551
|
Buss F, Arden SD, Lindsay M, Luzio J, Kendrick-Jones J. Myosin VI isoform localized to clathrin-coated vesicles with a role in clathrin-mediated endocytosis. EMBO J 2001; 20:3676-84. [PMID: 11447109 PMCID: PMC125554 DOI: 10.1093/emboj/20.14.3676] [Citation(s) in RCA: 224] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Myosin VI is involved in membrane traffic and dynamics and is the only myosin known to move towards the minus end of actin filaments. Splice variants of myosin VI with a large insert in the tail domain were specifically expressed in polarized cells containing microvilli. In these polarized cells, endogenous myosin VI containing the large insert was concentrated at the apical domain co-localizing with clathrin- coated pits/vesicles. Using full-length myosin VI and deletion mutants tagged with green fluorescent protein (GFP) we have shown that myosin VI associates and co-localizes with clathrin-coated pits/vesicles by its C-terminal tail. Myosin VI, precipitated from whole cytosol, was present in a protein complex containing adaptor protein (AP)-2 and clathrin, and enriched in purified clathrin-coated vesicles. Over-expression of the tail domain of myosin VI containing the large insert in fibroblasts reduced transferrin uptake in transiently and stably transfected cells by >50%. Myosin VI is the first motor protein to be identified associated with clathrin-coated pits/vesicles and shown to modulate clathrin-mediated endocytosis.
Collapse
Affiliation(s)
- Folma Buss
- Department of Clinical Biochemistry and Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2XY and
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding author e-mail:
| | | | | | | | - John Kendrick-Jones
- Department of Clinical Biochemistry and Wellcome Trust Centre for the Study of Molecular Mechanisms in Disease, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Addenbrooke’s Hospital, Hills Road, Cambridge CB2 2XY and
MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK Corresponding author e-mail:
| |
Collapse
|
552
|
Reddy AS, Day IS. Analysis of the myosins encoded in the recently completed Arabidopsis thaliana genome sequence. Genome Biol 2001; 2:RESEARCH0024. [PMID: 11516337 PMCID: PMC55321 DOI: 10.1186/gb-2001-2-7-research0024] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2001] [Revised: 04/27/2001] [Accepted: 05/21/2001] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Three types of molecular motors play an important role in the organization, dynamics and transport processes associated with the cytoskeleton. The myosin family of molecular motors move cargo on actin filaments, whereas kinesin and dynein motors move cargo along microtubules. These motors have been highly characterized in non-plant systems and information is becoming available about plant motors. The actin cytoskeleton in plants has been shown to be involved in processes such as transportation, signaling, cell division, cytoplasmic streaming and morphogenesis. The role of myosin in these processes has been established in a few cases but many questions remain to be answered about the number, types and roles of myosins in plants. RESULTS Using the motor domain of an Arabidopsis myosin we identified 17 myosin sequences in the Arabidopsis genome. Phylogenetic analysis of the Arabidopsis myosins with non-plant and plant myosins revealed that all the Arabidopsis myosins and other plant myosins fall into two groups - class VIII and class XI. These groups contain exclusively plant or algal myosins with no animal or fungal myosins. Exon/intron data suggest that the myosins are highly conserved and that some may be a result of gene duplication. CONCLUSIONS Plant myosins are unlike myosins from any other organisms except algae. As a percentage of the total gene number, the number of myosins is small overall in Arabidopsis compared with the other sequenced eukaryotic genomes. There are, however, a large number of class XI myosins. The function of each myosin has yet to be determined.
Collapse
Affiliation(s)
- A S Reddy
- Department of Biology and Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
| | | |
Collapse
|
553
|
Knebelmann B, Fakhouri F, Grünfeld JP. Hereditary nephritis with macrothrombocytopenia: no longer an Alport syndrome variant. Nephrol Dial Transplant 2001; 16:1101-3. [PMID: 11390704 DOI: 10.1093/ndt/16.6.1101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- B Knebelmann
- Service de Néphrologie and INSERM U 507, Hôpital Necker, 149 rue de Sevres, F-75015 Paris, France
| | | | | |
Collapse
|
554
|
Rogers MS, Strehler EE. The tumor-sensitive calmodulin-like protein is a specific light chain of human unconventional myosin X. J Biol Chem 2001; 276:12182-9. [PMID: 11278607 DOI: 10.1074/jbc.m010056200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human calmodulin-like protein (CLP) is an epithelial-specific Ca(2+)-binding protein whose expression is strongly down-regulated in cancers. Like calmodulin, CLP is thought to regulate cellular processes via Ca(2+)-dependent interactions with specific target proteins. Using gel overlays, we identified a approximately 210-kDa protein binding specifically and in a Ca(2+)-dependent manner to CLP, but not to calmodulin. Yeast two-hybrid screening yielded a CLP-interacting clone encoding the three light chain binding IQ motifs of human "unconventional" myosin X. Pull-down experiments showed CLP binding to the IQ domain to be direct and Ca(2+)-dependent. CLP interacted strongly with IQ motif 3 (K(d) approximately 0.5 nm) as determined by surface plasmon resonance. Epitope-tagged myosin X was localized preferentially at the cell periphery in MCF-7 cells, and CLP colocalized with myosin X in these cells. Myosin X was able to coprecipitate CLP and, to a lesser extent, calmodulin from transfected COS-1 cells, indicating that CLP is a specific light chain of myosin X in vivo. Because unconventional myosins participate in cellular processes ranging from membrane trafficking to signaling and cell motility, myosin X is an attractive CLP target. Altered myosin X regulation in (tumor) cells lacking CLP may have as yet unknown consequences for cell growth and differentiation.
Collapse
Affiliation(s)
- M S Rogers
- Tumor Biology Program, Department of Biochemistry and Molecular Biology, Mayo Graduate School and Mayo Clinic Cancer Center, Mayo Clinic/Foundation, Rochester, Minnesota 55905, USA
| | | |
Collapse
|
555
|
Yamashita RA, Sellers JR, Anderson JB. Identification and analysis of the myosin superfamily in Drosophila: a database approach. J Muscle Res Cell Motil 2001; 21:491-505. [PMID: 11206129 DOI: 10.1023/a:1026589626422] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The recent sequencing of the genome of Drosophila melanogaster has provided a valuable resource for mining the database for genes of interest. We took advantage of this opportunity in an attempt to identify novel myosins in Drosophila and confirm the presence of the previously identified myosins from classes I, II, III, V, VI, and VII. The Drosophila database annotators predicted the structure of three additional proteins which we identified as novel unconventional myosins, two of which fell into classes XV and XVIII, respectively. Our own efforts predicted the presence of four additional partial sequences that appear to be myosin proteins which did not fall into any specific class. In the future comparative genomics will hopefully lead to the placement of these myosins into new classes.
Collapse
Affiliation(s)
- R A Yamashita
- Laboratory of Molecular Cardiology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | | | | |
Collapse
|
556
|
Abstract
A polymerase chain reaction (PCR) screen was used to examine the diversity of myosins in 7 Apicomplexan parasites: Toxoplasma gondii, Plasmodium falciparum, Neospora caninum, Eimeria tenella, Sarcocystis muris, Babesia bovis, and Cryptosporidium parvum. Using degenerate PCR primers compatible with the majority of known myosin classes, putative myosin sequences were obtained from all of these species. All of the sequences obtained showed greatest similarity to previously identified apicomplexan myosins, suggesting that the diversity of myosins in these parasites is limited. Myosin classes that are known to be widespread across the phylogenetic spectrum, e.g., the myosins I, II, and V, were not seen in the Apicomplexa. Thus, like the plants, the Apicomplexa may have evolved their own unique cohort of myosins that are responsible for the myosin-driven cellular functions observed in these parasites.
Collapse
Affiliation(s)
- M B Heintzelman
- Department of Anatomy, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
| | | |
Collapse
|
557
|
Abstract
The past decade has seen a remarkable explosion in our knowledge of the size and diversity of the myosin superfamily. Since these actin-based motors are candidates to provide the molecular basis for many cellular movements, it is essential that motility researchers be aware of the complete set of myosins in a given organism. The availability of cDNA and/or draft genomic sequences from humans, Drosophila melanogaster, Caenorhabditis elegans, Arabidopsis thaliana, Saccharomyces cerevisiae, Schizosaccharomyces pombe, and Dictyostelium discoideum has allowed us to tentatively define and compare the sets of myosin genes in these organisms. This analysis has also led to the identification of several putative myosin genes that may be of general interest. In humans, for example, we find a total of 40 known or predicted myosin genes including two new myosins-I, three new class II (conventional) myosins, a second member of the class III/ninaC myosins, a gene similar to the class XV deafness myosin, and a novel myosin sharing at most 33% identity with other members of the superfamily. These myosins are in addition to the recently discovered class XVI myosin with N-terminal ankyrin repeats and two human genes with similarity to the class XVIII PDZ-myosin from mouse. We briefly describe these newly recognized myosins and extend our previous phylogenetic analysis of the myosin superfamily to include a comparison of the complete or nearly complete inventories of myosin genes from several experimentally important organisms.
Collapse
Affiliation(s)
- J S Berg
- Department of Cell and Molecular Physiology, CB#7545, University of North Carolina at Chapel Hill, 27599, USA
| | | | | |
Collapse
|
558
|
de la Roche MA, Côté GP. Regulation of Dictyostelium myosin I and II. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1525:245-61. [PMID: 11257438 DOI: 10.1016/s0304-4165(01)00110-6] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Dictyostelium expresses 12 different myosins, including seven single-headed myosins I and one conventional two-headed myosin II. In this review we focus on the signaling pathways that regulate Dictyostelium myosin I and myosin II. Activation of myosin I is catalyzed by a Cdc42/Rac-stimulated myosin I heavy chain kinase that is a member of the p21-activated kinase (PAK) family. Evidence that myosin I is linked to the Arp2/3 complex suggests that pathways that regulate myosin I may also influence actin filament assembly. Myosin II activity is stimulated by a cGMP-activated myosin light chain kinase and inhibited by myosin heavy chain kinases (MHCKs) that block bipolar filament assembly. Known MHCKs include MHCK A and MHCK B, which have a novel type of kinase catalytic domain joined to a WD repeat domain, and MHC-protein kinase C (PKC), which contains both diacylglycerol kinase and PKC-related protein kinase catalytic domains. A Dictyostelium PAK (PAKa) acts indirectly to promote myosin II filament formation, suggesting that the MHCKs may be indirectly regulated by Rac GTPases.
Collapse
Affiliation(s)
- M A de la Roche
- Department of Biochemistry, Queen's University, K7L 3N6, Kingston, Ont., Canada
| | | |
Collapse
|
559
|
Rupper A, Cardelli J. Regulation of phagocytosis and endo-phagosomal trafficking pathways in Dictyostelium discoideum. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1525:205-16. [PMID: 11257434 DOI: 10.1016/s0304-4165(01)00106-4] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Phagocytosis, a critically important process employed by leukocytes against invading pathogens, is an actin-dependent clathrin-independent process that results in the internalization of particles >0.5 microm in diameter. Phagocytosis consists of a number of stages, including the binding of particles to the cell surface via interaction with a receptor, engulfment of the particle by pseudopod extension, and fission and fusion reactions to form phago-lysosomes. Much remains to be learned concerning the molecular mechanisms that regulate particle internalization and phagosome maturation. Dictyostelium is a genetically tractable professional phagocyte that has proven useful in determining the molecular steps involved in these processes. We will summarize, in this chapter, what we currently understand concerning the molecular mechanisms that regulate the process of phagocytosis in Dictyostelium, and we will compare and contrast this body of information with that available describing phagocytosis in higher organisms. We will also present current information that suggests that macropinocytosis, a process morphologically similar to phagocytosis, utilizes a different signaling pathway than phagocytosis. Finally, we will discuss the process of maturation of phagosomes, which requires membrane trafficking events, and we will summarize data that support the use of Dictyostelium as a model to determine how intracellular pathogens survive.
Collapse
Affiliation(s)
- A Rupper
- Department of Microbiology and Immunology, Feist-Weiller Cancer Center, LSU Health Sciences Center, Shreveport, LA 71130, USA
| | | |
Collapse
|
560
|
Toya M, Motegi F, Nakano K, Mabuchi I, Yamamoto M. Identification and functional analysis of the gene for type I myosin in fission yeast. Genes Cells 2001; 6:187-99. [PMID: 11260263 DOI: 10.1046/j.1365-2443.2001.00414.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Type I myosin is highly conserved among eukaryotes, and apparently plays important roles in a number of cellular processes. In the budding yeast, two myosin I species have been identified and their role in F-actin assembly has been inferred. RESULTS We cloned the fission yeast myo1 gene, which apparently encoded a myosin I protein. Disruption of myo1 was not lethal, but it caused growth retardation at high and low temperatures, sensitivity to a high concentration of KCl, and aberrance in cell morphology associated with an abnormal distribution of F-actin patches. An abnormal deposition of cell wall materials was also seen. Homothallic myo1Delta cells could mate, but heterothallic myo1Delta cells were poor in conjugation. Myo1p was necessary for the encapsulation of spores. The tail domain of Myo1p was pivotal for its function. Calmodulin could bind to Myo1p through the IQ domain at the neck. CONCLUSIONS Myo1p appears to control the redistribution of F-actin patches during the cell cycle. Loss of Myo1p function is likely to slow down the actin assembly/disassembly process, which results in a failure of the actin cycle to catch up with other events in both the mitotic and meiotic cell cycles, including extension of the conjugation tubes.
Collapse
Affiliation(s)
- M Toya
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan
| | | | | | | | | |
Collapse
|
561
|
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.
Collapse
Affiliation(s)
- D L Cohen
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755-3576, USA.
| |
Collapse
|
562
|
Abstract
This first analysis of monocotyledon myosin genes showed that at least five genes, one of which was probably spliced to yield two isoforms, were expressed in maize (Zea mays L.). The complete coding sequence of ZMM1 was determined, as were most of the sequences of two other myosin cDNAs (ZMM2 and ZMM3). ZMM1 and ZMM2 belonged to myosin class XI while ZMM3 was in class VIII. ZMM1 was abundantly expressed in leaves, roots, coleoptiles, and stems. ZMM3 showed a similar distribution but was expressed poorly in pollen. ZMM2 was predominantly expressed in seeds and may be part of a suite of cytoskeletal proteins in reproductive tissues. Phylogenetic analysis suggested that the origin of myosin classes VIII and XI predated that of angiosperms. Immunofluorescence studies using M11L1, a myosin XI antibody specific for the exposed loop 1 head region of myosin, indicated that myosin XI occurred in the cytoplasm of all root tip cells. The highest concentration of myosin XI was in the differentiating epidermal cells. In dividing cells, myosin XI was present near the cytokinetic apparatus at approximately the same concentration seen in other portions of the cytoplasm. Western blot analysis of subcellular fractions indicated that myosin XI was concentrated in mitochondria and low-density membranes.
Collapse
Affiliation(s)
- L Liu
- Biological Laboratories, Harvard University, Cambridge, Massachusetts, USA
| | | | | |
Collapse
|
563
|
Abstract
Members of the kinesin superfamily of microtubule-based motors and the myosin superfamily of actin-based motors that move 'backwards' have been identified. As the core catalytic domains of myosins and kinesins are similar in structure, this raises the intriguing questions of how direction reversal is accomplished and whether kinesins and myosins share mechanisms for switching their motors into reverse.
Collapse
Affiliation(s)
- T Hasson
- Section of Cell and Developmental Biology, Division of Biology, University of California, San Diego, La Jolla, California 92093-0368, USA.
| | | |
Collapse
|
564
|
Takahashi M, Takahashi K, Hiratsuka Y, Uchida K, Yamagishi A, Uyeda TQ, Yazawa M. Functional characterization of vertebrate nonmuscle myosin IIB isoforms using Dictyostelium chimeric myosin II. J Biol Chem 2001; 276:1034-40. [PMID: 11042201 DOI: 10.1074/jbc.m005370200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The alternatively spliced isoform of nonmuscle myosin II heavy chain B (MHC-IIB) with an insert of 21 amino acids in the actin-binding surface loop (loop 2), MHC-IIB(B2), is expressed specifically in the central nervous system of vertebrates. To examine the role of the B2 insert in the motor activity of the myosin II molecule, we expressed chimeric myosin heavy chain molecules using the Dictyostelium myosin II heavy chain as the backbone. We replaced the Dictyostelium native loop 2 with either the noninserted form of loop 2 from human MHC-IIB or the B2-inserted form of loop 2 from human MHC-IIB(B2). The transformant Dictyostelium cells expressing only the B2-inserted chimeric myosin formed unusual fruiting bodies. We then assessed the function of chimeric proteins, using an in vitro motility assay and by measuring ATPase activities and binding to F-actin. We demonstrate that the insertion of the B2 sequence reduces the motor activity of Dictyostelium myosin II, with reduction of the maximal actin-activated ATPase activity and a decrease in the affinity for actin. In addition, we demonstrate that the native loop 2 sequence of Dictyostelium myosin II is required for the regulation of the actin-activated ATPase activity by phosphorylation of the regulatory light chain.
Collapse
Affiliation(s)
- M Takahashi
- Division of Biological Sciences and Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan.
| | | | | | | | | | | | | |
Collapse
|
565
|
Bauer CB, Holden HM, Thoden JB, Smith R, Rayment I. X-ray structures of the apo and MgATP-bound states of Dictyostelium discoideum myosin motor domain. J Biol Chem 2000; 275:38494-9. [PMID: 10954715 DOI: 10.1074/jbc.m005585200] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Myosin is the most comprehensively studied molecular motor that converts energy from the hydrolysis of MgATP into directed movement. Its motile cycle consists of a sequential series of interactions between myosin, actin, MgATP, and the products of hydrolysis, where the affinity of myosin for actin is modulated by the nature of the nucleotide bound in the active site. The first step in the contractile cycle occurs when ATP binds to actomyosin and releases myosin from the complex. We report here the structure of the motor domain of Dictyostelium discoideum myosin II both in its nucleotide-free state and complexed with MgATP. The structure with MgATP was obtained by soaking the crystals in substrate. These structures reveal that both the apo form and the MgATP complex are very similar to those previously seen with MgATPgammaS and MgAMP-PNP. Moreover, these structures are similar to that of chicken skeletal myosin subfragment-1. The crystallized protein is enzymatically active in solution, indicating that the conformation of myosin observed in chicken skeletal myosin subfragment-1 is unable to hydrolyze ATP and most likely represents the pre-hydrolysis structure for the myosin head that occurs after release from actin.
Collapse
Affiliation(s)
- C B Bauer
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706-1544, USA
| | | | | | | | | |
Collapse
|
566
|
Lalwani AK, Goldstein JA, Kelley MJ, Luxford W, Castelein CM, Mhatre AN. Human nonsyndromic hereditary deafness DFNA17 is due to a mutation in nonmuscle myosin MYH9. Am J Hum Genet 2000; 67:1121-8. [PMID: 11023810 PMCID: PMC1288554 DOI: 10.1016/s0002-9297(07)62942-5] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2000] [Accepted: 09/13/2000] [Indexed: 12/01/2022] Open
Abstract
The authors had previously mapped a new locus-DFNA17, for nonsyndromic hereditary hearing impairment-to chromosome 22q12.2-q13. 3. DFNA17 spans a 17- to 23-cM region, and MYH9, a nonmuscle-myosin heavy-chain gene, is located within the linked region. Because of the importance of myosins in hearing, MYH9 was tested as a candidate gene for DFNA17. Expression of MYH9 in the rat cochlea was confirmed using reverse transcriptase-PCR and immunohistochemistry. MYH9 was immunolocalized in the organ of Corti, the subcentral region of the spiral ligament, and the Reissner membrane. Sequence analysis of MYH9 in a family with DFNA17 identified, at nucleotide 2114, a G-->A transposition that cosegregated with the inherited autosomal dominant hearing impairment. This missense mutation changes codon 705 from an invariant arginine (R) to histidine (H), R705H, within a highly conserved SH1 linker region. Previous studies have shown that modification of amino acid residues within the SH1 helix causes dysfunction of the ATPase activity of the motor domain in myosin II. Both the precise role of MYH9 in the cochlea and the mechanism by which the R705H mutation leads to the DFNA17 phenotype (progressive hearing impairment and cochleosaccular degeneration) remain to be elucidated.
Collapse
Affiliation(s)
- A K Lalwani
- Laboratory of Molecular Otology, Epstein Laboratories, Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA 94143, USA.
| | | | | | | | | | | |
Collapse
|
567
|
Lalwani AK, Goldstein JA, Kelley MJ, Luxford W, Castelein CM, Mhatre AN. Human Nonsyndromic Hereditary Deafness DFNA17 Is Due to a Mutation in Nonmuscle MyosinMYH9. Am J Hum Genet 2000. [DOI: 10.1086/321212] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
|
568
|
Berg JS, Derfler BH, Pennisi CM, Corey DP, Cheney RE. Myosin-X, a novel myosin with pleckstrin homology domains, associates with regions of dynamic actin. J Cell Sci 2000; 113 Pt 19:3439-51. [PMID: 10984435 DOI: 10.1242/jcs.113.19.3439] [Citation(s) in RCA: 160] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Myosin-X is the founding member of a novel class of unconventional myosins characterized by a tail domain containing multiple pleckstrin homology domains. We report here the full-length cDNA sequences of human and bovine myosin-X as well as the first characterization of this protein's distribution and biochemical properties. The 235 kDa myosin-X contains a head domain with <45% protein sequence identity to other myosins, three IQ motifs, and a predicted stalk of coiled coil. Like several other unconventional myosins and a plant kinesin, myosin-X contains both a myosin tail homology 4 (MyTH4) domain and a FERM (band 4.1/ezrin/radixin/moesin) domain. The unique tail domain also includes three pleckstrin homology domains, which have been implicated in phosphatidylinositol phospholipid signaling, and three PEST sites, which may allow cleavage of the myosin tail. Most intriguingly, myosin-X in cultured cells is present at the edges of lamellipodia, membrane ruffles, and the tips of filopodial actin bundles. The tail domain structure, biochemical features, and localization of myosin-X suggest that this novel unconventional myosin plays a role in regions of dynamic actin.
Collapse
Affiliation(s)
- J S Berg
- Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | | | | | | | | |
Collapse
|
569
|
Affiliation(s)
- P Merrifield
- Department of Anatomy and Cell Biology, The University of Western Ontario, London, Ontario, Canada N6A 5C1.
| | | |
Collapse
|
570
|
Seri M, Cusano R, Gangarossa S, Caridi G, Bordo D, Lo Nigro C, Ghiggeri GM, Ravazzolo R, Savino M, Del Vecchio M, d'Apolito M, Iolascon A, Zelante LL, Savoia A, Balduini CL, Noris P, Magrini U, Belletti S, Heath KE, Babcock M, Glucksman MJ, Aliprandis E, Bizzaro N, Desnick RJ, Martignetti JA. Mutations in MYH9 result in the May-Hegglin anomaly, and Fechtner and Sebastian syndromes. The May-Heggllin/Fechtner Syndrome Consortium. Nat Genet 2000; 26:103-5. [PMID: 10973259 DOI: 10.1038/79063] [Citation(s) in RCA: 292] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The autosomal dominant, giant-platelet disorders, May-Hegglin anomaly (MHA; MIM 155100), Fechtner syndrome (FTNS; MIM 153640) and Sebastian syndrome (SBS), share the triad of thrombocytopenia, large platelets and characteristic leukocyte inclusions ('Döhle-like' bodies). MHA and SBS can be differentiated by subtle ultrastructural leukocyte inclusion features, whereas FTNS is distinguished by the additional Alport-like clinical features of sensorineural deafness, cataracts and nephritis. The similarities between these platelet disorders and our recent refinement of the MHA (ref. 6) and FTNS (ref. 7) disease loci to an overlapping region of 480 kb on chromosome 22 suggested that all three disorders are allelic. Among the identified candidate genes is the gene encoding nonmuscle myosin heavy chain 9 (MYH9; refs 8-10), which is expressed in platelets and upregulated during granulocyte differentiation. We identified six MYH9 mutations (one nonsense and five missense) in seven unrelated probands from MHA, SBS and FTNS families. On the basis of molecular modelling, the two mutations affecting the myosin head were predicted to impose electrostatic and conformational changes, whereas the truncating mutation deleted the unique carboxy-terminal tailpiece. The remaining missense mutations, all affecting highly conserved coiled-coil domain positions, imparted destabilizing electrostatic and polar changes. Thus, our results suggest that mutations in MYH9 result in three megakaryocyte/platelet/leukocyte syndromes and are important in the pathogenesis of sensorineural deafness, cataracts and nephritis.
Collapse
Affiliation(s)
- M Seri
- Laboratory of Molecular Genetics, Institute G. Gaslini, Genoa, Italy
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
571
|
Zhang Z, Gurr SJ. Walking into the unknown: a 'step down' PCR-based technique leading to the direct sequence analysis of flanking genomic DNA. Gene 2000; 253:145-50. [PMID: 10940551 DOI: 10.1016/s0378-1119(00)00289-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
We describe a novel and efficient PCR-based technique for walking into unknown flanking genomic DNA without recourse to protracted laborious library screening for overlapping sequences. This two component 'hot start' and 'step down' PCR method uses 6x1 microg of genomic DNA (ca 20kb in length) restricted with six different endonucleases and ligated to adaptors with the inclusion of two further restriction enzymes to prevent self-ligation. This allowed us to walk, in a single step, up to 6kb into flanking DNA and gave sufficient PCR products for up to 200 different walking experiments. This technology enabled us to clone and characterize the previously elusive 5' sequence of the barley powdery mildew chitin synthase gene, BgChs2, which includes a myosin motor-like sequence fused to a type V chitin synthase gene.
Collapse
Affiliation(s)
- Z Zhang
- Department of Plant Sciences, University of Oxford, South Parks Road, OX1 3RB, Oxford, UK
| | | |
Collapse
|