Lysosomal Proteases Are a Determinant of Coronavirus Tropism

Cell entry by coronaviruses involves two principal steps, receptor binding and membrane fusion; the latter requires activation by host proteases, particularly lysosomal proteases. Despite the importance of lysosomal proteases in both coronavirus entry and cell metabolism, the correlation between lysosomal proteases and cell tropism of coronaviruses has not been established. Here, we examined the roles of lysosomal proteases in activating coronavirus surface spike proteins for membrane fusion, using the spike proteins from severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) as the model system. To this end, we controlled the contributions from receptor binding and other host proteases, thereby attributing coronavirus entry solely or mainly to the efficiency of lysosomal proteases in activating coronavirus spike-mediated membrane fusion. Our results showed that lysosomal proteases from bat cells support coronavirus spike-mediated pseudovirus entry and cell-cell fusion more effectively than their counterparts from human cells. Moreover, purified lysosomal extracts from bat cells cleave cell surface-expressed coronavirus spikes more efficiently than their counterparts from human cells. Overall, our study suggests that different lysosomal protease activities from different host species and tissue cells are an important determinant of the species and tissue tropism of coronaviruses.IMPORTANCE Coronaviruses are capable of colonizing new species, as evidenced by the recent emergence of SARS and MERS coronaviruses; they can also infect multiple tissues in the same species. Lysosomal proteases play critical roles in coronavirus entry by cleaving coronavirus surface spike proteins and activating the fusion of host and viral membranes; they also play critical roles in cell physiology by processing cellular products. How do different lysosomal protease activities from different cells impact coronavirus entry? Here, we controlled the contributions from known factors that function in coronavirus entry so that lysosomal protease activities became the only or the main determinant of coronavirus entry. Using pseudovirus entry, cell-cell fusion, and biochemical assays, we showed that lysosomal proteases from bat cells activate coronavirus spike-mediated membrane fusion more efficiently than their counterparts from human cells. Our study provides the first direct evidence supporting lysosomal proteases as a determinant of the species and tissue tropisms of coronaviruses

Carbon sequestration assessment and analysis in the whole life cycle of seaweed

Methods for carbon sequestration are warranted to tackle climate change caused by greenhouse gases released from anthropogenic activities. Seaweed is a type of marine plant that utilizes carbon dioxide for photosynthesis and has a substantial capacity to sequestrate carbon. Despite the huge potential, the long-lasting carbon sequestration (LLCS) of seaweed has never been calculated throughout its whole life cycle (nursery, temporary rearing, maturation, harvesting, and processing). In this paper, we use a life cycle assessment (LCA) approach to calculate the LLCS of seaweed, which can be understood as the difference between carbon fixation and released carbon throughout the life cycle of seaweed. Using kelp ( Laminaria japonica ) as an example of seaweed, the present study validates the procedure of calculating the LLCS of seaweed throughout its whole life cycle in Ailian Bay from nursery to processing into biochar (fertilizer) as the final product. The results showed that the carbon sequestration (full life cycle) of kelp in Ailian Bay was 97.73 g C m ^−2 year. Biomass carbon accounts for approximately 86% of the total value (982.53 g C m ^−2 year) of carbon absorption source of kelp in Ailian Bay, with the remaining 14% consisting of recalcitrant dissolved organic carbon and sedimentary carbon. Moreover, we calculated the amount of biomass carbon that was sequestrated by seaweed production in China from 2010 to 2020. Thus, the present study demonstrates that the mass production of seaweed can be utilized as an efficient method to sequestrate carbon and a feasible method for evaluating the effect of kelp farms on climate change

Structure of mouse coronavirus spike protein complexed with receptor reveals mechanism for viral entry

Coronaviruses recognize a variety of receptors using different domains of their envelope-anchored spike protein. How these diverse receptor recognition patterns affect viral entry is unknown. Mouse hepatitis coronavirus (MHV) is the only known coronavirus that uses the N-terminal domain (NTD) of its spike to recognize a protein receptor, CEACAM1a. Here we determined the cryo-EM structure of MHV spike complexed with mouse CEACAM1a. The trimeric spike contains three receptor-binding S1 heads sitting on top of a trimeric membrane-fusion S2 stalk. Three receptor molecules bind to the sides of the spike trimer, where three NTDs are located. Receptor binding induces structural changes in the spike, weakening the interactions between S1 and S2. Using protease sensitivity and negative-stain EM analyses, we further showed that after protease treatment of the spike, receptor binding facilitated the dissociation of S1 from S2, allowing S2 to transition from pre-fusion to post-fusion conformation. Together these results reveal a new role of receptor binding in MHV entry: in addition to its well-characterized role in viral attachment to host cells, receptor binding also induces the conformational change of the spike and hence the fusion of viral and host membranes. Our study provides new mechanistic insight into coronavirus entry and highlights the diverse entry mechanisms used by different viruses

Potential of lncRNAs to regulate cuproptosis in hepatocellular carcinoma: Establishment and validation of a novel risk model

Cuproptosis, a distinct form of programmed cell death, is an emerging field in oncology with promising implications. This novel mode of cell death has the potential to become a regulatory target for tumor therapy, thus expanding the currently limited treatment options available for patients with cancer. Our research team focused on investigating the role of functional long non-coding RNA (lncRNAs) in hepatocellular carcinoma (HCC). We were particularly intrigued by the potential implications of HCC-lncRNAs on cuproptosis. Through a comprehensive analysis, we identified three cuproptosis-related lncRNAs (CRLs): AC018690.1, AL050341.2, and LINC02038. These lncRNAs were found to influence the sensitivity of HCC to cuproptosis. Based on our results, we constructed a risk model represented by the equation: risk score = 0.82 * AC018690.1 + 0.65 * AL050341.2 + 0.61 * LINC02038. Notably, significant disparities were observed in clinical features, such as the response rate to immunotherapy and targeted therapy, as well as in cellular characteristics, including the composition of the tumor immune microenvironment (TIME), when comparing the high- and low-risk groups. Most importantly, knockdown of these CRLs was confirmed to significantly weaken the resistance to cuproptosis in HCC. This effect resulted from the accelerated accumulation of lipoacylated-DLAT and lipoacylated-DLST. In summary, we identified three CRLs in HCC and established a novel risk model with potential clinical applications. Additionally, we proposed a potential therapeutic method consisting of sorafenib-copper ionophores-immunotherapy

Global trends in research of mitophagy in liver diseases over past two decades: A bibliometric analysis

Increasing evidence indicated that mitophagy might play a crucial role in the occurrence and progression of liver diseases. In order to enhance our understanding of the intricate relationship between mitophagy and liver diseases, a comprehensive bibliometric analysis of the existing literature in this field was conducted. This analysis aimed to identify key trends, potential areas of future research, and forecast the development of this specific field. We systematically searched the Web of Science Core Collection (WoSCC) for publications related to mitophagy in liver diseases from 2000 to 2022. We conducted the bibliometric analysis and data visualization through VOSviewer and CiteSpace. The analysis of publication growth revealed a substantial increase in articles published in this field over the past years, indicating mitophagy's growing interest and significance in liver diseases. China and USA emerged as the leading contributors in the number of papers, with 294 and 194 independent papers, respectively. Exploring the mechanism of mitophagy in the initiation and procession of liver diseases was the main content of studies in this field, and Parkin-independent mediated mitophagy has attracted much attention recently. “Lipid metabolism,” “cell death,” “liver fibrosis” and “oxidative stress” were the primary keywords clusters. Additionally, “nlrp3 inflammasome”, “toxicity” and “nonalcoholic steatohepatitis” were emerging research hotspots in this area and have the potential to continue to be focal areas of investigation in the future. This study represents the first systematic bibliometric analysis of research on mitophagy in liver diseases conducted over the past 20 years. By providing an overview of the existing literature and identifying current research trends, this analysis sheds light on the critical areas of investigation and paves the way for future studies in this field

Ultrasound Flow Imaging Study on Rat Brain with Ultrasound and Light Stimulations

Functional ultrasound (fUS) flow imaging provides a non-invasive method for the in vivo study of cerebral blood flow and neural activity. This study used functional flow imaging to investigate rat brain’s response to ultrasound and colored-light stimuli. Male Long-Evan rats were exposed to direct full-field strobe flashes light and ultrasound stimulation to their retinas, while brain activity was measured using high-frequency ultrasound imaging. Our study found that light stimuli, particularly blue light, elicited strong responses in the visual cortex and lateral geniculate nucleus (LGN), as evidenced by changes in cerebral blood volume (CBV). In contrast, ultrasound stimulation elicited responses undetectable with fUS flow imaging, although these were observable when directly measuring the brain’s electrical signals. These findings suggest that fUS flow imaging can effectively differentiate neural responses to visual stimuli, with potential applications in understanding visual processing and developing new diagnostic tools