title: Clathrin-independent endocytosis of ubiquitinated cargos.
abstract: Plasma membrane receptors can be endocytosed through clathrin-dependent and clathrin-independent pathways. Here, we show that the epidermal growth factor (EGF) receptor (EGFR), when stimulated with low doses of EGF, is internalized almost exclusively through the clathrin pathway, and it is not ubiquitinated. At higher concentrations of ligand, however, a substantial fraction of the receptor is endocytosed through a clathrin-independent, lipid raft-dependent route, as the receptor becomes ubiquitinated. An ubiquitination-impaired EGFR mutant was internalized through the clathrin pathway, whereas an EGFR/ubiquitin chimera, that can signal solely through its ubiquitin (Ub) moiety, was internalized exclusively by the non-clathrin pathway. Non-clathrin internalization of ubiquitinated EGFR depends on its interaction with proteins harboring the Ub-interacting motif, as shown through the ablation of three Ub-interacting motif-containing proteins, eps15, eps15R, and epsin. Thus, eps15s and epsin perform an important function in coupling ubiquitinated cargo to clathrin-independent internalization.
authors.affiliation: Istituto FIRC di Oncologia Molecolare, Via Adamello 16, 20139 Milan, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Sigismund
authors.forename: Tanja
authors.initials: T
authors.lastname: Woelk
authors.forename: Claudia
authors.initials: C
authors.lastname: Puri
authors.forename: Elena
authors.initials: E
authors.lastname: Maspero
authors.forename: Carlo
authors.initials: C
authors.lastname: Tacchetti
authors.forename: Pietro
authors.initials: P
authors.lastname: Transidico
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Di Fiore
authors.forename: Simona
authors.initials: S
authors.lastname: Polo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D016466:CHO Cells; D002135:Calcium-Binding Proteins / Q000502:physiology; D002966:Clathrin / Q000502:physiology*; D006224:Cricetinae; D004705:Endocytosis; D066246:ErbB Receptors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002135:Calcium-Binding Proteins; D002966:Clathrin; C486206:EPS15 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D025801:Ubiquitin; D066246:ErbB Receptors