The Host Interactome of Spike Expands the Tropism of SARS-CoV-2

The SARS-CoV-2 virus causes severe acute respiratory syndrome (COVID-19) and has rapidly created a global pandemic. Patients that survive may face a slow recovery with long lasting side effects that can afflict different organs. SARS-CoV-2 primarily infects epithelial airway cells that express the host entry receptor Angiotensin Converting Enzyme 2 (ACE2) which binds to spike protein trimers on the surface of SARS-CoV-2 virions. However, SARS-CoV-2 can spread to other tissues even though they are negative for ACE2. To gain insight into the molecular constituents that might influence SARS-CoV-2 tropism, we determined which additional host factors engage with the viral spike protein in disease-relevant human bronchial epithelial cells (16HBEo-). We found that spike recruited the extracellular proteins laminin and thrombospondin and was retained in the endoplasmatic reticulum (ER) by the proteins DJB11 and FBX2 which support re-folding or degradation of nascent proteins in the ER. Because emerging mutations of the spike protein potentially impact the virus tropism, we compared the interactome of D614 spike with that of the rapidly spreading G614 mutated spike. More D614 than G614 spike associated with the proteins UGGT1, calnexin, HSP7A and GRP78/BiP which ensure glycosylation and folding of proteins in the ER. In contrast to G614 spike, D614 spike was endoproteolytically cleaved, and the N-terminal S1 domain was degraded in the ER even though C-terminal S2 only proteoforms remained present. D614 spike also bound more laminin than G614 spike, which suggested that extracellular laminins may function as co-factor for an alternative, S2 only dependent virus entry. Because the host interactome determines whether an infection is productive, we developed a novel proteome-based cell type set enrichment analysis (pCtSEA). With pCtSEA we determined that the host interactome of the spike protein may extend the tropism of SARS-CoV-2 beyond mucous epithelia to several different cell types, including macrophages and epithelial cells in the nephron. An S2 only dependent, alternative infection of additional cell types with SARS-CoV-2 may impact vaccination strategies and may provide a molecular explanation for a severe or prolonged progression of disease in select COVID-19 patients.

The Role of Bile Acid Receptors in Chronic Inflammatory Diseases

With recent developments, biologic therapies has shown superior efficacy for rheumatic diseases compared with preexisting pharmacologic therapies, which are associated with high costs, non-response in certain patient groups, and severe adverse effects such as infections limiting their wide-spread use and revealing a need for the development of novel treatments. Since discovering the role of bile acid receptors in regulating inflammation, clinical trials evaluating the use of bile acid receptor agonists as a means to potentially treat various inflammatory disorders, such as alcoholic hepatitis, non-alcoholic steatohepatitis, primary biliary cirrhosis, primary sclerosing cholangitis have been ongoing. This review summarizes the results of studies on the anti-inflammatory effects and mechanisms of bile acid receptors and the results of previous to date looking at the use of bile acid receptor agonists in animal models of inflammatory disorders and clinical trials. Furthermore, we present the potentials of the bile acid receptor agonists in the treatment of inflammatory rheumatic diseases, including rheumatoid arthritis.

Gene Expression Profile in Patients with Axial Spondyloarthritis: Meta-analysis of Publicly Accessible Microarray Datasets

OBJECTIVE: To identify a gene expression signature in axial spondyloarthritis/ankylosing spondylitis (SpA/AS) and genomic pathways likely to be involved in pathogenesis of SpA/AS patients. METHODS: Four publicly accessible microarray studies from SpA/AS patients were integrated, and a transcriptomic and network-based meta-analysis was performed. This meta-analysis was compared with a published microarray study in whole blood of AS patients. RESULTS: According to our meta-analysis, 1,798 genes were differentially expressed in the whole blood of SpA/AS patients compared to healthy controls, while 674 genes were differentially expressed in the synovium of SpA/AS patients compared to healthy controls. When the whole blood meta-analysis data was compared with a published microarray study that also analyzed whole blood in SpA/AS patients, pathways involved in Toll-like receptor signaling, osteoclast differentiation, T cell receptor signaling and janus kinase–signal transducer and activator of transcription (Jak-STAT) signaling were often enriched in SpA/AS. On the other hand, eomesodermin, RUNX3, and interleukin-7 receptor (IL7R) were usually decreased in SpA/AS patients, suggesting that deficiency of these genes contributes to increased IL-17 production in AS. CONCLUSION: Several common enrichment pathways including Toll-like receptor signaling pathway, osteoclast differentiation, T cell receptor signaling pathway and Jak-STAT signaling pathway were identified in the differentially expressed genes of whole blood and synovium from SpA/AS patients, suggesting that these pathways are involved in the pathogenesis of SpA/AS.