title: The ubiquitin ligase RNF126 regulates the retrograde sorting of the cation-independent mannose 6-phosphate receptor.
abstract: The ubiquitin proteasome system is central to the regulation of a number of intracellular sorting pathways in mammalian cells including quality control at the endoplasmic reticulum and the internalization and endosomal sorting of cell surface receptors. Here we describe that RNF126, an E3 ubiquitin ligase, is involved in the sorting of the cation-independent mannose 6-phosphate receptor (CI-MPR). In cells transiently depleted of RNF126, the CI-MPR is dispersed into Rab4 positive endosomes and the efficiency of retrograde sorting is delayed. Furthermore, the stable knockdown of RNF126 leads to the lysosomal degradation of CI-MPR and missorting of cathepsin D. RNF126 specifically regulates the sorting of the CI-MPR as other cargo that follow the retrograde sorting route including the cholera toxin, furin and TGN38 are unaffected in the absence of RNF126. Lastly we show that the RING finger domain of RNF126 is required to rescue the decrease in CI-MPR levels, suggesting that the ubiquitin ligase activity of RNF126 is required for CI-MPR sorting. Together, our data indicate that the ubiquitin ligase RNF126 has a role in the retrograde sorting of the CI-MPR.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Canada.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Smith
authors.affiliation: Department of Medical Biophysics, University of Toronto, Canada; The Arthur and Sonia Labatt Brain Tumour Research Centre, The Hospital for Sick Children, Peter Gilgan Centre for Research and Learning, 686 Bay Street 17-9706, Toronto, Ontario, Canada M5G 0A4. Electronic address: jmcglade@sickkids.ca.
authors.forename: C Jane
authors.initials: CJ
authors.lastname: McGlade
mesh_terms: D002772:Cholera Toxin / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000235:genetics; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D045683:Furin / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects / Q000235:genetics; D034741:RNA, Small Interfering / Q000494:pharmacology; D017527:Receptor, IGF Type 2 / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D008562:Membrane Glycoproteins; D034741:RNA, Small Interfering; D017527:Receptor, IGF Type 2; C072237:TGOLN2 protein, human; D002772:Cholera Toxin; C578829:RNF126 protein, human; D044767:Ubiquitin-Protein Ligases; C468731:FURIN protein, human; D045683:Furin
keywords: CI-MPR; E3 ubiquitin ligase; EGFR; GGA; Golgi-localized ϒ ear containing, ARF binding protein; HEK; PACS; RNF126; Retrograde sorting; TGN; TfR; cation-independent mannose 6-phosphate receptor; epidermal growth factor receptor; human embryonic kidney; phosphofurin acidic cluster protein-1; siRNA; small interfering RNA; trans-Golgi network; transferrin receptor