CASK and infection: Importantly, siRNA-mediated knockdown of TJP1, CD63, 14-3-3 β, SUMO1 or GLUT4 reduced the infectivity of HCV by more than 50%, whereas knocking down either of the other two proteins (integrin β1 and CASK) did not affect infection of HCV JFH1 5A-Rluc [42] (Figure 4B).