Medical Research

Northern Arizona University

Kiisa Nishikawa, Brent Nelson, Christopher Mann, Matthew Gage
Flagstaff, AZ
June 2014

The research team will develop new techniques for characterizing protein interactions that will test a radical new theory on muscle contraction.  The prevailing “sliding filament” theory fails to adequately predict muscle behavior during natural movements.  PI Nishikawa’s winding filament hypothesis represents a paradigm shift for the theory of muscle contraction.  She proposes that the titin protein binds to actin upon calcium influx and winds on thin filaments as they are rotated by the cross-bridges during force development.  She has demonstrated that the hypothesis fills existing gaps between experiment and theory.  In order to directly characterize the proposed interactions, the team will develop and validate methods at or beyond the current state-of-the-art.  First, single molecule atomic force spectroscopy will be used to quantify interactions between synthetically produced titin fragments and actin.  Second, the investigators will use fluorescence resonance energy transfer reporters in a cell culture system and subsequently in transgenic mice to visualize and quantify these interactions in real time in living muscle fibers.  Third, to observe the winding of titin on actin filaments, electron holographic tomography will be used to generate 3D images.  The latter two approaches will require improvement of these technologies to yield sufficient data to either validate or disprove the winding filament hypothesis.  Even if the hypothesis is disproved, a set of improved technologies would add value to the field of biological mechanics.  If correct, her hypothesis could inspire new approaches for ameliorating neuromuscular disease and injury.

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