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Patel S, Barkell AM, Gupta D, Strong SL, Bruton S, Muskett FW, Addis PW, Renshaw PS, Slocombe PM, Doyle C, Clargo A, Taylor RJ, Prosser CE, Henry AJ, Robinson MK, Waters LC, Holdsworth G, Carr MD. Structural and functional analysis of Dickkopf 4 (Dkk4): New insights into Dkk evolution and regulation of Wnt signaling by Dkk and Kremen proteins. J Biol Chem 2018; 293:12149-12166. [PMID: 29925589 PMCID: PMC6078440 DOI: 10.1074/jbc.ra118.002918] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 06/11/2018] [Indexed: 11/06/2022] Open
Abstract
Dickkopf (Dkk) family proteins are important regulators of Wnt signaling pathways, which play key roles in many essential biological processes. Here, we report the first detailed structural and dynamics study of a full-length mature Dkk protein (Dkk4, residues 19–224), including determination of the first atomic-resolution structure for the N-terminal cysteine-rich domain (CRD1) conserved among Dkk proteins. We discovered that CRD1 has significant structural homology to the Dkk C-terminal cysteine-rich domain (CRD2), pointing to multiple gene duplication events during Dkk family evolution. We also show that Dkk4 consists of two independent folded domains (CRD1 and CRD2) joined by a highly flexible, nonstructured linker. Similarly, the N-terminal region preceding CRD1 and containing a highly conserved NXI(R/K) sequence motif was shown to be dynamic and highly flexible. We demonstrate that Dkk4 CRD2 mediates high-affinity binding to both the E1E2 region of low-density lipoprotein receptor–related protein 6 (LRP6 E1E2) and the Kremen1 (Krm1) extracellular domain. In contrast, the N-terminal region alone bound with only moderate affinity to LRP6 E1E2, consistent with binding via the conserved NXI(R/K) motif, but did not interact with Krm proteins. We also confirmed that Dkk and Krm family proteins function synergistically to inhibit Wnt signaling. Insights provided by our integrated structural, dynamics, interaction, and functional studies have allowed us to refine the model of synergistic regulation of Wnt signaling by Dkk proteins. Our results indicate the potential for the formation of a diverse range of ternary complexes comprising Dkk, Krm, and LRP5/6 proteins, allowing fine-tuning of Wnt-dependent signaling.
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Affiliation(s)
- Saleha Patel
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom
| | - Alice M Barkell
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom
| | - Deepti Gupta
- UCB, 208 Bath Road, Slough SL1 3WE, United Kingdom
| | - Sarah L Strong
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom
| | - Shaun Bruton
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom
| | - Frederick W Muskett
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom
| | - Philip W Addis
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom
| | - Philip S Renshaw
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom
| | | | - Carl Doyle
- UCB, 208 Bath Road, Slough SL1 3WE, United Kingdom
| | | | | | - Christine E Prosser
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; UCB, 208 Bath Road, Slough SL1 3WE, United Kingdom
| | | | | | - Lorna C Waters
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom.
| | | | - Mark D Carr
- Leicester Institute of Structural and Chemical Biology, Lancaster Road, Leicester LE1 7HB, United Kingdom; Department of Molecular and Cell Biology, University of Leicester, Lancaster Road, Leicester LE1 7HB, United Kingdom.
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Cai X, Yao Z, Li L, Huang J. Role of DKK4 in Tumorigenesis and Tumor Progression. Int J Biol Sci 2018; 14:616-621. [PMID: 29904276 PMCID: PMC6001654 DOI: 10.7150/ijbs.24329] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 03/26/2018] [Indexed: 11/05/2022] Open
Abstract
Tumor is the most public health problem. The Wnt signal pathway extensively participates in diverse progresses containing embryonic development, maintenance of homeostasis and tumor pathogenesis. The Wnt signal pathway consists of canonical signal pathway, noncanonical Wnt/PCP pathway and noncanonical Wnt/Ca2+ pathway. The deletion of the ligand of Wnts results in cytoplasmic β-catenin phosphorylation, stopping entry of β-catenin to nuclear in canonical Wnt signaling. Instead, binding of Wnts to frizzled (FZ/FZD) as well as LRP5/6 causes activation of Wnt signal pathways. This facilitates entry of β-catenin to nuclear. The Dickkopf proteins (DKKs) have been known as the antagonist of Wnt signal pathway. A number of research of DKK1, 2, 3 have been reported, however, the effect of DKK4 on tumor process is still mysterious. A more distinct comprehension about the effect of DKK4 on tumorigenesis and tumor process will shed light on biomedical research of DKK4 and tumor research. This review summarizes the current knowledge of DKK4 in various kinds of tumors.
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Affiliation(s)
- Xinjia Cai
- Department of Oral Pathology, Xiangya Stomalogical Hospital, Central South University, 410078, Chansha, Hunan, China
| | - Zhigang Yao
- Department of Oral Pathology, Xiangya Stomalogical Hospital, Central South University, 410078, Chansha, Hunan, China
| | - Long Li
- Department of Oral Pathology, Xiangya Stomalogical Hospital, Central South University, 410078, Chansha, Hunan, China
| | - Junhui Huang
- Department of Oral Pathology, Xiangya Stomalogical Hospital, Central South University, 410078, Chansha, Hunan, China
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