Gene expression andin situprotein profiling of candidate SARS-CoV-2 receptors in human airway epithelial cells and lung tissue

Abstract

In December 2019, SARS-CoV-2 emerged causing the COVID-19 pandemic. SARS-CoV, the agent responsible for the 2003 SARS outbreak, utilises ACE2 and TMPRSS2 host molecules for viral entry. ACE2 and TMPRSS2 have recently been implicated in SARS-CoV-2 viral infection. Additional host molecules including ADAM17, cathepsin L, CD147, and GRP78 may also function as receptors for SARS-CoV-2.To determine the expression and in situ localisation of candidate SARS-CoV-2 receptors in the respiratory mucosa, we analysed gene expression datasets from airway epithelial cells of 515 healthy subjects, gene promoter activity analysis using the FANTOM5 dataset containing 120 distinct sample types, single cell RNA sequencing (scRNAseq) of 10 healthy subjects, proteomic datasets, immunoblots on multiple airway epithelial cell types, and immunohistochemistry on 98 human lung samples.We demonstrate absent to low ACE2 promoter activity in a variety of lung epithelial cell samples and low ACE2 gene expression in both microarray and scRNAseq datasets of epithelial cell populations. Consistent with gene expression, rare ACE2 protein expression was observed in the airway epithelium and alveoli of human lung, confirmed with proteomics. We present confirmatory evidence for the presence of TMPRSS2, CD147, and GRP78 protein in vitro in airway epithelial cells and confirm broad in situ protein expression of CD147 and GRP78 in the respiratory mucosa.Collectively, our data suggest the presence of a mechanism dynamically regulating ACE2 expression in human lung, perhaps in periods of SARS-CoV-2 infection, and also suggest that alternate receptors for SARS-CoV-2 exist to facilitate initial host cell infection.

Paradoxical effects of cigarette smoke and COPD on SARS-CoV2 infection and disease

“…Zhang et al 6 assessed the ACE2 gene expression in NS and smokers. Consistently with theirs and others' findings 5,6,10 , we found ACE2 expression to be higher in central airways. While Zhang et al did not include COPD patients in their analyses, Cai et al 5 and Smith et al 9 analyzed several datasets of gene expression of COPD and control small and large airway epithelium samples, concluding that ever-smoking was the main factor associated with high ACE2 levels;…”

“…ACE2 expression is highest in the conducting airways, waning in the more distal bronchiolar and alveolar lung regions 3 . There have been mixed reports on the effect of CS and COPD on SARS-CoV-2 infection 4 , with most studies showing an up-regulation of ACE2 in clinical and experimental models of smoke-induced lung disease [5][6][7][8][9][10] . In this study, we evaluated: 1) ACE2 and TMPRSS2 expression in the airways of smokers with COPD, compared to smoker and never smoker (NS) controls, and 2) ACE2 expression in lungs of mice acutely and chronically exposed to CS; and 3) the effect of CS on SARS-CoV2 infection of bronchial epithelial cells in vitro.…”

Of Mice and Men: The Coronavirus MHV and Mouse Models as a Translational Approach to Understand SARS-CoV-2

“…This mode of infection may contribute to vascular pathology and thrombosis in COVID-19 patients [85,86]. Also, two other proteins CD147 and GRP78 were recently reported to aid in cell entry in the respiratory mucosa [87].…”

What’s Testosterone Got to Do with It? A Critical Assessment of the Contribution of Testosterone to Gender Disparities in COVID-19 Infections and Deaths

“…[18][19][20][21][22][23][41][42][43] However, multiple studies have shown no differences between males and females in ACE2 and TMPRSS2 mRNA or protein expression in human or murine lung tissue, indicating that T is unlikely to upregulate these gene products in lung, [44][45][46][47][48][49] using a microarray gene expression data set generated from bronchial brushings of 504 healthy subjects reported that gender did not correlate with gene expression of any candidate host molecule involved in COVID-19 infection, and that ACE2 and TMPRSS2 were the lowest expressed genes of interest among those examined. 49 The authors suggested that alternative mechanisms in the respiratory mucosa may become important during COVID-19 infection, perhaps including other coreceptors. Similarly, Asselta et al 50 found no significant evidence that ACE2 or TMPRSS2 are associated with disease severity/gender disparity in the Italian population.…”