Comparative Characterization of Two cxcl8 Homologs in Oplegnathus fasciatus: Genomic, Transcriptional and Functional Analyses

Abstract

CXCL8 (interleukin-8, IL-8) is a CXC family chemokine that recruits specific target cells and mediates inflammation and wound healing. This study reports the identification and characterization of two cxcl8 homologs from rock bream, Oplegnathus fasciatus. Investigation of molecular signature, homology, phylogeny, and gene structure suggested that they belonged to lineages 1 (L1) and 3 (L3), and designated Ofcxcl8-L1 and Ofcxcl8-L3. While Ofcxcl8-L1 and Ofcxcl8-L3 revealed quadripartite and tripartite organization, in place of the mammalian ELR (Glu-Leu-Arg) motif, their peptides harbored EMH (Glu-Met-His) and NSH (Asn-Ser-His) motifs, respectively. Transcripts of Ofcxcl8s were constitutively detected by Quantitative Real-Time PCR (qPCR) in 11 tissues examined, however, at different levels. Ofcxcl8-L1 transcript robustly responded to treatments with stimulants, such as flagellin, concanavalin A, lipopolysaccharide, and poly(I:C), and pathogens, including Edwardsiella tarda, Streptococcus iniae, and rock bream iridovirus, when compared with Ofcxcl8-L3 mRNA. The differences in the putative promoter features may partly explain the differential transcriptional modulation of Ofcxcl8s. Purified recombinant OfCXCL8 (rOfCXCL8) proteins were used in in vitro chemotaxis and proliferation assays. Despite the lack of ELR motif, both rOfCXCL8s exhibited leukocyte chemotactic and proliferative functions, where the potency of rOfCXCL8-L1 was robust and significant compared to that of rOfCXCL8-L3. The results, taken together, are indicative of the crucial importance of Ofcxcl8s in inflammatory responses and immunoregulatory roles in rock bream immunity.

Identification, Expression and Antimicrobial Functional Analysis of Interleukin-8 (IL-8) in Response to Streptococcus iniae and Flavobacterium covae in Asian Seabass (Lates calcarifer Bloch, 1790)

“…Such an amino acid substitution has never been reported in studies of other fish species. Despite the replacement of the ELR motif, which is responsible for recruiting neutrophils and promoting angiogenesis in mammals [18,33], with ILR or other motifs, the recombinant proteins of some fish IL-8 variants continue to demonstrate chemotactic activity on neutrophils and macrophages [34,35]. Therefore, LcIL-8 may represent an alternative form of ILR with similar functions.…”

Identification, Expression and Antimicrobial Functional Analysis of Interleukin-8 (IL-8) in Response to <em>Streptococcus iniae</em> and Flavobacterium Covae in Asian Seabass (Lates calcarifer Bloch, 1790)

“…Such an amino acid substitution has never been reported in studies of other fish species. Despite the replacement of the ELR motif, which is responsible for recruiting neutrophils and promoting angiogenesis in mammals [14,29], with ILR or other motifs, recombinant proteins of some fish IL-8 variants continue to demonstrate chemotactic activity on neutrophils and macrophages [30,31]. Therefore, LcIL-8 may represent an alternative form of ILR with similar functions.…”

Analysis of population structure and selection signatures for artificial domestication of Rock Bream (Oplegnathus fasciatus) in coastal China

“…Genome-wide association analysis and genomic selection for rock bream identi ed candidate genes associated with growth and revealed moderate heritability values for growth traits in rock bream (Gong et al, 2022b). Additionally, research has been conducted on both transcriptional and gene function analysis of chemokine ofcxcl8 in relation to in ammation and immune regulation in rock bream (Umasuthan et al, 2020). Due to its relatively recent domestication, rock bream provides an excellent opportunity to study the molecular mechanisms of domestication.…”