Biology subjects

Tan, C. S.

Publications and source records attributed to Tan, C. S..

2 recordsLinked to original sources

bioRxiv2024

Cannabinoids shift the basal ganglia miRNA m6A methylation profile towards an anti-inflammatory phenotype in SIV-infected Rhesus macaques

BackgroundEpitranscriptomic modifications modulate diverse biological processes like regulation of gene expression, abundance, location and function. N6-methyladenosine (m6A) methylation has been shown to regulate various diseases, including cancer and inflammation. While there is evidence that m6A modification is functionally relevant in neural development and differentiation, the role of m6A modification in HIV neuropathogenesis is unknown. MethodsHere, we used anti-N6-methyladenosine (m6A) antibody immunoprecipitation and microarray profiling to identify m6A modifications in miRNAs in basal ganglia (BG) of Rhesus macaques (RMs) that were uninfected (VEH) and SIV-infected on combination anti-retroviral therapy (cART) and either VEH-treated (VEH/SIV/cART), or THC:CBD-treated (THC:CBD/SIV/cART). Ingenuity pathway analysis was conducted to understand the biological implications of miRNA m6A methylation in HIV neuropathogenesis. Finally, to understand the functional significance of m6A modifications in miRNAs, we overexpressed FAM-labeled wild-type or m6A-modified miR-194-5p in SCC-25 cells and determined its impact on the expression of its target, STAT1, an interferon-stimulated transcription factor known to drive persistent neuroinflammation in several neurodegenerative diseases. ResultsHIV/SIV infection promoted an overall hypomethylated miRNA m6A profile. While the overall hypomethylated m6A profile was not significantly impacted by THC:CBD, specific miRNAs predicted to target proinflammatory genes showed markedly reduced m6A methylation levels compared to the VEH-treated RMs. Additionally, specific BG tissue miRNAs bearing m6A epi-transcriptomic marks were transferred and detected in BG-derived extracellular vesicles. Mechanistically, the DRACH motif in the seed region of miR-194-5p was significantly m6A hypomethylated in THC:CBD/SIV/cART RMs. In SCC-25 cells, unlike wild-type miR-194-5p, transfected m6A-modified miR-194-5p mimics failed to downregulate STAT1 protein expression. Further, compared to VEH/SIV/cART RMs, THC:CBD administration significantly reduced m6A methylation of 44 miRNAs directly involved in regulating CNS network genes. ConclusionsThese results underscore the need for investigating the qualitative, and posttranscriptional modifications in RNA along with the more traditional, quantitative alterations in pathological conditions or in response to disease modifying treatments. Our findings indicate that m6A epitranscriptomic marks in the seed nucleotide region can impair miRNA function and that cannabinoids may preserve it by reducing m6A methylation levels. Finally, these findings provide a novel mechanistic (miRNA m6A hypomethylation) explanation underlying the anti-neuroinflammatory effects of phytocannabinoids in HIV/SIV infection.

neuroscience↗

bioRxiv2023

Upregulation of the NKG2D ligand ULBP2 by JC polyomavirus infection promotes immune recognition by natural killer cells.

JC polyomavirus (JCPyV) establishes a chronic infection in 70-90% of the worlds population. In immunocompetent individuals, JCPyV chronic infection is asymptomatic and not associated with diseases. However, JCPyV causes progressive multifocal leukoencephalopathy (PML), a potentially fatal complication of severe immune suppression due to monoclonal antibody treatments for cancer, autoimmune diseases and transplantation, or due to uncontrolled HIV infection. There is currently no effective treatment against PML and novel immunotherapies are urgently needed to decrease the morbidity and mortality caused by JCPyV. The risk of developing PML increases with loss of immune control by JCPyV-specific T cells and antibodies. Natural killer (NK) cells play critical roles in defense against viral infections, yet NK cell contribution to the control of JCPyV infection remains largely unexplored. Here, we first compared NK and T cell responses against JCPyV VP1 peptide pools. In about 40% of healthy donors, we detected robust CD107a upregulation and IFN-{gamma} production by NK cells, extending beyond T cell responses. Next, using a novel flow cytometry-based killing assay, we showed that co-culture of NK cells and JCPyV-infected astrocyte-derived SVG-A cells leads to a 60% reduction in infection, on average. Expression of ligands for the activating NK cell receptor NKG2D was modulated in JCPyV-infected cells, with overall enhanced expression of ULBP2. To evaluate the impact of NKG2D triggering on NK cell-mediated elimination of JCPyV-infected cells, we performed co-cultures in the presence of NKG2D blocking antibodies, which resulted in decreased NK cell degranulation. Altogether, these findings suggest NKG2D-mediated activation may play a key role in controlling JCPyV replication and may be a promising immunotherapeutic target to boost NK cell anti-JCPyV activity. Author SummaryThe human polyomavirus JC (JCPyV) infects most people for life but only causes disease in persons with a compromised immune system. In particular, JCPyV reactivation in the brain is responsible for the development of progressive multifocal leukoencephalopathy (PML). There is currently no effective treatment for PML, which is often fatal. Natural killer (NK) cells are effector cells of the innate immune system that play critical roles in defense against viral infections, yet their contribution to the control of JCPyV infection remains largely unexplored. The current study shows that NK cells can eliminate cells infected with JCPyV and that immune recognition is partly mediated by NKG2D, an activating ligand expressed on NK cells, and its binding to ULBP2, a stress-induced ligand expressed on infected cells. Our findings provide new insights into immune mechanisms involved in JCPyV immunity, and unveil opportunities to harness NK cell function in future therapeutic strategies to target JCPyV.

immunology↗