measurement for asthma severity. Increased ECP levels correspond to symptom onset. In seasonal asthmatic patients, ECP measurement reflected changes in disease activity throughout the year.[17]

There are several mechanisms that can be combined to generate an asthma attack, including specific IgE antibodies, activated inflammatory cells, neurogenic mechanisms, hyperresponsiveness and individual hormonal imbalances. Allergic reactions in the lung typically have two phases. The late phase typically occurs several hours after exposure, upon which eosinophils accumulate in the bronchus and release granule proteins that cause bronchial irritability. ECP is also toxic to neurons, some epithelial cell lines, and isolated myocardial cells.[18] This could be a reason for itching disorders of the skin.

Serum ECP concentrations have also been linked to atopic dermatitis (AD) activity. ECP correlates with the symptoms (lichenification, sleep deprivation, erythema, papules, pruritus and excoriations) for AD and also correlates with the total clinical score.[18]

Serum ECP measurement for assessing asthma severity, monitoring therapy, and indicating severity of certain inflammatory skin conditions present an advantage over subjective clinical measures that are prone to inconsistencies due to broad variability of individual investigator and patient assessments, especially in young children.

The normal reference range for blood tests for eosinophil cationic protein is between 2.3 and 16 µg/L.[19]

See also

  • Ribonuclease A

References

  1. ↑ "Identification and characterization of human eosinophil cationic protein by an epitope-specific antibody". J. Leukoc. Biol. 69 (6): 1027–35. June 2001. doi:10.1189/jlb.69.6.1027. PMID 11404391. 
  2. ↑ "Localization of the human eosinophil Charcot-Leyden crystal protein (lysophospholipase) gene (CLC) to chromosome 19 and the human ribonuclease 2 (eosinophil-derived neurotoxin) and ribonuclease 3 (eosinophil cationic protein) genes (RNS2 and RNS3) to chromosome 14". Genomics 13 (1): 240–2. May 1992. doi:10.1016/0888-7543(92)90237-M. PMID 1577491. 
  3. ↑ Lee BioSolutions, Inc. http://www.leebio.com/eosinophil-cationic-protein-human-P359.html
  4. ↑ "Structure and chromosome localization of the human eosinophil-derived neurotoxin and eosinophil cationic protein genes: evidence for intronless coding sequences in the ribonuclease gene superfamily". Genomics 7 (4): 535–46. August 1990. doi:10.1016/0888-7543(90)90197-3. PMID 2387583. 
  5. ↑ Rosenberg HF (April 1995). "Recombinant human eosinophil cationic protein. Ribonuclease activity is not essential for cytotoxicity". J. Biol. Chem. 270 (14): 7876–81. doi:10.1074/jbc.270.14.7876. PMID 7713881. 
  6. ↑ "Antibacterial properties of eosinophil major basic protein and eosinophil cationic protein". Journal of Immunology 142 (12): 4428–34. June 1989. PMID 2656865. 
  7. ↑ 7.0 7.1 "Toxicity of eosinophil cationic proteins for guinea pig tracheal epithelium in vitro". Am. Rev. Respir. Dis. 139 (3): 801–5. March 1989. doi:10.1164/ajrccm/139.3.801. PMID 2923379. 
  8. ↑ "Surface-exposed amino acids of eosinophil cationic protein play a critical role in the inhibition of mammalian cell proliferation". Mol. Cell. Biochem. 272 (1–2): 1–7. April 2005. doi:10.1007/s11010-005-4777-2. PMID 16010966. 
  9. ↑ "Intercellular Cell Adhesion Molecule-1, Vascular Cell Adhesion Molecule-1, and Regulated on Activation Normal T Cell Expressed and Secreted Are Expressed by Human Breast Carcinoma Cells and Support Eosinophil Adhesion and Activation". Am. J. Pathol. 157 (1): 313–21. July 2000. doi:10.1016/S0002-9440(10)64542-7. PMID 10880401. 
  10. ↑ Venge P (January 2004). "Monitoring the allergic inflammation". Allergy 59 (1): 26–32. doi:10.1046/j.1398-9995.2003.00386.x. PMID 14674929. 
  11. ↑ "A heparan sulfate-facilitated and raft-dependent macropinocytosis of eosinophil cationic protein". Traffic 8 (12): 1778–95. December 2007. doi:10.1111/j.1600-0854.2007.00650.x. PMID 17944807. 
  12. ↑ 12.0 12.1 12.2 "TNF-α Mediates Eosinophil Cationic Protein-induced Apoptosis in BEAS-2B Cells". BMC Cell Biol. 11: 6. 2010. doi:10.1186/1471-2121-11-6. PMID 20089176. 
  13. ↑ "The cytotoxicity of eosinophil cationic protein/ribonuclease 3 on eukaryotic cell lines takes place through its aggregation on the cell membrane". Cell. Mol. Life Sci. 65 (2): 324–37. January 2008. doi:10.1007/s00018-007-7499-7. PMID 18087674. 
  14. ↑ "T cells and eosinophils cooperate in the induction of bronchial epithelial cell apoptosis in asthma". The Journal of Allergy and Clinical Immunology 109 (2): 329–37. February 2002. doi:10.1067/mai.2002.121460. PMID 11842305. 
  15. ↑ Wardlaw AJ (August 1994). "Eosinophils in the 1990s: new perspectives on their role in health and disease". Postgrad Med J 70 (826): 536–52. doi:10.1136/pgmj.70.826.536. PMID 7937446. 
  16. ↑ "Measurement of serum levels of eosinophil cationic protein to monitor patients with seasonal respiratory allergy induced by Parietaria pollen (treated and untreated with specific immunotherapy)". Allergy 51 (4): 245–50. April 1996. doi:10.1111/j.1398-9995.1996.tb00075.x. PMID 8792921. 
  17. ↑ "Serum levels of eosinophil cationic protein in allergic diseases and natural allergen exposure". The Journal of Allergy and Clinical Immunology 97 (6): 1350–5. June 1996. doi:10.1016/S0091-6749(96)70204-X. PMID 8648032. 
  18. ↑ 18.0 18.1 "Serum eosinophil cationic protein (ECP) is a sensitive measure for disease activity in atopic dermatitis". Br. J. Dermatol. 126 (4): 351–5. April 1992. doi:10.1111/j.1365-2133.1992.tb00677.x. PMID 1571256. 
  19. ↑ Reference range list from Uppsala University Hospital ("Laborationslista"). Artnr 40284 Sj74a. Issued on April 22, 2008

Further reading

External links




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