Identification of β-Catenin-Interacting Proteins in Nuclei of Aquaporin-2-Expressing Rat Collecting Duct Cells

ABSTRACT: The gene encoding the aquaporin-2 water channel is regulated transcriptionally in response to vasopressin. In the renal collecting duct, vasopressin stimulates the nuclear translocation and phosphorylation (at Ser552) of β-catenin, a multifunctional protein that can act as a transcriptional co-regulator in the nucleus. The purpose of this study was to identify β-catenin interacting proteins in nuclei of rat inner medullary collecting duct (IMCD) cells using both experimental and computational approaches. We used chromatin immunoprecipitation coupled to mass spectrometry (ChIP-MS) in nuclei isolated from rat IMCD suspensions to identify β-catenin interacting proteins. We reproducibly (n=4) identified 43 β-catenin binding proteins, which included a number of known β-catenin binding partners as well as novel interacting proteins. Multiple proteins involved in transcriptional regulation were identified (Taf1, Jup, Tdrd3, Cdh1, Cenpj, and several histones). Many of the identified β-catenin binding partners were found in prior studies to translocate to the nucleus in response to vasopressin. There was one DNA-binding transcription factor (TF), viz. Taf1, part of the RNA-polymerase II pre-initiation complex. To identify sequence-specific TFs that may interact with β-catenin but are expressed at abundance levels too low to be detected by MS, Bayes’ Theorem was used to integrate data from several information sources. The analysis identified several TFs with potential binding sites in the Aqp2 gene promoter that could interact with β-catenin in the regulation of Aqp2 gene transcription viz. Jun, Junb, Jund, Atf1, Atf2, Mef2d, Usf1, Max, Pou2f1, and Rxra. The findings provide information necessary for modeling the transcriptional response to vasopressin.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Rattus Norvegicus (rat)

TISSUE(S): Epithelial Cell, Kidney

SUBMITTER: Chung-Lin Chou  

LAB HEAD: Mark A. Knepper

PROVIDER: PXD005792 | Pride | 2018-10-26

REPOSITORIES: Pride