DECAV-RECAV

Mechanotransduction, that is the translation of mechanical stimuli into biochemical signals, has emerged as a key event in several fundamental cellular aspects, including cell motility, growth and differentiation. How mechanotransduction couples the sensing of mechanical forces with specific cellular responses remains however poorly understood. Inspired by a theoretical model by partner 1 (P1) for the budding and flattening of membrane domains, partners 3 & 4 (P3, P4) reported for the first time that caveolae act as membrane-mediated mechanosensors that respond instantaneously to mechanical stress to maintain membrane integrity and tension homeostasis. Caveolae, which are characteristic “cup-shaped” plasma membrane invaginations abundant in cells experiencing chronic stress, were classically assigned to a role in endocytosis and scaffolding of various signaling membrane proteins. But this newly evidenced mechanosensitive function of caveolae, based on their ability to disassemble under mechanical stress and to reassemble in resting (or stress-relaxed) conditions prompts us to revisit the role of caveolae. In the framework of this DECAV-RECAV project, our working hypothesis is that caveolae are not only a passive membrane reservoir that buffers changes in PM tension, but may also be envisioned as a potential key element in tuning mechanosignaling events. Therefore, the main objective of the project is to decipher how the disruption/reformation cycle of caveolae initiates and encodes the signaling information at the plasma membrane. More concretely, we plan to investigate theoretically (task 1) and experimentally (task 2-4): - the molecular interactions controlling the organization of caveolae in response to different types of mechanical stresses. By finely controlling the nature and magnitude of the imposed mechanical perturbations (task 3), quantitative observations on the actual numbers of caveolae constituents in nano-sized areas of the cell membrane, their diversity, as well as on the dynamics of complexes disruption and reformation will be obtained in resting conditions (task 2) and under mechanical stress (task 4); - the molecular pathways by which caveolae-mediated mechano-signaling occurs (task 4). At the early steps of the mechano-signaling process, we expect to decipher with appropriate spatio-temporal resolution the cascade of molecular events occurring during caveolae disassembly. We aim also to identify the more downstream molecular pathways using a high throughput proteomics approach. Our new transdisciplinary consortium assembles the staff, knowledge, tools, facilities and collaborations required for a sustained, effective research program into the functional inference of caveolae in mechanotransduction processes. The DECAV-RECAV program has the necessary technical ingredients for success plus the vision, the teamwork and laboratory commitment to sustain its progress with i) theoretical physicists specialized in biological membranes (P1), ii) cell biologists specialized in caveolae and membrane trafficking (P3), and iii) biophysicists with expertise in biophotonics applied to the analysis of plasma membrane organization (P2) and in micromechanics to design new micromechanical devices (P4). A challenging combination of original customized mechano-devices with advanced fluorescence spectroscopy and nanoscopy will be used to quantify pertinent observables on the principle of caveolae-mediated mechanosensing. Physical modeling will provide information on the coupling between the molecular constituents and the mechanical state of the membrane, and will a quantitative framework to extract relevant mechanical and dynamical parameters from experimental data. In brief, the rationalized and integrated collection of all types of data within reach should allow us to gain important new insights on the molecular mechanisms for pathways in which mechano-signaling represents a critical node of signaling.