Fish Shellfish Immunol 2019 Sep 01;92:460-468. doi: 10.1016/j.fsi.2019.06.038.

Cloning and characterization of the target protein subunit lst8 of rapamycin in Apostichopus japonicus.

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Autophagy plays an important role in the immune defense systems of vertebrates through the interaction between the lethal with SEC13 protein 8 (lst8) and the mechanistic target of rapamycin. In the present study, a novel invertebrate lst8 homologue is identified from Apostichopus japonicus (designated as Ajlst8) via polymerase chain reaction. The full-length complementary DNA of Ajlst8 comprises a 5''-untranslated region (UTR) of 78 base pair (bp), a 3''-UTR of 479 bp, and a putative open reading frame of 951 bp; hence, 316 amino acids are encoded. Structural analysis shows that the deduced amino acid of Ajlst8 shares six typical WD40 domains (28 aa-248 aa). Spatial expression analysis indicates that Ajlst8 is ubiquitously expressed in all the examined tissues, with a larger magnitude in coelomocytes. Vibrio splendidus infection in vivo and lipopolysaccharide exposure in vitro can significantly upregulate the messenger RNA expression of Ajlst8 by 2.39-fold and 1.93-fold compared with the control group, respectively. LPS exposure could also significantly induced the protein level of Ajlst8 to 2.38-fold and the autophagy level was markedly increased by 3.08-fold under same condition. The RNA interference of Ajlst8 in primary coelomocytes also reduces the relative expression of autophagy with a 0.71-fold decrease in the ratio of LC3-II/LC3-I compared with that in the control group. These results indicate that Ajlst8 is a novel immune regulator that may be involved in the antibacterial response process of sea cucumber by regulating autophagy.

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Genes referenced: LOC100887844 polr3a