Researcher(s)
- Abigail Stevens, Biological Sciences, University of Delaware
Faculty Mentor(s)
- Erica Selva, Biological Sciences, University of Delaware
Abstract
The Wnt signaling pathway is an evolutionarily conserved signal transduction pathway that governs organismal development and adult tissue homeostasis by regulating cell proliferation, polarity, motility, and differentiation in Drosophila melanogaster and all metazoans. When this pathway goes awry, it is recognized as a primary driver of human disease, examples include colorectal and breast cancers, or cardiac and vascular diseases1. Wnts are enigmatic, lipid-modified secreted glycoproteins. In the signal producing cells, Porcupine is the membrane-bound O-acyltransferase responsible for transferring a mono-unsaturated palmitoleic acid to a conserved serine residue on Wnt ligands. This modification is required to activate canonical Wnt signaling in receiving cells. The mature Wnt ligand binds to its cognate receptors Frizzled (Fz) and LRP5/6, culminating in β-catenin accumulation and downstream transcriptional activation of Wnt target genes. Wingless (Wg), the prototypical Drosophila Wnt, is an excellent model to study canonical Wnt signaling in a genetically tractable organism. My research aims to evaluate the impact of Wg modification on canonical pathway activation utilizing a dual-luciferase reporter assay and a β-catenin accumulation assay. I investigated the effect of a C-terminal EGFP tag as well as the mutation of the conserved serine palmitoylation site to alanine. These modifications were tested by transfecting Drosophila SR2+ cells with wild type Wg, Wg-EGFP, and Wg-S239A, and required Wnt secretion mediators. I found that the addition of EGFP to the C-terminus produced a fluorescent fusion protein that was secreted but was unable to activate canonical Wnt signaling. Whereas, mutation of the conserved palmitoylation site only decreased activity relative to wild type Wg. These results demonstrate the integrity of the Wg/Wnt structure is required for functional Wnt signal transduction. Future work will focus on understanding the role of Wnt lipidation and C-terminal integrity to Wg function.
References
- Liu, J., Xiao, Q., Xiao, J., Niu, C., Li, Y., Zhang, X., Zhou, Z., Shu, G., & Yin, G. (2022). Wnt/β-catenin signalling: Function, biological mechanisms, and therapeutic opportunities. Signal Transduction and Targeted Therapy, 7(1), 1-23. https://doi.org/10.1038/s41392-021-00762-6