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Radhakrishnan R, Dronamraju VR, Leung M, Gruesen A, Solanki AK, Walterhouse S, Roehrich H, Song G, da Costa Monsanto R, Cureoglu S, Martin R, Kondkar AA, van Kuijk FJ, Montezuma SR, Knöelker HJ, Hufnagel RB, Lobo GP. The role of motor proteins in photoreceptor protein transport and visual function. Ophthalmic Genet 2022; 43:285-300. [PMID: 35470760 DOI: 10.1080/13816810.2022.2062391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
BACKGROUND Rods and cones are photoreceptor neurons in the retina that are required for visual sensation in vertebrates, wherein the perception of vision is initiated when these neurons respond to photons in the light stimuli. The photoreceptor cell is structurally studied as outer segments (OS) and inner segments (IS) where proper protein sorting, localization, and compartmentalization are critical for phototransduction, visual function, and survival. In human retinal diseases, improper protein transport to the OS or mislocalization of proteins to the IS and other cellular compartments could lead to impaired visual responses and photoreceptor cell degeneration that ultimately cause loss of visual function. RESULTS Therefore, studying and identifying mechanisms involved in facilitating and maintaining proper protein transport in photoreceptor cells would help our understanding of pathologies involving retinal cell degeneration in inherited retinal dystrophies, age-related macular degeneration, and Usher Syndrome. CONCLUSIONS Our mini-review will discuss mechanisms of protein transport within photoreceptors and introduce a novel role for an unconventional motor protein, MYO1C, in actin-based motor transport of the visual chromophore Rhodopsin to the OS, in support of phototransduction and visual function.
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Affiliation(s)
- Rakesh Radhakrishnan
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Venkateshwara R Dronamraju
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Matthias Leung
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Andrew Gruesen
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Ashish K Solanki
- Department of Medicine, Drug Discovery Building, Medical University of South Carolina, South Carolina, USA
| | - Stephen Walterhouse
- Department of Medicine, Drug Discovery Building, Medical University of South Carolina, South Carolina, USA
| | - Heidi Roehrich
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Grace Song
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Rafael da Costa Monsanto
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Sebahattin Cureoglu
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - René Martin
- Faculty of Chemistry, Technische Universität Dresden, Dresden, Germany
| | - Altaf A Kondkar
- Department of Ophthalmology.,Glaucoma Research Chair in Ophthalmology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Frederik J van Kuijk
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | - Sandra R Montezuma
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Robert B Hufnagel
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Glenn P Lobo
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA.,Department of Medicine, Drug Discovery Building, Medical University of South Carolina, South Carolina, USA.,Department of Ophthalmology, Medical University of South Carolina, South Carolina, USA
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Thoreson WB. Transmission at rod and cone ribbon synapses in the retina. Pflugers Arch 2021; 473:1469-1491. [PMID: 33779813 DOI: 10.1007/s00424-021-02548-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 02/23/2021] [Accepted: 02/25/2021] [Indexed: 12/29/2022]
Abstract
Light-evoked voltage responses of rod and cone photoreceptor cells in the vertebrate retina must be converted to a train of synaptic vesicle release events for transmission to downstream neurons. This review discusses the processes, proteins, and structures that shape this critical early step in vision, focusing on studies from salamander retina with comparisons to other experimental animals. Many mechanisms are conserved across species. In cones, glutamate release is confined to ribbon release sites although rods are also capable of release at non-ribbon sites. The role of non-ribbon release in rods remains unclear. Release from synaptic ribbons in rods and cones involves at least three vesicle pools: a readily releasable pool (RRP) matching the number of membrane-associated vesicles along the ribbon base, a ribbon reserve pool matching the number of additional vesicles on the ribbon, and an enormous cytoplasmic reserve. Vesicle release increases in parallel with Ca2+ channel activity. While the opening of only a few Ca2+ channels beneath each ribbon can trigger fusion of a single vesicle, sustained release rates in darkness are governed by the rate at which the RRP can be replenished. The number of vacant release sites, their functional status, and the rate of vesicle delivery in turn govern replenishment. Along with an overview of the mechanisms of exocytosis and endocytosis, we consider specific properties of ribbon-associated proteins and pose a number of remaining questions about this first synapse in the visual system.
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Affiliation(s)
- Wallace B Thoreson
- Truhlsen Eye Institute, Departments of Ophthalmology & Visual Sciences and Pharmacology & Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, 68198, USA.
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Wang W, Halasz E, Townes-Anderson E. Actin Dynamics, Regulated by RhoA-LIMK-Cofilin Signaling, Mediates Rod Photoreceptor Axonal Retraction After Retinal Injury. Invest Ophthalmol Vis Sci 2019; 60:2274-2285. [PMID: 31112612 PMCID: PMC6530517 DOI: 10.1167/iovs.18-26077] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Purpose Retraction of the axon terminals of rod photoreceptors after retinal detachment breaks the first synapse in the visual pathway, resulting in visual impairment. Previous work showed that the mechanism of axonal retraction involves RhoA signaling and its downstream effector LIM Kinase (LIMK) activation. We examined the response of the downstream component cofilin, a direct binding protein of actin filaments, as well as the regulation by RhoA-LIMK-Cofilin signaling of actin assembly/disassembly, in the presynaptic ribbon terminal of injured rod cells. Methods Injury was produced by retinal detachment or rod cell isolation. Detached porcine retina was probed for levels and localization of phosphorylated cofilin with Western blots and confocal microscopy, whereas rod cell cultures of dissociated salamander retina were examined for filamentous actin assembly/disassembly with a barbed end assay and phalloidin staining. Results A detachment increased phosphorylation of cofilin in retinal explants; phosphorylation occurred in rod terminals in sections of detached retina. Isolation of rod cells resulted in axon retraction accompanied by an increase in actin barbed ends and a decrease in net filament labeling. All changes were significantly reduced by either Rho kinase (ROCK) or LIMK inhibition, using Y27632 or BMS-5, respectively. Cytochalasin D also reduced retraction and stabilized filaments in isolated rod cells. Conclusions These results indicate that actin depolymerization via activation of RhoA downstream kinases and cofilin contributes to axon retraction. Preventing depolymerization, in addition to actomyosin contraction, may stabilize ribbon synapses after trauma.
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Affiliation(s)
- Weiwei Wang
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Graduate School of Biomedical Sciences, Rutgers Biomedical and Health Sciences, Rutgers, The State University of New Jersey, Newark, New Jersey, United States
| | - Eva Halasz
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Graduate School of Biomedical Sciences, Rutgers Biomedical and Health Sciences, Rutgers, The State University of New Jersey, Newark, New Jersey, United States
| | - Ellen Townes-Anderson
- Department of Pharmacology, Physiology and Neuroscience, New Jersey Medical School, Graduate School of Biomedical Sciences, Rutgers Biomedical and Health Sciences, Rutgers, The State University of New Jersey, Newark, New Jersey, United States
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4
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Bazellières E, Aksenova V, Barthélémy-Requin M, Massey-Harroche D, Le Bivic A. Role of the Crumbs proteins in ciliogenesis, cell migration and actin organization. Semin Cell Dev Biol 2017; 81:13-20. [PMID: 29056580 DOI: 10.1016/j.semcdb.2017.10.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 10/09/2017] [Accepted: 10/18/2017] [Indexed: 02/07/2023]
Abstract
Epithelial cell organization relies on a set of proteins that interact in an intricate way and which are called polarity complexes. These complexes are involved in the determination of the apico-basal axis and in the positioning and stability of the cell-cell junctions called adherens junctions at the apico-lateral border in invertebrates. Among the polarity complexes, two are present at the apical side of epithelial cells. These are the Par complex including aPKC, PAR3 and PAR6 and the Crumbs complex including, CRUMBS, PALS1 and PATJ/MUPP1. These two complexes interact directly and in addition to their already well described functions, they play a role in other cellular processes such as ciliogenesis and polarized cell migration. In this review, we will focus on these aspects that involve the apical Crumbs polarity complex and its relation with the cortical actin cytoskeleton which might provide a more comprehensive hypothesis to explain the many facets of Crumbs cell and tissue properties.
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Affiliation(s)
- Elsa Bazellières
- Aix-Marseille University, CNRS, IBDM, Case 907, 13288 Marseille, Cedex 09, France
| | - Veronika Aksenova
- Aix-Marseille University, CNRS, IBDM, Case 907, 13288 Marseille, Cedex 09, France
| | | | | | - André Le Bivic
- Aix-Marseille University, CNRS, IBDM, Case 907, 13288 Marseille, Cedex 09, France.
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Wöllert T, Patel A, Lee YL, Provance DW, Vought VE, Cosgrove MS, Mercer JA, Langford GM. Myosin5a tail associates directly with Rab3A-containing compartments in neurons. J Biol Chem 2011; 286:14352-61. [PMID: 21349835 DOI: 10.1074/jbc.m110.187286] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myosin-Va (Myo5a) is a motor protein associated with synaptic vesicles (SVs) but the mechanism by which it interacts has not yet been identified. A potential class of binding partners are Rab GTPases and Rab3A is known to associate with SVs and is involved in SV trafficking. We performed experiments to determine whether Rab3A interacts with Myo5a and whether it is required for transport of neuronal vesicles. In vitro motility assays performed with axoplasm from the squid giant axon showed a requirement for a Rab GTPase in Myo5a-dependent vesicle transport. Furthermore, mouse recombinant Myo5a tail revealed that it associated with Rab3A in rat brain synaptosomal preparations in vitro and the association was confirmed by immunofluorescence imaging of primary neurons isolated from the frontal cortex of mouse brains. Synaptosomal Rab3A was retained on recombinant GST-tagged Myo5a tail affinity columns in a GTP-dependent manner. Finally, the direct interaction of Myo5a and Rab3A was determined by sedimentation velocity analytical ultracentrifugation using recombinant mouse Myo5a tail and human Rab3A. When both proteins were incubated in the presence of 1 mm GTPγS, Myo5a tail and Rab3A formed a complex and a direct interaction was observed. Further analysis revealed that GTP-bound Rab3A interacts with both the monomeric and dimeric species of the Myo5a tail. However, the interaction between Myo5a tail and nucleotide-free Rab3A did not occur. Thus, our results show that Myo5a and Rab3A are direct binding partners and interact on SVs and that the Myo5a/Rab3A complex is involved in transport of neuronal vesicles.
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Affiliation(s)
- Torsten Wöllert
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA
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Lin-Jones J, Sohlberg L, Dosé A, Breckler J, Hillman DW, Burnside B. Identification and localization of myosin superfamily members in fish retina and retinal pigmented epithelium. J Comp Neurol 2009; 513:209-23. [PMID: 19137585 PMCID: PMC2785712 DOI: 10.1002/cne.21958] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Myosins are cytoskeletal motors critical for generating the forces necessary for establishing cell structure and mediating actin-dependent cell motility. In each cell type a multitude of myosins are expressed, each myosin contributing to aspects of morphogenesis, transport, or motility occurring in that cell type. To examine the roles of myosins in individual retinal cell types, we first used polymerase chain reaction (PCR) screening to identify myosins expressed in retina and retinal pigmented epithelium (RPE), followed by immunohistochemistry to examine the cellular and subcellular localizations of seven of these expressed myosins. In the myosin PCR screen of cDNA from striped bass retina and striped bass RPE, we amplified 17 distinct myosins from eight myosin classes from retinal cDNA and 11 distinct myosins from seven myosin classes from RPE cDNA. By using antibodies specific for myosins IIA, IIB, IIIA, IIIB, VI, VIIA, and IXB, we examined the localization patterns of these myosins in retinas and RPE of fish, and in isolated inner/outer segment fragments of green sunfish photoreceptors. Each of the myosins exhibited unique expression patterns in fish retina. Individual cell types expressed multiple myosin family members, some of which colocalized within a particular cell type. Because much is known about the functions and properties of these myosins from studies in other systems, their cellular and subcellular localization patterns in the retina help us understand which roles they might play in the vertebrate retina and RPE.
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Affiliation(s)
- Jennifer Lin-Jones
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA.
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Rancura KGO, Montaño MR, Carvalho RF, Martins C, Wasko AP, Casaletti L, Azevedo A. Brain distribution of myosin Va in rainbow trout Oncorhynchus mykiss. ACTA ZOOL-STOCKHOLM 2007. [DOI: 10.1111/j.1463-6395.2007.00289.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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8
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Lanuza MA, Besalduch N, Garcia N, Sabaté M, Santafé MM, Tomàs J. Plastic-embedded semithin cross-sections as a tool for high-resolution immunofluorescence analysis of the neuromuscular junction molecules: Specific cellular location of protease-activated receptor-1. J Neurosci Res 2007; 85:748-56. [PMID: 17265467 DOI: 10.1002/jnr.21192] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In the neuromuscular junction (NMJ), three cellular elements (nerve ending, postsynaptic muscle component, and teloglial Schwann cell) are closely juxtaposed and functionally interdependent. It is important to determine the precise location of the relevant molecules involved in structural stability and neurotransmission at the three cellular components of this synapse in order to understand the molecular mechanisms underlying NMJ formation, maintenance, and functionality. In this paper, we show that plastic-embedded 0.5-mum semithin cross-sections from whole-mount multiple-immunofluorescence-stained muscles provide a simple and sensitive high-resolution procedure for analyzing the cellular and subcellular distribution of molecules at the NMJ. We have used this procedure to resolve the location of protease-activated receptor 1 (PAR-1). Previously, by immunohistochemistry we had detected PAR-1 in muscle fibers concentrated in the synaptic area but could not determine whether PAR-1 is expressed only in the muscle fiber at the NMJ. Our present results demonstrate that PAR-1 is concentrated in the postsynaptic region but not in the presynaptic terminal and that the labelling pattern for PAR-1 overlapped with Schwann cell staining.
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Affiliation(s)
- Maria A Lanuza
- Unitat d'Histologia i Neurobiologia (UHN), Facultat de Medicina i Ciències de la Salut, Universitat Rovira i Virgili, Reus, Spain.
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tom Dieck S, Brandstätter JH. Ribbon synapses of the retina. Cell Tissue Res 2006; 326:339-46. [PMID: 16775698 DOI: 10.1007/s00441-006-0234-0] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Accepted: 04/27/2006] [Indexed: 11/24/2022]
Abstract
Vision is a highly complex task that involves several steps of parallel information processing in various areas of the central nervous system. Complex processing of visual signals occurs as early as at the retina, the first stage in the visual system. Various aspects of visual information are transmitted in parallel from the photoreceptors (the input neurons of the retina) through their interconnecting bipolar cells to the ganglion cells (the output neurons). Photoreceptors and bipolar cells transfer information via the release of the neurotransmitter glutamate at a specialized synapse, the ribbon synapse. Although known from early days of electron microscopy, the precise functioning of ribbon synapses has yet to be explained. In this review, we highlight recent advances towards understanding the molecular composition and function of this enigmatic synapse.
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Affiliation(s)
- Susanne tom Dieck
- Institute for Biology, Department of Zoology, University of Erlangen-Nuernberg, Staudtstrasse 5, 91058 Erlangen, Germany
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10
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McNeil EL, Tacelosky D, Basciano P, Biallas B, Williams R, Damiani P, Deacon S, Fox C, Stewart B, Petruzzi N, Osborn C, Klinger K, Sellers JR, Smith CK. Actin-dependent motility of melanosomes from fish retinal pigment epithelial (RPE) cells investigated using in vitro motility assays. ACTA ACUST UNITED AC 2005; 58:71-82. [PMID: 15083529 DOI: 10.1002/cm.10179] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Melanosomes (pigment granules) within retinal pigment epithelial (RPE) cells of fish and amphibians undergo massive migrations in response to light conditions to control light flux to the retina. Previous research has shown that melanosome motility within apical projections of dissociated fish RPE cells requires an intact actin cytoskeleton, but the mechanisms and motors involved in melanosome transport in RPE have not been identified. Two in vitro motility assays, the Nitella assay and the sliding filament assay, were used to characterize actin-dependent motor activity of RPE melanosomes. Melanosomes applied to dissected filets of the Characean alga, Nitella, moved along actin cables at a mean rate of 2 microm/min, similar to the rate of melanosome motility in dissociated, cultured RPE cells. Path lengths of motile melanosomes ranged from 9 to 37 microm. Melanosome motility in the sliding filament assay was much more variable, ranging from 0.4-33 microm/min; 70% of velocities ranged from 1-15 microm/min. Latex beads coated with skeletal muscle myosin II and added to Nitella filets moved in the same direction as RPE melanosomes, indicating that the motility is barbed-end directed. Immunoblotting using antibodies against myosin VIIa and rab27a revealed that both proteins are enriched on melanosome membranes, suggesting that they could play a role in melanosome transport within apical projections of fish RPE.
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Affiliation(s)
- E L McNeil
- Department of Biology, Saint Joseph's University, Philadelphia, Pennsylvania 19131, USA
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Gibbs D, Azarian SM, Lillo C, Kitamoto J, Klomp AE, Steel KP, Libby RT, Williams DS. Role of myosin VIIa and Rab27a in the motility and localization of RPE melanosomes. J Cell Sci 2004; 117:6473-83. [PMID: 15572405 PMCID: PMC2942070 DOI: 10.1242/jcs.01580] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Myosin VIIa functions in the outer retina, and loss of this function causes human blindness in Usher syndrome type 1B (USH1B). In mice with mutant Myo7a, melanosomes in the retinal pigmented epithelium (RPE) are distributed abnormally. In this investigation we detected many proteins in RPE cells that could potentially participate in melanosome transport, but of those tested, only myosin VIIa and Rab27a were found to be required for normal distribution. Two other expressed proteins, melanophilin and myosin Va, both of which are required for normal melanosome distribution in melanocytes, were not required in RPE, despite the association of myosin Va with the RPE melanosome fraction. Both myosin VIIa and myosin Va were immunodetected broadly in sections of the RPE, overlapping with a region of apical filamentous actin. Some 70-80% of the myosin VIIa in RPE cells was detected on melanosome membranes by both subcellular fractionation of RPE cells and quantitative immunoelectron microscopy, consistent with a role for myosin VIIa in melanosome motility. Time-lapse microscopy of melanosomes in primary cultures of mouse RPE cells demonstrated that the melanosomes move in a saltatory manner, interrupting slow movements with short bursts of rapid movement (>1 RR01183m/second). In RPE cells from Myo7a-null mice, both the slow and rapid movements still occurred, except that more melanosomes underwent rapid movements, and each movement extended approximately five times longer (and further). Hence, our studies demonstrate the presence of many potential effectors of melanosome motility and localization in the RPE, with a specific requirement for Rab27a and myosin VIIa, which function by transporting and constraining melanosomes within a region of filamentous actin. The presence of two distinct melanosome velocities in both control and Myo7a-null RPE cells suggests the involvement of at least two motors other than myosin VIIa in melanosome motility, most probably, a microtubule motor and myosin Va.
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Affiliation(s)
- Daniel Gibbs
- Departments of Pharmacology and Neurosciences, UCSD School of Medicine, La Jolla, CA 92093-0912, USA
| | - Sassan M. Azarian
- Departments of Pharmacology and Neurosciences, UCSD School of Medicine, La Jolla, CA 92093-0912, USA
| | - Concepcion Lillo
- Departments of Pharmacology and Neurosciences, UCSD School of Medicine, La Jolla, CA 92093-0912, USA
| | - Junko Kitamoto
- Departments of Pharmacology and Neurosciences, UCSD School of Medicine, La Jolla, CA 92093-0912, USA
| | - Adriana E. Klomp
- Departments of Pharmacology and Neurosciences, UCSD School of Medicine, La Jolla, CA 92093-0912, USA
| | - Karen P. Steel
- MRC Institute of Hearing Research, University Park, Nottingham, NG7 2RD, UK
| | - Richard T. Libby
- MRC Institute of Hearing Research, University Park, Nottingham, NG7 2RD, UK
| | - David S. Williams
- Departments of Pharmacology and Neurosciences, UCSD School of Medicine, La Jolla, CA 92093-0912, USA
- Author for correspondence ()
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Libby RT, Lillo C, Kitamoto J, Williams DS, Steel KP. Myosin Va is required for normal photoreceptor synaptic activity. J Cell Sci 2004; 117:4509-15. [PMID: 15316067 DOI: 10.1242/jcs.01316] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Myosin Va is an actin-based motor molecule, one of a large family of unconventional myosins. In humans, mutations in MYO5A cause Griscelli syndrome type 1 and Elejalde syndrome, diseases characterized by pigmentation defects and the prepubescent onset of severe neurological deficits that ultimately lead to a shortened lifespan. Mutations in the Myo5a gene in mouse cause the dilute series of mouse mutants, demonstrating that myosin Va is involved in pigmentation and neural function. Although the reason for the pigmentation abnormalities is well understood, the role of myosin Va in neural function is not. Myosin Va has been found in synaptic terminals in the retina and brain. We report here new physiological evidence for a role of myosin Va in synaptic function. Photoreceptor synapses in neurologically affected myosin Va mutant mice have both anatomical and physiological abnormalities. Thus, myosin Va is required for normal photoreceptor signalling, suggesting that it might function in central nervous system synapses in general, with aberrant synaptic activity potentially underlying the neurological defects observed in dilute lethal mice and patients with Griscelli syndrome type 1 and Elejalde syndrome.
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Affiliation(s)
- Richard T Libby
- MRC Institute of Hearing Research, University Park, Nottingham, NG7 2RD, UK
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13
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Futter CE, Ramalho JS, Jaissle GB, Seeliger MW, Seabra MC. The role of Rab27a in the regulation of melanosome distribution within retinal pigment epithelial cells. Mol Biol Cell 2004; 15:2264-75. [PMID: 14978221 PMCID: PMC404021 DOI: 10.1091/mbc.e03-10-0772] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Melanosomes within the retinal pigment epithelium (RPE) of mammals have long been thought to exhibit no movement in response to light, unlike fish and amphibian RPE. Here we show that the distribution of melanosomes within the mouse RPE undergoes modest but significant changes with the light cycle. Two hours after light onset, there is a threefold increase in the number of melanosomes in the apical processes that surround adjacent photoreceptors. In skin melanocytes, melanosomes are motile and evenly distributed throughout the cell periphery. This distribution is due to the interaction with the cortical actin cytoskeleton mediated by a tripartite complex of Rab27a, melanophilin, and myosin Va. In ashen (Rab27a null) mice RPE, melanosomes are unable to move beyond the adherens junction axis and do not enter apical processes, suggesting that Rab27a regulates melanosome distribution in the RPE. Unlike skin melanocytes, the effects of Rab27a are mediated through myosin VIIa in the RPE, as evidenced by the similar melanosome distribution phenotype observed in shaker-1 mice, defective in myosin VIIa. Rab27a and myosin VIIa are likely to be required for association with and movement through the apical actin cytoskeleton, which is a prerequisite for entry into the apical processes.
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Affiliation(s)
- Clare E Futter
- Division of Cell Biology, Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
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14
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Tilelli CQ, Martins AR, Larson RE, Garcia-Cairasco N. Immunohistochemical localization of myosin Va in the adult rat brain. Neuroscience 2004; 121:573-86. [PMID: 14568019 DOI: 10.1016/s0306-4522(03)00546-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Brain myosin Va (MVa) is a molecular motor associated with plastic changes during development. MVa has previously been detected in the cell body and in dendrites of neuronal cells in culture, in cells of the guinea-pig cochlea, as well as in cerebellar cells. Adult Wistar rats (n=14), 250-300 g, were perfused with standard methods for immunohistochemistry, using a polyclonal, affinity-purified rabbit antibody against MVa tail domain. Anti-MVa antibody specifically stained neuronal nuclei from forebrain to cerebellar regions, and more intensely sensory nuclei. Differences in MVa immunoreactivity were detected between brain nuclei, ranging from very intense to weak staining. The analysis of MVa and glial fibrillary acidic protein staining in adjacent brain sections demonstrated a clear-cut neuronal labeling rather than an astroglial staining. The studies presented here represent a comprehensive map of MVa regional distribution in the CNS of the adult rat and may contribute to the basic understanding of its role in brain function and plasticity, particularly in relationship to phenomena that involve molecular motors, such as neurite outgrowth, organelle transport and neurotransmitter-vesicle cycling. It is important to highlight that this is a pioneer immunohistochemical study on the distribution of MVa on the whole brain of adult rats, a first step toward the understanding of its function in the CNS.
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Affiliation(s)
- C Q Tilelli
- Department of Physiology, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Av Bandeirantes, 3900, 14049-900 Ribeirão Preto, São Paulo, Brazil
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Heidelberger R, Sterling P, Matthews G. Roles of ATP in depletion and replenishment of the releasable pool of synaptic vesicles. J Neurophysiol 2002; 88:98-106. [PMID: 12091535 DOI: 10.1152/jn.2002.88.1.98] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Synaptic terminals of retinal bipolar neurons contain a pool of readily releasable synaptic vesicles that undergo rapid calcium-dependent release. ATP hydrolysis is required for the functional refilling of this vesicle pool. However, it was unclear which steps required ATP hydrolysis: delivery of vesicles to their anatomical release sites or preparation of synaptic vesicles and/or the secretory apparatus for fusion. To address this, we dialyzed single synaptic terminals with ATP or the poorly hydrolyzable analogue ATP-gammaS and examined the size of the releasable pool, refilling of the releasable pool, and the number of vesicles at anatomical active zones. After minutes of dialysis with ATP-gammaS, vesicles already in the releasable pool could still be discharged. This pool was not functionally refilled despite the fact that its anatomical correlate, the number of synaptic vesicles tethered to active zone synaptic ribbons, was completely normal. We conclude 1) because the existing releasable pool is stable during prolonged inhibition of ATP hydrolysis, whereas entry into the functional pool is blocked, a vesicle on entering the pool will tend to remain there until it fuses; 2) because the anatomical pool is unaffected by inhibition of ATP hydrolysis, failure to refill the functional pool is not caused by failure of vesicle movement; 3) local vesicle movements important for pool refilling and fusion are independent of conventional ATP-dependent motor proteins; and 4) ATP hydrolysis is required for the biochemical transition of vesicles and/or release sites to fusion-competent status.
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Affiliation(s)
- Ruth Heidelberger
- Department of Neurobiology and Anatomy and The W. M. Keck Center for the Neurobiology of Learning and Memory, University of Texas Medical School, Houston, Texas 77030, USA.
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16
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Cohen DL. Squid p196, a new member of the myosin-V class of motor proteins, is associated with motile axoplasmic organelles. Brain Res 2001; 890:233-45. [PMID: 11164789 DOI: 10.1016/s0006-8993(00)03165-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Axoplasmic organelles obtained from the squid giant axon move on actin filaments at an average velocity of 1 microm/s [Nature 356 (1992) 722]. The unconventional myosins, in particular, the myosin-V class of motor proteins, represent the most likely candidates to have a role in this motility. Experiments were performed to determine whether a member of the myosin-V class of unconventional myosins is present in axoplasm and optic lobes. Western blots of axoplasm probed with an affinity purified antibody to chicken brain myosin-V (CBM-V) showed cross-reactivity with a protein of Mr 196 kD (p196) which was subsequently purified from squid optic lobes using a modification of a protocol for the purification of CBM-V [Methods Enzymol. 298 (1998) 3; Cell 75 (1993) 215]. Western blots of CBM-V probed with an alpha-p196 polyclonal IgG showed cross-reactivity with CBM-V. Purified p196 has been found to be a calmodulin (CaM) binding protein that possesses calcium-stimulated actin-activated ATPase activity. Equilibrium density fractionation of motile axoplasmic organelle preparations has revealed that p196 cosedimented with the peak organelle fraction into Percoll gradients in the presence of cytochalasin B and ATP. Based on this evidence, we conclude that the p196 present in axoplasm and purified from optic lobes is a squid homolog of CBM-V and functions as a motor for fast transport of membranous organelles on actin filaments in neurons.
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Affiliation(s)
- D L Cohen
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3576, USA.
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Lionne C, Buss F, Hodge T, Ihrke G, Kendrick-Jones J. Localization of myosin Va is dependent on the cytoskeletal organization in the cell. Biochem Cell Biol 2001. [DOI: 10.1139/o00-089] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Myosin V plays an important role in membrane trafficking events. Its implication in the transport of pigment granules in melanocytes and synaptic vesicles in neurons is now well established. However, less is known about its function(s) in other cell types. Finding a common function is complicated by the diversity of myosin V expression in different tissues and organisms and by its association with different subcellular compartments. Here we show that myosin V is present in a variety of cells. Within the same cell type under different physiological conditions, we observed two main cellular locations for myosin V that were dependent on the dynamics of the plasma membrane: in cells with highly dynamic membranes, myosin V was specifically concentrated at the leading edge in membrane ruffles, whereas in cells with less dynamic membranes, myosin V was enriched around the microtubule-organizing center. The presence of myosin V in the leading ruffling edge of the cell was induced by growth factor stimulation and was dependent on the presence of a functional motor domain. Moreover, myosin V localization at the microtubule-organizing center was dependent on the integrity of the microtubules. In polarized epithelial cells (WIF-B), where the microtubule-organizing region is close to the actin-rich apical surface, one single pool of myosin V, sensitive to the integrity of both microtubules and actin filaments, was observed.Key words: cell motility, cytoskeleton dynamics, molecular motors, mouse brain unconventional myosin Va, ruffles.
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18
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Smith RS, John SW, Zabeleta A, Davisson MT, Hawes NL, Chang B. The bst locus on mouse chromosome 16 is associated with age-related subretinal neovascularization. Proc Natl Acad Sci U S A 2000; 97:2191-5. [PMID: 10681427 PMCID: PMC15776 DOI: 10.1073/pnas.040531597] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ocular neovascularization is the leading cause of blindness in developed countries and often causes rapid loss of vision in age-related macular degeneration. Acute visual loss is most often due to hemorrhage from new vessels that have extended from the choroid into the subretinal space. Growth of abnormal vessels beneath the retina in this condition is known as subretinal neovascularization (SRN). Age-related animal models of macular degeneration and SRN have not been described. Current animal models of SRN depend on chemical or physical stimuli to initiate growth of subretinal vessels. The genes responsible for age-related human macular degeneration with SRN have not been firmly identified. We report an angiogenic phenotype in Bst/+ mice that is age-related, clinically evident, and resembles human SRN. This represents a spontaneous, genetically determined model of SRN. Bst/+ mice offer the possibility of exploring the molecular mechanisms of SRN without the need for exogenous agents.
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Affiliation(s)
- R S Smith
- The Jackson Laboratory, Bar Harbor, ME 04609, USA.
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19
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Costa MC, Mani F, Santoro W, Espreafico EM, Larson RE. Brain myosin-V, a calmodulin-carrying myosin, binds to calmodulin-dependent protein kinase II and activates its kinase activity. J Biol Chem 1999; 274:15811-9. [PMID: 10336484 DOI: 10.1074/jbc.274.22.15811] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myosin-V, an unconventional myosin, has two notable structural features: (i) a regulatory neck domain having six IQ motifs that bind calmodulin and light chains, and (ii) a structurally distinct tail domain likely responsible for its specific intracellular interactions. Myosin-V copurifies with synaptic vesicles via its tail domain, which also is a substrate for calmodulin-dependent protein kinase II. We demonstrate here that myosin-V coimmunoprecipitates with CaM-kinase II from a Triton X-100-solubilized fraction of isolated nerve terminals. The purified proteins also coimmunoprecipitate from dilute solutions and bind in overlay experiments on Western blots. The binding region on myosin-V was mapped to its proximal and medial tail domains. Autophosphorylated CaM-kinase II binds to the tail domain of myosin-V with an apparent Kd of 7.7 nM. Surprisingly, myosin-V activates CaM-kinase II activity in a Ca2+-dependent manner, without the need for additional CaM. The apparent activation constants for the autophosphorylation of CaM-kinase II were 10 and 26 nM, respectively, for myosin-V versus CaM. The maximum incorporation of 32P into CaM-kinase II activated by myosin-V was twice that for CaM, suggesting that myosin-V binding to CaM-kinase II entails alterations in kinetic and/or phosphorylation site parameters. These data suggest that myosin-V, a calmodulin-carrying myosin, binds to and delivers CaM to CaM-kinase II, a calmodulin-dependent enzyme.
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Affiliation(s)
- M C Costa
- Department of Biochemistry, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, São Paulo 14049-900, Brazil
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20
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Langford GM, Molyneaux BJ. Myosin V in the brain: mutations lead to neurological defects. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 1998; 28:1-8. [PMID: 9795099 DOI: 10.1016/s0165-0173(98)00020-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- G M Langford
- Department of Biological Sciences, Dartmouth College, 6044 Gilman Laboratory, Hanover, NH 03755-3576, USA.
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Abstract
It is an exciting time to be studying myosins and their roles in the function of cells and organisms. Past efforts aimed at finding new members of this family have now given way to a focus on identifying individual functions for each motor protein. These actin-based motors are now known to be intimately involved in the following processes: neurosensory function; vesicle trafficking; determinant partitioning; and cortical function. The following article reviews the inroads made into the functions of myosins in these processes over the past several years.
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Affiliation(s)
- J P Baker
- Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA
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22
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Hasson T, Mooseker MS. The growing family of myosin motors and their role in neurons and sensory cells. Curr Opin Neurobiol 1997; 7:615-23. [PMID: 9384540 DOI: 10.1016/s0959-4388(97)80080-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Biochemical and physiological evidence has suggested that myosins, both conventional and unconventional, are critical for neurosensory activities. In the past few years, this premise has been supported by genetic evidence that has shown that unconventional myosins are essential for the proper functioning of neurons, retina and the sensory cells of the inner ear.
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Affiliation(s)
- T Hasson
- Department of Biology, Yale University 266 Whitney Avenue, Room 342, Kline Biology Tower, New Haven, Connecticut 06520, USA.
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