Phospholipase A/Acyltransferase enzyme activity of H-rev107 inhibits the H-RAS signaling pathway

• Published in: Journal of biomedical science Vol. 21; no. 1; p. 36
• Main Authors: Wang, Chun-Hua, Shyu, Rong-Yaun, Wu, Chang-Chieh, Tsai, Tzung-Chieh, Wang, Lu-Kai, Chen, Mao-Liang, Jiang, Shun-Yuan, Tsai, Fu-Ming
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 01.05.2014; BioMed Central
• Subjects: Acylation; Acyltransferases - metabolism; Apoptosis; Buddhism; Cancer; Cell culture; Cervical cancer; E coli; Enzymes; Epidermal Growth Factor; Experiments; Gene Expression Regulation; Genes, ras - genetics; Genetic research; Humans; Intracellular Signaling Peptides and Proteins; Lipids; Phospholipases; Phospholipases A2 - metabolism; Phospholipases A2, Calcium-Independent - antagonists & inhibitors; Phospholipases A2, Calcium-Independent - metabolism; Physiological aspects; Proteins; Signal Transduction - genetics; Tumor Suppressor Proteins - antagonists & inhibitors; Tumor Suppressor Proteins - metabolism
• ISSN: 1423-0127; 1021-7770; 1423-0127
• DOI: 10.1186/1423-0127-21-36

H-rev107, also called HRASLS3 or PLA2G16, is a member of the HREV107 type II tumor suppressor gene family. Previous studies showed that H-rev107 exhibits phospholipase A/acyltransferase (PLA/AT) activity and downregulates H-RAS expression. However, the mode of action and the site of inhibition of H-RAS by H-rev107 are still unknown. Our results indicate that H-rev107 was co-precipitated with H-RAS and downregulated the levels of activated RAS (RAS-GTP) and ELK1-mediated transactivation in epidermal growth factor-stimulated and H-RAS-cotransfected HtTA cervical cancer cells. Furthermore, an acyl-biotin exchange assay demonstrated that H-rev107 reduced H-RAS palmitoylation. H-rev107 has been shown to be a PLA/AT that is involved in phospholipid metabolism. Treating cells with the PLA/AT inhibitor arachidonyl trifluoromethyl ketone (AACOCF3) or methyl arachidonyl fluorophosphate (MAFP) alleviated H-rev107-induced downregulation of the levels of acylated H-RAS. AACOCF3 and MAFP also increased activated RAS and ELK1-mediated transactivation in H-rev107-expressing HtTA cells following their treatment with epidermal growth factor. In contrast, treating cells with the acyl-protein thioesterase inhibitor palmostatin B enhanced H-rev107-mediated downregulation of acylated H-RAS in H-rev107-expressing cells. Palmostatin B had no effect on H-rev107-induced suppression of RAS-GTP levels or ELK1-mediated transactivation. These results suggest that H-rev107 decreases H-RAS activity through its PLA/AT activity to modulate H-RAS acylation. We made the novel observation that H-rev107 decrease in the steady state levels of H-RAS palmitoylation through the phospholipase A/acyltransferase activity. H-rev107 is likely to suppress activation of the RAS signaling pathway by reducing the levels of palmitoylated H-RAS, which decreases the levels of GTP-bound H-RAS and also the activation of downstream molecules. Our study further suggests that the PLA/AT activity of H-rev107 may play an important role in H-rev107-mediated RAS suppression.