Coupling of SARS-CoV-2 to Amyloid Fibrils and Liquid-Liquid Phase Separation.

Targeting the liquid-liquid phase separation of nucleocapsid broadly inhibits the replication of SARS-CoV-2 strains.

The etiologic agent of the Covid-19 pandemic is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The viral membrane of SARS-CoV-2 surrounds a helical nucleocapsid in which the viral genome is encapsulated by the nucleocapsid protein. The nucleocapsid protein of SARS-CoV-2 is produced at high levels within infected cells, enhances the efficiency of viral RNA transcription, and is essential for viral replication. Here, we show that RNA induces cooperative liquid–liquid phase separation of the SARS-CoV-2 nucleocapsid protein. In agreement with its ability to phase separate in vitro, we show that the protein associates in cells with stress granules, cytoplasmic RNA/protein granules that form through liquid-liquid phase separation and are modulated by viruses to maximize replication efficiency. Liquid–liquid phase separation generates high-density protein/RNA condensates that recruit the RNA-dependent RNA polymerase complex of SARS-CoV-2 providing a mechanism for efficient transcription of viral RNA. Inhibition of RNA-induced phase separation of the nucleocapsid protein by small molecules or biologics thus can interfere with a key step in the SARS-CoV-2 replication cycle.

Coronavirus membrane (M) protein can form virus-like particles (VLPs) when coexpressedwith nucleocapsid (N) or envelope (E) proteins, suggesting a pivotal role for M in virionassembly. Here we demonstrate the self-assembly and release of severe acute respiratorysyndrome coronavirus (SARS-CoV) M protein in medium in the form of membrane-envelopedvesicles with densities lower than those of VLPs formed by M plus N. Although efficientN-N interactions require the presence of RNA, we found that M-M interactions wereRNA-independent. SARS-CoV M was observed in both the Golgi area and plasma membranes of avariety of cells. Blocking M glycosylation does not appear to significantly affect Mplasma membrane labeling intensity, M-containing vesicle release, or VLP formation.Results from a genetic analysis indicate involvement of the third transmembrane domain ofM in plasma membrane-targeting signal. Fusion proteins containing M amino-terminal 50residues encompassing the first transmembrane domain were found to be sufficient formembrane binding, multimerization, and Golgi retention. Surprisingly, we found that fusionproteins lacking all three transmembrane domains were still capable of membrane binding,Golgi retention, and interacting with M. The data suggest that multiple SARS-CoV M regionsare involved in M self-assembly and subcellular localization.

COVID-19 caused by the novel coronavirus, severe acute respiratory syndrome coronavirus 2, (SARS-CoV-2) is a highly contagious disease known for its significant lung damage. Although the impact of the COVID-19 pandemic on our daily lives has been limited, the virus has not vanished entirely and continues to undergo mutations. This calls for a concentrated focus on the matter of SARS-CoV-2 immune evasion. Drawing on observations of immune escape mechanisms in other viruses, some scholars have proposed that liquid-liquid phase separation might play a crucial role in SARS-CoV-2's ability to evade the immune system. Within the structure of SARS-CoV-2, the nucleocapsid protein plays a pivotal role in RNA replication and transcription. Concurrently, this protein can engage in phase separation with RNA. A thorough examination of the phase separation related to the nucleocapsid protein may unveil the mechanism by which SARS-CoV-2 accomplishes immune evasion. Moreover, this analysis may provide valuable insights for future development of innovative antiviral drugs or vaccines.

Care of patients with liver disease during the COVID-19 pandemic: EASL-ESCMID position paper.

SARS-CoV-2 nucleocapsid protein phase separates with G3BPs to disassemble stress granules and facilitate viral production

The coronavirus disease 2019 (COVID-19) pandemic has been linked to long-term neurological effects with multifaceted complications of neurodegenerative diseases. Several studies have found that pathological changes in transactive response DNA-binding protein of 43 kDa (TDP-43) are involved in these cases. This review explores the causal interactions between severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and TDP-43 from multiple perspectives. Some viral proteins of SARS-CoV-2 have been shown to induce pathological changes in TDP-43 through its cleavage, aggregation, and mislocalization. SARS-CoV-2 infection can cause liquid-liquid phase separation and stress granule formation, which accelerate the condensation of TDP-43, resulting in host RNA metabolism disruption. TDP-43 has been proposed to interact with SARS-CoV-2 RNA, though its role in viral replication remains to be fully elucidated. This interaction potentially facilitates viral replication, while viral-induced oxidative stress and protease activity accelerate TDP-43 pathology. Evidence from both clinical and experimental studies indicates that SARS-CoV-2 infection may contribute to long-term neurological sequelae, including amyotrophic lateral sclerosis-like and frontotemporal dementia-like features, as well as increased phosphorylated TDP-43 deposition in the central nervous system. Biomarker studies further support the link between TDP-43 dysregulation and neurological complications of long-term effects of COVID-19 (long COVID). In this review, we presented a novel integrative framework of TDP-43 pathology, bridging a gap between SARS-CoV-2 infection and mechanisms of neurodegeneration. These findings underscore the need for further research to clarify the TDP-43-related neurodegeneration underlying SARS-CoV-2 infection and to develop therapeutic strategies aimed at mitigating long-term neurological effects in patients with long COVID.

Olfactory dysfunction in COVID-19: pathology and long-term implications for brain health.

Manifestations and mechanisms of central nervous system damage caused by SARS-CoV-2

The interaction of the β-coronavirus severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) nucleocapsid (N) protein with genomic RNA is initiated by specific RNA regions and subsequently induces the formation of a continuous polymer with characteristic structural units for viral formation. We hypothesized that oligomeric RNAs, whose sequences are absent in the 29.9-kb genome sequence of SARS-CoV-2, might affect RNA-N protein interactions. We identified two such hexameric RNAs, In-1 (CCGGCG) and G6 (GGGGGG), and investigated their effects on the small filamentous/droplet-like structures (< a few μm) of N protein-genomic RNA formed by liquid-liquid phase separation. The small N protein structures were sequence-specifically enhanced by In-1, whereas G6 caused them to coalesce into large droplets. Moreover, we found that a guanosine 12-mer (G12, GGGGGGGGGGGG) expelled preexisting genomic RNA from the small N protein structures. The presence of G12 with the genomic RNA suppressed the formation of the small N protein structures, and alternatively apparently altered phase separation to induce the formation of large droplets with unclear phase boundaries. We showed that the N-terminal RNA-binding domain is required for the stability of the small N protein structures. Our results suggest that G12 may be a strong inhibitor of the RNA-N protein interaction.

Tightly packed complexes of nucleocapsid protein and genomic RNA form the core of viruses and assemble within viral factories, dynamic compartments formed within the host cells associated with human stress granules. Here, we test the possibility that the multivalent RNA‐binding nucleocapsid protein (N) from severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) condenses with RNA via liquid–liquid phase separation (LLPS) and that N protein can be recruited in phase‐separated forms of human RNA‐binding proteins associated with SG formation. Robust LLPS with RNA requires two intrinsically disordered regions (IDRs), the N‐terminal IDR and central‐linker IDR, as well as the folded C‐terminal oligomerization domain, while the folded N‐terminal domain and the C‐terminal IDR are not required. N protein phase separation is induced by addition of non‐specific RNA. In addition, N partitions in vitro into phase‐separated forms of full‐length human hnRNPs (TDP‐43, FUS, hnRNPA2) and their low‐complexity domains (LCs). These results provide a potential mechanism for the role of N in SARS‐CoV‐2 viral genome packing and in host‐protein co‐opting necessary for viral replication and infectivity.

Will bacille Calmette-Guerin immunization arrest the COVID-19 pandemic?

IntroductionAlzheimer’s disease (AD) is the most prevalent neurodegenerative disease in the world, but our understanding of causation is still lacking. A current evidence-based hypothesis proposes that certain infectious agents initiate the neurodegeneration consistent with AD. Two infectious agents correlated to AD pathogenesis are Chlamydia pneumoniae (Cpn), a respiratory obligate intracellular bacterium, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the coronavirus responsible for the COVID-19 pandemic. Both organisms may predispose susceptible populations to disease manifestations, such as AD.MethodsThis review focused on peer-reviewed original research and review articles evaluating the potential association of Cpn and SARS-CoV-2 with AD. Our focus included: genetic risk with expression of APOEε4 and other biomarkers common to AD including interleukin-6 (IL-6), chemokine ligand 2 (CCL2), neuropilin-1 (NRP1), and structural/functional aspects of the infectious processes and resultant neuroinflammation.ResultsBoth Cpn and SARS-CoV-2 may infect the neuroepithelium of the olfactory system to enter the brain. Cpn binds to heparan sulfate proteoglycans for entry into mucosal cells. SARS-CoV-2 infects epithelia after binding to ACE2 receptors. Once inside the neuroepithelium, the pathogens may traffic to the olfactory bulbs. NRP1, an abundant receptor in AD, also potentiates SARS-CoV-2 infection. Furthermore, both pathogens may enter the systemic circulation for eventual entry through the blood brain barrier. The SARS-CoV-2 spike protein, in conjunction with CCL2, co-stimulates macrophages, resulting in IL-6 cytokine release. Likewise, Cpn infection leads to an increase of CCL2 and IL-6 cytokine release. The primary infection of either organism may lead to chronically elevated levels of IL-6 and secondary infection(s). Additionally, host APOEε4 expression appears to increase susceptibility to Cpn and SARS-CoV-2 infections.DiscussionCpn and SARS-CoV-2 may enter the brain through olfactory neuroepithelial cells and/or through the blood brain barrier. SARS-CoV-2 utilizes specific receptors for infection, while Cpn utilizes binding of proteoglycans. Neuroinflammation may be an outcome of infection with one or both organisms as observed by increased levels of CCL2 and IL-6 leading to AD pathogenesis. Genetic risk is noted for infection with both organisms with expression of APOEε4. Ongoing and future studies will further dissect mechanisms of infection with SARS-CoV-2 and Cpn as they may inform on causation and diagnostic factors for AD.

Bioengineered self-assembled nanofibrils for high-affinity SARS-CoV-2 capture and neutralization

The pandemic of Coronavirus Disease 2019 (COVID-19) caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) continues, and SARS-CoV-2 variants continue to emerge. In addition to typical fever and respiratory symptoms, many patients with COVID-19 experience a variety of neurological complications. In this review, we analyzed and reviewed the current status and possible mechanisms between COVID-19 and several typical neurodegenerative diseases, particularly Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis, hoping to propose the potential direction of further research and concern. Electronic literature search of the databases (Medline/PubMed, Web of Science, and Google Scholar). The keywords used were COVID-19, SARS-CoV-2, neurodegenerative disease, Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. The retrieved relevant articles were reviewed and critically analyzed. SARS-CoV-2 is a highly neuroinvasive neurotropic virus that invades cells through angiotensin-converting enzyme 2 (ACE2) receptor-driven pathway. SARS-CoV-2 neuroinvasion, neuroinflammation, and blood-brain barrier (BBB) dysfunction may contribute to the pathogenesis of neurodegenerative diseases. Some patients with neurodegenerative diseases have already shown more susceptibility to SARS-CoV-2 infection and significantly higher mortality due to the elderly population with underlying diseases. Moreover, SARS-CoV-2 could cause damage to the central nervous system (CNS) that may substantially increase the incidence of neurodegenerative diseases and accelerate the progression of them.