Klaus M. Hahn

TL;DR: A new approach to produce genetically encoded photoactivatable derivatives of Rac1, a key GTPase regulating actin cytoskeletal dynamics in metazoan cells, which was shown to inhibit RhoA in mouse embryonic fibroblasts, with inhibition modulated at protrusions and ruffles.

TL;DR: GTPase coordination in mouse embryonic fibroblasts is examined both through simultaneous visualization of two GTPase biosensors and using a ‘computational multiplexing’ approach capable of defining the relationships between multiple protein activities visualized in separate experiments, finding that RhoA is activated at the cell edge synchronous with edge advancement, whereas Cdc42 and Rac1 are activated 2 μm behind the edge with a delay of 40 s.

TL;DR: Fluorescent biosensor data show that different extracellular cues induce distinct patterns of RhoA signalling during membrane protrusion, potentially because PDGF strongly activates Rac, which has previously been shown to antagonize RHoA activity.

TL;DR: Inhibitors of Na+/H+ exchange proteins block macropinocytosis by lowering the pH near the plasma membrane, which in turn inhibits actin remodeling by Rho family GTPases.

TL;DR: A method called FLAIR (fluorescence activation indicator for Rho proteins) was developed to quantify the spatio-temporal dynamics of the Rac1 nucleotide state in living cells, revealing precise spatial control of growth factor-induced Rac activation, in membrane ruffles and in a gradient of activation at the leading edge of motile cells.