Fig. 5

ApoE interacts with ACE2 and the spike protein in an isoform-independent manner. A Representative images of individual immunofluorescence staining of ApoE and ACE2 interaction tested by Duolink PLA in HEK-293 T cells after 48 h of cotransfected by Myc-tagged ACE2 and 3 × Flag-tagged ApoE. The red particles (ApoE/ACE2 interaction) represent their interaction. DAPI as a nuclear marker. Scale bar: 5 μm. B Plasmids carrying Myc-tagged ACE2 and 3 × Flag-tagged ApoE (ApoE2, ApoE3 or ApoE4) were transiently cotransfected into HEK-293 T cells. After 48 h of transfection, the cell lysates were immunoprecipitated with anti-Myc antibody and subsequently immunoblotted with anti-Myc and anti-Flag antibodies. The data are presented as the mean ± SD, *P < 0.05, **P < 0.01, ***P < 0.001. C Schematic of the working principles of the BLI assay, which include loading, binding and dissociation. The binding affinities of ApoE and ACE2 were determined through BLI experiments. D The sensor surfaces were immersed in a solution of human ACE2 protein (20 µg/ml), and functionalized sensorgrams were captured upon incubation with human ApoE2, ApoE3, and ApoE4 at 735.3 (blue), 1471 (red), 2941 (light blue), and 5882 nM (green) (binding phase); then, the sensors were immersed in washing buffer (dissociation phase). E The binding affinities of ApoE and the SARS-CoV-2 RBD were determined through BLI experiments. The sensors were immersed in a solution of SARS-CoV-2 RBD (20 µg/ml), and functionalized sensorgrams were captured upon incubation with ApoE2, ApoE3, and ApoE4 at 367.6 (green), 735.3 (yellow), 1471 (light blue), 2941 (brown), and 5882 nM (blue); then, the sensors were immersed in washing buffer (dissociation phase)