title: Clathrin-mediated endocytosis in AP-2-depleted cells.
abstract: We have used RNA interference to knock down the AP-2 mu2 subunit and clathrin heavy chain to undetectable levels in HeLaM cells. Clathrin-coated pits associated with the plasma membrane were still present in the AP-2-depleted cells, but they were 12-fold less abundant than in control cells. No clathrin-coated pits or vesicles could be detected in the clathrin-depleted cells, and post-Golgi membrane compartments were swollen. Receptor-mediated endocytosis of transferrin was severely inhibited in both clathrin- and AP-2-depleted cells. Endocytosis of EGF, and of an LDL receptor chimera, were also inhibited in the clathrin-depleted cells; however, both were internalized as efficiently in the AP-2-depleted cells as in control cells. These results indicate that AP-2 is not essential for clathrin-coated vesicle formation at the plasma membrane, but that it is one of several endocytic adaptors required for the uptake of certain cargo proteins including the transferrin receptor. Uptake of the EGF and LDL receptors may be facilitated by alternative adaptors.
authors.affiliation: University of Cambridge, Department of Clinical Biochemistry, Cambridge Institute for Medical Research, Cambridge CB2 2XY, UK.
authors.forename: Alison
authors.initials: A
authors.lastname: Motley
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Bright
authors.forename: Matthew N J
authors.initials: MN
authors.lastname: Seaman
authors.forename: Margaret S
authors.initials: MS
authors.lastname: Robinson
mesh_terms: D033962:Adaptor Protein Complex 2 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002966:Clathrin / Q000235:genetics / Q000378:metabolism*; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D003034:Coated Pits, Cell-Membrane / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D066246:ErbB Receptors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D011973:Receptors, LDL / Q000378:metabolism; D011990:Receptors, Transferrin / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism
chemical_list: D033962:Adaptor Protein Complex 2; D002966:Clathrin; D021122:Protein Subunits; D034741:RNA, Small Interfering; D011973:Receptors, LDL; D011990:Receptors, Transferrin; D014168:Transferrin; D066246:ErbB Receptors