Epsin 1 is a polyubiquitin-selective clathrin-associated sorting protein.
Epsin 1 engages several core components of the endocytic clathrin coat, yet the precise mode of operation of the protein remains controversial. The occurrence of tandem ubiquitin-interacting motifs (UIMs) suggests that epsin could recognize a ubiquitin internalization tag, but the association of epsin with clathrin-coat components or monoubiquitin is reported to be mutually exclusive. Here, we show that endogenous epsin 1 is clearly an integral component of clathrin coats forming at the cell surface and is essentially absent from caveolin-1-containing structures under normal conditions. The UIM region of epsin 1 associates directly with polyubiquitin chains but has extremely poor affinity for monoubiquitin. Polyubiquitin binding is retained when epsin synchronously associates with phosphoinositides, the AP-2 adaptor complex and clathrin. The enrichment of epsin within clathrin-coated vesicles purified from different tissue sources varies and correlates with sorting of multiubiquitinated cargo, and in cultured cells, polyubiquitin, rather than non-conjugable monoubiquitin, promotes rapid internalization. As epsin interacts with eps15, which also contains a UIM region that binds to polyubiquitin, epsin and eps15 appear to be central components of the vertebrate poly/multiubiquitin-sorting endocytic clathrin machinery.
Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
Matthew J
MJ
Hawryluk
Peter A
PA
Keyel
Sanjay K
SK
Mishra
Simon C
SC
Watkins
John E
JE
Heuser
Linton M
LM
Traub
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry / Q000235:genetics / Q000502:physiology* / Q000648:ultrastructure; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D022163:Clathrin-Coated Vesicles / Q000502:physiology* / Q000648:ultrastructure; D004705:Endocytosis; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D025821:Polyubiquitin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D002135:Calcium-Binding Proteins; C486206:EPS15 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C114154:epsin; D025821:Polyubiquitin; D004815:Epidermal Growth Factor; D005982:Glutathione Transferase