About the Seminar:
Raf is an important kinase that initiates the three-tiered Raf-MEK-ERK signaling cascade in response to diverse receptor stimuli. Understanding the regulation of Raf membrane binding is crucial to fully grasp its activation mechanisms, as Raf activation exclusively occurs on membrane surfaces. However, there is a notable lack of quantitative experimental studies exploring how Raf integrates both protein and lipid inputs for proper activation and deactivation. To address this gap, we used single-molecule total internal reflection fluorescence microscopy (smTIRF) and fluorescence correlation spectroscopy (FCS) to examine the molecular binding and diffusion of Raf on supported lipid membranes. Our findings reveal functional coupling between the Ras binding domain (RBD) and the cysteine-rich domain (CRD) within Raf’s regulatory region. This coupling gives rise to distinct modulation of the membrane association and dissociation rates of Raf, demonstrating a strong dependency of membrane binding kinetics on the surface density of Ras and anionic lipids. Additionally, we investigated how Ras-Raf complex formation and membrane environments resist deactivation by GTPase-activating proteins (GAPs). Our results provide new insights into the kinetic mechanisms underlying Raf activation, particularly the release of its autoinhibited complex and the transition from monomer to dimer in the context of Ras nanoclusters.
About the Speaker:
Dr. Lee is an Assistant Professor in the Department of Chemistry and Biochemistry at San Diego State University. He earned his Bachelor’s and Master’s degrees in Chemistry from Kookmin University, followed by a Ph.D. in Chemistry from Seoul National University. After completing his doctoral studies, he conducted postdoctoral research at UC Berkeley before joining the faculty at SDSU in 2018. Dr. Lee is a recipient of the NSF CAREER award, and his research focuses on understanding the molecular mechanisms of signal transduction using optical microscopy and spectroscopy techniques.
