Role of Motor/cargo Attachment Mechanics in Collective Kinesin Transport

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

Cell survival depends on the efficient transport and sorting of protein and chemical species into different functional compartments. Nanoscale motor proteins that grasp membrane-bound cargos and move them along polymer filaments enable this transport. The resultant cargo motion is thought to arise from the cooperative action of multiple motor proteins, but the extent of cooperation and the molecular mechanisms that enable it are poorly understood. One possible mechanism for cooperation lies in the ability of multiple motors to share the load necessary to move the cargo. Such load splitting is expected to depend strongly on the mechanical properties of the cargo surface, but the detailed relationship between load splitting, transport efficiency, and cargo mechanics is unknown. The objective of this research project is to determine how membrane mechanics influences the ability of motor proteins to cooperatively transport cargos. To this end, biomimetic cargos with well-controlled interfacial chemistry and mechanical properties will be generated and coupled to motor proteins in vitro. The mechanical properties of the cargo surfaces will be varied from purely rigid surfaces with immobile motor attachment sites to purely fluid surfaces made of lipids that can rearrange their positions. The fluid cargos, which are thought to better mimic the properties of cargos in living cells, would allow motor binding sites to easily move on the cargo surface as the motor proteins move. The impact of these interfacial lipid rearrangements on cargo motion will be assessed using precision biophysical tools. Specifically, the ability of motors to cooperatively move fluid and rigid cargos against an external force will be determined and quantitatively compared. Computer simulations and analytical theory will be developed to understand the experimental data and generate testable predictions for the effects of membrane mechanics on cargo transport in cells. If successful, this research will provide important new insight into the fundamental mechanisms and regulation of intracellular transport, while creating outreach and training activities at the interface of biology, physics, and engineering. In particular, community college and undergraduate students will participate in hands-on research, and this work will form the thesis project of one graduate student, who will develop expertise in experiments, computation and analytical theory. The outcomes of this project will be incorporated into interdisciplinary biophysics/biomechanics courses at UCSB and the Santa Barbara Advanced School for Quantitative Biology, and will be disseminated broadly in publications and conferences.