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Chinowsky CR, Pinette JA, Meenderink LM, Lau KS, Tyska MJ. Nonmuscle myosin-2 contractility-dependent actin turnover limits the length of epithelial microvilli. Mol Biol Cell 2020; 31:2803-2815. [PMID: 33026933 PMCID: PMC7851865 DOI: 10.1091/mbc.e20-09-0582] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 09/24/2020] [Accepted: 09/28/2020] [Indexed: 12/14/2022] Open
Abstract
Brush border microvilli enable functions that are critical for epithelial homeostasis, including solute uptake and host defense. However, the mechanisms that regulate the assembly and morphology of these protrusions are poorly understood. The parallel actin bundles that support microvilli have their pointed-end rootlets anchored in a filamentous meshwork referred to as the "terminal web." Although classic electron microscopy studies revealed complex ultrastructure, the composition and function of the terminal web remain unclear. Here we identify nonmuscle myosin-2C (NM2C) as a component of the terminal web. NM2C is found in a dense, isotropic layer of puncta across the subapical domain, which transects the rootlets of microvillar actin bundles. Puncta are separated by ∼210 nm, the expected size of filaments formed by NM2C. In intestinal organoid cultures, the terminal web NM2C network is highly dynamic and exhibits continuous remodeling. Using pharmacological and genetic perturbations in cultured intestinal epithelial cells, we found that NM2C controls the length of growing microvilli by regulating actin turnover in a manner that requires a fully active motor domain. Our findings answer a decades-old question on the function of terminal web myosin and hold broad implications for understanding apical morphogenesis in diverse epithelial systems.
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Affiliation(s)
- Colbie R. Chinowsky
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Julia A. Pinette
- Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Leslie M. Meenderink
- Division of Infectious Diseases, Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232
| | - Ken S. Lau
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
| | - Matthew J. Tyska
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232
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Meenderink LM, Gaeta IM, Postema MM, Cencer CS, Chinowsky CR, Krystofiak ES, Millis BA, Tyska MJ. Actin Dynamics Drive Microvillar Motility and Clustering during Brush Border Assembly. Dev Cell 2019; 50:545-556.e4. [PMID: 31378589 DOI: 10.1016/j.devcel.2019.07.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 05/03/2019] [Accepted: 07/02/2019] [Indexed: 12/12/2022]
Abstract
Transporting epithelial cells generate arrays of microvilli, known as a brush border, to enhance functional capacity. To understand brush border formation, we used live cell imaging to visualize apical remodeling early in this process. Strikingly, we found that individual microvilli exhibit persistent active motility, translocating across the cell surface at ∼0.2 μm/min. Perturbation with inhibitors and photokinetic experiments revealed that microvillar motility is driven by actin assembly at the barbed ends of core bundles, which in turn is linked to robust treadmilling of these structures. Actin regulatory factors IRTKS and EPS8 localize to the barbed ends of motile microvilli, where they control the kinetics and nature of movement. As the apical surface of differentiating epithelial cells is crowded with nascent microvilli, persistent motility promotes collisions between protrusions and ultimately clustering and consolidation into higher-order arrays. Thus, microvillar motility represents a previously unrecognized driving force for apical surface remodeling and maturation during epithelial differentiation.
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Affiliation(s)
- Leslie M Meenderink
- Department of Medicine, Division of Infectious Diseases, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Isabella M Gaeta
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Meagan M Postema
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Caroline S Cencer
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Colbie R Chinowsky
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Evan S Krystofiak
- Cell Imaging Shared Resource, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Bryan A Millis
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Department of Biomedical Engineering, Vanderbilt University School of Engineering, Nashville, TN 37232, USA; Cell Imaging Shared Resource, Vanderbilt University School of Medicine, Nashville, TN 37232, USA; Vanderbilt Biophotonics Center, Vanderbilt University, Nashville, TN 37232, USA
| | - Matthew J Tyska
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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