title: Down-regulation of intestinal apical calcium entry channel TRPV6 by ubiquitin E3 ligase Nedd4-2.
abstract: Nedd4-2 is an archetypal HECT ubiquitin E3 ligase that disposes target proteins for degradation. Because of the proven roles of Nedd4-2 in degradation of membrane proteins, such as epithelial Na(+) channel, we examined the effect of Nedd4-2 on the apical Ca(2+) channel TRPV6, which is involved in transcellular Ca(2+) transport in the intestine using the Xenopus laevis oocyte system. We demonstrated that a significant amount of Nedd4-2 protein was distributed to the absorptive epithelial cells in ileum, cecum, and colon along with TRPV6. When co-expressed in oocytes, Nedd4-2 and, to a lesser extent, Nedd4 down-regulated the protein abundance and Ca(2+) influx of TRPV6 and TRPV5, respectively. TRPV6 ubiquitination was increased, and its stability was decreased by Nedd4-2. The Nedd4-2 inhibitory effects on TRPV6 were partially blocked by proteasome inhibitor MG132 but not by the lysosome inhibitor chloroquine. The rate of TRPV6 internalization was not significantly altered by Nedd4-2. The HECT domain was essential to the inhibitory effect of Nedd4-2 on TRPV6 and to their association. The WW1 and WW2 domains interacted with TRPV6 terminal regions, and a disruption of the interactions by D204H and D376H mutations in the WW1 and WW2 domains increased TRPV6 ubiquitination and degradation. Thus, WW1 and WW2 may serve as a molecular switch to limit the ubiquitination of TRPV6 by the HECT domain. In conclusion, Nedd4-2 may regulate TRPV6 protein abundance in intestinal epithelia by controlling TRPV6 ubiquitination.
authors.affiliation: Nephrology Research and Training Center, Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Tao
authors.initials: T
authors.lastname: Na
authors.forename: Guojin
authors.initials: G
authors.lastname: Wu
authors.forename: Haiyan
authors.initials: H
authors.lastname: Jing
authors.forename: Ji-Bin
authors.initials: JB
authors.lastname: Peng
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D000075702:Nedd4 Ubiquitin Protein Ligases; D009865:Oocytes / Q000166:cytology / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D029867:Xenopus Proteins; D014982:Xenopus laevis
chemical_list: D015220:Calcium Channels; D056827:Endosomal Sorting Complexes Required for Transport; D012333:RNA, Messenger; D050916:TRPV Cation Channels; C422827:TRPV6 protein, human; D025801:Ubiquitin; D029867:Xenopus Proteins; C000618479:NEDD4L protein, rat; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618482:Nedd4 protein, Xenopus; C000618483:Nedd4 protein, human; C000618484:Nedd4 protein, rat; C000618485:Nedd4L protein, human; C000618460:nedd4l protein, Xenopus; D044767:Ubiquitin-Protein Ligases; D002118:Calcium