Abstract: Actin is an essential protein. For over four decades, intracellular actin filaments have been thought to elongate at their barbed ends and depolymerize from pointed ends. This process, referred to as “treadmilling” has formed the central bedrock of our understanding of actin dynamics. Using a combination of microfluidics-assisted TIRF imaging and multispectral single molecule approaches which my lab has pioneered, our recent discoveries have called into question the universality of the treadmilling dogma. First, we recently discovered a new actin depolymerase, twinfilin, which induces depolymerization at filament barbed ends. Interestingly, we find that the depolymerase twinfilin, polymerase formin and blocker CP form a multicomponent protein ecosystem at the filament ends. Together, these proteins allow temporal and spatial tuning of actin assembly and remodeling. Second, I will present our discovery of a new actin polymerase VopF, which processively polymerizes actin filaments from their pointed ends. Our findings thus challenge the classical dogma of actin treadmilling and call for reevaluation of molecular mechanisms governing intracellular actin dynamics.

Biography: Dr. Shashank Shekhar is an assistant professor of cell biology, physics and biochemistry at Emory University. His research interests are in biological self-assembly at the molecular and organismal scale. He is the recipient of several awards including the NIH MIRA, Whitman Early Career Award at the Marine Biological Laboratory and the Grand advances in Biology Prize from the French Academy of Sciences. He received his PhD in experimental cell biophysics from University of Twente (The Netherlands). He earned his master’s in Nanoscience and Molecular Bioengineering from TU Delft (Netherlands) and TU Dresden (Germany) and undergraduate degree in Physics in India.

Tea/Coffee Time: 5 PM