The long-term goal of this project is to understand the molecular mechanisms by which retromer controls cellular processes during development. Retromer is an evolutionarily conserved multi-subunit complex, consisting of two complexes, the cargo recognition Vps26-Vps29- Vps35 heterotrimer and a membrane-targeting heterodimer or homodimer. Early studies in yeast and mammalian cell culture have demonstrated its roles in mediating endosome-Golgi trafficking of several proteins including mammalian cation-independent mannose-6-phosphate receptor. However, the roles of retromer complex in development have not been examined until recently. Our recent studies have uncovered an essential role of retromer complex in Wnt secretion. We showed that retromer is involved in endosome-to-Golgi transport of Wntless (Wls), a seven-pass transmembrane protein required for Wnt secretion. In the absence of retromer activity, Wls is unstable and is degraded, thereby causing Wnt secretion defects. Importantly, while retromer is not involved in many other developmental signaling pathways, we found that retromer is crucial for other two essential developmental processes including (1) the apicobasal polarity of epithelium during Drosophila embryogenesis and (2) hematopoeisis during larval development. Our preliminary studies have demonstrated that retromer regulates the trafficking of Crumbs (crb) to control the apicobasal polarity of epithelium, while it is involved in regulating Toll/Dorsal signaling pathway to control hematopoeisis. Thus, our studies have uncovered three essential roles of the retromer complex in development. In this application, we will further investigate the roles of retromer in Wnt secretion, in the apicobasal polarity control and in Toll/dorsal signaling pathway.
In Aim1, we will examine the roles of ubiquitination and retromer in regulating Wls stability and recycling.
In Aim2, we will examine whether retromer controls epithelium polarity by regulating Crumb trafficking and stability.
In Aim3, we will determine the mechanism by which retromer regulates Toll trafficking and signaling. Together, our proposed studies will provide new insights into the mechanisms by which retromer regulates Wnt secretion, epithelium polarity and Toll/dorsal signaling during development.

Public Health Relevance

Retromer controls Wnt and Toll signaling pathways as well as epithelium polarity. These signaling pathways and cell biology processes are essential for embryonic development. Defects in Wnt and Toll signaling pathways as well as epithelium polarity are associated with many human diseases including cancers. The outcomes of this application will help understanding related human disease processes.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM087517-03
Application #
8231491
Study Section
Intercellular Interactions (ICI)
Program Officer
Hoodbhoy, Tanya
Project Start
2010-03-01
Project End
2014-02-28
Budget Start
2012-03-01
Budget End
2013-02-28
Support Year
3
Fiscal Year
2012
Total Cost
$287,793
Indirect Cost
$99,693
Name
Cincinnati Children's Hospital Medical Center
Department
Type
DUNS #
071284913
City
Cincinnati
State
OH
Country
United States
Zip Code
45229
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