Pharmacological Targeting of Sphingosine Kinases Impedes HIV-1 Infection of CD4 T Cells through SAMHD1 Modulation

Virus infection and sphingolipid metabolism

Cellular sphingolipids have vital roles in human virus replication and spread as they are exploited by viruses for cell entry, membrane fusion, genome replication, assembly, budding, and propagation. Intracellular sphingolipid biosynthesis triggers conformational changes in viral receptors and facilitates endosomal escape. However, our current understanding of how sphingolipids precisely regulate viral replication is limited, and further research is required to comprehensively understand the relationships between viral replication and endogenous sphingolipid species. Emerging evidence now suggests that targeting and manipulating sphingolipid metabolism enzymes in host cells is a promising strategy to effectively combat viral infections. Additionally, serum sphingolipid species and concentrations could function as potential serum biomarkers to help monitor viral infection status in different patients. In this work, we comprehensively review the literature to clarify how viruses exploit host sphingolipid metabolism to accommodate viral replication and disrupt host innate immune responses. We also provide valuable insights on the development and use of antiviral drugs in this area.

Monkeypox Virus Crosstalk with HIV: An Integrated Skin Transcriptome and Machine Learning Study

The emergence of the monkeypox virus (MPXV) outbreak presents a formidable challenge to human health. Emerging evidence suggests that individuals with HIV have been disproportionately affected by MPXV, with adverse clinical outcomes and higher mortality rates. However, the shared molecular mechanisms underlying MPXV and HIV remain elusive. We identified differentially expressed genes (DEGs) from two public data sets, GSE219036 and GSE184320, and extracted common DEGs between MPXV and HIV. We further performed gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), protein-protein interactions (PPI), candidate drug assessment, and immune correlation of hub genes analysis. We validated the key biomarkers using multiple machine learning (ML) methods including random forest (RF), t-distributed stochastic neighbor embedding (tSNE), and uniform manifold approximation and projection (UMAP). A total of 59 common DEGs were identified between MPXV and HIV. Our functional analysis highlighted multiple pathways, including the ERK cascade, NF-κB signaling, and various immune responses, playing a collaborative role in the progression of both diseases. The PPI and gene co-expression networks were constructed, and five key genes with significant immune correlations were identified and validated by multiple ML models, including SPRED1, SPHK1, ATF3, AKT3, and AKT1S1. Our study emphasizes the common pathogenesis of HIV and MPXV and highlights the pivotal genes and shared pathways, providing new opportunities for evidence-based management strategies in HIV patients co-infected with MPXV.

Enzymatic independent role of sphingosine kinase 2 in regulating the expression of type I interferon during influenza A virus infection

Influenza virus has the ability to circumvent host innate immune system through regulating certain host factors for its effective propagation. However, the detailed mechanism is still not fully understood. Here, we report that a host sphingolipid metabolism-related factor, sphingosine kinase 2 (SPHK2), upregulated during influenza A virus (IAV) infection, promotes IAV infection in an enzymatic independent manner. The enhancement of the virus replication is not abolished in the catalytic-incompetent SPHK2 (G212E) overexpressing cells. Intriguingly, the sphingosine-1-phosphate (S1P) related factor HDAC1 also plays a crucial role in SPHK2-mediated IAV infection. We found that SPHK2 cannot facilitate IAV infection in HDAC1 deficient cells. More importantly, SPHK2 overexpression diminishes the IFN-β promoter activity upon IAV infection, resulting in the suppression of type I IFN signaling. Furthermore, ChIP-qPCR assay revealed that SPHK2 interacts with IFN-β promoter through the binding of demethylase TET3, but not with the other promoters regulated by TET3, such as TGF-β1 and IL6 promoters. The specific regulation of SPHK2 on IFN-β promoter through TET3 can in turn recruit HDAC1 to the IFN-β promoter, enhancing the deacetylation of IFN-β promoter, therefore leading to the inhibition of IFN-β transcription. These findings reveal an enzymatic independent mechanism on host SPHK2, which associates with TET3 and HDAC1 to negatively regulate type I IFN expression and thus facilitates IAV propagation.

Schlafen family is a prognostic biomarker and corresponds with immune infiltration in gastric cancer

The Schlafen (SLFN) gene family plays an important role in immune cell differentiation and immune regulation. Previous studies have found that the increased SLFN5 expression in patients with intestinal metaplasia correlates with gastric cancer (GC) progression. However, no investigation has been conducted on the SLFN family in GC. Therefore, we systematically explore the expression and prognostic value of SLFN family members in patients with GC, elucidating their possible biological function and its correlation with tumor immune cells infiltration. TCGA database results indicated that the SLFN5, SLFN11, SLFN12, SLFN12L, and SLFN13 expression was significantly higher in GC. The UALCAN and KM plotter databases indicated that enhanced the SLFN family expression was associated with lymph node metastasis, tumor stage, and tumor grade and predicted an adverse prognosis. cBioportal database revealed that the SLFN family had a high frequency of genetic alterations in GC (about 12%), including mutations and amplification. The GeneMANIA and STRING databases identified 20 interacting genes and 16 interacting proteins that act as potential targets of the SLFN family. SLFN5, SLFN11, SLFN12, SLFN12L, and SLFN14 may be implicated in the immunological response, according to Gene Set Enrichment Analysis (GSEA) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Additionally, Timer and TISIDB databases indicate that SLFN5, SLFN11, SLFN12, SLFN12L, and SLFN14 are involved in the immune response. Furthermore, Timer, TCGA, and TISIDB databases suggested that the SLFN5, SLFN11, SLFN12, SLFN12L, and SLFN14 expression in GC is highly linked with immune cell infiltration levels, immune checkpoint, and the many immune cell marker sets expression. We isolated three samples of peripheral blood mononuclear cell (PBMC) and activated T cells; the results showed the expression of SLFN family members decreased significantly when T cell active. In conclusion, the SLFN family of proteins may act as a prognostic indicator of GC and is associated with immune cell infiltration and immune checkpoint expression in GC. Additionally, it may be involved in tumor immune evasion by regulating T cell activation.