title: A complement component C3a-like peptide stimulates chemotaxis by hemocytes from an invertebrate chordate-the tunicate, Pyura stolonifera.
abstract: Recent evidence suggests that the complement system evolved as a critical host defence mechanism among invertebrates, long before the origin among vertebrates of adaptive immune responses mediated by somatically re-arranging antibodies. The current study supports that contention by identifying a complement component C3a-like peptide in the tunicate, Pyura stolonifera. Activation of P. stolonifera serum with common inflammatory elicitors (lipopolysaccharide and zymosan) resulted in the proteolytic generation of an 8.5 kDa peptide, and concomitantly conferred chemoattractant activity on the serum. The 8.5 kDa peptide shares substantial amino acid sequence homology with a previously characterised tunicate complement component C3-like protein (72% amino acid identity in an 18 amino acid overlap). It is also recognised by an anti-C3 antiserum that is known to cross react with tunicate C3 homologues. Hemocyte migration assays performed with the 8.5 kDa peptide that had been partially purified by gel filtration confirmed that the molecule acts as a powerful chemotactic agent. This suggests that the proteolytic activation of tunicate C3-like molecules can initiate inflammatory responses involving cellular recruitment by liberating a pro-inflammatory peptide akin to the vertebrate anaphylatoxin, C3a.
authors.affiliation: Department of Biological Sciences, Macquarie University, NSW 2109, North Ryde, Australia. draftos@rna.bio.mp.edu.au
authors.forename: David A
authors.initials: DA
authors.lastname: Raftos
authors.forename: Jennifer
authors.initials: J
authors.lastname: Robbins
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Newton
authors.forename: Sham V
authors.initials: SV
authors.lastname: Nair
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001769:Blood / Q000187:drug effects; D002465:Cell Movement; D002630:Chemotactic Factors / Q000097:blood; D002633:Chemotaxis; D006434:Hemocytes / Q000187:drug effects* / Q000502:physiology*; D007106:Immune Sera / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D017386:Sequence Homology, Amino Acid; D014561:Urochordata / Q000502:physiology*; D015054:Zymosan / Q000494:pharmacology
chemical_list: D002630:Chemotactic Factors; D007106:Immune Sera; D008070:Lipopolysaccharides; D011506:Proteins; D015054:Zymosan