View Point: Semaphorin-3E: An Emerging Modulator of Natural Killer Cell Functions?

Sema-3E/PlexinD1 axis modulates dendritic cell phenotypes and functions: Current status and future implications

This comprehensive research review explores the complex interplay between the Sema-3E/PlexinD1 axis and dendritic cells (DCs), highlighting its critical role in immune modulation with implications for clinical application Critical regulators of immune responses Dendritic cells are central to adaptive immunity, and the Sema-3E /PlexinD1 axis emerges as a key modulator affecting their phenotypes and functions Review delineates the impact of this signaling axis on DC maturation, migration, antigen presentation, and cytokine production, unravels its multifaceted role in shaping the immune response. Recognizing the limitations and gaps in current knowledge, the study highlights the need for further studies to condition downstream signaling events and related information experienced by the Sema-3E/PlexinD1 axis emphasizes the clarity of the immune system. The review concludes by identifying opportunities for translation, focusing on therapeutic and diagnostic potential. It highlights the importance of collaborative, interdisciplinary efforts to address the challenges and harness the therapeutic and pathological potential of targeting the Sema-3E/PlexinD1 axis, thus opening the way for transformative advances in immunology and clinical medicine.

FOXP1 regulates the development of excitatory synaptic inputs onto striatal neurons and induces phenotypic reversal with reinstatement

Long-range glutamatergic inputs originating from the cortex and thalamus are indispensable for striatal development, providing the foundation for motor and cognitive functions. Despite their significance, transcriptional regulation governing these inputs remains largely unknown. We investigated the role of a transcription factor encoded by a high-risk autism-associated gene, FOXP1, in sculpting glutamatergic inputs onto spiny projection neurons (SPNs) within the striatum. We find a neuron subtype-specific role of FOXP1 in strengthening and maturing glutamatergic inputs onto dopamine receptor 2-expressing SPNs (D2 SPNs). We also find that FOXP1 promotes synaptically driven excitability in these neurons. Using single-nuclei RNA sequencing, we identify candidate genes that mediate these cell-autonomous processes through postnatal FOXP1 function at the post-synapse. Last, we demonstrate that postnatal FOXP1 reinstatement rescues electrophysiological deficits, cell type-specific gene expression changes, and behavioral phenotypes. Together, this study enhances our understanding of striatal circuit development and provides proof of concept for a therapeutic approach for FOXP1 syndrome and other neurodevelopmental disorders.

Plexin D1 mediates disturbed flow-induced M1 macrophage polarization in atherosclerosis

Atherosclerosis preferentially develops at bifurcations exposed to disturbed flow. Plexin D1 (PLXND1) responds to mechanical forces and drives macrophage accumulation in atherosclerosis. Here, multiple strategies were used to identify the role of PLXND1 in site-specific atherosclerosis. Using computational fluid dynamics and three-dimensional light-sheet fluorescence-microscopy, the elevated PLXND1 in M1 macrophages was mainly distributed in disturbed flow area of ApoE^-/- carotid bifurcation lesions, and visualization of atherosclerosis in vivo was achieved by targeting PLXND1. Subsequently, to simulate the microenvironment of bifurcation lesions in vitro, we co-cultured oxidized low-density lipoprotein (oxLDL)-treated THP-1-derived macrophages with shear-treated human umbilical vein endothelial cells (HUVECs). We found that oscillatory shear induced the increase of PLXND1 in M1 macrophages, and knocking down PLXND1 inhibited M1 polarization. Semaphorin 3E, the ligand of PLXND1 which was highly expressed in plaques, strongly enhanced M1 macrophage polarization via PLXND1 in vitro. Our findings provide insights into pathogenesis in site-specific atherosclerosis that PLXND1 mediates disturbed flow-induced M1 macrophage polarization.

Semaphorin 4C promotes motility and immunosuppressive activity of cancer cells via CRMP3 and PD-L1

Semaphorins (SEMAs) are membrane-bound or soluble proteins that participate in organ development and cancer progression, however, the detailed role of SEMAs in carcinogenesis is not fully elucidated yet. Our in silico analysis showed among the differentially expressed SEMAs in colon cancer tissues, patients with higher SEMA4C expression tumors had worse survival. The migration and invasion of the HCT116 and CT26 colon cancer cells were significantly suppressed by SEMA4C neutralizing antibody treatment; while enhanced by ectopic expression of SEMA4C. Subsequently, RNA sequencing study revealed microtubule polymerization- and nucleation-related genes are highly enriched in SEMA4C overexpression HCT116 cells. Western blotting showed the negative correlation between the levels of SEMA4C expression and tubulin acetylation. Mechanistic study showed SEMA4C interacted with and stabilized collapsin response mediator protein 3 (CRMP3), a novel deacetylase, to increase α-tubulin deacetylation and cell motility, which could be effectively attenuated after HDAC inhibitors treatment. We also found that a tumor-suppressive miRNA let-7b can target SEMA4C and act synergistically with SEMA4C neutralizing antibody to suppress the motility of colon cancer cells. In addition, blockade of SEMA4C could attenuate the expression of program death ligand 1 (PD-L1). Collectively, our results highlight that SEMA4C may promote colon cancer progression through modulating CRMP3-mediated tubulin deacetylation and PD-L1-mediated immunosuppression.

Integrative Transcriptomic Analysis Reveals the Immune Mechanism for a CyHV-3-Resistant Common Carp Strain

Anti-disease breeding is becoming the most promising solution to cyprinid herpesvirus-3 (CyHV-3) infection, the major threat to common carp aquaculture. Virus challenging studies suggested that a breeding strain of common carp developed resistance to CyHV-3 infection. This study illustrates the immune mechanisms involved in both sensitivity and anti-virus ability for CyHV3 infection in fish. An integrative analysis of the protein-coding genes and long non-coding RNAs (lncRNAs) using transcriptomic data was performed. Tissues from the head kidney of common carp were extracted at days 0 (the healthy control) and 7 after CyHV-3 infection (the survivors) and used to analyze the transcriptome through both Illumina and PacBio sequencing. Following analysis of the GO terms and KEGG pathways involved, the immune-related terms and pathways were merged. To dig out details on the immune aspect, the DEGs were filtered using the current common carp immune gene library. Immune gene categories and their corresponding genes in different comparison groups were revealed. Also, the immunological Gene Ontology terms for lncRNA modulation were retained. The weighted gene co-expression network analysis was used to reveal the regulation of immune genes by lncRNA. The results demonstrated that the breeding carp strain develops a marked resistance to CyHV-3 infection through a specific innate immune mechanism. The featured biological processes were autophagy, phagocytosis, cytotoxicity, and virus blockage by lectins and MUC3. Moreover, the immune-suppressive signals, such as suppression of IL21R on STAT3, PI3K mediated inhibition of inflammation by dopamine upon infection, as well as the inhibition of NLRC3 on STING during a steady state. Possible susceptible factors for CyHV-3, such as ITGB1, TLR18, and CCL4, were also revealed from the non-breeding strain. The results of this study also suggested that Nramp and PAI regulated by LncRNA could facilitate virus infection and proliferation for infected cells respectively, while T cell leukemia homeobox 3 (TLX3), as well as galectin 3 function by lncRNA, may play a role in the resistance mechanism. Therefore, immune factors that are immunogenetically insensitive or susceptible to CyHV-3 infection have been revealed.

Targeting Prostate Cancer Using Intratumoral Cytotopically Modified Interleukin-15 Immunotherapy in a Syngeneic Murine Model

Background

The prostate cancer microenvironment is highly immunosuppressive; immune cells stimulated in the periphery by systemic immunotherapies will be rendered inactive once entering this environment. Immunotherapies for prostate cancer need to break this immune tolerance. We have previously identified interleukin-15 (IL-15) as the only cytokine tested that activates and expands immune cells in the presence of prostate cancer cells. In the current study, we aimed to identify a method of boosting the efficacy of IL-15 in prostate cancer.

Methods

We engineered, by conjugation to a myristoylated peptide, a membrane-localising form of IL-15 (cyto-IL-15) and the checkpoint inhibitor antibodies cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed death ligand 1 (PD-L1) (cyto-abs) to enable them to bind to cell surfaces by non-specific anchoring to the phospholipid bilayer. The efficacy of these agents was investigated by intratumoral administration either alone (cyto-IL-15 or cyto-abs) or in combination (cyto-combo) in subcutaneous TRAMP-C2 prostate tumors in C57BL/6J mice and compared with their non-modified equivalents in vivo. Following the survival endpoint, histological analyses and RNA sequencing were performed on the tumors.

Results

Intratumoral injection of cyto-IL-15 or cyto-combo delayed tumor growth by 50% and increased median survival to 28 and 25 days, respectively, compared with vehicle (17 days), whereas non-modified IL-15 or antibodies alone had no significant effects on tumor growth or survival. Histological analysis showed that cyto-IL-15 and cyto-combo increased necrosis and infiltration of natural killer (NK) cells and CD8 T cells in the tumors compared with vehicle and non-modified agents. Overall, the efficacy of cyto-combo was not superior to that of cyto-IL-15 alone.

Conclusion

We have demonstrated that intratumoral injection of cyto-IL-15 leads to prostate cancer growth delay, induces tumor necrosis and increases survival. Hence, cytotopic modification in combination with intratumoral injection appears to be a promising novel approach for prostate cancer immunotherapy.

Semaphorin-3E Produced by Immature Dendritic Cells Regulates Activated Natural Killer Cells Migration

Natural killer (NK) cells and dendritic cells (DCs) are two innate immune cells that are critical in regulating innate and adaptive immunity. Cellular functions and migratory responses of NK or DC can be further regulated in NK-DC crosstalk that involves multiple cytokine signals and/or direct cell-cell contacts. Semaphorin-3E (Sema-3E) is a member of a large family of Semaphorin proteins that play diverse regulatory functions in different biological systems upon its binding to the cognate receptors. However, possible role(s) of Sema-3E on the regulation of NK-cell functions has not been elucidated. Here, we first demonstrated that DC and NK cells expressed Sema-3E and its receptors, respectively. To formally address the importance of DC-derived Sema-3E in regulating NK-cell migration, we compared in vitro migratory responses of activated NK cells (aNKs) toward different conditioned media of DCs (immature, lipopolysaccharide- or Poly I:C-stimulated) derived from Sema-3E^+/+ or Sema-3E^-/- mice. We observed that aNKs exhibited enhanced migrations toward the conditioned medium of the immature Sema-3E^-/- DC, when compared with that of the immature Sema-3E^+/+ DC. Addition of exogenous recombinant Sema-3E to the conditioned medium of the Sema-3E^-/- immature DC (iDC) abrogated such enhanced NK-cell migration. Our current work revealed a novel role of Sema-3E in limiting NK-cell migrations toward iDC in NK-DC crosstalk.