The focus of this proposal is to study the effect of higher ordered actin structure and of actin binding proteins for the processivity and movement behavior of myosin V molecule. Recently, many in vitro motility studies investigated how myosin V moves on actin filament, measuring parameters such as the run length, velocity and step size, but these studies almost always have used only single actin filaments for the track. However, actin filaments form many kinds of higher ordered structures such as branching networks, loose bundles and highly ordered bundles inside cells. This study will give insight into fundamental questions such as can myosin V step laterally from one filament to another? when moving on a bundle? Does this result in longer run lengths than observed on single filaments? Does binding of tropomyosin to actin affect the velocity or run length? To answer these questions, I will use three different actin formations.
As AIM 1, (1) single actin filaments decorated by nonmuscle tropomyosin, or the actin binding proteins, fascin, and a-actinin. (2) Two dimensional paracrystalline arrays of actin filaments bundled on lipid monolayers with a-actinin or fascin. (3) Three dimensional bundles of actin filaments mediated by a-actinin or fascin formed in solution. I will measured run-length and speed of myosin V on two dimentional actin bundles and will use to test for a fiexibility of the myosin neck using these above different types of actin tracks.
As AIM 2, 1 will prepare Triton-insoluble cytoskeletons by treatment of cells growing on a coverslip surface by treatment with Triton X-100 to remove membranes and with rhodamine phalloidin to stabilize the acfin filaments. The movement of fiuorescently labeled myosin V molecules will be measured using total internal reflection fiuorescent microscopy and an analysis technique, termed FIONA (Fluorescent Imaging at One Nanometer Accuracy) which measures the position of a single fiuorophor to 1.5 nm accuracy with 0.5 s temporal resolution.
In AIM 1 and 2,1 will answer how does myosin V step over different kinds of actin bundles and how does myosin V move along a highly ordered actin structure as a transporter.
AIM 3, 1 have completed thi project.

Public Health Relevance

The molecular motor, myosin V, is responsible for a wide variety of subcellular movements, such as the motion of melanosomes in melanocytes, mRNA in yeast, and smooth ER in neuron. For example, mutations of myosin Va lead to Griscelli's disease, which is an autosomal recessive disorder. It is a key to know how myosin V transpors a cargo, such as traffic path way, the detail of the motion on actin.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Transition Award (R00)
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Special Emphasis Panel (NSS)
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Liang, Isabella Y
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Wayne State University
Schools of Arts and Sciences
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Gunther, Laura K; Feng, Han-Zhong; Wei, Hongguang et al. (2016) Effect of N-Terminal Extension of Cardiac Troponin I on the Ca(2+) Regulation of ATP Binding and ADP Dissociation of Myosin II in Native Cardiac Myofibrils. Biochemistry 55:1887-97
Bao, Jianjun; Wang, Shuo; Gunther, Laura K et al. (2015) The actin-bundling protein TRIOBP-4 and -5 promotes the motility of pancreatic cancer cells. Cancer Lett 356:367-73
Gunther, Laura K; Furuta, Ken'ya; Bao, Jianjun et al. (2014) Coupling of two non-processive myosin 5c dimers enables processive stepping along actin filaments. Sci Rep 4:4907
Bao, Jianjun; Bielski, Elizabeth; Bachhawat, Ankita et al. (2013) R1 motif is the major actin-binding domain of TRIOBP-4. Biochemistry 52:5256-64
Nagy, Nikolett T; Chakraborty, Saikat; Harami, Gabor M et al. (2013) A subdomain interaction at the base of the lever allosterically tunes the mechanochemical mechanism of myosin 5a. PLoS One 8:e62640
Bao, Jianjun; Huck, Daniel; Gunther, Laura K et al. (2013) Actin structure-dependent stepping of myosin 5a and 10 during processive movement. PLoS One 8:e74936