Human coronavirus HKU1 recognition of the TMPRSS2 host receptor

Abstract

The human coronavirus HKU1 spike (S) glycoprotein engages host cell surface sialoglycans and transmembrane protease serine 2 (TMPRSS2) to initiate infection. The molecular basis of HKU1 binding to TMPRSS2 and determinants of host receptor tropism remain elusive. Here, we designed an active human TMPRSS2 construct enabling high-yield recombinant production in human cells of this key therapeutic target. We determined a cryo-electron microscopy structure of the HKU1 RBD bound to human TMPRSS2 providing a blueprint of the interactions supporting viral entry and explaining the specificity for TMPRSS2 among human type 2 transmembrane serine proteases. We found that human, rat, hamster and camel TMPRSS2 promote HKU1 S-mediated entry into cells and identified key residues governing host receptor usage. Our data show that serum antibodies targeting the HKU1 RBD TMPRSS2 binding-site are key for neutralization and that HKU1 uses conformational masking and glycan shielding to balance immune evasion and receptor engagement.

Structural basis of TMPRSS2 zymogen activation and recognition by the HKU1 seasonal coronavirus

“…This inhibition is further supported by the clashes observed between the HKU1B RBD and a nanobody that mimics an incoming substrate. Our results are in line with a recent report on the structure of HKU1A RBD complexed with cleaved TMPRSS2 and the inhibition of TMPRSS2 proteolytic activity by the HKU1A RBD 35…”

“…It is thus likely that the two HKU1 spikes similarly interact with TMPRSS2. The recent description by cryoEM of a TMPRSS2/ HKU1A RBD complex 35 , revealed a similar mode of interaction for both HKU1A and B. Secondly, we did not solve the structure of the whole spike in association with its receptor. We circumvented this problem by superposing the structure of the RBD in complex with TMPRSS2 to the known structure of the HKU1 spike in order to characterize the conformational changes observed in both the spike and its receptor during viral binding and fusion.…”

Engineering customized viral receptors for various coronaviruses

“…Efforts in the past decades have led to the identification of four widely acknowledged protein entry receptors for coronaviruses: ACE2, Aminopeptidase N (APN), Dipeptidyl peptidase-4 DPP4, and mCEACAM1a 2 . TMPRSS2 has also been recently reported as an entry receptor for human coronavirus HKU1 18,19 . ACE2 represents the most extensively studied receptor supporting entry of various coronaviruses, including NL63, SARS-CoV-1, SARS-CoV-2, and several clades of bat sarbecoviruses and merbecoviruses 16,20–22 .…”