title: OS-9 regulates the transit and polyubiquitination of TRPV4 in the endoplasmic reticulum.
abstract: Transient receptor potential (TRP) proteins constitute a family of cation-permeable channels that are formed by homo- or heteromeric assembly of four subunits. Despite recent progress in the identification of protein domains required for the formation of tetramers, the mechanisms governing TRP channel assembly, and biogenesis in general, remain largely elusive. In particular, little is known about the involvement of regulatory proteins in these processes. Here we report that OS-9, a ubiquitously expressed endoplasmic reticulum (ER)-associated protein, interacts with the cytosolic N-terminal tail of TRPV4. Using a combination of co-expression and knockdown approaches we have found that OS-9 impedes the release of TRPV4 from the ER and reduces its amount at the plasma membrane. Consistent with these in vitro findings, OS-9 protected zebrafish embryos against the detrimental effects of TRPV4 expression in vivo. A detailed analysis of the underlying mechanisms revealed that OS-9 preferably binds TRPV4 monomers and other ER-localized, immature variants of TRPV4 and attenuates their polyubiquitination. Thus, OS-9 regulates the secretory transport of TRPV4 and appears to protect TRPV4 subunits from the precocious ubiquitination and ER-associated degradation. Our data suggest that OS-9 functions as an auxiliary protein for TRPV4 maturation.
authors.affiliation: Renal Division, University Hospital Freiburg, Hugstetter Strasse 55, Freiburg 79106, Germany.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiao
authors.initials: X
authors.lastname: Fu
authors.forename: Stephanie
authors.initials: S
authors.lastname: Gaiser
authors.forename: Michael
authors.initials: M
authors.lastname: Köttgen
authors.forename: Albrecht
authors.initials: A
authors.lastname: Kramer-Zucker
authors.forename: Gerd
authors.initials: G
authors.lastname: Walz
authors.forename: Tomasz
authors.initials: T
authors.lastname: Wegierski
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D037102:Lectins; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*; D025801:Ubiquitin / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination / Q000502:physiology*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D037102:Lectins; D009363:Neoplasm Proteins; C098898:OS9 protein, human; D050916:TRPV Cation Channels; C416986:TRPV4 protein, human; C486576:Trpv4 protein, mouse; D025801:Ubiquitin; D029961:Zebrafish Proteins