Cryo-EM structure of human Wntless in complex with Wnt3a

Qing Zhong,Zaiyu Xiao,Jizhong Zhang,Yanyu Zhao,Yuanyuan Zhang,Dan Ma,Peilong Lu,Wenqing Xu,Meng Xu,Gaoxingyu Huang,Xiuxiu Zhao,Xiechao Zhan,Fangfei Ye,Shanshan Cheng,Shan Feng,Qiang Zhou,Zhizhi Wang,Ke Sun

doi:10.1038/s41467-021-24731-3

Qing Zhong, Zaiyu Xiao + Show 16 more

Open Access

https://doi.org/10.1038/s41467-021-24731-3

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Abstract

Wntless (WLS), an evolutionarily conserved multi-pass transmembrane protein, is essential for secretion of Wnt proteins. Wnt-triggered signaling pathways control many crucial life events, whereas aberrant Wnt signaling is tightly associated with many human diseases including cancers. Here, we report the cryo-EM structure of human WLS in complex with Wnt3a, the most widely studied Wnt, at 2.2 Å resolution. The transmembrane domain of WLS bears a GPCR fold, with a conserved core cavity and a lateral opening. Wnt3a interacts with WLS at multiple interfaces, with the lipid moiety on Wnt3a traversing a hydrophobic tunnel of WLS transmembrane domain and inserting into membrane. A β-hairpin of Wnt3a containing the conserved palmitoleoylation site interacts with WLS extensively, which is crucial for WLS-mediated Wnt secretion. The flexibility of the Wnt3a loop/hairpin regions involved in the multiple binding sites indicates induced fit might happen when Wnts are bound to different binding partners. Our findings provide important insights into the molecular mechanism of Wnt palmitoleoylation, secretion and signaling.

Highlights

Wntless (WLS), an evolutionarily conserved multi-pass transmembrane protein, is essential for secretion of Wnt proteins
We coexpressed full-length human WLS and Wnt3a in HEK293S GnTI− cells co-infected with viruses generated from pEG BacMam vector[30]
We purified the WLS-Wnt3a complex by affinity chromatography followed by size exclusion chromatography (SEC)

Summary

Introduction

Wntless (WLS), an evolutionarily conserved multi-pass transmembrane protein, is essential for secretion of Wnt proteins. We report the cryo-EM structure of human WLS in complex with Wnt3a, the most widely studied Wnt, at 2.2 Å resolution. A β-hairpin of Wnt3a containing the conserved palmitoleoylation site interacts with WLS extensively, which is crucial for WLS-mediated Wnt secretion. Wnt proteins comprise a family of secreted proteins[7,8] They bind to highly conserved cell surface receptors[9,10,11,12] and trigger signaling cascades in target cells in either paracrine or autocrine manner[13]. A comparison of the two WLS-Wnt structures provides structural basis for understanding the molecular mechanism of WLS-mediated Wnt secretion, Wnt signaling, and development of drugs for treatment of Wnt-driven cancers

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