Dynamic early recruitment of GAK-Hsc70 regulates coated pit maturation

GAK and its chaperone protein, Hsc70, are known to be recruited to clathrin-coated vesicles (CCVs) to mediate clathrin uncoating. Previous studies have proposed that early recruitment ofGAK–Hsc70 to CCPs could function to remodel nascent flat clathrin lattices, replacing hexagonswith pentagons and introducing curvature into the assembling polymeric coat. However, there areconflicting views, and direct functional evidence is lacking. Here, we show that GAK knockdown inhibits CCP stabilization and invagination, increasing the percentage of abortive pits. A detailed domain-specific mutational analysis of GAK pinpointed the importance of J domain–Hsc70 interactions in regulating these crucial early steps of CME. These findings support a hypothesis that GAK–Hsc70 promotes turnover of clathrin at nascent CCPs required for curvaturedevelopment.