A single motif responsible for ubiquitin recognition and monoubiquitination in endocytic proteins.
Ubiquitination is a post-translation modification in which ubiquitin chains or single ubiquitin molecules are appended to target proteins, giving rise to poly- or monoubiquitination, respectively. Polyubiquitination targets proteins for destruction by the proteasome. The role of monoubiquitination is less understood, although a function in membrane trafficking is emerging, at least in yeast. Here we report that a short amino-acid stretch at the carboxy-termini of the monoubiquitinated endocytic proteins Eps15 and eps15R is indispensable for their monoubiquitination. A similar sequence, also required for this modification, is found in other cytosolic endocytic proteins, such as epsins and Hrs. These sequences comprise a protein motif, UIM (ref. 6), which has been proposed to bind to ubiquitin. We confirm this for the UIMs of eps15, eps15R, epsins and Hrs. Thus, the same motif in several endocytic proteins is responsible for ubiquitin recognition and monoubiquitination. Our results predict the existence of a UIM:ubiquitin-based intracellular network. Eps15/eps15R, epsins and Hrs may function as adaptors between ubiquitinated membrane cargo and either the clathrin coat or other endocytic scaffolds. In addition, through their own ubiquitination, they may further contribute to the amplification of this network in the endocytic pathway.
Polo
Simona
S
Department of Experimental Oncology, European Institute of Oncology, Via Ripamonti 435, 20141, Milan, Italy.
Sigismund
Sara
S
Faretta
Mario
M
Guidi
Monica
M
Capua
Maria Rosaria
MR
Bossi
Giovanna
G
Chen
Hong
H
De Camilli
Pietro
P
Di Fiore
Pier Paolo
PP
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008025:Ligases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D017386:Sequence Homology, Amino Acid; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D033921:Vesicular Transport Proteins
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; C486206:EPS15 protein, human; D056827:Endosomal Sorting Complexes Required for Transport; C082729:Eps15 protein, mouse; C094318:Eps15-rs protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D010750:Phosphoproteins; D025801:Ubiquitin; D033921:Vesicular Transport Proteins; C114154:epsin; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; D044767:Ubiquitin-Protein Ligases; D008025:Ligases