Fig. 3: E protein activates platelets.

Washed human platelets from healthy donors were incubated with the SARS-CoV-2 E protein (0.5, 1, 2 μg/ml) or the SARS-CoV-2 S protein (1, 2, 4 μg/ml) for 5 min at 37 °C as a pretreatment step. a Aggregation of pretreated platelets was measured in response to ADP (10 μM) (n = 4). Both the E protein and the S protein enhanced platelet aggregation in a dose-dependent manner. The E protein exhibited a stronger ability to enhance platelet aggregation than S protein. b and c The E protein dose-dependently promoted platelet P-selectin exposure and integrin αIIbβ3 activation. P-selectin exposure and fibrinogen (Fg) binding in pretreated platelets with or without stimulation of 0.05U/ml thrombin were detected by flow cytometry (n = 4). d Pretreated platelets were allowed to spread on immobilized Fg at 37 °C for 20, 40, and 60 min. Area (pixel numbers) of 3 random fields of spreading platelets were quantified (n = 4). e The E protein concentration-dependently accelerated clot retraction. Pretreated platelets were added into platelet-free plasma, and then clot retraction was induced by 1 U/ml thrombin (n = 4). Quantification of clot retraction at 20, 40, and 60 min, respectively. Data were analyzed by 1-way ANOVA with Tukey multiple-comparisons test (a–c) or 2-way ANOVA with Tukey multiple-comparisons test (d and e). Data are presented as mean ± SEM. Source data are provided as a Source Data file.