Human herpesvirus 8 molecular mimicry of ephrin ligands facilitates cell entry and triggers EphA2 signaling

Seneca valley virus 3C protease blocks EphA2-Mediated mTOR activation to facilitate viral replication

The Seneca Valley virus (SVV) is a recently discovered porcine pathogen that causes vesicular diseases and poses a significant threat to the pig industry worldwide. Erythropoietin-producing hepatoma receptor A2 (EphA2) is involved in the activation of the AKT/mTOR signaling pathway, which is involved in autophagy. However, the regulatory relationship between SVV and EphA2 remains unclear. In this study, we demonstrated that EphA2 is proteolysed in SVV-infected BHK-21 and PK-15 cells. Overexpression of EphA2 significantly inhibited SVV replication, as evidenced by decreased viral protein expression, viral titers, and viral load, suggesting an antiviral function of EphA2. Subsequently, viral proteins involved in the proteolysis of EphA2 were screened, and the SVV 3C protease (3Cpro) was found to be responsible for this cleavage, depending on its protease activity. However, the protease activity sites of 3Cpro did not affect the interactions between 3Cpro and EphA2. We further determined that EphA2 overexpression inhibited autophagy by activating the mTOR pathway and suppressing SVV replication. Taken together, these results indicate that SVV 3Cpro targets EphA2 for cleavage to impair its EphA2-mediated antiviral activity and emphasize the potential of the molecular interactions involved in developing antiviral strategies against SVV infection.

Investigations of membrane protein interactions in cells using fluorescence microscopy

The interactions between proteins in membranes govern many cellular functions. Our ability to probe for such interactions has greatly evolved in recent years due to the introduction of new fluorescence techniques. As a result, we currently have a choice of methods that can be used to assess the spatial distribution of a membrane protein, its association state, and the thermodynamic stability of the oligomers in the native milieu. These biophysical measurements have revealed new insights into important biological processes in cellular membranes.

Lymphedema and Kaposi sarcoma: A narrative review

BACKGROUND

Kaposi sarcoma (KS), due to HHV-8 infection is classified in 4 subtypes: epidemic, endemic, HIV-related and iatrogenic essentially after organ transplant. Lymphedema is a complication of KS. We reviewed the interactions between HHV-8 infection and lymphedema according an analysis of the literature.

MAIN BODY

HHV-8 can infect different types of cells, among them a privileged tropism for lymphatic endothelial cells. It induces multi-centric endothelial proliferation leading to the occlusion of lymphatic vascular lumen. Lymphatic obstruction progressively lead to the blockage of lymphatic drainage, lymph stasis and lymphedema. Lymphedema mostly involved the lower limb affected by KS. It can then develop simultaneously or after the appearance of KS lesions but also be the first sign of KS, a long time before KS skin lesion onset. Lymphedema diagnosis is clinical and lymphoscintigraphy can confirm it if necessary. Lymphedema may be associated with active lesions of KS or non-evolutive, with only cicatricial lesions. KS should be treated according to the KS subtype, aggressive form, with local or systemic treatments associating with causal treatment, such as HIV infection or reducing immuno-suppressive drugs in transplant patients. In most of the cases, KS treatment may slightly reduce (or not) lymphedema volume which remains a chronic disease. Lymphedema management should be associated in order to reduce the volume and then stabilizing it. Low-stretch bandage, elastic garments and skin care are the cornerstone of treatment.

CONCLUSION

Lymphedema is a frequent complication of KS, and may reveal KS or occurs throughout its course. Association of KS and lymphedema must be known because lymphedema is a chronic disease affecting the quality of life. Beyond the treatment of KS, its management must be specific including a long follow-up to optimize the patient's observance required to maintain the best lymphedema control.

Progressing nanotechnology to improve targeted cancer treatment: overcoming hurdles in its clinical implementation

The use of nanotechnology has the potential to revolutionize the detection and treatment of cancer. Developments in protein engineering and materials science have led to the emergence of new nanoscale targeting techniques, which offer renewed hope for cancer patients. While several nanocarriers for medicinal purposes have been approved for human trials, only a few have been authorized for clinical use in targeting cancer cells. In this review, we analyze some of the authorized formulations and discuss the challenges of translating findings from the lab to the clinic. This study highlights the various nanocarriers and compounds that can be used for selective tumor targeting and the inherent difficulties in cancer therapy. Nanotechnology provides a promising platform for improving cancer detection and treatment in the future, but further research is needed to overcome the current limitations in clinical translation.

Lipofectamine 2000™ at transfection dose promotes EphA2 transcription in an HDAC4-dependent manner to reduce its cytotoxicity

The cationic liposome is well-known as an efficient nucleic acid delivery tool; however, the stress responses induced by liposome per se have been rarely revealed. In this study, we found that Lipofectamine™ 2000 (lipo2000), a commonly used commercial cationic liposome transfection, could upregulate EphA2 mRNA expression in multiple cells at transfection dose. Furthermore, lipo2000 treatment could increase the level of EphA2 hnRNA (heterogeneous nuclear RNA). Lipo2000-induced EphA2 upregulation could be depleted upon global transcription inhibition, proving that lipo2000 upregulates EphA2 expression via activating its transcription. Moreover, HDAC4 depletion, a known EphA2 trans-acting regulatory factor, could eliminate the lipo2000-induced EphA2 upregulation, demonstrating that lipo2000 promotes EphA2 transcription in an HDAC4 dependent manner. Functionally, EphA2 knockdown did not affect GFP expression level and the interfering efficacy of siGAPDH, suggesting that EphA2 is unrelated to the nucleic acid delivery capacity of lipo2000. Nevertheless, EphA2 depletion significantly activated autophagy and apoptosis, increasing the cytotoxic effects of lipo2000, which could be rescued by EphA2 restoration, indicating that EphA2 is essential to overcome liposome-related cytotoxicity. Finally, we found that lipo2000 could activate EphA2 transcription in an HDAC4-dependent manner. EphA2 is not associated with the transfection efficiency of lipo2000, but it is vital to reduce lipo2000 cytotoxicity, suggesting that when conducting liposome-mediated gene function studies, especially for EphA2, the stress response of liposomes should be considered to obtain objective results.

Cytomegalovirus US28 regulates cellular EphA2 to maintain viral latency

Cytomegalovirus (CMV) reactivation from latency following immune dysregulation remains a serious risk for patients, often causing substantial morbidity and mortality. Here, we demonstrate the CMV-encoded G protein-coupled receptor, US28, in coordination with cellular Ephrin receptor A2, attenuates mitogen-activated protein kinase signaling, thereby limiting viral replication in latently infected primary monocytes. Furthermore, treatment of latently infected primary monocytes with dasatinib, a Food and Drug Association-approved kinase inhibitor used to treat a subset of leukemias, results in CMV reactivation. These ex vivo data correlate with our retrospective analyses of the Explorys electronic health record database, where we find dasatinib treatment is associated with a significant risk of CMV-associated disease (odds ratio 1.58, P = 0.0004). Collectively, our findings elucidate a signaling pathway that plays a central role in the balance between CMV latency and reactivation and identifies a common therapeutic cancer treatment that elevates the risk of CMV-associated disease.

Ligands with different dimeric configurations potently activate the EphA2 receptor and reveal its potential for biased signaling

The EphA2 receptor tyrosine kinase activates signaling pathways with different, and sometimes opposite, effects in cancer and other pathologies. Thus, highly specific and potent biased ligands that differentially control EphA2 signaling responses could be therapeutically valuable. Here, we use EphA2-specific monomeric peptides to engineer dimeric ligands with three different geometric configurations to combine a potential ability to differentially modulate EphA2 signaling responses with the high potency and prolonged receptor residence time characteristic of dimeric ligands. The different dimeric peptides readily induce EphA2 clustering, autophosphorylation and signaling, the best with sub-nanomolar potency. Yet, there are differences in two EphA2 signaling responses induced by peptides with different configurations, which exhibit distinct potency and efficacy. The peptides bias signaling when compared with the ephrinA1-Fc ligand and do so via different mechanisms. These findings provide insights into Eph receptor signaling, and proof-of-principle that different Eph signaling responses can be distinctly modulated.

Antibodies Targeting KSHV gH/gL Reveal Distinct Neutralization Mechanisms

Kaposi’s sarcoma herpesvirus (KSHV) is associated with a significant disease burden, in particular in Sub-Sahara Africa. A KSHV vaccine would be highly desirable, but the mechanisms underlying neutralizing antibody responses against KSHV remain largely unexplored. The complex made of glycoproteins H and L (gH/gL) activates gB for the fusion of viral and cellular membranes in all herpesviruses. KSHV gH/gL also interacts with cellular Eph family receptors. To identify optimal antigens for vaccination and to elucidate neutralization mechanisms, we primed mice with recombinantly expressed, soluble gH/gL (gHecto/gL) that was either wildtype (WT), lacking defined glycosylation sites or bearing modified glycosylation, followed by boosts with WT gHecto/gL. We also immunized with a gL-gHecto fusion protein or a gHecto-ferritin/gL nanoparticle. Immune sera neutralized KSHV and inhibited EphA2 receptor binding. None of the regimens was superior to immunization with WT gHecto/gL with regard to neutralizing activity and EphA2 blocking activity, the gL-gHecto fusion protein was equally effective, and the ferritin construct was inferior. gH/gL-targeting sera inhibited gB-mediated membrane fusion and inhibited infection also independently from receptor binding and gL, as demonstrated by neutralization of a novel KSHV mutant that does not or only marginally incorporate gL into the gH/gL complex and infects through an Eph-independent route.