Figure 4: Antibodies penetrate SK-N-SH cells via clathrin-mediated endocytosis. A. Addition of Pitstop2 reagent prevented clathrin-mediated endocytosis of both anti-hnRNP A1 and IgG into SK-N-SH cells. Addition of nystatin did not block penetration. B. Clathrin immunoprecipitation on agarose A-linked anti-hnRNPA1 and control IgG. L=SK-N-SH cell lysate. B=Agarose A beads, IgG=control IgG attached to agarose A beads, A1=anti-hnRNPA1 antibodies attached to agarose A beads. Both control IgG and anti-hnRNP A1 antibodies bound clathrin, confirming the observation by immunocytochemistry in figure 4A.