title: Transport of LAPTM5 to lysosomes requires association with the ubiquitin ligase Nedd4, but not LAPTM5 ubiquitination.
abstract: LAPTM5 is a lysosomal transmembrane protein expressed in immune cells. We show that LAPTM5 binds the ubiquitin-ligase Nedd4 and GGA3 to promote LAPTM5 sorting from the Golgi to the lysosome, an event that is independent of LAPTM5 ubiquitination. LAPTM5 contains three PY motifs (L/PPxY), which bind Nedd4-WW domains, and a ubiquitin-interacting motif (UIM) motif. The Nedd4-LAPTM5 complex recruits ubiquitinated GGA3, which binds the LAPTM5-UIM; this interaction does not require the GGA3-GAT domain. LAPTM5 mutated in its Nedd4-binding sites (PY motifs) or its UIM is retained in the Golgi, as is LAPTM5 expressed in cells in which Nedd4 or GGA3 is knocked-down with RNAi. However, ubiquitination-impaired LAPTM5 can still traffic to the lysosome, suggesting that Nedd4 binding to LAPTM5, not LAPTM5 ubiquitination, is required for targeting. Interestingly, Nedd4 is also able to ubiquitinate GGA3. These results demonstrate a novel mechanism by which the ubiquitin-ligase Nedd4, via interactions with GGA3 and cargo (LAPTM5), regulates cargo trafficking to the lysosome without requiring cargo ubiquitination.
authors.affiliation: Program in Cell Biology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada, M5G 1X8.
authors.forename: Youngshil
authors.initials: Y
authors.lastname: Pak
authors.forename: Wioletta K
authors.initials: WK
authors.lastname: Glowacka
authors.forename: M Christine
authors.initials: MC
authors.lastname: Bruce
authors.forename: Nam
authors.initials: N
authors.lastname: Pham
authors.forename: Daniela
authors.initials: D
authors.lastname: Rotin
mesh_terms: D020727:ADP-Ribosylation Factors / Q000737:chemistry; D033942:Adaptor Proteins, Vesicular Transport / Q000737:chemistry; D020816:Amino Acid Motifs; D000818:Animals; D003713:Dendritic Cells / Q000648:ultrastructure; D056827:Endosomal Sorting Complexes Required for Transport; D006056:Golgi Apparatus / Q000648:ultrastructure; D006801:Humans; D008247:Lysosomes / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D050505:Mutant Proteins / Q000737:chemistry; D000075702:Nedd4 Ubiquitin Protein Ligases; D011485:Protein Binding; D021381:Protein Transport; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D056827:Endosomal Sorting Complexes Required for Transport; C407306:GGA adaptor proteins; D008565:Membrane Proteins; D050505:Mutant Proteins; D025801:Ubiquitin; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases; D020727:ADP-Ribosylation Factors