Biochemistry and Biophysics of Signaling Proteins
The central goal of the Falke lab is a molecular understanding of cellular signaling on membrane surfaces, specifically the lipid signaling pathways that control macrophage chemotaxis and phagocytosis in the innate immune response. Macrophages and other white blood cells possess a remarkable chemosensory pathway that enables these first responders to follow chemical trails to sites of infection, inflammation, and tissue damage. Upon arrival, the phagocytosis pathway triggers the engulfment and destruction of invading bacteria, viruses, and damaged cells. The regulatory hubs of these pathways are lipid kinases (PI-3-kinases or PI3Ks) that phosphorylate substrate phosphatidylinositol (PI) lipids at the 3-position of the inositol sugar headgroup, yielding the essential signaling lipids PI-3,4,5-trisphosphate (PIP3) in the chemosensory pathway, and PI-3-phosphate (PI3P) in phagocytosis. More broadly, PIP3 and PI3P signals are essential in all cell types where they control multiple cell processes, and their dysregulation triggers a diverse array of pathologies including cancer. Understanding the molecular mechanisms of these signals is crucial for optimal therapeutic targeting.
The Falke lab seeks to elucidate the mechanisms by which PIP3 and PI3P signaling pathways are regulated by native signals, disease-linked mutations, and potential therapeutic drugs. The group employs a unique approach combining complementary in vitro single molecule and live cell methods to probe the switching of signaling proteins between their 'on' and 'off' signaling states, as well as sequential information transfer between signalng proteins in a working biological circuit. The approach begins with single molecule TIRF studies of a reconstituted, multi-protein circuit on a supported lipid bilayer mimicking the native membrane. These single molecule studies elucidate the regulatory mechanisms underlying signal transduction. Subsequently, the hypothesized mechanisms are tested by fluorescence imaging studies in live macrophages, thereby revealing which mechanisms are most important in the cellular context. Projects are available to carry out single molecule studies of reconstituted signaling circuits, or model testing via cell imaging in live macrophages, or both. The lab also employs a broad array of other biophysical and biochemical tools as needed to address key biomedical questions.
