Blanc SVSE 2 - Sciences de la vie, de la santé et des écosystèmes : Biologie cellulaire, développement

Cell and structural biology of Rab GTPases/molecular motors interactions – Motorab

Cell and structural biology

Task 1: - We have determined the 2.0Å and 2.2Å resolution crystal structure of Rab6A in complex with RK6 fragment (Rab6-binding domain) and of Rab6A’ in complex with R6K fragment, respectively. - We have also determined a crystal structure of Rab6A’ A87E:R6K complex. - Several shorter Myosin IIA fragments have been designed, cloned and purified using different affinity tags.
Task 2: - We have been working on shortening Rabk6 and Myosin II fragments responsible for the protein complex formation using combination of cell biology and biochemistry approaches. - We have produced several fragments of each protein in bacterial cells that are ready to be tested.
Task 3: - We are currently testing the in vivo effects (Golgi morphology, transport assays) of mutations in RK6 and Myosin IIA that impair interactions with Rab6, and of mutations that impair RK6/Myosin IIA interaction.
Task 4: - Several Myosin Vb fragments that interact with Rab6 have been produced and purified. We have designed a new set of minimal Myosin Vb constructs potentially interacting with Rab6 whose production is ongoing. - The recombinant human Myosin Vb cargo-binding domain (CBD) fragment and human Rab11A have been produced and purified. The crystal structure model of the complex has been built and its refinement is ongoing.
Task 5: - We have mapped the domains of Myosin Vb that interact with Rab6, Rab8 or Rab11. - We are currently expressing these domains to test their effects on transport markers.
Task 6: - We have completed a study on Myosin Va, a protein closely related to Myosin Vb. These results indicate that myosin Va is a major regulator of the topology of membrane compartments belonging to the endocytic recycling and post-Golgi secretory systems. A manuscript will be soon sent for publication.

We expect to be the firsts to solve the 3D structure of a Rab GTP-ase in complex with a motor protein.

Manuscript in preparation

Submission summary

Intracellular traffic is a fundamental biological process in which 10 to 20% of the proteins present in a eukaryotic cell have been estimated to, directly or indirectly, participate. Among them, small GTPases of the Rab family (over sixty proteins in humans) play a central regulatory role. Localized on the external side of all cellular compartments, they cycle between an inactive (GDP-bound) and active (GTP-bound) form. The GDP/GTP cycle is tightly coupled to a membrane association/dissociation process. Rab proteins are involved in many aspects of the life of transport intermediates (vesicles or tubules) that shuttle between compartments, such as budding from donor membranes, movement along components of the cytoskeleton, and docking/fusion events. Another important function of Rab GTPases is to regulate the dynamic formation of membrane domains on organelles.

To perform their multiple tasks, Rab GTPases interact with a wide variety of effectors. Rab effectors include scaffolding proteins, adaptor proteins, lipid kinases, lipid phosphatases and tethering factors. This proposal will focus on one important class of Rab effectors, i.e. molecular motors. Three motor protein superfamilies are present in mammalian cells (kinesin, dynein and myosin) and members of all of them have been involved in a wide variety of transport events. Our group was the first to identify a direct interaction between a Rab GTPase (Rab6) and a kinesin-like protein (Rabkinesin-6, also named MKlP2 or KIF20A). Since then, several motors have been shown to be specific effectors of many Rab GTPases. It is generally thought that Rab GTPases are involved in the recruitment of molecular motors to specific membranes and/or in the regulation of motor activity. However, direct evidence for such a role for Rab GTPases is still lacking.

The general objective of the present proposal is to use a combination of cell biology, biochemical and biophysical approaches to assemble a comprehensive model for the functional basis of the interactions between three Rab GTPase (Rab6, Rab8 and Rab11) with their molecular motor partners throughout their functional cycle during intracellular traffic. It involves two groups of the UMR 144 (Institut Curie, Paris) who have strong expertise in their respective fields, Rab GTPases (Bruno Goud) and 3D structure of molecular motors (Anne Houdusse). We propose to perform extensive structural-functional characterization of a range of complexes between several Rab GTPases and their interacting motor proteins to reveal the molecular basis of their selectivity.

Project coordination


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.



Help of the ANR 550,000 euros
Beginning and duration of the scientific project: - 36 Months

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