Authored: Jupe, S, 2011-04-28 Reviewed: McDermott, AM, 2011-11-03 Edited: Jupe, S, 2011-07-27 The defensins are a family of antimicrobial cationic peptide molecules which in mammals have a characteristic beta-sheet-rich fold and framework of six disulphide-linked cysteines (Selsted & Ouellette 2005, Ganz 2003). Human defensin peptides have two subfamilies, alpha- and beta-defensins, differing in the length of peptide chain between the six cysteines and the order of disulphide bond pairing between them. A third subfamily, the theta defensins, is derived from alpha-defensins prematurely truncated by a stop codon between the third and fourth cysteine residues. The translated products are shortened to nonapeptides, covalently dimerized by disulfide linkages, and cyclized via new peptide bonds between the first and ninth residues. Humans have one pseudogene but no translated representatives of the theta class.<br>In solution most alpha and beta defensins are monomers but can form dimers and higher order structures. The primary cellular sources of defensins are neutrophils, epithelial cells and intestinal Paneth cells.Those expressed in neutrophils and the gut are predominantly constitutive, while those in epithelial tissues such as skin are often inducible by proinflammatory stimuli such as LPS or TNF-alpha. Defensins are translated as precursor polypeptides that include a typical signal peptide or prepiece that is cleaved in the Golgi body, and a propiece, cleaved by differing mechanisms to produce the mature defensin. Mature defensin peptides can be further processed by removal of individual N-terminal residues (Yang et al. 2004). This may be a mechanism to broaden the activity profile of defensins (Ghosh et al. 2002). Defensins have direct antimicrobial effects and kill a wide range of Gram-positive and negative bacteria, fungi and some viruses. The primary antimicrobial action of defensins is permeabilization of microbial target membranes but several additional mechanisms have been suggested (Brogden 2005, Wilmes et al. 2011). Defensins and related antimicrobial peptides such as cathelicidin bridge the innate and acquired immune responses. In addition to their antimicrobial properties, cathelicidin and several defensins show receptor-mediated chemotactic activity for immune cells such as monocytes, T cells or immature DCs, induce cytokine production by monocytes and epithelial cells, modulate angiogenesis and stimulate wound healing (Yang et al. 1999, 2000, 2004, Rehaume & Hancock 2008, Yeung et al. 2011).

http://purl.obolibrary.org/obo/HINO_0022266

Authored: Jupe, S, 2011-04-28

Reviewed: McDermott, AM, 2011-11-03

Edited: Jupe, S, 2011-07-27

The defensins are a family of antimicrobial cationic peptide molecules which in mammals have a characteristic beta-sheet-rich fold and framework of six disulphide-linked cysteines (Selsted & Ouellette 2005, Ganz 2003). Human defensin peptides have two subfamilies, alpha- and beta-defensins, differing in the length of peptide chain between the six cysteines and the order of disulphide bond pairing between them. A third subfamily, the theta defensins, is derived from alpha-defensins prematurely truncated by a stop codon between the third and fourth cysteine residues. The translated products are shortened to nonapeptides, covalently dimerized by disulfide linkages, and cyclized via new peptide bonds between the first and ninth residues. Humans have one pseudogene but no translated representatives of the theta class.
In solution most alpha and beta defensins are monomers but can form dimers and higher order structures. The primary cellular sources of defensins are neutrophils, epithelial cells and intestinal Paneth cells.Those expressed in neutrophils and the gut are predominantly constitutive, while those in epithelial tissues such as skin are often inducible by proinflammatory stimuli such as LPS or TNF-alpha. Defensins are translated as precursor polypeptides that include a typical signal peptide or prepiece that is cleaved in the Golgi body, and a propiece, cleaved by differing mechanisms to produce the mature defensin. Mature defensin peptides can be further processed by removal of individual N-terminal residues (Yang et al. 2004). This may be a mechanism to broaden the activity profile of defensins (Ghosh et al. 2002). Defensins have direct antimicrobial effects and kill a wide range of Gram-positive and negative bacteria, fungi and some viruses. The primary antimicrobial action of defensins is permeabilization of microbial target membranes but several additional mechanisms have been suggested (Brogden 2005, Wilmes et al. 2011). Defensins and related antimicrobial peptides such as cathelicidin bridge the innate and acquired immune responses. In addition to their antimicrobial properties, cathelicidin and several defensins show receptor-mediated chemotactic activity for immune cells such as monocytes, T cells or immature DCs, induce cytokine production by monocytes and epithelial cells, modulate angiogenesis and stimulate wound healing (Yang et al. 1999, 2000, 2004, Rehaume & Hancock 2008, Yeung et al. 2011).

Pubmed10914484

Pubmed10521347

Reactome, http://www.reactome.org

Pubmed12021776

Pubmed19024344

Pubmed21617811

Pubmed12949495

Pubmed15908936

Pubmed21573784

Pubmed15703760

Pubmed15032578

Pubmed15372083

Defensins

http://purl.obolibrary.org/obo/NCBITaxon_9606

HINO:0022266

Defensins

ReactomeREACT_115846

Reactome Database ID Release 431461973

http://purl.obolibrary.org/obo/INO_0000021

http://purl.obolibrary.org/obo/HINO_0022264

http://purl.obolibrary.org/obo/HINO_0022267

http://purl.obolibrary.org/obo/HINO_0008072

http://purl.obolibrary.org/obo/HINO_0008035