CE13 - Biologie Cellulaire, Biologie du Développement et Evolution

Control of actin on endosomes and ciliogenesis by the Rab35 GTPase and two novel effectors: An integrated view. – RabEndoCilio

Control of actin on endosomes and ciliogenesis

Control of actin on endosomes and ciliogenesis by the Rab35 GTPase and two novel effectors: An integrated view.

What is the role of the actin cytoskeleton during ciliogenesis?

The aim of the 4-year RabEndoCilio proposal is to characterize how Rab35 and two new effectors regulate the actin cytoskeleton, endosomal trafficking and functions of motile and primary cilia, from the molecular and structural level to the functional and in vivo level using human cells and zebrafish as models. <br /> <br />We aim at addressing the following questions: <br /> <br />1- What are the Rab35 effectors that specifically and directly control actin dynamics on endosomes? <br />2- How, at the mechanistic level, do these effectors regulate the actin cytoskeleton on endosomes? <br />3-Which functions really depend on Rab35-regulated actin remodeling in vivo, at the organism level? <br />4- Do the novel Rab35 effectors regulating endosomal actin dynamics control these functions in vivo?

One of the unique assets of this proposal is the strong synergy and complementarity between the three Teams.
The consortium will allow us to develop and establish a multi-scale program that will bring together different scientific areas:
- Cell Biology (Team 1, Pasteur Institute),
- Structural Biology (Team 2, Curie Institute)
- and Developmental Biology (Team 3, Ecole Polytechnique).

We have already
- characterized the MiniBAR/Rac1/Rab35 complex
- solved the 3D structure of MiniBAR domains interacting with either Rab35 or Rac1
- determined mutations that disrupt the interaction with each GTPase - generated specific antibodies against MiniBAR
- efficiently depleted MiniBAR in cellullo and in vivo
- shown a role of MiniBAR in controling the length of primary and motils cilia
- found that MiniBAR lead to all signs characterisitic of ciliopathy

We will now determine how MiniBAR controls actin and IFT88 trafficking to explain the observed phenotypes.

Talks:
22 May 2019 — Cytoskeleton club, Institut Jacques Monod, Paris
3-5 October 2019 — BCI Retreat, Spain

Posters:
2018 — BCI Day
27-29 November 2019 — International Conference on Cilia, Flagella and Centrosomes, Institut Imagine, Paris

Rab GTPases are key regulators of membrane traffic in eukaryotic cells. Given the importance of trafficking in cell physiology, Rab GTPases, their effectors or regulators have been implicated in numerous human diseases, including neurodegeneration, immune syndromes and tumorigenesis. In the past few years, plasma membrane- and endosomal-associated Rab35 has attracted a lot of attention from the endocytic community since it controls the trafficking of key cargoes. In addition, the importance of Rab35 in human disease has been revealed recently since Rab35 mutations found in cancer patients drive tumor formation by perturbing the trafficking of the PDGF and EGF receptors. The interest into Rab35 rapidly spread beyond the trafficking community, and Rab35 has been involved in functions connected with immunology, microbiology and neurobiology. However, it is unclear how Rab35 controls so many functions. Whether Rab35 is essential for these functions in vivo, at the organism level, also remains to be established.

Many of these apparently unrelated functions are linked to a central role of Rab35 and its effectors in endosomal trafficking, in particular by controlling actin polymerization/depolymerization on endosomes. However, none of the Rab35 effectors involved in membrane trafficking identified so far directly explain how this Rab GTPase is able to regulate actin dynamics on endosomes. This is an important issue, since the role of actin on recycling endosomes is crucial but poorly understood and how it is regulated is currently under active investigation.

The aim of the 4-year RabEndoCilio proposal is to characterize how Rab35 and two new effectors regulate the actin cytoskeleton, endosomal trafficking and functions of motile and primary cilia, from the molecular and structural level to the functional and in vivo level using human cells and zebrafish as models.

One of the unique assets of this proposal is the strong synergy and complementarity between the three Teams. The consortium will allow us to develop and establish a multi-scale program that will bring together different scientific areas: Cell Biology (Team 1, Pasteur Institute), Structural Biology (Team 2, Curie Institute) and Developmental Biology (Team 3, Ecole Polytechnique).

The program feasibility is supported by strong preliminary data. Team 1 identified two new partners of Rab35 that are excellent candidates to regulate actin dynamics. Teams 1 and 2 obtained preliminary structural information on these proteins. Teams 1 and 3 obtained first evidence for a role of Rab35 and at least one partner in cilium formation in vitro and in vivo.


We will address the following questions:

1- What are the Rab35 effectors that specifically and directly control actin dynamics on endosomes?
2- How, at the mechanistic level, do these effectors regulate the actin cytoskeleton on endosomes?
3-Which functions really depend on Rab35-regulated actin remodeling in vivo, at the organism level?
4- Do the novel Rab35 effectors regulating endosomal actin dynamics control these functions in vivo?


Through the use of different and complementary approaches, this proposal should provide novel and high impact knowledge regarding the role of actin dynamics in endosomal trafficking. In addition, it will provide for the first time an integrated view of the role of the Rab35 GTPase and of endosomal actin in cellular physiology, bridging scales ranging from molecules to an entire organism.

We believe that the molecular framework thus revealed will also help explain the crucial role of Rab35 in other apparently unrelated cellular functions, ranging from phagocytosis, cell-cell fusion, exosome release, immune synapse formation, cell migration and metastasis to neuron development.

Project coordinator

Monsieur Arnaud Echard (INSTITUT PASTEUR)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

IP INSTITUT PASTEUR
IC INSTITUT CURIE - SECT DE RECHERCHE
LOB Laboratoire d'optique et biosciences

Help of the ANR 587,688 euros
Beginning and duration of the scientific project: March 2019 - 48 Months

Useful links

Explorez notre base de projets financés

 

 

ANR makes available its datasets on funded projects, click here to find more.

Sign up for the latest news:
Subscribe to our newsletter