A critical function for all living organisms is the ability to move when needed. These movements-- intracellular trafficking, cell division, muscle contraction, and cell motility-- are driven by molecular machines that exert an amazing amount of force considering that they are only a few nanometers across. Given the variety of motor proteins in the cell, a key question is how motors cooperate and compete while moving cargoes and applying forces. An emerging paradigm is the notion of "specialized" motors, or motors that are fine-tuned to perform a specific function. Despite the importance of these motor proteins, relatively little is known about their individual adaptations and how these relate to the motility patterns found in the cell. In prior studies, we discovered two myosins with new and distinct processive stepping patterns on actin. Myosin X walks along multiple filaments in a fascin-actin bundle. Nonmuscle myosin IIB (NMIIB), on the other hand, walks along the long-pitch helix of a single actin filament. Both myosins play pivotal roles in migrating cells, including metastasizing tumor cells. Myosin X delivers essential cargoes such as integrins, cadherins and netrin receptors to filopodia at the leading edge of the cell;NMIIB appears in the rear of the cell, wher it maintains cell polarity and internal organization. Thus, it is essential that we understand how both myosins operate so that we can control cell motility through these players. For both myosins, we propose that their two motor domains are synchronized through strain-sensitive gating mechanisms. For both NMIIB and myosin X, gating is tuned to accommodate their unique stepping patterns along actin tracks. We hypothesize that NMIIB has adaptations for tension maintenance, myosin X has adaptations for bundle-selection, and both may have adaptations for twisting single actin filaments. To test these gating mechanisms, we will pursue the following specific aims:
Aim 1 : We will determine how NMIIB takes short, processive steps along actin and maintains cytoskeletal tension.
Aim 2 : We will determine how myosin X is gated in the environment of an actin filament bundle.
Aim 3 : We will determine how both myosins twist actin filaments.
Motile cells use the motor activity of nonmuscle myosin IIB and myosin X to organize and reposition their contents. We will use a battery of advanced single-molecule methods, as well as the tools of molecular genetics, to determine how these myosins are coordinated on their distinct types of actin tracks. Together this work will illuminate how cancer cells escape from the primary tumor, migrate, and invade surrounding tissues.
|Vavra, Kevin C; Xia, Youlin; Rock, Ronald S (2016) Competition between Coiled-Coil Structures and the Impact on Myosin-10 Bundle Selection. Biophys J 110:2517-27|
|Alcala, Diego B; Haldeman, Brian D; Brizendine, Richard K et al. (2016) Myosin light chain kinase steady-state kinetics: comparison of smooth muscle myosin II and nonmuscle myosin IIB as substrates. Cell Biochem Funct 34:469-474|
|Surcel, Alexandra; Ng, Win Pin; West-Foyle, Hoku et al. (2015) Pharmacological activation of myosin II paralogs to correct cell mechanics defects. Proc Natl Acad Sci U S A 112:1428-33|
|Zimmermann, Dennis; Santos, Alicja; Kovar, David R et al. (2015) Actin age orchestrates myosin-5 and myosin-6 run lengths. Curr Biol 25:2057-62|
|Engelmann, Brett W; Kim, Yohan; Wang, Miaoyan et al. (2014) The development and application of a quantitative peptide microarray based approach to protein interaction domain specificity space. Mol Cell Proteomics 13:3647-62|
|Rock, Ronald S (2012) Molecular motors: a finicky myosin V chooses its own path. Curr Biol 22:R606-8|
|Spudich, James A; Rice, Sarah E; Rock, Ronald S et al. (2011) Attachment of anti-GFP antibodies to microspheres for optical trapping experiments. Cold Spring Harb Protoc 2011:1370-1|
|Spudich, James A; Rice, Sarah E; Rock, Ronald S et al. (2011) Optical traps to study properties of molecular motors. Cold Spring Harb Protoc 2011:1305-18|
|Spudich, James A; Rice, Sarah E; Rock, Ronald S et al. (2011) The optical trapping dumbbell assay for nonprocessive motors or motors that turn around filaments. Cold Spring Harb Protoc 2011:1372-4|
|Skau, Colleen T; Courson, David S; Bestul, Andrew J et al. (2011) Actin filament bundling by fimbrin is important for endocytosis, cytokinesis, and polarization in fission yeast. J Biol Chem 286:26964-77|
Showing the most recent 10 out of 24 publications