Biophysical Society Thematic Meeting - June 28-July 1, 2015

New Biological Frontiers Illuminated by Molecular Sensors and Actuators

Poster Abstracts

42-POS Board 42 Curvature-Generating Proteins and Subcellular Pattern Formation Maohan Su , Cheesan Tong, Min Wu. National University of Singapore, Singapore.

Ordered assembly of cellular processes in the form of oscillations and waves is an emerging theme in living cells. Occurrences of such patterns indicate the presence of local and global coupling mechanisms. However, the nature of the coupling remains to be determined. In our recent work, we discovered a striking appearance of FBP17, one of the Bin1/amphiphysin/Rvs167 (BAR) domain proteins, in actin waves of stimulated mast cells. In addition to being a reporter, FBP17 is essential for wave formation. BAR domain proteins are widely known for their curvature sensing and inducing capabilities, motivating us to directly visualize membrane shape and test its function. We will discuss our findings on the role of physical parameters such as membrane curvature and plasma membrane tension in the propagation of waves. Collectively, our work suggests a mechanochemical basis for pattern formation, which regulates the dynamic reorganization of cell cortex in response to external stimulation, the first and essential step of cellular activation. Board 43 Imaging Intraorganellar Ca 2+ at Subcellular Resolution Using CEPIA Junji Suzuki 1 , Kazunori Kanemaru 1 , Kuniaki Ishii 2 , Masamichi Ohkura 3 , Yohei Okubo 1 , Masamitsu Iino 1 . 1 The University of Tokyo, Bunkyo-ku, Tokyo, Japan, 2 Yamagata University, Iida-nishi, Yamagata, Japan, 3 Saitama University, Sakura-ku, Saitama, Japan. The endoplasmic reticulum (ER) and mitochondria accumulate Ca 2+ within their lumens to regulate numerous cell functions. However, determining the dynamics of intraorganellar Ca 2+ has proven to be difficult. Here, we developed a family of genetically-encoded Ca 2+ indicators, named calcium-measuring organelle-entrapped protein indicators (CEPIA), which can be utilized for intra-organellar Ca 2+ imaging. CEPIA, which emit green, red or blue/green fluorescence, were engineered to bind Ca 2+ at intra-organellar Ca 2+ concentrations. They can be targeted to different organelles and may be used alongside other fluorescent molecular markers, expanding the range of cell functions that can be simultaneously analyzed. The spatiotemporal resolution of CEPIA made it possible to resolve Ca 2+ import into individual mitochondria while simultaneously measuring ER and cytosolic Ca 2+ . We used these imaging capabilities to reveal differential Ca 2+ handling in individual mitochondria. CEPIA will provide a useful new approach to further the understanding of organellar functions. 43-POS

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