1
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Sung CYW, Barzik M, Costain T, Wang L, Cunningham LL. Semi-automated Quantification of Hair Cells in the Mature Mouse Utricle. Hear Res 2022; 416:108429. [PMID: 35081508 PMCID: PMC9034969 DOI: 10.1016/j.heares.2021.108429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 11/19/2021] [Accepted: 12/28/2021] [Indexed: 02/09/2023]
Abstract
The mouse utricle model system is the best-characterized ex vivo preparation for studies of mature mammalian hair cells (HCs). Despite the many advantages of this model system, efficient and reliable quantification of HCs from cultured utricles has been a persistent challenge with this model system. Utricular HCs are commonly quantified by counting immunolabeled HCs in regions of interest (ROIs) placed over an image of the utricle. Our data indicate that the accuracy of HC counts obtained using this method can be impacted by variability in HC density across different regions of the utricle. In addition, the commonly used HC marker myosin 7a results in a diffuse cytoplasmic stain that is not conducive to automated quantification and must be quantified manually, a labor-intensive task. Furthermore, myosin 7a immunoreactivity is retained in dead HCs, resulting in inaccurate quantification of live HCs using this marker. Here we have developed a method for semi-automated quantification of surviving HCs that combines immunoreactivity for the HC-specific transcription factor Pou4f3 with labeling of activated caspase 3/7 (AC3/7) to detect apoptotic HCs. The discrete nuclear Pou4f3 signal allowed us to utilize the binary or threshold function within ImageJ to automate HC quantification. To further streamline this process, we created an ImageJ macro that automates the process from raw image loading to a final quantified image that can be immediately evaluated for accuracy. Within this quantified image, the user can manually correct the quantification via an image overlay indicating the counted HC nuclei. Pou4f3-positive HCs that also express AC3/7 are subtracted to yield accurate counts of surviving HCs. Overall, we present a semi-automated method that is faster than manual HC quantification and identifies surviving HCs with high accuracy.
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2
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Hochberg I, Demain LA, Richer J, Thompson K, Urquhart JE, Rea A, Pagarkar W, Rodríguez-Palmero A, Schlüter A, Verdura E, Pujol A, Quijada-Fraile P, Amberger A, Deutschmann AJ, Demetz S, Gillespie M, Belyantseva IA, McMillan HJ, Barzik M, Beaman GM, Motha R, Ng KY, O’Sullivan J, Williams SG, Bhaskar SS, Lawrence IR, Jenkinson EM, Zambonin JL, Blumenfeld Z, Yalonetsky S, Oerum S, Rossmanith W, Yue WW, Zschocke J, Munro KJ, Battersby BJ, Friedman TB, Taylor RW, O’Keefe RT, Newman WG, Newman WG. Bi-allelic variants in the mitochondrial RNase P subunit PRORP cause mitochondrial tRNA processing defects and pleiotropic multisystem presentations. Am J Hum Genet 2021; 108:2195-2204. [PMID: 34715011 PMCID: PMC8595931 DOI: 10.1016/j.ajhg.2021.10.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 10/07/2021] [Indexed: 02/03/2023] Open
Abstract
Human mitochondrial RNase P (mt-RNase P) is responsible for 5′ end processing of mitochondrial precursor tRNAs, a vital step in mitochondrial RNA maturation, and is comprised of three protein subunits: TRMT10C, SDR5C1 (HSD10), and PRORP. Pathogenic variants in TRMT10C and SDR5C1 are associated with distinct recessive or x-linked infantile onset disorders, resulting from defects in mitochondrial RNA processing. We report four unrelated families with multisystem disease associated with bi-allelic variants in PRORP, the metallonuclease subunit of mt-RNase P. Affected individuals presented with variable phenotypes comprising sensorineural hearing loss, primary ovarian insufficiency, developmental delay, and brain white matter changes. Fibroblasts from affected individuals in two families demonstrated decreased steady state levels of PRORP, an accumulation of unprocessed mitochondrial transcripts, and decreased steady state levels of mitochondrial-encoded proteins, which were rescued by introduction of the wild-type PRORP cDNA. In mt-tRNA processing assays performed with recombinant mt-RNase P proteins, the disease-associated variants resulted in diminished mitochondrial tRNA processing. Identification of disease-causing variants in PRORP indicates that pathogenic variants in all three subunits of mt-RNase P can cause mitochondrial dysfunction, each with distinct pleiotropic clinical presentations.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - William G Newman
- Division of Evolution, Infection, and Genomics, School of Biological Sciences, University of Manchester, Manchester M13 9PL, UK; Manchester Centre for Genomic Medicine, St Mary's Hospital, Manchester University NHS Foundation Trust, Manchester M13 9WL, UK.
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3
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McGrath J, Tung CY, Liao X, Belyantseva IA, Roy P, Chakraborty O, Li J, Berbari NF, Faaborg-Andersen CC, Barzik M, Bird JE, Zhao B, Balakrishnan L, Friedman TB, Perrin BJ. Actin at stereocilia tips is regulated by mechanotransduction and ADF/cofilin. Curr Biol 2021; 31:1141-1153.e7. [PMID: 33400922 PMCID: PMC8793668 DOI: 10.1016/j.cub.2020.12.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 10/21/2020] [Accepted: 12/07/2020] [Indexed: 11/30/2022]
Abstract
Stereocilia on auditory sensory cells are actin-based protrusions that mechanotransduce sound into an electrical signal. These stereocilia are arranged into a bundle with three rows of increasing length to form a staircase-like morphology that is required for hearing. Stereocilia in the shorter rows, but not the tallest row, are mechanotransducing because they have force-sensitive channels localized at their tips. The onset of mechanotransduction during mouse postnatal development refines stereocilia length and width. However, it is unclear how actin is differentially regulated between stereocilia in the tallest row of the bundle and the shorter, mechanotransducing rows. Here, we show actin turnover is increased at the tips of mechanotransducing stereocilia during bundle maturation. Correspondingly, from birth to postnatal day 6, these stereocilia had increasing amounts of available actin barbed ends, where monomers can be added or lost readily, as compared with the non-mechanotransducing stereocilia in the tallest row. The increase in available barbed ends depended on both mechanotransduction and MYO15 or EPS8, which are required for the normal specification and elongation of the tallest row of stereocilia. We also found that loss of the F-actin-severing proteins ADF and cofilin-1 decreased barbed end availability at stereocilia tips. These proteins enriched at mechanotransducing stereocilia tips, and their localization was perturbed by the loss of mechanotransduction, MYO15, or EPS8. Finally, stereocilia lengths and widths were dysregulated in Adf and Cfl1 mutants. Together, these data show that actin is remodeled, likely by a severing mechanism, in response to mechanotransduction.
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Affiliation(s)
- Jamis McGrath
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Chun-Yu Tung
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Xiayi Liao
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Inna A Belyantseva
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Pallabi Roy
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Oisorjo Chakraborty
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Jinan Li
- Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, 1160 West Michigan Street, Indianapolis, IN 46202, USA
| | - Nicolas F Berbari
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Christian C Faaborg-Andersen
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Melanie Barzik
- Section on Sensory Cell Biology, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Jonathan E Bird
- Department of Pharmacology and Therapeutics, University of Florida, 1200 Newell Drive, Gainesville, FL 32610, USA
| | - Bo Zhao
- Department of Otolaryngology-Head and Neck Surgery, Indiana University School of Medicine, 1160 West Michigan Street, Indianapolis, IN 46202, USA
| | - Lata Balakrishnan
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
| | - Thomas B Friedman
- Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, NIH, 35A Convent Drive, Bethesda, MD 20892, USA
| | - Benjamin J Perrin
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA.
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Alexander CJ, Barzik M, Fujiwara I, Remmert K, Wang YX, Petralia RS, Friedman TB, Hammer JA. Myosin 18Aα targets the guanine nucleotide exchange factor β-Pix to the dendritic spines of cerebellar Purkinje neurons and promotes spine maturation. FASEB J 2021; 35:e21092. [PMID: 33378124 PMCID: PMC8357457 DOI: 10.1096/fj.202001449r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/24/2020] [Accepted: 09/22/2020] [Indexed: 12/13/2022]
Abstract
Myosin 18Aα is a myosin 2-like protein containing unique N- and C-terminal protein interaction domains that co-assembles with myosin 2. One protein known to bind to myosin 18Aα is β-Pix, a guanine nucleotide exchange factor (GEF) for Rac1 and Cdc42 that has been shown to promote dendritic spine maturation by activating the assembly of actin and myosin filaments in spines. Here, we show that myosin 18A⍺ concentrates in the spines of cerebellar Purkinje neurons via co-assembly with myosin 2 and through an actin binding site in its N-terminal extension. miRNA-mediated knockdown of myosin 18A⍺ results in a significant defect in spine maturation that is rescued by an RNAi-immune version of myosin 18A⍺. Importantly, β-Pix co-localizes with myosin 18A⍺ in spines, and its spine localization is lost upon myosin 18A⍺ knockdown or when its myosin 18A⍺ binding site is deleted. Finally, we show that the spines of myosin 18A⍺ knockdown Purkinje neurons contain significantly less F-actin and myosin 2. Together, these data argue that mixed filaments of myosin 2 and myosin 18A⍺ form a complex with β-Pix in Purkinje neuron spines that promotes spine maturation by enhancing the assembly of actin and myosin filaments downstream of β-Pix's GEF activity.
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Affiliation(s)
- Christopher J Alexander
- Molecular Cell Biology Laboratory, Cell and Developmental Biology Center, NHLBI, NIH, Bethesda, MD, USA
| | - Melanie Barzik
- Laboratory of Molecular Genetics, NIDCD, NIH, Bethesda, MD, USA
| | - Ikuko Fujiwara
- Graduate School of Science, Osaka City University, Osaka, Japan
| | | | - Ya-Xian Wang
- Advanced Imaging Core, NIDCD, NIH, Betheda, MD, USA
| | | | | | - John A Hammer
- Molecular Cell Biology Laboratory, Cell and Developmental Biology Center, NHLBI, NIH, Bethesda, MD, USA
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5
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Weghorst F, Mirzakhanyan Y, Samimi K, Dhillon M, Barzik M, Cunningham LL, Gershon PD, Cramer KS. Caspase-3 Cleaves Extracellular Vesicle Proteins During Auditory Brainstem Development. Front Cell Neurosci 2020; 14:573345. [PMID: 33281555 PMCID: PMC7689216 DOI: 10.3389/fncel.2020.573345] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Accepted: 10/05/2020] [Indexed: 12/26/2022] Open
Abstract
Sound localization requires extremely precise development of auditory brainstem circuits, the molecular mechanisms of which are largely unknown. We previously demonstrated a novel requirement for non-apoptotic activity of the protease caspase-3 in chick auditory brainstem development. Here, we used mass spectrometry to identify proteolytic substrates of caspase-3 during chick auditory brainstem development. These auditory brainstem caspase-3 substrates were enriched for proteins previously shown to be cleaved by caspase-3, especially in non-apoptotic contexts. Functional annotation analysis revealed that our caspase-3 substrates were also enriched for proteins associated with several protein categories, including proteins found in extracellular vesicles (EVs), membrane-bound nanoparticles that function in intercellular communication. The proteome of EVs isolated from the auditory brainstem was highly enriched for our caspase-3 substrates. Additionally, we identified two caspase-3 substrates with known functions in axon guidance, namely Neural Cell Adhesion Molecule (NCAM) and Neuronal-glial Cell Adhesion Molecule (Ng-CAM), that were found in auditory brainstem EVs and expressed in the auditory pathway alongside cleaved caspase-3. Taken together, these data suggest a novel developmental mechanism whereby caspase-3 influences auditory brainstem circuit formation through the proteolytic cleavage of extracellular vesicle (EV) proteins.
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Affiliation(s)
- Forrest Weghorst
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States
| | - Yeva Mirzakhanyan
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
| | - Kian Samimi
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States
| | - Mehron Dhillon
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States
| | - Melanie Barzik
- Section on Sensory Cell Biology, NIDCD, NIH, Bethesda, MD, United States
| | - Lisa L. Cunningham
- Section on Sensory Cell Biology, NIDCD, NIH, Bethesda, MD, United States
| | - Paul D. Gershon
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA, United States
| | - Karina S. Cramer
- Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States
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6
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Breglio AM, May LA, Barzik M, Welsh NC, Francis SP, Costain TQ, Wang L, Anderson DE, Petralia RS, Wang YX, Friedman TB, Wood MJ, Cunningham LL. Exosomes mediate sensory hair cell protection in the inner ear. J Clin Invest 2020; 130:2657-2672. [PMID: 32027617 PMCID: PMC7190999 DOI: 10.1172/jci128867] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 01/30/2020] [Indexed: 12/17/2022] Open
Abstract
Hair cells, the mechanosensory receptors of the inner ear, are responsible for hearing and balance. Hair cell death and consequent hearing loss are common results of treatment with ototoxic drugs, including the widely used aminoglycoside antibiotics. Induction of heat shock proteins (HSPs) confers protection against aminoglycoside-induced hair cell death via paracrine signaling that requires extracellular heat shock 70-kDa protein (HSP70). We investigated the mechanisms underlying this non-cell-autonomous protective signaling in the inner ear. In response to heat stress, inner ear tissue releases exosomes that carry HSP70 in addition to canonical exosome markers and other proteins. Isolated exosomes from heat-shocked utricles were sufficient to improve survival of hair cells exposed to the aminoglycoside antibiotic neomycin, whereas inhibition or depletion of exosomes from the extracellular environment abolished the protective effect of heat shock. Hair cell-specific expression of the known HSP70 receptor TLR4 was required for the protective effect of exosomes, and exosomal HSP70 interacted with TLR4 on hair cells. Our results indicate that exosomes are a previously undescribed mechanism of intercellular communication in the inner ear that can mediate nonautonomous hair cell survival. Exosomes may hold potential as nanocarriers for delivery of therapeutics against hearing loss.
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Affiliation(s)
- Andrew M. Breglio
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- Icahn School of Medicine at Mount Sinai, New York, New York, USA
- NIH Oxford-Cambridge Scholars Program, Bethesda, Maryland, USA
| | - Lindsey A. May
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Melanie Barzik
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Nora C. Welsh
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Shimon P. Francis
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Tucker Q. Costain
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Lizhen Wang
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - D. Eric Anderson
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), NIH, Bethesda, Maryland, USA
| | - Ronald S. Petralia
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Ya-Xian Wang
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Thomas B. Friedman
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
| | - Matthew J.A. Wood
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- Department of Paediatrics, University of Oxford, Oxford, United Kingdom
| | - Lisa L. Cunningham
- National Institute on Deafness and Other Communication Disorders (NIDCD), NIH, Bethesda, Maryland, USA
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7
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Bird JE, Barzik M, Drummond MC, Sutton DC, Goodman SM, Morozko EL, Cole SM, Boukhvalova AK, Skidmore J, Syam D, Wilson EA, Fitzgerald T, Rehman AU, Martin DM, Boger ET, Belyantseva IA, Friedman TB. Harnessing molecular motors for nanoscale pulldown in live cells. Mol Biol Cell 2016; 28:463-475. [PMID: 27932498 PMCID: PMC5341729 DOI: 10.1091/mbc.e16-08-0583] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Revised: 11/08/2016] [Accepted: 11/29/2016] [Indexed: 11/13/2022] Open
Abstract
Nanoscale pulldown (NanoSPD) miniaturizes the concept of affinity pulldown to detect protein–protein interactions in live cells. NanoSPD hijacks the myosin-based intracellular trafficking machinery to assess interactions under physiological buffer conditions and is microscopy-based, allowing for sensitive detection and quantification. Protein–protein interactions (PPIs) regulate assembly of macromolecular complexes, yet remain challenging to study within the native cytoplasm where they normally exert their biological effect. Here we miniaturize the concept of affinity pulldown, a gold-standard in vitro PPI interrogation technique, to perform nanoscale pulldowns (NanoSPDs) within living cells. NanoSPD hijacks the normal process of intracellular trafficking by myosin motors to forcibly pull fluorescently tagged protein complexes along filopodial actin filaments. Using dual-color total internal reflection fluorescence microscopy, we demonstrate complex formation by showing that bait and prey molecules are simultaneously trafficked and actively concentrated into a nanoscopic volume at the tips of filopodia. The resulting molecular traffic jams at filopodial tips amplify fluorescence intensities and allow PPIs to be interrogated using standard epifluorescence microscopy. A rigorous quantification framework and software tool are provided to statistically evaluate NanoSPD data sets. We demonstrate the capabilities of NanoSPD for a range of nuclear and cytoplasmic PPIs implicated in human deafness, in addition to dissecting these interactions using domain mapping and mutagenesis experiments. The NanoSPD methodology is extensible for use with other fluorescent molecules, in addition to proteins, and the platform can be easily scaled for high-throughput applications.
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Affiliation(s)
- Jonathan E Bird
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Melanie Barzik
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Meghan C Drummond
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Daniel C Sutton
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Spencer M Goodman
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Eva L Morozko
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Stacey M Cole
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | | | - Jennifer Skidmore
- Department of Pediatrics, University of Michigan, Ann Arbor, MI 48109
| | - Diana Syam
- Department of Pediatrics, University of Michigan, Ann Arbor, MI 48109
| | - Elizabeth A Wilson
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Tracy Fitzgerald
- Mouse Auditory Testing Core Facility, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20814
| | - Atteeq U Rehman
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Donna M Martin
- Department of Pediatrics, University of Michigan, Ann Arbor, MI 48109.,Department of Human Genetics, University of Michigan, Ann Arbor, MI 48109
| | - Erich T Boger
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Inna A Belyantseva
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
| | - Thomas B Friedman
- Laboratory of Molecular Genetics, National Institutes of Health, Bethesda, MD 20814
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8
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Drummond MC, Barzik M, Bird JE, Zhang DS, Lechene CP, Corey DP, Cunningham LL, Friedman TB. Live-cell imaging of actin dynamics reveals mechanisms of stereocilia length regulation in the inner ear. Nat Commun 2015; 6:6873. [PMID: 25898120 PMCID: PMC4411292 DOI: 10.1038/ncomms7873] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 03/06/2015] [Indexed: 02/05/2023] Open
Abstract
The maintenance of sensory hair cell stereocilia is critical for lifelong hearing; however, mechanisms of structural homeostasis remain poorly understood. Conflicting models propose that stereocilia F-actin cores are either continually renewed every 24-48 h via a treadmill or are stable, exceptionally long-lived structures. Here to distinguish between these models, we perform an unbiased survey of stereocilia actin dynamics in more than 500 utricle hair cells. Live-imaging EGFP-β-actin or dendra2-β-actin reveal stable F-actin cores with turnover and elongation restricted to stereocilia tips. Fixed-cell microscopy of wild-type and mutant β-actin demonstrates that incorporation of actin monomers into filaments is required for localization to stereocilia tips. Multi-isotope imaging mass spectrometry and live imaging of single differentiating hair cells capture stereociliogenesis and explain uniform incorporation of (15)N-labelled protein and EGFP-β-actin into nascent stereocilia. Collectively, our analyses support a model in which stereocilia actin cores are stable structures that incorporate new F-actin only at the distal tips.
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Affiliation(s)
- Meghan C Drummond
- Laboratory of Molecular Genetics, Section on Human Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Melanie Barzik
- Laboratory of Molecular Genetics, Section on Human Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Jonathan E Bird
- Laboratory of Molecular Genetics, Section on Human Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Duan-Sun Zhang
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
| | - Claude P Lechene
- 1] National Resource for Imaging Mass Spectrometry, Brigham and Women's Hospital and Harvard Medical School, Cambridge, Massachusetts 02139, USA [2] Division of Genetics, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Cambridge, Massachusetts 02139, USA
| | - David P Corey
- Department of Neurobiology, Harvard Medical School and Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
| | - Lisa L Cunningham
- Section on Sensory Cell Biology, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Thomas B Friedman
- Laboratory of Molecular Genetics, Section on Human Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892, USA
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9
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Abstract
Filopodia are long plasma membrane extensions involved in the formation of adhesive, contractile, and protrusive actin-based structures in spreading and migrating cells. Whether filopodia formed by different molecular mechanisms equally support these cellular functions is unresolved. We used Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP)-deficient MV(D7) fibroblasts, which are also devoid of endogenous mDia2, as a model system to investigate how these different actin regulatory proteins affect filopodia morphology and dynamics independently of one another. Filopodia initiated by either Ena/VASP or mDia2 contained similar molecular inventory but differed significantly in parameters such as number, length, F-actin organization, lifetime, and protrusive persistence. Moreover, in the absence of Ena/VASP, filopodia generated by mDia2 did not support initiation of integrin-dependent signaling cascades required for adhesion and subsequent lamellipodial extension, thereby causing a defect in early cell spreading. Coexpression of VASP with constitutively active mDia2(M/A) rescued these early adhesion defects. We conclude that Ena/VASP and mDia2 support the formation of filopodia with significantly distinct properties and that Ena/VASP regulates mDia2-initiated filopodial morphology, dynamics, and function.
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Affiliation(s)
- Melanie Barzik
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Leslie M McClain
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Stephanie L Gupton
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Frank B Gertler
- David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139
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10
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Neel NF, Barzik M, Raman D, Sobolik-Delmaire T, Sai J, Ham AJ, Mernaugh RL, Gertler FB, Richmond A. VASP is a CXCR2-interacting protein that regulates CXCR2-mediated polarization and chemotaxis. J Cell Sci 2009; 122:1882-94. [PMID: 19435808 DOI: 10.1242/jcs.039057] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Chemotaxis regulates the recruitment of leukocytes, which is integral for a number of biological processes and is mediated through the interaction of chemokines with seven transmembrane G-protein-coupled receptors. Several studies have indicated that chemotactic signaling pathways might be activated via G-protein-independent mechanisms, perhaps through novel receptor-interacting proteins. CXCR2 is a major chemokine receptor expressed on neutrophils. We used a proteomics approach to identify unique ligand-dependent CXCR2-interacting proteins in differentiated neutrophil-like HL-60 cells. Using this approach, vasodilator-stimulated phosphoprotein (VASP) was identified as a CXCR2-interacting protein. The interaction between CXCR2 and VASP is direct and enhanced by CXCL8 stimulation, which triggers VASP phosphorylation via PKA- and PKCdelta-mediated pathways. The interaction between CXCR2 and VASP requires free F-actin barbed ends to recruit VASP to the leading edge. Finally, knockdown of VASP in HL-60 cells results in severely impaired CXCR2-mediated chemotaxis and polarization. These data provide the first demonstration that direct interaction of VASP with CXCR2 is essential for proper CXCR2 function and demonstrate a crucial role for VASP in mediating chemotaxis in leukocytes.
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Affiliation(s)
- Nicole F Neel
- Department of Veterans Affairs, Nashville, TN 37212, USA
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Applewhite DA, Barzik M, Kojima SI, Svitkina TM, Gertler FB, Borisy GG. Ena/VASP proteins have an anti-capping independent function in filopodia formation. Mol Biol Cell 2007; 18:2579-91. [PMID: 17475772 PMCID: PMC1924831 DOI: 10.1091/mbc.e06-11-0990] [Citation(s) in RCA: 164] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Filopodia have been implicated in a number of diverse cellular processes including growth-cone path finding, wound healing, and metastasis. The Ena/VASP family of proteins has emerged as key to filopodia formation but the exact mechanism for how they function has yet to be fully elucidated. Using cell spreading as a model system in combination with small interfering RNA depletion of Capping Protein, we determined that Ena/VASP proteins have a role beyond anticapping activity in filopodia formation. Analysis of mutant Ena/VASP proteins demonstrated that the entire EVH2 domain was the minimal domain required for filopodia formation. Fluorescent recovery after photobleaching data indicate that Ena/VASP proteins rapidly exchange at the leading edge of lamellipodia, whereas virtually no exchange occurred at filopodial tips. Mutation of the G-actin-binding motif (GAB) partially compromised stabilization of Ena/VASP at filopodia tips. These observations led us to propose a model where the EVH2 domain of Ena/VASP induces and maintains clustering of the barbed ends of actin filaments, which putatively corresponds to a transition from lamellipodial to filopodial localization. Furthermore, the EVH1 domain, together with the GAB motif in the EVH2 domain, helps to maintain Ena/VASP at the growing barbed ends.
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Affiliation(s)
- Derek A. Applewhite
- *Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Melanie Barzik
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Shin-ichiro Kojima
- *Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
| | - Tatyana M. Svitkina
- Department of Biology, University of Pennsylvania, Philadelphia, PA 19104; and
| | - Frank B. Gertler
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Gary G. Borisy
- *Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611
- Marine Biological Laboratory, Woods Hole, MA 02453
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Barzik M, Kotova TI, Higgs HN, Hazelwood L, Hanein D, Gertler FB, Schafer DA. Ena/VASP proteins enhance actin polymerization in the presence of barbed end capping proteins. J Biol Chem 2005; 280:28653-62. [PMID: 15939738 PMCID: PMC1747414 DOI: 10.1074/jbc.m503957200] [Citation(s) in RCA: 243] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ena/VASP proteins influence the organization of actin filament networks within lamellipodia and filopodia of migrating cells and in actin comet tails. The molecular mechanisms by which Ena/VASP proteins control actin dynamics are unknown. We investigated how Ena/VASP proteins regulate actin polymerization at actin filament barbed ends in vitro in the presence and absence of barbed end capping proteins. Recombinant His-tagged VASP increased the rate of actin polymerization in the presence of the barbed end cappers, heterodimeric capping protein (CP), CapG, and gelsolin-actin complex. Profilin enhanced the ability of VASP to protect barbed ends from capping by CP, and this required interactions of profilin with G-actin and VASP. The VASP EVH2 domain was sufficient to protect barbed ends from capping, and the F-actin and G-actin binding motifs within EVH2 were required. Phosphorylation by protein kinase A at sites within the VASP EVH2 domain regulated anti-capping and F-actin bundling by VASP. We propose that Ena/VASP proteins associate at or near actin filament barbed ends, promote actin assembly, and restrict the access of barbed end capping proteins.
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Affiliation(s)
- Melanie Barzik
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139 the
| | - Tatyana I. Kotova
- From the Department of Biology, University of Virginia, Charlottesville, VA 22903, the
| | - Henry N. Higgs
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755 and the
| | | | - Dorit Hanein
- Cell Adhesion Program, The Burnham Institute, La Jolla, CA 92037
| | - Frank B. Gertler
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139 the
| | - Dorothy A. Schafer
- From the Department of Biology, University of Virginia, Charlottesville, VA 22903, the
- Address correspondence to: Dorothy A. Schafer, Department of Biology, University of Virginia, Charlottesville, VA 22903, Tel. 434-243-5297; Fax. 434-982-5626;
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Machner MP, Urbanke C, Barzik M, Otten S, Sechi AS, Wehland J, Heinz DW. ActA from Listeria monocytogenes can interact with up to four Ena/VASP homology 1 domains simultaneously. J Biol Chem 2001; 276:40096-103. [PMID: 11489888 DOI: 10.1074/jbc.m104279200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The facultative intracellular human pathogenic bacterium Listeria monocytogenes actively recruits host actin to its surface to achieve motility within infected cells. The bacterial surface protein ActA is solely responsible for this process by mimicking fundamental steps of host cell actin dynamics. ActA, a modular protein, contains an N-terminal actin nucleation site and a central proline-rich motif of the 4-fold repeated consensus sequence FPPPP (FP(4)). This motif is specifically recognized by members of the Ena/VASP protein family. These proteins additionally recruit the profilin-G-actin complex increasing the local concentration of G-actin close to the bacterial surface. By using analytical ultracentrifugation, we show that a single ActA molecule can simultaneously interact with four Ena/VASP homology 1 (EVH1) domains. The four FP(4) sites have roughly equivalent affinities with dissociation constants of about 4 microm. Mutational analysis of the FP(4) motifs indicate that the phenylalanine is mandatory for ActA-EVH1 interaction, whereas in each case exchange of the third proline was tolerated. Finally, by using sedimentation equilibrium centrifugation techniques, we demonstrate that ActA is a monomeric protein. By combining these results, we formulate a stoichiometric model to describe how ActA enables Listeria to utilize efficiently resources of the host cell microfilament for its own intracellular motility.
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Affiliation(s)
- M P Machner
- Department of Structural Biology, German Research Center for Biotechnology (GBF), Mascheroder Weg 1, D-38124 Braunschweig, Germany
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Abstract
Cellular activities controlled by signal transduction processes such as cell motility and cell growth depend on the tightly regulated assembly of multiprotein complexes. Adapter proteins that specifically interact with their target proteins are key components required for the formation of these assemblies. Ena/VASP-homology 1 (EVH1) domains are small constituents of large modular proteins involved in microfilament assembly that specifically recognize proline-rich regions. EVH1 domain-containing proteins are present in neuronal cells, like the Homer/Vesl protein family that is involved in memory-generating processes. Here, we describe the crystal structure of the murine EVH1 domain of Vesl 2 at 2.2 A resolution. The small globular protein consists of a seven-stranded antiparallel beta-barrel with a C-terminal alpha-helix packing alongside the barrel. A shallow groove running parallel with beta-strand VI forms an extended peptide-binding site. Using peptide library screenings, we present data that demonstrate the high affinity of the Vesl 2 EVH1 domain towards peptide sequences containing a proline-rich core sequence (PPSPF) that requires additional charged amino acid residues on either side for specific binding. Our functional data, substantiated by structural data, demonstrate that the ligand-binding of the Vesl EVH1 domain differs from the interaction characteristics of the previously examined EVH1 domains of the Evl/Mena proteins. Analogous to the Src homology 3 (SH3) domains that bind their cognate ligands in two distinct directions, we therefore propose the existence of two distinct classes of EVH1 domains.
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Affiliation(s)
- M Barzik
- Department of Structural Biology and German National Center of Biotechnology (GBF), Braunschweig
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15
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Barzik M, Schubert WD, Carl U, Wehland J, Heinz DW. Crystallization and preliminary X-ray analysis of the EVH1 domain of Vesl-2b. Acta Crystallogr D Biol Crystallogr 2000; 56:930-2. [PMID: 10930849 DOI: 10.1107/s0907444900005758] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2000] [Accepted: 04/12/2000] [Indexed: 11/10/2022]
Abstract
Proteins of the Homer/Vesl family are enriched at excitatory synapses and selectively bind to a proline-rich consensus sequence in group 1 metabotropic glutamate receptors via a domain that shows a strong similarity to the Ena/VASP homology 1 (EVH1) domains. EVH1 domains play an important role in actin cytoskeleton dynamics. Crystals of the EVH1 domain of murine Vesl-2b were obtained that diffract X-rays to 2.4 A resolution. They belong to space group C2, with unit-cell parameters a = 112.8, b = 69.9, c = 54.9 A, beta = 110.7 degrees, consistent with three molecules per asymmetric unit and a solvent content of 53%.
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Affiliation(s)
- M Barzik
- Department of Structural Biology, German National Center of Biotechnology (GBF), Mascheroder Weg 1, D-38124 Braunschweig, Germany
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