Interferon-induced Transmembrane Protein Research Articles

Mechanism of Action of Natural Compounds in Peripheral Multiorgan Dysfunction and Hippocampal Neuroinflammation Induced by Sepsis.

Bacterial sepsis induces the production of excessive pro-inflammatory cytokines and oxidative stress, resulting in tissue injury and hyperinflammation. Patients recovering from sepsis have increased rates of central nervous system (CNS) morbidities, which are linked to long-term cognitive impairment, such as neurodegenerative pathologies. This paper focuses on the tissue injury and hyperinflammation observed in the acute phase of sepsis and on the development of long-term neuroinflammation associated with septicemia. Here we evaluate the effects of Coriolus versicolor administration as a novel approach to treat polymicrobial sepsis. Rats underwent cecal ligation and perforation (CLP), and Coriolus versicolor (200 mg/kg in saline) was administered daily by gavage. Survival was monitored, and tissues from vital organs that easily succumb to infection were harvested after 72 h to evaluate the histological changes. Twenty-eight days after CLP, behavioral analyses were performed, and serum and brain (hippocampus) samples were harvested at four weeks from surgery. Coriolus versicolor increased survival and reduced acute tissue injury. Indeed, it reduced the release of pro-inflammatory cytokines in the bloodstream, leading to a reduced chronic inflammation. In the hippocampus, Coriolus versicolor administration restored tight junction expressions, reduce cytokines accumulation and glia activation. It also reduced toll-like receptor 4 (TLR4) and neuronal nitric oxide synthase (nNOS) and the NLR family pyrin domain containing 3 (NLRP3) inflammasome components expression. Coriolus versicolor showed antioxidant activities, restoring glutathione (GSH) levels and catalase and superoxide dismutase (SOD) activities and reducing lipid peroxidation, nitrite and reactive oxygen species (ROS) levels. Importantly, Coriolus versicolor reduced amyloid precursor protein (APP), phosphorylated-Tau (p-Tau), pathologically phosphorylated tau (PHF1), phosphorylated tau (Ser202 and Thr205) (AT8), interferon-induced transmembrane protein 3 (IFITM3) expression, and β-amyloid accumulation induced by CLP. Indeed, Coriolus versicolor restored synaptic dysfunction and behavioral alterations. This research shows the effects of Coriolus versicolor administration on the long-term development of neuroinflammation and brain dysfunction induced by sepsis. Overall, our results demonstrated that Coriolus versicolor administration was able to counteract the degenerative process triggered by sepsis.

IFITM3 rs12252 polymorphism and coronavirus disease 2019 severity: A meta‑analysis.

Interferon-induced transmembrane protein 3 (IFITM3) serves a critical role in the immune defense against viral infection, including that of severe acute respiratory syndrome coronavirus 2. To the best of our knowledge, the association between IFITM3 rs12252 polymorphism and coronavirus disease 2019 (COVID-19) severity has not been determined. In the present study, a meta-analysis of published case-control studies assessing the association between the IFITM3 rs12252 polymorphism and COVID-19 severity was performed. PubMed, EMBASE, China National Knowledge Infrastructure, Wanfang and preprint servers were searched up to March 30, 2022. A fixed-effect model was used to calculate odds ratio (OR) and 95% confidence interval (95% CI). Analyses were conducted for additive, dominant and recessive genetic models. A total of five studies were identified, with 1,443 mild-to-moderate cases and 667 severe cases, including 121 deaths. Overall, the CC genotype of IFITM3 rs12252 was associated with increased risk of severe COVID-19 (OR=1.97, 95% CI, 1.06-3.69) and mortality (OR=4.61, 95% CI, 1.44-14.75) compared with the CT/TT genotypes. Stratified analysis by ethnicity revealed that this association was strong in Chinese individuals (severity, OR=2.84, 95% CI, 1.34-6.04; mortality, OR=7.91, 95% CI, 1.29-48.44), but not notable in Caucasians (severity, OR=0.79, 95% CI, 0.23-2.80; mortality, OR=2.16, 95% CI, 0.37-12.55). A significant association with mortality was observed in Caucasians when comparing patients with the C allele of IFITM3 rs12252 and those without (CC/CT vs. TT: OR=1.73, 95% CI, 1.09-2.75). The results suggested that the IFTM3-rs12252 CC genotype is associated with severe COVID-19 and mortality in Chinese individuals and the IFTM3-rs12252 C allele may be associated with COVID-19 mortality in Caucasians. Large-scale studies are needed to confirm the association in different global populations.

DMP1 and IFITM5 Regulate Osteogenic Differentiation of MC3T3-E1 on PEO-Treated Ti-6Al-4V-Ca2+/Pi surface.

Despite numerous studies on various surface modifications on titanium and its alloys, it remains unclear what kind of titanium-based surface modifications are capable of controlling cell activity. This study aimed to understand the mechanism at the cellular and molecular levels and investigate the in vitro response of osteoblastic MC3T3-E1 cultured on the Ti-6Al-4V surface modified by plasma electrolytic oxidation (PEO) treatment. A Ti-6Al-4V surface was prepared by PEO at 180, 280, and 380 V for 3 or 10 min in an electrolyte containing Ca2+/Pi ions. Our results showed that PEO-treated Ti-6Al-4V-Ca2+/Pi surfaces enhanced the cell attachment and differentiation of MC3T3-E1 compared to the untreated Ti-6Al-4V control but did not affect cytotoxicity as shown by cell proliferation and cell death. Interestingly, on the Ti-6Al-4V-Ca2+/Pi surface treated by PEO at 280 V for 3 or 10 min, MC3T3-E1 showed a higher initial adhesion and mineralization. In addition, the alkaline phosphatase (ALP) activity significantly increased in MC3T3-E1 on the PEO-treated Ti-6Al-4V-Ca2+/Pi (280 V for 3 or 10 min). In RNA-seq analysis, the expression of dentin matrix protein 1 (DMP1), sortilin 1 (Sort1), signal-induced proliferation-associated 1 like 2 (SIPA1L2), and interferon-induced transmembrane protein 5 (IFITM5) was induced during the osteogenic differentiation of MC3T3-E1 on the PEO-treated Ti-6Al-4V-Ca2+/Pi. DMP1 and IFITM5 silencing decreased the expression of bone differentiation-related mRNAs and proteins and ALP activity in MC3T3-E1. These results suggest that the PEO-treated Ti-6Al-4V-Ca2+/Pi surface induces osteoblast differentiation by regulating the expression of DMP1 and IFITM5. Therefore, surface microstructure modification through PEO coatings with Ca2+/Pi ions could be used as a valuable method to improve biocompatibility properties of titanium alloys.

Immune surveillance of brain metastatic cancer cells is mediated by IFITM1.

Brain metastasis, most commonly originating from lung cancer, increases cancer morbidity and mortality. Although metastatic colonization is the rate-limiting and most complex step of the metastatic cascade, the underlying mechanisms are poorly understood. Here, in vivo genome-wide CRISPR-Cas9 screening revealed that loss of interferon-induced transmembrane protein 1 (IFITM1) promotes brain colonization of human lung cancer cells. Incipient brain metastatic cancer cells with high expression of IFITM1 secrete microglia-activating complement component 3 and enhance the cytolytic activity of CD8+ T cells by increasing the expression and membrane localization of major histocompatibility complex class I. After activation, microglia (of the innate immune system) and cytotoxic CD8+ T lymphocytes (of the adaptive immune system) were found to jointly eliminate cancer cells by releasing interferon-gamma and inducing phagocytosis and T-cell-mediated killing. In human cancer clinical trials, immune checkpoint blockade therapy response was significantly correlated with IFITM1 expression, and IFITM1 enhanced the brain metastasis suppression efficacy of PD-1 blockade in mice. Our results exemplify a novel mechanism through which metastatic cancer cells overcome the innate and adaptive immune responses to colonize the brain, and suggest that a combination therapy increasing IFITM1 expression in metastatic cells with PD-1 blockade may be a promising strategy to reduce metastasis.

Abnormal signal pathways and tumor heterogeneity in osteosarcoma

BackgroundOsteosarcoma (OS) is the most frequent and aggressive primary malignant sarcoma among adolescents and chemotherapy has not substantially progressed for decades. New insights into OS development and therapeutic strategies are urgently needed.MethodsWe analyzed integrated single-cell transcriptomes, bulk RNA-seq, and microarray data from Gene Expression Omnibus (GEO) datasets. We also used Weighted Gene Co-expression Network Analysis (WGCNA), Gene set enrichment analysis (GSEA), and Gene set variation analysis (GSVA), along with Simple ClinVar and Enrichr web servers.ResultsThe findings of integrated single-cell analysis showed that OS arises from imperfect osteogenesis during development. Novel abnormalities comprised deficient TGFβ and P53 signal pathways, and cell cycle pathway activation, and a potentially new driver mutation in the interferon induced transmembrane protein 5 (IFITM5) that might function as a pathogenic factor in OS. Osteosarcoma is characterized by oncocyte heterogeneity, especially in immunogenic and adipocyte-like subtypes that respectively promote and hamper OS treatment. Etoposide is a promising chemotherapeutic that provides palliation by affecting the subtype of OS and correcting the abnormal pathways.ConclusionVarious abnormal signal pathways play indispensable roles in OS development. We explored the heterogeneity and underlying mechanisms of OS and generated findings that will assist with OS assessment and selecting optimal therapies.

Spatial correlation of cholesterol and amphipathic helix of IFITM3.

Interferon-induced transmembrane (IFITM) proteins are involved in antiviral activity. It has been hypothesized that the amphipathic helix (AH) of IFITM3 acts by stalling viral fusion to the late endosome at the hemifusion or nascent fusion pore stage.

Clinical-Epidemiological Characteristics and IFITM-3 (rs12252) Variant Involvement in HIV-1 Mother-to-Children Transmission Susceptibility in a Brazilian Population.

Mother-to-children transmission (MTCT) is the main infection route for HIV-1 in children, and may occur during pregnancy, delivery, and/or postpartum. It is a multifactorial phenomenon, where genetic variants play an important role. This study aims at analyzing the influence of clinical epidemiological characteristics and a variant (rs12252) in interferon-induced transmembrane protein 3 (IFITM-3), a gene encoding an important viral restriction factor, on the susceptibility to HIV-1 mother-to-children transmission (MTCT). A case-control study was performed on 209 HIV-1-infected mothers and their exposed infected (87) and uninfected (122) children from Pernambuco, Brazil. Clinical-epidemiological characteristics are significantly associated with MTCT susceptibility. Transmitter mothers have a significantly lower age at delivery, late diagnosis, deficiency in ART use (pregnancy and delivery), and detectable viral load in the third trimester of pregnancy compared with non-transmitter mothers. Infected children show late diagnosis, vaginal delivery frequency, and tend to breastfeed, differing significantly from uninfected children. The IFITM-3 rs12252-C allele and TC/CC genotypes (dominant model) are significantly more frequent among infected than uninfected children, but the statistical significance does not remain when adjusted for clinical factors. No significant differences are observed between transmitter and non-transmitter mothers in relation to the IFITM-3 variant.

IFITMs from Naturally Infected Animal Species Exhibit Distinct Restriction Capacities against Toscana and Rift Valley Fever Viruses.

Rift Valley Fever virus (RVFV) and Toscana virus (TOSV) are two pathogenic arthropod-borne viruses responsible for zoonotic infections in both humans and animals; as such, they represent a growing threat to public and veterinary health. Interferon-induced transmembrane (IFITM) proteins are broad inhibitors of a large panel of viruses belonging to various families and genera. However, little is known on the interplay between RVFV, TOSV, and the IFITM proteins derived from their naturally infected host species. In this study, we investigated the ability of human, bovine, and camel IFITMs to restrict RVFV and TOSV infection. Our results indicated that TOSV was extremely sensitive to inhibition by all the animal IFITMs tested, while RVFV was inhibited by human IFITM-2 and IFITM-3, but not IFITM-1, and exhibited a more heterogeneous resistance phenotype towards the individual bovine and camel IFITMs tested. Overall, our findings shed some light on the complex and differential interplay between two zoonotic viruses and IFITMs from their naturally infected animal species.

Spike-mediated viral membrane fusion is inhibited by a specific anti-IFITM2 monoclonal antibody

The early steps of viral infection involve protein complexes and structural lipid rearrangements which characterize the peculiar strategies of each virus to invade permissive host cells. Members of the human immune-related interferon-induced transmembrane (IFITM) protein family have been described as inhibitors of the entry of a broad range of viruses into the host cells. Recently, it has been shown that SARS-CoV-2 is able to hijack IFITM2 for efficient infection. Here, we report the characterization of a newly generated specific anti-IFITM2 mAb able to impair Spike-mediated internalization of SARS-CoV-2 in host cells and, consequently, to reduce the SARS-CoV-2 cytopathic effects and syncytia formation. Furthermore, the anti-IFITM2 mAb reduced HSVs- and RSV-dependent cytopathic effects, suggesting that the IFITM2-mediated mechanism of host cell invasion might be shared with other viruses besides SARS-CoV-2. These results show the specific role of IFITM2 in mediating viral entry into the host cell and its candidacy as a cell target for antiviral therapeutic strategies.

Determining the Protective Efficacy of Toll-Like Receptor Ligands to Minimize H9N2 Avian Influenza Virus Transmission in Chickens.

Low-pathogenicity avian influenza viruses (AIV) of the H9N2 subtype can infect and cause disease in chickens. Little is known about the efficacy of immune-based strategies for reducing the transmission of these viruses. The present study investigated the efficacy of Toll-like receptor (TLR) ligands (CpG ODN 2007 and poly(I:C)) to reduce H9N2 AIV transmission from TLR-treated seeder (trial 1) or inoculated chickens (trial 2) to naive chickens. The results from trial 1 revealed that a low dose of CpG ODN 2007 led to the highest reduction in oral shedding, and a high dose of poly(I:C) was effective at reducing oral and cloacal shedding. Regarding transmission, the recipient chickens exposed to CpG ODN 2007 low-dose-treated seeder chickens showed a maximum reduction in shedding with the lowest number of AIV+ chickens. The results from trial 2 revealed a maximum reduction in oral and cloacal shedding in the poly(I:C) high-dose-treated chickens (recipients), followed by the low-dose CpG ODN 2007 group. In these two groups, the expression of type I interferons (IFNs), protein kinase R (PKR), interferon-induced transmembrane protein 3 (IFITM3), viperin, and (interleukin) IL-1β, IL-8, and 1L-18 was upregulated in the spleen, cecal tonsils and lungs. Hence, TLR ligands can reduce AIV transmission in chickens.

Does IFITM3 link inflammation to tumorigenesis?

Uncontrolled chronic inflammation, in most cases due to excessive cytokine signaling through their receptors, is known to contribute to the development of tumorigenesis. Recently, it has been reported that the antiviral membrane protein interferon-induced transmembrane protein 3 (IFITM3), induced by interferon signaling as part of the inflammatory response after viral infection, contributes to the development of B-cell malignancy. The unexpected oncogenic signaling of IFITM3 upon malignant B cell activation elucidated the mechanism by which the uncontrolled expression of inflammatory proteins contributes to leukemogenesis. In this review, the potential effects of inflammatory cytokines on upregulation of IFITM3 and its contribution to tumorigenesis are discussed. [BMB Reports 2022; 55(12): 602-608].

IFITM3 is a host restriction factor that inhibits porcine transmissible gastroenteritis virus infection

Interferon-induced transmembrane proteins (IFITMs) play an important role in the innate immune response triggered by viral infection. Transmissible gastroenteritis virus (TGEV) causes severe diarrhea, vomiting and dehydration in piglets, resulting in huge economic losses to the swine industry. In this study, we showed that IFITM3 inhibits the replication of TGEV and interferes with the binding of TGEV to PK15 cells. Moreover, the inhibitory effect of IFITM3 on TGEV circumvents the upregulation of inflammatory cytokines. Subsequently, we found that the M22A mutant loses part of the antiviral effect of IFITM3 on TGEV; in contrast, the K24A mutant enhances the antiviral effect of IFITM3. Notably, our data shows a synergistic effect between IFITM3 and CQ, which further amplifies the antiviral effect against TGEV.

IFITM proteins assist cellular uptake of diverse linked chemotypes.

The search for cell-permeable drugs has conventionally focused on low-molecular weight (MW), nonpolar, rigid chemical structures. However, emerging therapeutic strategies break traditional drug design rules by employing flexibly linked chemical entities composed of more than one ligand. Using complementary genome-scale chemical-genetic approaches we identified an endogenous chemical uptake pathway involving interferon-induced transmembrane proteins (IFITMs) that modulates the cell permeability of a prototypical biopic inhibitor of MTOR (RapaLink-1, MW: 1784 g/mol). We devised additional linked inhibitors targeting BCR-ABL1 (DasatiLink-1, MW: 1518 g/mol) and EIF4A1 (BisRoc-1, MW: 1466 g/mol), uptake of which was facilitated by IFITMs. We also found that IFITMs moderately assisted some proteolysis-targeting chimeras and examined the physicochemical requirements for involvement of this uptake pathway.

IFITM3 regulates fibrinogen endocytosis and platelet reactivity in nonviral sepsis.

Platelets and megakaryocytes are critical players in immune responses. Recent reports suggest infection and inflammation alter the megakaryocyte and platelet transcriptome to induce altered platelet reactivity. We determined whether nonviral sepsis induces differential platelet gene expression and reactivity. Nonviral sepsis upregulated IFN-induced transmembrane protein 3 (IFITM3), an IFN-responsive gene that restricts viral replication. As IFITM3 has been linked to clathrin-mediated endocytosis, we determined whether IFITM3 promoted endocytosis of α-granule proteins. IFN stimulation enhanced fibrinogen endocytosis in megakaryocytes and platelets from Ifitm+/+ mice, but not Ifitm-/- mice. IFITM3 overexpression or deletion in megakaryocytes demonstrated IFITM3 was necessary and sufficient to regulate fibrinogen endocytosis. Mechanistically, IFITM3 interacted with clathrin and αIIb and altered their plasma membrane localization into lipid rafts. In vivo IFN administration increased fibrinogen endocytosis, platelet reactivity, and thrombosis in an IFITM-dependent manner. In contrast, Ifitm-/- mice were completely rescued from IFN-induced platelet hyperreactivity and thrombosis. During murine sepsis, platelets from Ifitm+/+ mice demonstrated increased fibrinogen content and platelet reactivity, which was dependent on IFN-α and IFITMs. Platelets from patients with nonviral sepsis had increases in platelet IFITM3 expression, fibrinogen content, and hyperreactivity. These data identify IFITM3 as a regulator of platelet endocytosis, hyperreactivity, and thrombosis during inflammatory stress.

Increased risk of COVID-19 mortality rate in IFITM3 rs6598045 G allele carriers infected by SARS-CoV-2 delta variant

BackgroundThe interferon-induced transmembrane-protein 3 (IFITM3) is a vital component of the immune system's defense against viral infection. Variants in the IFITM3 gene have been linked to changes in expression and the risk of severe Coronavirus disease 2019 (COVID-19). This study aimed to investigate whether IFITM3 rs6598045, quantitative polymerase chain reaction (qPCR) cycle threshold (Ct) values, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants are associated with an increased mortality rate of COVID-19.MethodsThe genotyping of IFITM3 rs6598045 polymorphism was analyzed using the amplification refractory mutation system-polymerase chain reaction in 1342 recovered and 1149 deceased patients positive for SARS-CoV-2.ResultsIn this study, IFITM3 rs6598045 G allele as minor allele frequency was significantly more common in the deceased patients than in the recovered ones. Furthermore, the highest mortality rates were observed in Delta variant and lowest qPCR Ct values. COVID-19 mortality was associated with IFITM3 rs6598045 GG and AG in Delta variant and IFITM3 rs6598045 AG in Alpha variant. A statistically significant difference was observed in the qPCR Ct values between individuals with GG and AG genotypes and those with an AA genotype.ConclusionA possible correlation was observed between the mortality rate of COVID-19, the G allele of IFITM3 rs6598045, and SARS-CoV-2 variants. However, large-scale research is still required to validate our results.

Effect of chronic ammonia nitrogen stress on the SOD activity and interferon-induced transmembrane protein 1 expression in the clam Cyclina sinensis

Ammonia nitrogen plays a crucial part in oxidative stress in aquatic animals. To elucidate the effect of ammonia nitrogen stress on the superoxide dismutase (SOD) activity and interferon-induced transmembrane protein 1 (IFITM1) expression in the clam Cyclina sinensis, clams were exposed to ammonia nitrogen (8.07 mg/L) for 768 h (32 days) and then challenged with Vibrio parahaemolyticus. The results showed that the SOD activity in the hepatopancreas of C. sinensis exposed to ammonia nitrogen first increased and then decreased with time, returning to the control group’s normal level at 768 h. Following infection with V. parahaemolyticus, the SOD activity in the hepatopancreas fluctuated over time. The SOD activity in clams infected with V. parahaemolyticus at 144 h did not return to the control group’s normal level. The full-length cDNA of CsIFITM1 was 2,434 bases in length, including a 2,301-bp open reading frame (ORF) encoding 714 amino acids, with a putative molecular weight of 83.86 kDa. CsIFITM1 contains an RNA helicase domain (DEXHc_RLR, DR) and a Helicase_C (HC) domain. The transcriptional levels of CsIFITM1 were upregulated by exposure to ammonia nitrogen and were significantly higher from 6 to 768 h compared to the control (0 h) (p < 0.05). Following infection with V. parahaemolyticus, the transcript levels of CsIFITM1 in the hepatopancreas were upregulated and were significantly higher from 6 to 144 h, in contrast to those of the control (0 h) (p < 0.05). The present data provide the first evidence of the SOD activity and CsIFITM1 transcript levels being able to reflect the effect of ammonia on the clam C. sinensis.

IFITM protein regulation and functions: Far beyond the fight against viruses.

Interferons (IFNs) are important cytokines that regulate immune responses through the activation of hundreds of genes, including interferon-induced transmembrane proteins (IFITMs). This evolutionarily conserved protein family includes five functionally active homologs in humans. Despite the high sequence homology, IFITMs vary in expression, subcellular localization and function. The initially described adhesive and antiproliferative or pro-oncogenic functions of IFITM proteins were diluted by the discovery of their antiviral properties. The large set of viruses that is inhibited by these proteins is constantly expanding, as are the possible mechanisms of action. In addition to their beneficial antiviral effects, IFITM proteins are often upregulated in a broad spectrum of cancers. IFITM proteins have been linked to most hallmarks of cancer, including tumor cell proliferation, therapeutic resistance, angiogenesis, invasion, and metastasis. Recent studies have described the involvement of IFITM proteins in antitumor immunity. This review summarizes various levels of IFITM protein regulation and the physiological and pathological functions of these proteins, with an emphasis on tumorigenesis and antitumor immunity.

IFITM3 Acts As a PIP3 Scaffold in TCR-PI3K Signaling

Background: Phosphatidylinositol 3-kinase (PI3K) signaling is an indispensable element of T-cell receptor (TCR), co-stimulatory receptor, and cytokine receptor activation in T cells and in the oncogenic signaling underlying T-cell malignancies. We recently identified interferon-inducible transmembrane protein 3 (IFITM3) as an unexpected but essential component of antigen receptor signaling and malignant transformation in B cells. In contrast to its previously characterized role as an interferon-stimulated gene which restricts viral entry through endosomal membranes, IFITM3 also directly binds to the lipid PIP3 - the product of PI3K - at the B cell surface and amplifies PI3K-mediated signal transduction. Whether IFITM3 serves an analogous function in other lymphocytes is currently unknown. Here, we demonstrate that IFITM3 is also required for robust PI3K-driven signaling and proliferation in primary and transformed human T cells. Results: We found that resting primary human T cells express low levels of IFITM3 but robustly upregulate IFITM3 protein following CD3/CD28 stimulation. To test whether IFITM3 participates in TCR signaling, we analyzed IFITM3 and PIP3 subcellular localization in Jurkat cells. Proximity ligation assays revealed that IFITM3 co-localizes with CD3δ at the cell surface, indicating recruitment of IFITM3 to TCR signaling complexes. Moreover, in the absence of IFITM3, a fluorescent reporter of PIP3 localization failed to redistribute from a diffuse cytosolic pattern to discrete foci at the cell surface upon TCR stimulation. We further explored whether these aberrant PIP3 dynamics were associated with broader defects in PIP3-dependent signaling axes important in T cells. In accord with prior findings in B cells, both Jurkat and primary T cells lacking IFITM3 expression exhibited diminished TCR signaling, including Ca2+ flux and PI3K-dependent AKT phosphorylation, and impaired cell proliferation relative to controls. These results demonstrate that T cells require IFITM3 for optimal antigen receptor- and PI3K-driven signaling. Mechanistically, IFITM3 is phosphorylated by Src family kinases at Y20, promoting retention at the plasma membrane, and specifically binds to PIP3, a highly negatively charged phospholipid, through basic residues in its conserved intracellular loop (CIL). We assessed the functional relevance of these residues in T cells by comparing the effects of wild-type and mutant IFITM3 variants. Overexpression of wild-type IFITM3 or a mutant with constitutive plasma membrane localization (Y20E) increased TCR-induced AKT phosphorylation, but a CIL mutant incapable of binding to PIP3 (K83A/K104A) lacked this activity and instead compromised cell viability and growth. Primary T cells expressing CIL-mutant IFITM3 were more apoptotic and demonstrated impaired cell cycle progression and proliferation, highlighting PIP3 binding as an essential feature of IFITM3 in T cell biology. Beyond normal T cells, PI3K signaling also enables the transformation of malignant T cells, with PI3K inhibitors emerging as promising agents in the treatment of peripheral T cell lymphomas (PTCLs). To determine whether IFITM3 contributes to the oncogenic signaling in PTCLs, we developed disease models incorporating both the expression of PTCL-derived oncogenes in T cells and the capability to assess candidate genes as functional players in pathogenesis. In a mouse bone marrow chimera system, conditional expression (via CD4-Cre) of a lentivirus-delivered oncogene (e.g., ITK-SYK) gave rise to circulating transgenic donor T cells and oncogene-dependent morbidity and mortality. In a humanized mouse system, a T cell-specific promoter controlled transgene expression upon transduction of CD34+ cord blood progenitors. In a separate approach, transduction of mature human T cells differentiated in vitro from CD34+ cells permitted a constitutive promoter. These results establish tractable systems to assess IFITM3 as a requisite factor for oncogenic signaling in PTCLs. Conclusion: We conclude that IFITM3 is essential for antigen receptor and oncogenic signaling not only in B cells but also in T cells. These findings identify a novel component of TCR signaling and suggest a shared mechanism for lymphocyte dependency on IFITM3 through scaffolding the lipid PIP3, a mechanism which can be leveraged to amplify oncogenic signaling in T cell malignancies. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The P681H Mutation in the Spike Glycoprotein of the Alpha Variant of SARS-CoV-2 Escapes IFITM Restriction and Is Necessary for Type I Interferon Resistance.

The appearance of new dominant variants of concern (VOC) of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) threatens the global response to the coronavirus disease 2019 (COVID-19) pandemic. Of these, the alpha variant (also known as B.1.1.7), which appeared initially in the United Kingdom, became the dominant variant in much of Europe and North America in the first half of 2021. The spike (S) glycoprotein of alpha acquired seven mutations and two deletions compared to the ancestral virus, including the P681H mutation adjacent to the polybasic cleavage site, which has been suggested to enhance S cleavage. Here, we show that the alpha spike protein confers a level of resistance to beta interferon (IFN-β) in human lung epithelial cells. This correlates with resistance to an entry restriction mediated by interferon-induced transmembrane protein 2 (IFITM2) and a pronounced infection enhancement by IFITM3. Furthermore, the P681H mutation is essential for resistance to IFN-β and context-dependent resistance to IFITMs in the alpha S. P681H reduces dependence on endosomal cathepsins, consistent with enhanced cell surface entry. However, reversion of H681 does not reduce cleaved spike incorporation into particles, indicating that it exerts its effect on entry and IFN-β downstream of furin cleavage. Overall, we suggest that, in addition to adaptive immune escape, mutations associated with VOC may well also confer a replication and/or transmission advantage through adaptation to resist innate immune mechanisms. IMPORTANCE Accumulating evidence suggests that variants of concern (VOC) of SARS-CoV-2 evolve to evade the human immune response, with much interest focused on mutations in the spike protein that escape from antibodies. However, resistance to the innate immune response is essential for efficient viral replication and transmission. Here, we show that the alpha (B.1.1.7) VOC of SARS-CoV-2 is substantially more resistant to type I interferons than the parental Wuhan-like virus. This correlates with resistance to the antiviral protein IFITM2 and enhancement by its paralogue IFITM3. The key determinant of this is a proline-to-histidine change at position 681 in S adjacent to the furin cleavage site, which in the context of the alpha spike modulates cell entry pathways of SARS-CoV-2. Reversion of the mutation is sufficient to restore interferon and IFITM2 sensitivity, highlighting the dynamic nature of the SARS CoV-2 as it adapts to both innate and adaptive immunity in the humans.

Chicken interferon-induced transmembrane protein 1 promotes replication of coronavirus infectious bronchitis virus in a cell-specific manner

Interferon-induced transmembrane proteins (IFITMs) are broad-spectrum antiviral proteins that inhibit numerous virus infections by impeding viral entry into target cells. However, increasing evidence suggests diverse functions of IFITMs in virus infection, especially with the coronavirus. We analyzed the effect of chicken interferon-induced transmembrane proteins (chIFITMs) on coronavirus infectious bronchitis virus (IBV) infection in vitro. We demonstrated that the antiviral effects of IFITMs are dependent on cell and virus types. The overexpression of chIFITM1 dramatically promoted the replication of IBV Beaudette strain in the chicken hepatocellular carcinoma cell line, LMH. Mechanistically, chIFITMs share roughly the same subcellular localization in different host cells, and overexpressed of chIFITM1 have no effect of viral attachment and entry. Further studies revealed that mutations of amino acids at key positions (60KSRD63, 68KDFV71) in the intracellular loop domain (CIL) caused loss of the promoted function. Interaction with downstream proteins in co-response to viral infection could be the primary reason behind variable functions of chIFITM1 in different cells. In all, our study explored the functions of chIFITMs in viral infection from a new perspective.