TBC domain family 7-like enhances the tolerance of Penaeus vannamei to ammonia nitrogen by the up-regulation of autophagy

TBC domain family 7 (TBC1D7) is one of the subunits of tuberous sclerosis complex (TSC) and an important regulator of autophagosome biogenesis. However, the function of TBC1D7 is not fully understood in crustaceans. In the present study, TBC1D7 was identified from Penaeus vannamei. The complete coding sequence of Pv TBC1D7 was of 960 bp encoding a predicted polypeptide of 319 amino acids with one conserved TBC domain, which shared high similarity with TBC1D7 of that other species. The mRNA of Pv TBC1D7 was highly expressed in hemocyte and hepatopancreas, and the Pv TBC1D7 protein was localized specifically in the cytoplasm of hemocyte of shrimp. Besides, Pv TBC1D7 was co-localized with Pv TSC1 in the cytoplasm of shrimp, indicating that there might existed a binding relationship between Pv TBC1D7 and Pv TSC1. During the ammonia nitrogen stress, the mRNA transcripts of Pv TBC1D7 were significantly upregulated in hemocyte, hepatopancreas, and gill. Functionally, overexpression of Pv TBC1D7 in vitro restored the inhibition to autophagy caused by chloroquine (CLQ) and increased the autophagy level, while the silencing of Pv TBC1D7 could inhibit the autophagy. More importantly, after interfering with Pv TBC1D7, the autophagy level decreased significantly both in hepatopancreas and hemocyte of P. vannamei, the mRNA expression of Pv mTOR was increased remarkably with the significantly decrease of autophagy-related genes ( Pv ATG12 and Pv ATG14). And the reduction of Pv TBC1D7 remarkably exacerbated the damage of hepatopancreas, increased the accumulation of ROS, and reduced the survival proportion of shrimp under ammonia nitrogen stress. Altogether, these results indicated that Pv TBC1D7 might positively regulate the autophagy by stabilizing the negative regulation of mTOR by TSC complex, reduce the oxidative stress damage and improve shrimp ammonia nitrogen tolerance.