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Early Competition of Actin and Vinculin for Talin-Binding Dictates Nascent Adhesions’ Maturation and Force Transmission

Dr. Sangyoon J. Han

Assistant Professor, Department of Biomedical Engineering

Michigan Technological University

Abstract

The adhesion proteins talin, vinculin and paxillin act together to help form integrin-based adhesions. However, their spatiotemporal coordination, at the seconds and single-micrometer dimensions typical of individual protrusion events, remains unknown. Here we used high-resolution traction force microscopy, single-particle-tracking, machine learning and time-series analysis to investigate how the mechanical force and the molecular recruitment of talin, vinculin and paxillin synergistically affect nascent adhesions (NAs)’ assembly, disassembly and maturation. From two-channel experiments imaging a protein – either talin, vinculin or paxillin – tagged with eGFP in CHOK cells and TFM beads on a gel, we classified all NAs into nine different sub-classes and quantified a time delay between eGFP signal vs. traction force in the two groups: non-maturing vs. maturing NAs. In non-maturing NAs, both talin and vinculin were recruited ~4 sec before initial traction rise whereas paxillin was recruited at the same time with the initial traction rise. On the contrary, in successfully maturing NAs, talin was recruited ~7 sec earlier than vinculin that was recruited at the same time with the initial traction rise. We also found faster vinculin binding rate, in the first five seconds, in maturing NAs than ones in non-maturing NAs. The traction force growth rate in the maturing vinculin complex was also higher than that in non-maturing vinculin complex. Paxillin showed a signal that comes to NAs, regardless of their fate, concurrently with the traction force and showed also the highest spatial correlation with the force.  Altogether, our data and analyses suggest that talin’s recruitment earlier than vinculin determines NA’s maturation by effective unfolding by actin, which effectively promotes vinculin recruitment and force transmission, whereas paxillin has a passive, force-reporting role in adhesions.

Biography

Sangyoon Han received B.S and M.S. degree in Mechanical Engineering at Seoul National University, Seoul, Korea in 2002 and 2004. He received his Ph.D. from Mechanical Engineering at University of Washington (UW) with Nathan Sniadecki in 2012. He carried out his postdoctoral studies with Gaudenz Danuser in the Department of Cell Biology at University of Texas Southwestern Medical Center. In fall 2017, Sangyoon joined the department of Biomedical Engineering at Michigan Tech as an Assistant Professor. His research interests are in understanding the dynamic nature in force modulation occurring across cell adhesions and cytoskeleton that regulates molecular sensing and downstream signaling response. His lab develops a minimally-perturbing experimental approach and captures heterogeneity of dynamic mechanochemical states using live cell microscopy, computer vision and inverse dynamics to probe feedbacks between cellular structure and mechanical forces.