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

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.