LRRC15 mediates an accessory interaction with the SARS-CoV-2 spike protein.
The interactions between Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and human host factors enable the virus to propagate infections that lead to Coronavirus Disease 2019 (COVID-19). The spike protein is the largest structural component of the virus and mediates interactions essential for infection, including with the primary angiotensin-converting enzyme 2 (ACE2) receptor. We performed two independent cell-based systematic screens to determine whether there are additional proteins by which the spike protein of SARS-CoV-2 can interact with human cells. We discovered that in addition to ACE2, expression of LRRC15 also causes spike protein binding. This interaction is distinct from other known spike attachment mechanisms such as heparan sulfates or lectin receptors. Measurements of orthologous coronavirus spike proteins implied the interaction was functionally restricted to SARS-CoV-2 by accessibility. We localized the interaction to the C-terminus of the S1 domain and showed that LRRC15 shares recognition of the ACE2 receptor binding domain. From analyzing proteomics and single-cell transcriptomics, we identify LRRC15 expression as being common in human lung vasculature cells and fibroblasts. Levels of LRRC15 were greatly elevated by inflammatory signals in the lungs of COVID-19 patients. Although infection assays demonstrated that LRRC15 alone is not sufficient to permit viral entry, we present evidence that it can modulate infection of human cells. This unexpected interaction merits further investigation to determine how SARS-CoV-2 exploits host LRRC15 and whether it could account for any of the distinctive features of COVID-19.
Acknowledgements: An RPE-1 cell line expressing dCas9-SunTag10x_v4-P2A-mCherry and scFv-GCN4-GFP-VP64 was provided by Marvin Tanenbaum and Jonathan Weissman. pCCI-4K-SARS-CoV-2-ZsGreen was a gift from Sam Wilson, University of Glasgow. The viral isolate SARS-CoV-2/human/Liverpool/REMRQ0001/2020 was a gift from Ian Goodfellow, University of Cambridge. FACS experiments were enabled by Dr. Anna Petrunkina Harrison, and Arrayscan experiments were enabled by Veronika Romashova at the JCBC FACS core facilities. Thanks to Liane Dupont and Zheng-Shan Chong for useful advice on the design of CRISPRa screens.
Funder: Addenbrooke’s Charitable Trust, Cambridge University Hospitals; funder-id: http://dx.doi.org/10.13039/501100002927
Funder: NIHR Cambridge Biomedical Research Centre; funder-id: http://dx.doi.org/10.13039/501100018956
Funder: NIHR Cambridge Biomedical Research Centre
Wellcome Trust (210688/Z/18/Z)
Wellcome Trust (215477/Z/19/Z)
MRC (via University of Birmingham) (MR/V028448/1)