Molecular characterization, expression and function analysis of Epinephelus coioides MKK4 response to SGIV and Vibrio alginolyticus infection.

Mitogen-activated protein kinase 4 (MKK4), a member of the MAP kinase family, play important roles in response to many environmental and cellular stresses in mammals. In this study, three MKK4 subtypes, EcMKK4-1, EcMKK4-2 and EcMKK4-3, were obtained from grouper Epinephelus coioides. The open reading frame (ORF) of EcMKK4s are obtained and the EcMKK4s proteins contain highly conserved domains: a S_TKc domain, a canonical diphosphorylation group and two conserved MKKK ATP binding motifs, Asp-Phe-Gly (DFG) and Ala-Pro-Glu (APE). EcMKK4s could be found both in the cytoplasmic and nuclear. The EcMKK4s mRNA were detected in all E. coioides tissues examined with the different expression levels, and the expression were up-regulated during SGIV (Singapore grouper iridescent virus) or Vibrio alginolyticus infection. EcMKK4 could significantly reduce the activation of AP-1 reporter gene. The results suggested that EcMKK4s might play important roles in pathogen-caused inflammation.

Transcripts' Evolutionary History and Structural Dynamics Give Mechanistic Insights into the Functional Diversity of the JNK Family.

Alternative splicing and alternative initiation/termination transcription sites have the potential to greatly expand the proteome in eukaryotes by producing several transcript isoforms from the same gene. Although these mechanisms are well described at the genomic level, little is known about their contribution to protein evolution and their impact at the protein structure level. Here, we address both issues by reconstructing the evolutionary history of transcripts and by modeling the tertiary structures of the corresponding protein isoforms. We reconstruct phylogenetic forests relating 60 protein-coding transcripts from the c-Jun N-terminal kinase (JNK) family observed in seven species. We identify two alternative splicing events of ancient origin and show that they induce subtle changes in the protein's structural dynamics. We highlight a previously uncharacterized transcript whose predicted structure seems stable in solution. We further demonstrate that orphan transcripts, for which no phylogeny could be reconstructed, display peculiar sequence and structural properties. Our approach is implemented in PhyloSofS (Phylogenies of Splicing Isoforms Structures), a fully automated computational tool freely available at https://github.com/PhyloSofS-Team/PhyloSofS.

Diverse physiological functions of MKK4 and MKK7 during early embryogenesis.

Mitogen-activated protein kinase kinases (MAPKKs) are important components of the stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) signalling pathway. Two MAPKKs that are crucial transducers upstream of JNK signalling are MKK4 and MKK7. These two MAPKKs directly phosphorylate specific Tyr and Thr residues located in the activation loop of the JNK protein and activate this kinase in response to environmental stress, pro-inflammatory cytokines or developmental cues. Although much is known about the biochemical and structural bases of the catalytic mechanism of the MAPKKs, the regulation and physiological functions of these enzymes during early embryogenesis have remained a mystery until relatively recently. Studies employing a range of animal models have now revealed the essential roles that MAPKKs play in diverse developmental contexts, including in dorsoventral patterning, convergent extension and somitogenesis. Focusing primarily on extensive work done in mouse and zebrafish models, this review summarizes the functional properties of MKK4 and MKK7 during vertebrate and invertebrate development, and the mechanisms by which these kinases regulate multiple steps in the establishment of the body plan of an organism.