Venue: Centre Broca
Yann Lanoiselée
BCAM – Basque Center for Applied Mathematics
Invited by Isabel Alves (CBMN) and Rémi Galland (IINS)
Title
Single-molecule trajectory analysis for unraveling receptor–b-arrestin interactions
Abstract
At the mesoscopic scale of cellular processes, the passive motion of proteins and receptors is dominated by diffusion. While diffusion is a rather inefficient transport mechanism, cells through evolution have found strategies to improve molecular reaction rates. These strategies rely on the interplay between protein structures and cell organization to exploit diffusion mechanisms. Measuring diffusion properties and their variations in space and time allows one to understand microscopic mechanisms of dynamical cellular processes and their interplay with cell organization.
We will discuss how fluorescence microscopy techniques and single-molecule trajectory analysis can be combined to understand some aspects of signal transduction [1]. Despite recent structural advances, the mechanisms that govern interactions of membrane-bound receptors with intracellular arrestin molecules at the plasma membrane remain elusive. We dissect the complex sequence of events involved in b-arrestin interactions with both receptors and the lipid bilayer. We carefully characterize the spatiotemporal co-dynamics of receptors and arrestins. We show that receptor and arrestin diffusion have multiple states linked to biological function.
Unexpectedly, our results reveal that b-arrestin spontaneously inserts into the lipid bilayer and transiently interacts with receptors via lateral diffusion on the plasma membrane. Moreover, they indicate that following receptor interaction, the plasma membrane stabilizes b-arrestin in a longer-lived membrane-bound state, allowing it to diffuse to clathrin-coated pits separately from the activating receptor.
[1] Grimes J, Koszegi Z, Lanoiselée Y, et al. Plasma membrane preassociation drives β-arrestin coupling to receptors and activation. Cell. 2023;186(10):2238-2255.e20.
About the speaker
I am a statistical physicist specializing in the theory and analysis of diffusion processes in complex/heterogeneous environments. My main topic is the diffusion of proteins and receptors in living cells.
I completed my theoretical PhD with Dr Denis Grebenkov on the analysis of Single Particle Trajectory experiments: extraction of the maximum of physical information from individual experimental trajectories and physical modeling of experimentally observed diffusive behaviors. Then, decided to learn more about cell biology and how experiments are done, I did a 4 years post-doc in the experimental group of Pr Davide Calebiro where I collaborated with many biologists/pharmacologists/medical doctors on the analysis of the mechanisms underlying signal transduction of G protein-coupled receptors at the single-molecule level. I studied dimer formation of mu/delta/kappa opioid receptors. With Marie-Lise Jobin, I studied the neuronal diffusion of GABA B receptors and their colocalization dynamics with Filamin A molecules:
https://drive.google.com/file/d/1TUBD3pjdhBLhOwyuCR4CLMYNhhYK5HvE
My main contribution during this post-doc is the analysis of the interaction between adrenergic receptors (b1AR, B2AR, chimeric b2V2) and b-arrestin and the reconstruction of the sequence of events leading to their recruitment to clathrin-coated pits with the discovery that b-arrestin can preassociate with the plasma membrane even without a receptor:
https://drive.google.com/file/d/1T_1IjxHeYHaxxORf2gQUyhmwl9RBcPOe
In the next years, I plan to theoretically model the diffusion processes related to the GPCR lifecycle. The main steps I want to study are: the diffusion of ligands until reaching GPCRs, the diffusion of GPCRs until CCP/caveolae internalization, and the cargo motion up to intracellular sites to take explicitly into account the diversity of motion type that can be observed (free diffusion, trapping, diffusion coefficient changes resulting from conformational changes, etc.). This work calls for experimental teams studying GPCR at the single molecule level, to whom I could offer my expertise in analysing and characterizing diffusion, and interaction (association/dissociation rates).