Acyl-CoA synthetase 5 (ACSL5), a mitochondrially localized
enzyme, catalyzes the synthesis of long-chain
fatty acid thioesters and is physiologically involved in pro-apoptotic sensing of enterocytes. The aim of the present study is to identify an ACSL5-dependent regulation of mitochondrially expressed
proteins and the characterization of related pathways in normal and diseased human intestinal mucosa. Proteomics of isolated mitochondria from ACSL5 transfectants and CaCo2 controls were performed. ACSL5-dependent
protein synthesis was verified with quantitative reverse transcription plus the polymerase chain reaction, Western blotting,
short-interfering-RNA-mediated gene silencing and additional cell culture experiments.
Lipid changes were analyzed with tandem mass spectrometry. ACSL5-related pathways were characterized in normal mucosa and sporadic
adenocarcinomas of the human intestine. In CaCo2 cells transfected with ACSL5,
mortalin (HSPA9) was about two-fold increased in mitochondria, whereas cytoplasmic
mortalin levels were unchanged. Disturbance of
acyl-CoA/
sphingolipid metabolism, induced by ACSL5 over-expression, was characterized as crucial. ACSL5-related over-expression of mitochondrial
mortalin was found in HEK293 and Lovo (wild-type TP53 [
tumor protein p53]) and CaCo2 (p53-negative; TP53 mutated) cells but not in Colo320DM cells (mutated TP53). In normal human intestinal mucosa, an increasing gradient of both ACSL5 and
mortalin from bottom to top was observed, whereas p53 (wild-type TP53) decreased. In sporadic intestinal
adenocarcinomas with strong p53 immunostaining (mutated TP53), ACSL5-related
mortalin expression was heterogeneous. ACSL5-induced mitochondrial
mortalin expression is assumed to be a stress response to ACSL5-related changes in lipid metabolism and is regulated by the TP53 status. Uncoupling of ACSL5 and mitochondrial
mortalin by mutated TP53 could be important in colorectal
carcinogenesis.