Résumé : MyosinV is an unconventional actin-based molecular motor that acts as a transporter or a tether for a variety of membrane cargoes. In the resting state MyosinV adopts an autoinhibited conformation, forming a cytosolic pool of inactive motors. Several Rab GTPases and their effectors directly bind and cooperate with MyosinV to regulate membrane trafficking. Structural studies of MyosinV motor and its complexes with interacting partners provide insights into the mechanism of the motor’s membrane recruitment and how that is coupled with myosin activation. Discovery and characterization of the direct interaction between the actin assembly regulator Spir and MyosinV, and Spir/MyosinV/Rab11 complex provide evidence for a synergic recruitment to promote both actin track generation and myosin motor activity in vesicle transport processes.
Invitée par Julie MENETREY, Equipe Biochimie Structurale des Microtubules, des Kinésines et de leurs Cargos. Vous pouvez contacter Julie pour rencontrer Olena Pylypenko
Lieu : Bibliothèque - Bâtiment 34, campus de Gif
Résumé : During the past decade, many studies shed light on cilia as sensory and motile organelles which play major roles in vertebrate development and homeostasis. The building and maintenance of all cilia is dependent upon a complex transport system referred to as the intraflagellar transport (IFT). This IFT system is composed of several adaptor complexes that are fundamental during ciliogenesis. The high number of IFT proteins in these complexes (almost 20 in the IFT complex B) indicates that the IFT proteins have different functions. Although work on several ciliated model systems have been able to help our understanding of IFT proteins functions, notably through temperature sensitive mutants, studies in mammalian systems remain challenging. Indeed, in mammals, the absence of most of the IFT subunits leads to absence of cilia formation, thus preventing us from gaining much insight in their ciliary role. Hence, it is fundamental to try to develop systems in which we can uncouple intraflagellar transport and primary cilia formation. To do that, we first reasoned that some proteins of the IFT complex might be absent in some ciliated organisms, revealing proteins that could be dispensable during cilia formation. This led to the discovery of the unique function of two IFT-B proteins, IFT25 and IFT27, which mouse mutants die at birth with hedgehog-like phenotypes but are able to form primary and motile cilia. Building on these results, we designed a cellular system using rapamycin-induced dimerization in order to sequester IFT proteins from their ciliary pool into other cell compartments and show that this might be a powerful tool to study IFT proteins.
Lieu : Auditorium - bâtiment 21 - Campus de Gif