Identification and characterization of properdin in amphioxus: Implications for a functional alternative complement pathway in the basal chordate. Issue 65 (June 2017)

• Record Type: Journal Article
• Authors: Gao, Zhan; Ma, Zengyu; Qu, Baozhen; Jiao, Deyan; Zhang, Shicui
• Is Part Of: Fish & shellfish immunology. Issue 65(2017)
• Page Start: 1
• Page End: 8
• Publication Date: 2017-06
• Subjects: Amphioxus -- Branchiostoma japonicum -- Complement system -- Alternative pathway -- Properdin; Fishes -- Immunology -- Periodicals; Shellfish -- Immunology -- Periodicals; Poissons -- Immunologie -- Périodiques; Crustacés -- Immunologie -- Périodiques; 571.9617
• DOI: 10.1016/j.fsi.2017.03.052
• Languages: English
• ISSNs: 1050-4648

Abstract

Abstract: A complement system operating via the alternative pathway similar to that of vertebrates has been demonstrated in the primitive chordate amphioxus. However, the factor P (fP), a positive regulator of the alternative pathway, remains elusive in amphioxus to date. In this study, we identified and characterized a properdin gene in the amphioxus B. japonicum, BjfP, which represents an archetype of vertebrate properdins. Real-time PCR analysis showed that the BjfP was ubiquitously expressed and its expression was significantly up-regulated following the challenge with bacteria or lipopolysaccharide (LPS) and lipoteichoic acid (LTA). Recombinant BjfP (rBjfP) and its truncated proteins including rTSR1-3, rTSR4-6 and rTSR7-8, were all capable of interacting with both Gram-negative and positive bacteria as well as LPS and LTA. Moreover, rBjfP, rTSR1-3 and rTSR4-6 could also specifically bind to C3b. Importantly, both rTSR1-3 and rTSR4-6 could inhibit the binding of rBjfP to C3b, and thus suppress the activation of the alternative pathway of complement, suggesting the involvement of BjfP in the alternative pathway. This is the first report showing that a properdin protein in invertebrates plays similar roles to vertebrate properdins. Collectively, these data suggest that BjfP might represent the ancient molecule from which vertebrate properdins evolved. Highlights: A properdin gene, designated BjfP, was identified in amphioxus. BjfP was markedly up-regulated following challenge with bacteria, LPS or LTA. rBjfP, rTSR1-3, rTSR4-6 and rTSR7-8 all showed affinity to bacteria, LPS and LTA. rBjfP, rTSR1-3 and rTSR4-6 could specifically bind to C3b. BjfP seems the ancient molecule from which vertebrate properdins evolved.