Wingless secretion requires endosome-to-Golgi retrieval of
Wntless/Evi/Sprinter by the retromer complex
Presented by: Lecturer:
Lidija Berke Dr. Madelon Maurice
Renske Bolder
Liliana Joachín
October 9, 2008
Overview
Introduction
Experimental work Results Conclusions
General conclusions Final model for Wnt
secretion
IntroductionWnt proteins
Family of secreted glycoproteins (highly conserved).
Act as signaling molecules, local mediators and morphogens.
Regulate cell-to-cell interaction during embryogenesis.
Examples: Wingless, Hedgehog.
IntroductionDrosophila imaginal disc
Group of cells that are set aside, apparently undifferenciated in the Drosophila embryo and which will develop into an adult structure, e.g eye, leg, wing.
IntroductionSignal proteins in the wing imaginal disc
Hedgehog Posterior expression Short-range signal
Wingless
Ventral
Dorsal
Hedgehog
Anterior Posterior
Wingless Dorso-ventral action Long-range signal
IntroductionRetromer complex
Multiprotein complex that assembles on endosomes and form vesicles that return cargos to the Golgi apparatus.
It is formed only when:
It can bind to the cytoplasmic tails of the cargo (Vps35).
It can interact directly with a curved phospholipid bilayer.
It can bind to a specific phosphorilated PI lipid.
IntroductionPrevious findings about Wnt
Wnts undergo up to two lipid modifications Affect trafficking and spreading along epithelia. Hypothesis: They are transported by lipoprotein particles which
would shield lipid moieties, reducing membrane anchoring.
EGL-20 (a C. elegans Wnt) Its long-range action is impaired in retromer-deficient worms. Hypothesis: A retromer-dependent process might be required for
Wnt-producing cells to package Wnts into lipoprotein particles.
Research question
Is the retromer involved in Wingless secretion?
Important note
Wingless ---- Wingless (Wg)
Wntless ---- Wls/Evi (Wls)
Experimental work Loss of Vps35 affects the spread of Wingless
Generation of Drosophila mutants (deficient in Vps35)
Results: Melanotic tumors Wingless accumulation Incomplete wings
Conclusion:
Wingless trafficking might be affected in absence of Vps35 activity
Experimental work Loss of Vps35 affects the spread of Wingless
Mutation: posterior compartment deficient in Vps35
Results: Concentration of Wingless Wingless spreading reduced Reduction in extracellullar
Wingless
Conclusion:
In the absence of retromer function, progression of Wingless along the secretory pathway becomes blocked or impaired.
Experimental work Effects on short or long range wingless signaling
Senseless Distalless
Conclusion:
Vps35 has an important role in short range Wingless signalling
Experimental work Is vps35 also involved in Hedgehog secretion?
Hedgehog Wingless Patched
Conclusion:
Vps35 is required for a specific step in the secretion of Wingless
Experimental work Overexpression of Wls/Evi
Conclusion:
Overexpression of Wls/Evi rescues the wingless secretion phenotype of Vps35
Experimental work Stability of Wls/Evi
HEK293 cells
Conclusion:
Stability of Wls/Evi is reduced in the absence of Vps35 activity
Experimental work What happens after internalization of Wls/Evi in
the absence of retromer?
Conclusion:
In the absence of retromer function, Wls/Evi is diverted to MVBs.
Experimental work Physical interactions between retromer
components and Wls/Evi
Conclusion:
hWls/Evi forms a a complex with retromer components.
Experimental workTracking internalized Wls/Evi
Conclusions:Wls/Evi undergoes retrograde transport to the Golgi in a retromer dependent manner.
General conclusions Schematic representation of the role
of Wls/Evi in Wingless secretion
?
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