Mitochondria, essential organelles of all eukaryotic cells, serve critical function to many cellular processes. They are the main power house of cells and cell survival depends on their integrity and dynamics. The majority of mitochondrial proteins are synthesized in the cytosol in the form of preproteins and transported into the organelle with the help of targeting presequence peptides. After import into the mitochondria, the presequence peptides are cleaved off from the protein and subsequently degraded. Failed degradation and accumulation of these peptides may cause mitochondria toxicity since they are generally rich in charged and hydrophobic residues. One member of the M16 family metalloprotease, PreP (presequence peptidase), was postulated to degrade mitochondria presequence peptides. However, the exact location of PreP in mitochondria is unclear. Whether PreP can degrade presequence peptides and other physiological substrates in vivo remain to be elucidated. For better understanding of PreP''s function and signaling regulation in vivo, we used C. elegans as a genetic model system to approach these questions. Sequence analysis shows PreP proteins are highly evolutionarily conserved. Based on a structure homology modeling search, we identified one PreP-like protein (Gene C05D11.1) in the entire C. elegans genome. An allele of gene knockout animal,
tm989, which has a ~1.8 kb deletion, was obtained from National Bioresource Project (Tokyo, Japan). The deletion in gene C05D11.1 does not affect viability, thus the PreP-like gene product is not essential for C. elegans survival. Consistent with the reported data, out crossed knockout animals have normal reproduction ability and no obvious developmental defects under routine culture condition. However, we found two interesting phenotypes. PreP-like knockout strain shows increased sensitivity to heat stress. Upon heat shock at 33 deg C, TM989 has 50% survival time at 25 hours in comparison with 40 hours for wildtype animals. Interestingly, this mutant strain of C. elegans is also more sensitive to alcohol intoxication. On alcohol saturated plates, PreP knockout animals were instantly intoxicated with complete motility loss, while wild type worms remain only partial paralyzed. This establishes a clear association of the PreP-like gene with hyper-sensitivity to heat and alcohol, both are associated with mitochondrial dysfunction. Thus, our studies suggest that PreP plays an important role in stress response and detoxification processes by modulating mitochondria function.