title: Rab5 and Ndfip1 are involved in Pten ubiquitination and nuclear trafficking.
abstract: The spatial regulation of Pten is critical for its role as a tumour suppressor with both nuclear and cytoplasmic locations being implicated with distinct functions. In the cytoplasm, Pten plays a central role in opposing PI3K/Akt cell signalling, whereas in the nucleus, Pten is important for maintaining genome stability and enhancing the tumour suppressor activity of APC-CDH1. Despite this diversity in protein function at different subcellular locations, there is limited knowledge on how Pten is able to find different cellular niches. Here, we report that Rab5 GTPase is required for efficient trafficking and ubiquitination of Pten on endosomes inside the cytosol. Using bimolecular fluorescence complementation (BiFC) for imaging protein interactions, we observed that ubiquitinated Pten is localized to peri-nuclear and nuclear regions of the cell. Nuclear trafficking of Pten required both Rab5 as well as the E3 ligase adaptor protein Ndfip1. Rab5 colocalization with Pten was observed on endosomes and expression of a dominant negative form of Rab5 significantly reduced Pten ubiquitination and nuclear trafficking. Genomic deletion of Ndfip1 abrogated nuclear trafficking of ubiquitinated Pten, even in the presence of Rab5. Our findings show that endosomal trafficking and ubiquitination are important mechanisms for the subcellular distribution of Pten.
authors.affiliation: Brain Development and Regeneration Division, Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Victoria, 3010, Australia.
authors.forename: Yijia
authors.initials: Y
authors.lastname: Li
authors.forename: Ley-Hian
authors.initials: LH
authors.lastname: Low
authors.forename: Ulrich
authors.initials: U
authors.lastname: Putz
authors.forename: Choo-Peng
authors.initials: CP
authors.lastname: Goh
authors.forename: Seong-Seng
authors.initials: SS
authors.lastname: Tan
authors.forename: Jason
authors.initials: J
authors.lastname: Howitt
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D011992:Endosomes / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D021381:Protein Transport; D054875:Ubiquitination; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C499188:Ndfip1 protein, mouse; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse; D020696:rab5 GTP-Binding Proteins
keywords: BiFC; cancer; endosome; ubiquitin; ubiquitin ligase; vesicular trafficking