SIT1 transporter as a potential novel target in treatment of COVID-19

Applications of the Microscale Thermophoresis Binding Assay in COVID-19 Research

As the COVID-19 pandemic progresses, new variants of SARS-CoV-2 continue to emerge. This underscores the need to develop optimized tools to study such variants, along with new coronaviruses that may arise in the future. Such tools will also be instrumental in the development of new antiviral drugs. Here, we introduce microscale thermophoresis (MST) as a reliable and versatile tool for coronavirus research, which we demonstrate through three different applications described in this report: (1) binding of the SARS-CoV-2 spike receptor binding domain (RBD) to peptides as a strategy to prevent virus entry, (2) binding of the RBD to the viral receptor ACE2, and (3) binding of the RBD to ACE2 in complex with the amino acid transporter SLC6A20/SIT1 or its allelic variant rs61731475 (p.Ile529Val). Our results demonstrate that MST is a highly precise approach to studying protein-protein and/or protein-ligand interactions in coronavirus research, making it an ideal tool for studying viral variants and developing antiviral agents. Moreover, as shown in our results, a unique advantage of the MST assay over other available binding assays is the ability to measure interactions with membrane proteins in their near-native plasma membrane environment.

Pan-Cancer Analysis of the COVID-19 Causal Gene SLC6A20

Genome-wide association studies demonstrated that the chromosome 3p31.21 locus was linked to the severity of COVID-19 disease. The SLC6A20 gene was reported to be one of the critical causal genes regulated by this locus. Various studies focused on demonstrating the severity of COVID-19 in cancer patients and reported that elevated SARS-CoV-2-associated gene expression might contribute to increased susceptibility for COVID-19 in cancer patients. Given that pan-cancer association for the COVID-19 causal gene SLC6A20 is lacking, we aimed to perform systematic profiling of SLC6A20 in different malignancies. Human Protein Atlas, UALCAN, and Hepatocellular Carcinoma (HCCDB) databases were used to assess SLC6A20 gene expression changes in The Cancer Genome Atlas samples with respect to their normal counterparts. GEPIA and TIMER2.0 databases were used to determine the correlation between SLC6A20 and COVID-19-associated genes. Different databases were used for identification of the correlation of SCL6A20 with infiltrating immune cells. The canSAR database was utilized to determine the association of SCL6A20 with immune profiling in different malignancies. The STRING database was utilized to determine the protein network interacting with SLC6A20. Here, we showed SLC6A20 mRNA expression in pan-cancer samples and their normal counterparts. Increased SCL6A20 expression was associated with tumor grade, and there was a positive correlation with SARS-CoV-2-associated genes. Furthermore, SLC6A20 expression was positively correlated with infiltrating neutrophils and immune-related signatures. Lastly, SLC6A20 expression was found to be associated with the angiotensin converting enzyme 2 homologue, TMEM27, suggesting a potential link between SLC6A20 and COVID-19. Taken together, these results suggest that elevated SLC6A20 levels might be partly responsible for increased susceptibility of cancer patients to COVID-19 disease. Therapeutic intervention strategies against SLC6A20 in cancer patients, alongside other treatment modalities, might offer a benefit in delaying COVID-19 disease.

Host Genetic Variants Linked to COVID-19 Neurological Complications and Susceptibility in Young Adults-A Preliminary Analysis

To date, multiple efforts have been made to use genome-wide association studies (GWAS) to untangle the genetic basis for SARS-CoV-2 infection susceptibility and severe COVID-19. However, data on the genetic-related effects of SARS-CoV-2 infection on the presence of accompanying and long-term post-COVID-19 neurological symptoms in younger individuals remain absent. We aimed to examine the possible association between SNPs found in a GWAS of COVID-19 outcomes and three phenotypes: SARS-CoV-2 infection, neurological complications during disease progression, and long-term neurological complications in young adults with a mild-to-moderate disease course. University students (N = 336, age 18-25 years, European ancestry) with or without COVID-19 and neurological symptoms in anamnesis comprised the study sample. Logistic regression was performed with COVID-19-related phenotypes as outcomes, and the top 25 SNPs from GWAS meta-analyses and an MR study linking COVID-19 and cognitive deficits were found. We replicated previously reported associations of the FURIN and SLC6A20 gene variants (OR = 2.36, 95% CI 1.31-4.24) and OR = 1.94, 95% CI 1.08-3.49, respectively) and remaining neurological complications (OR = 2.12, 95% CI 1.10-4.35 for SLC6A20), while NR1H2 (OR = 2.99, 95% CI 1.39-6.69) and TMPRSS2 (OR = 2.03, 95% CI 1.19-3.50) SNPs were associated with neurological symptoms accompanying COVID-19. Our findings indicate that genetic variants related to a severe COVID-19 course in adults may contribute to the occurrence of neurological repercussions in individuals at a young age.

Intrinsic Exercise Capacity Affects Glycine and Angiotensin-Converting Enzyme 2 (ACE2) Levels in Sedentary and Exercise Trained Rats

Angiotensin-converting enzyme 2 (ACE2) has been identified as the cellular entry receptor for the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). High ACE2 tissue expression and low glycine levels were suggested to increase susceptibility for SARS-CoV-2 infection and increasing circulating ACE2 has been proposed as one possible strategy to combat COVID-19. In humans, aerobic physical exercise induces an increase in plasma ACE2 in some individuals. However, it is not clear whether glycine and ACE2 levels depend on intrinsic exercise capacity or on exercise training. We used rats selectively bred for high intrinsic exercise capacity (HCR) or low exercise capacity (LCR) and tested the influence of this genetic predetermination and/or aerobic exercise on metabolites, ACE2 tissue expression and circulating ACE 2. ACE2 expression was measured in different tissues in the sedentary animals and again after 4 weeks of high-intensity aerobic exercise in both LCRs and HCRs. Sedentary HCRs exhibited significantly higher circulating ACE2 concentrations compared to LCRs, but a lower expression of ACE2 in all investigated tissues except for adipose tissue. Body weight was negatively correlated with serum ACE2 and positively correlated with ACE2 expression in the heart. Aerobic exercise caused a significant decrease in ACE2 expression in the lung, heart, muscle, and kidney both in LCRs and HCRs. Our results suggest that ACE2 expression, circulating ACE2 and glycine serum concentration are related to aerobic intrinsic exercise capacity and can be influenced with exercise. These results may support the hypothesis that physically fit individuals have a lower susceptibility for COVID-19 infection.