Lymphoid Enhancer-binding Factor-1 (LEF1) Interacts with the DNA-binding Domain of the Vitamin D Receptor

Hilary F Luderer,Francesca Gori,Marie B Demay

doi:10.1074/jbc.m110.188219

Hilary F Luderer, Francesca Gori + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m110.188219

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Abstract

Ligand-independent actions of the vitamin D receptor (VDR) are required for normal post-morphogenic hair cycles; however, the molecular mechanisms by which the VDR exerts these actions are not clear. Previous studies demonstrated impaired regulation of the canonical Wnt signaling pathway in primary keratinocytes lacking the VDR. To identify the key effector of canonical Wnt signaling that interacts with the VDR, GST pulldown studies were performed. A novel interaction between the VDR and LEF1 (lymphoid enhancer-binding factor-1) that is independent of β-catenin was identified. This interaction is dependent upon sequences within the N-terminal region of the VDR, a domain required for VDR-DNA interactions and normal hair cycling in mice. Mutation of specific residues within the N-terminal region of the VDR not only abrogated interactions between the VDR and LEF1 but also impaired the ability of the VDR to enhance Wnt signaling in vdr(-/-) primary keratinocytes. Thus, this study demonstrates a novel interaction between the VDR and LEF1 that is mediated by the DNA-binding domain of the VDR and that is required for normal canonical Wnt signaling in keratinocytes.

Highlights

Renewal and lineage commitment of keratinocyte stem cells (KSCs), multipotent progenitor cells that can give rise to all lineages of the pilosebaceous unit [9]
Because LEF1 and ␤-catenin interact directly and ␤-catenin has been shown to interact with the vitamin D receptor (VDR) in the presence of ligand [25], studies were performed to determine whether the unliganded VDR interacts with LEF1, ␤-catenin, or both using GST pulldown assays
The regulatory regions of shh and gli1 were. These investigations identify a novel interaction between the endogenous VDR and LEF1 that is independent of both ␤-catenin and ligand

Summary

Introduction

Renewal and lineage commitment of keratinocyte stem cells (KSCs), multipotent progenitor cells that can give rise to all lineages of the pilosebaceous unit [9]. Because the unliganded VDR modulates the canonical Wnt signaling pathway in primary keratinocytes and co-immunoprecipitates with LEF1 and ␤-catenin [9], studies were undertaken to examine the molecular interactions of the VDR with effectors of this pathway and to determine the consequences of VDR ablation on the expression of shh and its downstream effector gli1 [22].

Results

Conclusion