The study of MDM2 binding protein (MTBP) in response to apoptosis in Litopenaeus vannamei under ammonia and nitrite nitrogen stress

Abstract

MDM2 binding protein (MTBP) is a protein that interacts directly with MDM2. This study characterized the LvMTBP, revealing a 2752 bp cDNA sequence encoding an 834-amino acid hydrophilic protein with conserved MTBP_N and MTBP_C domains. Phylogenetic analysis demonstrated close evolutionary relationships with Penaeus species. LvMTBP exhibited ubiquitous tissue expression, with highest levels in muscle. Under ammonia and nitrite nitrogen stress, LvMTBP expression was downregulated in gills and muscle. RNAi experiments showed that LvMTBP knockdown dramatically reduced shrimp survival rates under both stress conditions. Histopathological examination revealed severe tissue damage in hepatopancreas and gills following LvMTBP silencing. Mechanistic investigations demonstrated that LvMTBP depletion activated the p53-mediated mitochondrial apoptosis pathway, evidenced by upregulated Bax, p53, and Caspase 9 expression, downregulated Bcl-2 and MDM2, and increased Caspase-3 activity. Apoptosis assays confirmed higher apoptotic indices in LvMTBP-knockdown groups. Complementary experiments in HEK293T cells showed MTBP overexpression reduced apoptosis rates, supporting its anti-apoptotic function. These findings establish LvMTBP as a crucial regulator of environmental stress responses in L. vannamei, functioning through modulation of the p53-MDM2 axis and apoptosis pathways. The study provides newly identified insights into crustacean stress adaptation mechanisms and suggests LvMTBP as a potential molecular target for improving shrimp tolerance in aquaculture systems.