title: Cargo and dynamin regulate clathrin-coated pit maturation.
abstract: Total internal reflection fluorescence microscopy (TIR-FM) has become a powerful tool for studying clathrin-mediated endocytosis. However, due to difficulties in tracking and quantifying their heterogeneous dynamic behavior, detailed analyses have been restricted to a limited number of selected clathrin-coated pits (CCPs). To identify intermediates in the formation of clathrin-coated vesicles and factors that regulate progression through these stages, we used particle-tracking software and statistical methods to establish an unbiased and complete inventory of all visible CCP trajectories. We identified three dynamically distinct CCP subpopulations: two short-lived subpopulations corresponding to aborted intermediates, and one longer-lived productive subpopulation. In a manner dependent on AP2 adaptor complexes, increasing cargo concentration significantly enhances the maturation efficiency of productive CCPs, but has only minor effects on their lifetimes. In contrast, small interfering RNA (siRNA) depletion of dynamin-2 GTPase and reintroduction of wild-type or mutant dynamin-1 revealed dynamin's role in controlling the turnover of abortive intermediates and the rate of CCP maturation. From these data, we infer the existence of an endocytic restriction or checkpoint, responsive to cargo and regulated by dynamin.
authors.affiliation: Department of Cell Biology, The Scripps Research Institute, La Jolla, CA, USA.
authors.forename: Dinah
authors.initials: D
authors.lastname: Loerke
authors.forename: Marcel
authors.initials: M
authors.lastname: Mettlen
authors.forename: Defne
authors.initials: D
authors.lastname: Yarar
authors.forename: Khuloud
authors.initials: K
authors.lastname: Jaqaman
authors.forename: Henry
authors.initials: H
authors.lastname: Jaqaman
authors.forename: Gaudenz
authors.initials: G
authors.lastname: Danuser
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Schmid
mesh_terms: D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002966:Clathrin / Q000235:genetics / Q000378:metabolism*; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism*; D034281:Dynamins / Q000235:genetics / Q000378:metabolism*; D004705:Endocytosis; D008856:Microscopy, Fluorescence / Q000379:methods; D051381:Rats
chemical_list: D002352:Carrier Proteins; D002966:Clathrin; D034281:Dynamins