Encephalitis is mediated by ROP18 of Toxoplasma gondii, a severe pathogen in AIDS patients.

The neurotropic parasite Toxoplasma gondii is a globally distributed parasitic protozoan among mammalian hosts, including humans. During the course of infection, the CNS is the most commonly damaged organ among invaded tissues. The polymorphic rhoptry protein 18 (ROP18) is a key serine (Ser)/threonine (Thr) kinase that phosphorylates host proteins to modulate acute virulence. However, the basis of neurotropism and the specific substrates through which ROP18 exerts neuropathogenesis remain unknown. Using mass spectrometry, we performed proteomic analysis of proteins that selectively bind to active ROP18 and identified RTN1-C, an endoplasmic reticulum (ER) protein that is preferentially expressed in the CNS. We demonstrated that ROP18 is associated with the N-terminal portion of RTN1-C and specifically phosphorylates RTN1-C at Ser7/134 and Thr4/8/118. ROP18 phosphorylation of RTN1-C triggers ER stress-mediated apoptosis in neural cells. Remarkably, ROP18 phosphorylation of RTN1-C enhances glucose-regulated protein 78 (GRP78) acetylation by attenuating the activity of histone deacetylase (HDAC), and this event is associated with an increase of neural apoptosis. These results clearly demonstrate that both RTN1-C and HDACs are involved in T. gondii ROP18-mediated pathogenesis of encephalitis during Toxoplasma infection.

Demethylation of HACE1 gene promoter by propofol promotes autophagy of human A549 cells.

Propofol (2,6-diisopropylphenol) is one of the most commonly used intravenous anesthetics and possesses a number of non-anesthetic effects, including antitumor function. The aim of the present study was to elucidate the antitumor molecular mechanism of propofol on A549 and H1299 cells. A549 and H1299 cells were treated in the presence or absence of different concentrations (0, 60 or 120 µmol) of propofol for different durations (0, 24, 48 or 72 h), and proliferation was detected by MTT and colony formation assays; the protein levels of optineurin (OPTN) ubiquitination, HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1 (HACE1), methyl-CpG binding domain protein 3 (MBD3) and Microtubule-associated protein 1A/1B-light chain 3 were detected by immunoblotting or quantitative (q)PCR; the methylation state of the HACE1 gene promoter was detected by bisulfite DNA sequencing; and binding of MBD3 on HACE1 gene promoter was detected by chromatin immunoprecipitation-qPCR. Propofol inhibited proliferation of A549 and H1299 cells and promoted HACE1-OPTN axis-mediated selective autophagy activity by increasing the protein expression levels of HACE1 via demethylating its promoter region. Furthermore, propofol promoted expression levels of MBD3 and binding to the -1,000 to -1 bp (transcription start site) region of HACE1 gene promoter. MBD3-knockdown experiments indicated that propofol inhibited proliferation of A549 cells in a MBD3-dependent manner. Thus, the findings of the present study provided a potential antitumor molecular mechanism mediated by propofol.