MAPK/MAK/MRK overlapping kinase mediated apoptosis through caspase signaling pathway from Cristaria plicata

MAPK/MAK/MRK Overlapping Kinase (MOK) belongs to MAP kinase superfamily, which plays an important role in regulating cell growth, division, and differentiation. Caspase-3, as the final executor of apoptosis, has an important position in the caspase-mediated apoptotic signaling pathway. The full-length cDNA of MOK and caspase-3 were cloned from Cristaria plicata (designated CpMOK and CpCaspase-3). The CpMOK gene was sequence with a full-length of 1413 bp, encoding a total of 470 amino acids, and containing an S_TKc structural domain. CpCaspase-3 has a sequence of 2425 bp, encoding 322 amino acids, containing a CASc domain. Real-time fluorescence quantitative PCR analysis showed that CpMOK and CpCaspase-3 distributed in various tissues of C. plicata, and the highest expression of CpMOK and CpCaspase-3 mRNA was in hepatopancreas. The expression of CpMOK was significantly changed in hepatopancreas, gills, and kidneys by the construction of wound model as well as stimulation of LPS, PGN, Poly I: C and Aeromonas hydrophila. Subcellular localization experiments confirmed that CpMOK was localized in the nucleus. Furthermore, the double-stranded RNA (dsRNA) of CpMOK was constructed for interference experiment, and the results showed that the mRNA expression of apoptotic gene signals caspase-1, caspase-3, caspase-7, caspase-8, and caspase-9 were increased. The expression of caspase-1, -3, -7, -9, cytochrome C (Cyt-c) and tumor necrosis factor-α (TNF-α) was detected by ELISA. Fluorescent staining of apoptotic cells using the Tunnel method revealed an increase in the number of apoptotic cells after interference. These results suggested that CpMOK knockdown could induce caspase-mediated apoptosis in C. plicata, and the phosphorylation of the kinase was disrupted during the process.