The atypical protein arginine methyltrasferase of Entamoeba histolytica (EhPRMTA) is involved in cell proliferation, heat shock response and in vitro virulence

Lysine Methyltransferase EhPKMT2 Is Involved in the In Vitro Virulence of Entamoeba histolytica

Lysine methylation, a posttranslational modification catalyzed by protein lysine methyltransferases (PKMTs), is involved in epigenetics and several signaling pathways, including cell growth, cell migration and stress response, which in turn may participate in virulence of protozoa parasites. Entamoeba histolytica, the etiologic agent of human amebiasis, has four PKMTs (EhPKMT1 to EhPKMT4), but their role in parasite biology is unknown. Here, to obtain insight into the role of EhPKMT2, we analyzed its expression level and localization in trophozoites subjected to heat shock and during phagocytosis, two events that are related to amoeba virulence. Moreover, the effect of EhPKMT2 knockdown on those activities and on cell growth, migration and cytopathic effect was investigated. The results indicate that this enzyme participates in all these cellular events, suggesting that it could be a potential target for development of novel therapeutic strategies against amebiasis.

Adriamycin induces cardiac fibrosis in mice via PRMT5-mediated cardiac fibroblast activation

Long-term treatment with adriamycin (ADR) is associated with higher incidences of cumulative cardiotoxicity manifest as heart failure. ADR-induced cardiomyopathy is characterized by extensive fibrosis that is caused by cardiac fibroblast activation. To date, however, no specific treatment is available to alleviate ADR-induced cardiotoxicity. Protein arginine methyltransferase 5 (PRMT5), a major enzyme responsible for methylation of arginine, regulates numerous cellular processes such as cell differentiation. In the present study we investigated the role of PRMT5 in cardiac fibrosis. Mice were administered ADR (3 mg/kg, i.p., every 2 days) for 2 weeks. We showed that aberrant PRMT5 expression was largely co-localized with α-SMA-positive activated cardiac fibroblasts in ADR-injected mice and in ADR-treated cardiac fibroblasts in vitro. PRMT5-overexpression exacerbated, whereas PRMT5 knockdown alleviated ADR-induced cardiac fibrosis in vivo and TGF-β1-induced cardiac fibroblast activation in vitro. We demonstrated that PRMT5-overexpression enhanced methylated-Smad3 levels in vivo and in vitro. Pretreatment with a specific PRMT5 inhibitor EPZ015666 (5 nM) or overexpression of a catalytically inactive mutant of PRMT5, PRMT5(E444Q), reduced PRMT5-induced methylation of Smad3, thus suppressing PRMT5-mediated cardiac fibroblast activation in vitro. Furthermore, ADR activated cardiac fibroblasts was depending on autocrine TGF-β1. Taken together, our results demonstrate that PRMT5 promotes ADR-induced cardiac fibrosis via activating cardiac fibroblasts, suggesting that it may be a potential therapeutic target of ADR-caused cardiotoxicity.

Protein arginine methyltransferases in protozoan parasites

Arginine methylation is a post-translational modification involved in gene transcription, signalling pathways, DNA repair, RNA metabolism and splicing, among others, mechanisms that in protozoa parasites may be involved in pathogenicity-related events. This modification is performed by protein arginine methyltransferases (PRMTs), which according to their products are divided into three main types: type I yields monomethylarginine (MMA) and asymmetric dimethylarginine; type II produces MMA and symmetric dimethylarginine; whereas type III catalyses MMA only. Nine PRMTs (PRMT1 to PRMT9) have been characterized in humans, whereas in protozoa parasites, except for Giardia intestinalis, three to eight PRMTs have been identified, where in each group there are at least two enzymes belonging to type I, the majority with higher similarity to human PRMT1, and one of type II, related to human PRMT5. However, the information on the role of most of these enzymes in the parasites biology is limited so far. Here, current knowledge of PRMTs in protozoan parasites is reviewed; these enzymes participate in the cell growth, stress response, stage transitions and virulence of these microorganisms. Thus, PRMTs are attractive targets for developing new therapeutic strategies against these pathogens.