Regulation of the plasma membrane tension during cell shape changes
Membrane tension measurement tools
Together with the group of Stefan Matile (organic chemistry, Unige), we developed a Fluorescent Membrane tension probe called “FliptR” for Fluorescent Lipid Tension Reporter (Colom et al. Nat Chem 2018), belonging to the family of Flipper mechanosensitive probes. The flippers are composed of two fluorophores twisted out of plane, but that can be planarized by mechanical forces applied to them, and which headgroup targets a specific flipper probe to a specific organelle (Goujon et al. JACS 2019). We use these tools in the lab to study how membrane tension regulates and is regulated in cell processes.
TORC2 and membrane tension homeostasis
TORC2 is the second complex formed around the kinase Target Of Rapamycin TOR, and is a major regulator of membrane homeostasis, and in particular of membrane tension (Berchtold et al. Nat Cell Biol 2012). Using the Flipper technology, together with the Loewith lab, we showed that TORC2 regulates and is regulated by plasma membrane tension (Riggi et al. Nat Cell Biol 2018), and that TORC2 regulates endocytosis through tension (Riggi et al JCB 2019). We further studied the quantitative changes of membrane tension during osmotic shocks (Roffay et al. PNAS 2021), which could not be performed without flippers. The initial response seconds after the shock is purely passive, and can be quantitatively described by the folding-unfolding of the membrane onto the acto-myosin cortex. It also revealed a fast, TORC2 dependent, active recovery of tension during hypotonic shocks, while hypertonic shocks were essentially passive for several tens of minutes.