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Fineberg A, Takagi Y, Thirumurugan K, Andrecka J, Billington N, Young G, Cole D, Burgess SA, Curd AP, Hammer JA, Sellers JR, Kukura P, Knight PJ. Myosin-5 varies its step length to carry cargo straight along the irregular F-actin track. Proc Natl Acad Sci U S A 2024; 121:e2401625121. [PMID: 38507449 PMCID: PMC10990141 DOI: 10.1073/pnas.2401625121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 02/15/2024] [Indexed: 03/22/2024] Open
Abstract
Molecular motors employ chemical energy to generate unidirectional mechanical output against a track while navigating a chaotic cellular environment, potential disorder on the track, and against Brownian motion. Nevertheless, decades of nanometer-precise optical studies suggest that myosin-5a, one of the prototypical molecular motors, takes uniform steps spanning 13 subunits (36 nm) along its F-actin track. Here, we use high-resolution interferometric scattering microscopy to reveal that myosin takes strides spanning 22 to 34 actin subunits, despite walking straight along the helical actin filament. We show that cumulative angular disorder in F-actin accounts for the observed proportion of each stride length, akin to crossing a river on variably spaced stepping stones. Electron microscopy revealed the structure of the stepping molecule. Our results indicate that both motor and track are soft materials that can adapt to function in complex cellular conditions.
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Affiliation(s)
- Adam Fineberg
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
- Laboratory of Single Molecule Biophysics, Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Yasuharu Takagi
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Kavitha Thirumurugan
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
| | - Joanna Andrecka
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
| | - Neil Billington
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Gavin Young
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
| | - Daniel Cole
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
| | - Stan A. Burgess
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
| | - Alistair P. Curd
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
| | - John A. Hammer
- Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - James R. Sellers
- Laboratory of Molecular Physiology, Cell and Developmental Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD20892
| | - Philipp Kukura
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, OxfordOX1 3QZ, United Kingdom
- The Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin Building, University of Oxford, OxfordOX1 3QU, United Kingdom
| | - Peter J. Knight
- Astbury Centre for Structural Molecular Biology, and School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, LeedsLS2 9JT, United Kingdom
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Silverman JB, Krystofiak EE, Caplan LR, Lau KS, Tyska MJ. Intestinal tuft cells assemble a cytoskeletal superstructure composed of co-aligned actin bundles and microtubules. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.19.585757. [PMID: 38562898 PMCID: PMC10983963 DOI: 10.1101/2024.03.19.585757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Background & Aims All tissues consist of a distinct set of cell types, which collectively support organ function and homeostasis. Tuft cells are a rare epithelial cell type found in diverse epithelia, where they play important roles in sensing antigens and stimulating downstream immune responses. Exhibiting a unique polarized morphology, tuft cells are defined by an array of giant actin filament bundles that support ∼2 μm of apical membrane protrusion and extend over 7 μm towards the cell's perinuclear region. Despite their established roles in maintaining intestinal epithelial homeostasis, tuft cells remain understudied due to their rarity (e.g. ∼ 1% in the small intestinal epithelium). Details regarding the ultrastructural organization of the tuft cell cytoskeleton, the molecular components involved in building the array of giant actin bundles, and how these cytoskeletal structures support tuft cell biology remain unclear. Methods To begin to answer these questions, we used advanced light and electron microscopy to perform quantitative morphometry of the small intestinal tuft cell cytoskeleton. Results We found that tuft cell core bundles consist of actin filaments that are crosslinked in a parallel "barbed-end out" configuration. These polarized structures are also supported by a unique group of tuft cell enriched actin-binding proteins that are differentially localized along the giant core bundles. Furthermore, we found that tuft cell actin bundles are co-aligned with a highly ordered network of microtubules. Conclusions Tuft cells assemble a cytoskeletal superstructure that is well positioned to serve as a track for subcellular transport along the apical-basolateral axis and in turn, support the dynamic sensing functions that are critical for intestinal epithelial homeostasis. SYNOPSIS This research leveraged advanced light and electron microscopy to perform quantitative morphometry of the intestinal tuft cell cytoskeleton. Three-dimensional reconstructions of segmented image data revealed a co-aligned actin-microtubule superstructure that may play a fundamental role in tuft cell function.
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Miller MD, Phillips GN. Moving beyond static snapshots: Protein dynamics and the Protein Data Bank. J Biol Chem 2021; 296:100749. [PMID: 33961840 PMCID: PMC8164045 DOI: 10.1016/j.jbc.2021.100749] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 04/28/2021] [Accepted: 04/30/2021] [Indexed: 01/02/2023] Open
Abstract
Proteins are the molecular machines of living systems. Their dynamics are an intrinsic part of their evolutionary selection in carrying out their biological functions. Although the dynamics are more difficult to observe than a static, average structure, we are beginning to observe these dynamics and form sound mechanistic connections between structure, dynamics, and function. This progress is highlighted in case studies from myoglobin and adenylate kinase to the ribosome and molecular motors where these molecules are being probed with a multitude of techniques across many timescales. New approaches to time-resolved crystallography are allowing simple “movies” to be taken of proteins in action, and new methods of mapping the variations in cryo-electron microscopy are emerging to reveal a more complete description of life’s machines. The results of these new methods are aided in their dissemination by continual improvements in curation and distribution by the Protein Data Bank and their partners around the world.
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Affiliation(s)
| | - George N Phillips
- Department of Biosciences, Rice University, Houston, Texas, USA; Department of Chemistry, Rice University, Houston, Texas, USA.
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