Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i>
Complement factor I (CFI), a complement inhibitor, is well known for regulating the complement system activation by degrading complement component 3b (C3b) in animal serum, thus becoming involved in innate defense. Nevertheless, the functional mechanisms of CFI in the complement system and in host-p...
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MDPI AG
2022-09-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/23/19/11369 |
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| author | Yi Liu Zhao Lv Tiaoyi Xiao Xuewen Zhang Chunhua Ding Beibei Qin Baohong Xu Qiaolin Liu |
| author_facet | Yi Liu Zhao Lv Tiaoyi Xiao Xuewen Zhang Chunhua Ding Beibei Qin Baohong Xu Qiaolin Liu |
| author_sort | Yi Liu |
| collection | DOAJ |
| description | Complement factor I (CFI), a complement inhibitor, is well known for regulating the complement system activation by degrading complement component 3b (C3b) in animal serum, thus becoming involved in innate defense. Nevertheless, the functional mechanisms of CFI in the complement system and in host-pathogen interactions are far from being clarified in teleost fish. In the present study, we cloned and characterized the CFI gene, CiCFI, from grass carp (<i>Ctenopharyngodon idella</i>) and analyzed its function in degrading serum C3b and expression changes after grass carp reovirus (GCRV) infection. The open reading frame of CiCFI was found to be 2121 bp, encoding 706 amino acids with a molecular mass of 79.06 kDa. The pairwise alignments showed that CiCFI shared the highest identity (66.9%) with CFI from <i>Carassius gibelio</i> and the highest similarity (78.7%) with CFI from <i>Danio rerio</i>. The CiCFI protein was characterized by a conserved functional core Tryp_SPc domain with the catalytic triad and substrate binding sites. Phylogenetic analysis indicated that CiCFI and the homologs CFIs from other teleost fish formed a distinct evolutionary branch. Similar with the CFIs reported in mammals, the recombinant CiCFI protein could significantly reduce the C3b content in the serum, demonstrating the conserved function of CiCFI in the complement system in the grass carp. CiCFI mRNA and protein showed the highest expression level in the liver. After GCRV infection, the mRNA expressions of CiCFI were first down-regulated, then up-regulated, and then down-regulated to the initial level, while the protein expression levels maintained an overall downward trend to the late stage of infection in the liver of grass carps. Unexpectedly, the protein levels of CiCFI were also continuously down-regulated in the serum of grass carps during GCRV infection, while the content of serum C3b proteins first increases and then returns to the initial level, suggesting a distinct role of CiCFI in regulating complement activation and fish-virus interaction. Combining our previous results that complement factor D, a complement enhancer, shows continuously up-regulated expression levels in grass carps during GCRV infection, and this study may provide the further essential data for the full picture of complex complement regulation mechanism mediated by Df and CFI of the grass carp during pathogen infection. |
| first_indexed | 2024-03-09T21:40:19Z |
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| issn | 1661-6596 1422-0067 |
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| last_indexed | 2024-03-09T21:40:19Z |
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| spelling | doaj.art-8f77473fa6364a0290357f367187f2842023-11-23T20:31:58ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672022-09-0123191136910.3390/ijms231911369Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i>Yi Liu0Zhao Lv1Tiaoyi Xiao2Xuewen Zhang3Chunhua Ding4Beibei Qin5Baohong Xu6Qiaolin Liu7Hunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaHunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaHunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaHunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaHunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaHunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaHunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaHunan Engineering Technology Research Center of Featured Aquatic Resources Utilization, Hunan Agricultural University, Changsha 410128, ChinaComplement factor I (CFI), a complement inhibitor, is well known for regulating the complement system activation by degrading complement component 3b (C3b) in animal serum, thus becoming involved in innate defense. Nevertheless, the functional mechanisms of CFI in the complement system and in host-pathogen interactions are far from being clarified in teleost fish. In the present study, we cloned and characterized the CFI gene, CiCFI, from grass carp (<i>Ctenopharyngodon idella</i>) and analyzed its function in degrading serum C3b and expression changes after grass carp reovirus (GCRV) infection. The open reading frame of CiCFI was found to be 2121 bp, encoding 706 amino acids with a molecular mass of 79.06 kDa. The pairwise alignments showed that CiCFI shared the highest identity (66.9%) with CFI from <i>Carassius gibelio</i> and the highest similarity (78.7%) with CFI from <i>Danio rerio</i>. The CiCFI protein was characterized by a conserved functional core Tryp_SPc domain with the catalytic triad and substrate binding sites. Phylogenetic analysis indicated that CiCFI and the homologs CFIs from other teleost fish formed a distinct evolutionary branch. Similar with the CFIs reported in mammals, the recombinant CiCFI protein could significantly reduce the C3b content in the serum, demonstrating the conserved function of CiCFI in the complement system in the grass carp. CiCFI mRNA and protein showed the highest expression level in the liver. After GCRV infection, the mRNA expressions of CiCFI were first down-regulated, then up-regulated, and then down-regulated to the initial level, while the protein expression levels maintained an overall downward trend to the late stage of infection in the liver of grass carps. Unexpectedly, the protein levels of CiCFI were also continuously down-regulated in the serum of grass carps during GCRV infection, while the content of serum C3b proteins first increases and then returns to the initial level, suggesting a distinct role of CiCFI in regulating complement activation and fish-virus interaction. Combining our previous results that complement factor D, a complement enhancer, shows continuously up-regulated expression levels in grass carps during GCRV infection, and this study may provide the further essential data for the full picture of complex complement regulation mechanism mediated by Df and CFI of the grass carp during pathogen infection.https://www.mdpi.com/1422-0067/23/19/11369grass carpcomplement factor Icomplement component 3bgrass carp reovirus infectioncomplement regulation mechanism |
| spellingShingle | Yi Liu Zhao Lv Tiaoyi Xiao Xuewen Zhang Chunhua Ding Beibei Qin Baohong Xu Qiaolin Liu Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i> International Journal of Molecular Sciences grass carp complement factor I complement component 3b grass carp reovirus infection complement regulation mechanism |
| title | Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i> |
| title_full | Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i> |
| title_fullStr | Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i> |
| title_full_unstemmed | Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i> |
| title_short | Functional and Expressional Analyses Reveal the Distinct Role of Complement Factor I in Regulating Complement System Activation during GCRV Infection in <i>Ctenopharyngodon idella</i> |
| title_sort | functional and expressional analyses reveal the distinct role of complement factor i in regulating complement system activation during gcrv infection in i ctenopharyngodon idella i |
| topic | grass carp complement factor I complement component 3b grass carp reovirus infection complement regulation mechanism |
| url | https://www.mdpi.com/1422-0067/23/19/11369 |
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