Presented by : Lecturer: Lidija BerkeDr. Madelon Maurice Renske Bolder Liliana Joach í n
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Transcript of Presented by : Lecturer: Lidija BerkeDr. Madelon Maurice Renske Bolder Liliana Joach í n
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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
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Overview
Introduction
Experimental work Results Conclusions
General conclusions Final model for Wnt
secretion
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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.
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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.
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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
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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.
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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.
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Research question
Is the retromer involved in Wingless secretion?
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Important note
Wingless ---- Wingless (Wg)
Wntless ---- Wls/Evi (Wls)
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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
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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.
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Experimental work Effects on short or long range wingless signaling
Senseless Distalless
Conclusion:
Vps35 has an important role in short range Wingless signalling
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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
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Experimental work Overexpression of Wls/Evi
Conclusion:
Overexpression of Wls/Evi rescues the wingless secretion phenotype of Vps35
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Experimental work Stability of Wls/Evi
HEK293 cells
Conclusion:
Stability of Wls/Evi is reduced in the absence of Vps35 activity
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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.
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Experimental work Physical interactions between retromer
components and Wls/Evi
Conclusion:
hWls/Evi forms a a complex with retromer components.
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Experimental workTracking internalized Wls/Evi
Conclusions:Wls/Evi undergoes retrograde transport to the Golgi in a retromer dependent manner.
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General conclusions Schematic representation of the role
of Wls/Evi in Wingless secretion
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?