Biophysical investigation of lipid droplet fusion

ORAL

Abstract

Lipid droplets are important intracellular organelles. Aside from maintaining internal energy stability these intracellular organelles function in processes as diverse as lipid signaling, synthesis of steroid hormones and viral replication. Lipid droplets mature through cell processes like fusion. Recently, we showed that oil droplet fusion can be followed via a specially designed optical trap method whereby two oil droplets are captured in two traps, then brought together. The top trap is turned off so that oil droplets join in the bottom trap. The process of merging within the trap can be separated into two stages: (a) A docking stage which depends strongly on the concentration of ions in the solution and type of anion in solution according to the Hoffmeister series; (b) The physical fusion of the two droplets. To further investigate mechanism of the observed behavior, especially effect of ions, we used a home-built liquid droplet tensiometer to determine the interfacial tension of an oil droplet in solution and its dependence on the type of anion and its concentration. Results show that interfacial tension alone cannot explain the fusion of lipid droplet. The interfacial tension does not significantly change from 10 to 50 mM ion concentration, while the docking rate of oil droplet fusion increases 10 fold. The interfacial tension also shows no trend with the Hoffmeister anion series.

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Authors

  • Mona Mirheydari

    Department of Physics, Kent State University

  • Chiran Ghimire

    Department of Chemistry and Biochemistry, Kent State University

  • Frazier Baker

    Youngstown State University, Kent State University, Liquid Crystal Institute, Kent State University, Department of Biological Sciences, Kent State University, Department of Physics, Department of Chemistry and Biochemistry, Kent State University, Stony Brook Univ, Ohio Univ, Institute for Advanced Simulation, Institut fur Kernphysik, and Julich Center, Bowling Green State University, Dept. of Physics, Hiram College, Ohio State Univ - Columbus, Kent State University, Psychology Dept, Cleveland State University, Physics Dept, Cleveland State University, Chemical Physics Interdisciplinary Program and Liquid Crystal Institute, Kent State University, Kent, OH 44242-0001, USA, Univ of Konstanz, Univ College London, NIST, Hiroshima Univ, KIT, Missouri University of Science and Technology, University of California, San Diego, Georgia Institute of Technology, KSU, SKKU, Lock Haven Univ, Massachusetts General Hospital, University of Science and Technology of China, Yale University, Shanghai Institute of Microsystem and Information Technology, CAS, Nanjing University, Liquid Crystal Institute and Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242, USA, Department of Physics, Kent State University, Kent OH 44242, Department of Electro-Optic Engineering Ilse Katz Institute for Nanoscale Science and Technology Ben Gurion University, Beer Sheva 84105, Israel, Ohio University Zanesville

  • Elizabeth K. Mann

    Department of Physics, Kent State University

  • Edgar E. Kooijman

    Department of Biological Sciences, Kent State University