The LDL receptor related protein 1 (LRP1) facilitates ACE2-mediated endocytosis of SARS-CoV2 spike protein-containing pseudovirions.

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, employs the viral spike (S) protein to associate with host cells. While angiotensin-converting enzyme 2 (ACE2) is a major receptor for the SARS-CoV-2 spike protein, evidence reveals that other cellular receptors may also contribute to viral entry. We interrogated the role of the low-density lipoprotein receptor-related protein 1 (LRP1) in the involvement of SARS-CoV-2 viral entry. Employing surface plasmon resonance studies, we demonstrated high affinity binding of the trimeric SARS-CoV-2 spike protein to purified LRP1. Further, we observed high affinity interaction of the SARS-CoV-2 spike protein with other low-density lipoprotein receptor (LDLR) family members as well, including LRP2 and the very low-density lipoprotein receptor (VLDLR). Binding of the SARS-CoV-2 spike protein to LRP1 was mediated by its receptor binding domain (RBD). Several LRP1 ligands require surface exposed lysine residues for their interaction with LRP1, and chemical modification of lysine residues on the RBD with sulfo-NHS-acetate ablated binding to LRP1. Using cellular model systems, we demonstrated that cells expressing LRP1, but not those lacking LRP1, rapidly internalized purified 125I-labeled S1 subunit of the SARS-CoV-2 spike protein. LRP1-mediated internalization of the 125I-labeled S1 subunit was enhanced in cells expressing ACE2. By employing pseudovirion particles containing a murine leukemia virus core and luciferase reporter that express the SARS-CoV-2 spike protein on their surface, we confirmed that LRP1 facilitates ACE2-mediated psuedovirion endocytosis. Together, these data implicate LRP1, and perhaps other LDLR family members as host factors for SARS-CoV-2 infection.