101
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Tani K, Sato S, Sukezane T, Kojima H, Hirose H, Hanafusa H, Shishido T. Abl interactor 1 promotes tyrosine 296 phosphorylation of mammalian enabled (Mena) by c-Abl kinase. J Biol Chem 2003; 278:21685-92. [PMID: 12672821 DOI: 10.1074/jbc.m301447200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian Enabled (Mena) is a mammalian homologue of Drosophila Enabled (Ena), which genetically interacts with Drosophila Abl tyrosine kinase. The signaling pathway involving c-Abl and Mena (Ena) is not fully understood. To find molecules that participate in the c-Abl/Mena pathway, we searched for Mena-binding proteins using a yeast two-hybrid system. We identified Abl interactor 1 (Abi-1), which is known to interact with c-Abl, as a binding protein for Mena. Binding analysis revealed that the Ena/Vasp homology 1 domain of Mena and the polyproline structure of Abi-1 are necessary for the interaction. The interaction between Mena and Abi-1 was also observed in a mammalian expression system. Importantly, Abi-1 dramatically promoted c-Abl-mediated tyrosine phosphorylation of Mena but not other substrates such as c-Cbl. Mutational analysis demonstrated that the phosphorylation site of Mena is Tyr-296. Our results suggest that Abi-1 regulates c-Abl-mediated phosphorylation of Mena by interacting with both proteins.
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Affiliation(s)
- Katsuko Tani
- School of Life Science, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo 192-0392, Japan.
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102
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Desai C, Purdy J. The neural receptor protein tyrosine phosphatase DPTP69D is required during periods of axon outgrowth in Drosophila. Genetics 2003; 164:575-88. [PMID: 12807778 PMCID: PMC1462576 DOI: 10.1093/genetics/164.2.575] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have isolated and characterized a series of 18 chemically induced alleles of Ptp69D ranging in strength from viable to worse than null, which represent unique tools for probing the structure, function, and signaling pathway of DPTP69D. Three alleles are strongly temperature sensitive and were used to define the developmental periods requiring DPTP69D function; adult health requires DPTP69D during the mid- to late-pupal stage, eclosion requires DPTP69D during the early to mid-larval stage, and larval survival requires DPTP69D during embryogenesis. Mutations predicted to abolish the phosphatase activity of the membrane proximal D1 domain severely reduce but do not abolish DPTP69D function. Six alleles appear null; only 20% of null homozygotes pupate and <5% eclose, only to fall into the food and drown. One allele, Ptp69D(7), confers axon and viability defects more severe than those of the null phenotype. Sequence analysis predicts that Ptp69D(7) encodes a mutant protein that may bind but not release substrate. Like mutations in the protein tyrosine phosphatase gene Dlar, strong Ptp69D alleles cause the ISNb nerve to bypass its muscle targets. Genetic analysis reveals that the bypass defect in Dlar and Ptp69D mutants is dependent upon DPTP99A function, consistent with the hypothesis that DPTP69D and DLAR both counteract DPTP99A, allowing ISNb axons to enter their target muscle field.
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Affiliation(s)
- Chand Desai
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA.
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103
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Crowner D, Le Gall M, Gates MA, Giniger E. Notch steers Drosophila ISNb motor axons by regulating the Abl signaling pathway. Curr Biol 2003; 13:967-72. [PMID: 12781136 DOI: 10.1016/s0960-9822(03)00325-7] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The central problem in axon guidance is to understand how guidance signals interact to determine where an axon will grow. Here we investigate a specific axon guidance decision in Drosophila embryos, the sharp inward turn taken by the ISNb motor nerve to approach its muscle targets. We find that this turn requires Notch and its ligand Delta. We show that Delta is expressed on cells adjacent to the ISNb turning point, and we know from previous work that Notch is present on axonal growth cones, suggesting that Delta and Notch might provide a guidance signal to ISNb. To induce the turning of ISNb axons, Notch interacts genetically with multiple components of a signal transduction pathway that includes the Abl tyrosine kinase and its affiliated accessory proteins. In contrast, genetic interaction experiments fail to provide evidence for a major role of the "canonical" Notch/Su(H) signaling pathway in this process. We suggest that the Notch/Abl interaction promotes the turning of ISNb axons by attenuating the Abl-dependent adhesion of ISNb axons to their substratum, thus releasing the axons to respond to attraction from target muscles.
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Affiliation(s)
- Daniel Crowner
- Division of Basic Sciences and Program in Developmental Biology, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue, North, Seattle, WA 98109, USA
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104
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105
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Koleske AJ. Do filopodia enable the growth cone to find its way? SCIENCE'S STKE : SIGNAL TRANSDUCTION KNOWLEDGE ENVIRONMENT 2003; 2003:pe20. [PMID: 12759482 DOI: 10.1126/stke.2003.183.pe20] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Ena/VASP family proteins are required for accurate axon pathfinding in developing Drosophila, Caenorhabditis elegans, and mouse nervous systems. Recent papers by Bear et al. and Svitkina et al. provide evidence that Ena/VASP proteins regulate actin filament elongation in the lamellipodia and filopodia of nonneuronal cells. Neuronal growth cones use filopodia as their "sensory organs" that steer the growth cone by reading guidance cues in the environment. Together, these studies suggest that Ena/VASP proteins regulate axon guidance by controlling the formation or rearrangement of growth cone filopodia.
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Affiliation(s)
- Anthony J Koleske
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, Box 208024, 333 Cedar Street, New Haven, CT 06520-8024, USA.
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106
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Abstract
How the dendritic branching patterns of different neurons are specified is a fascinating question in developmental neurobiology. This question can now be addressed in detail in Drosophila, owing to technological advances that allow in vivo labeling of the dendrites of identifiable neurons. Recent genetic analyses in flies have uncovered several molecules, including transcription factors, cytoskeleton-associated proteins and membrane receptor-like molecules, that provide a glimpse into the complex regulatory network that controls dendritic morphogenesis.
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Affiliation(s)
- Fen-Biao Gao
- Gladstone Institute of Neurological Disease, Neuroscience Graduate Program, University of California, San Francisco, CA 94141-9100, USA.
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107
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Affiliation(s)
- Ann Marie Pendergast
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710, USA
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108
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Gianni D, Zambrano N, Bimonte M, Minopoli G, Mercken L, Talamo F, Scaloni A, Russo T. Platelet-derived growth factor induces the beta-gamma-secretase-mediated cleavage of Alzheimer's amyloid precursor protein through a Src-Rac-dependent pathway. J Biol Chem 2003; 278:9290-7. [PMID: 12645527 DOI: 10.1074/jbc.m211899200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The beta-amyloid peptide (Abeta) present in the senile plaques of Alzheimer's disease derives from the cleavage of a membrane protein, named APP, driven by two enzymes, known as beta- and gamma-secretases. The mechanisms regulating this cleavage are not understood. We have developed an experimental system to identify possible extracellular signals able to trigger the cleavage of an APP-Gal4 fusion protein, which is detected by measuring the expression of the CAT gene transcribed under the control of the Gal4 transcription factor, which is released from the membrane upon the cleavage of APP-Gal4. By using this assay, we purified a protein contained in the C6 cell-conditioned medium, which activates the cleavage of APP-Gal4 and which we demonstrated to be PDGF-BB. The APP-Gal4 processing induced by PDGF is dependent on the gamma-secretase activity, being abolished by an inhibitor of this enzyme, and is the consequence of the activation of a pathway downstream of the PDGF-receptor, which includes the non-receptor tyrosine kinase Src and the small G-protein Rac1. These findings are confirmed by the observation that a constitutively active form of Src increases Abeta generation and that, in cells stably expressing APP, the generation of A is strongly decreased by the Src tyrosine kinase inhibitor PP2.
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Affiliation(s)
- Davide Gianni
- Dipartimento di Biochimica e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Napoli 80131, Italy
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109
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Moresco EMY, Scheetz AJ, Bornmann WG, Koleske AJ, Fitzsimonds RM. Abl family nonreceptor tyrosine kinases modulate short-term synaptic plasticity. J Neurophysiol 2003; 89:1678-87. [PMID: 12626632 DOI: 10.1152/jn.00892.2002] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Abl family nonreceptor tyrosine kinases regulate cell morphogenesis through functional interactions with the actin cytoskeleton. The vertebrate Abl family kinases, Abl and Arg, are expressed in the adult mouse brain, where they may regulate actin cytoskeletal dynamics in mature neurons. Using immunoelectron microscopy, we have localized Abl and Arg to the pre- and postsynaptic compartments of synapses in the mouse hippocampal area CA1. Paired-pulse facilitation (PPF) was significantly reduced at the Schaffer collateral-CA1 (SC-CA1) excitatory synapses in hippocampal slices from abl-/- and arg-/- mice as compared with wild-type mice. Furthermore, treatment of wild-type slices with the specific Abl family kinase inhibitor STI571 also reduced PPF. Basal synaptic transmission, posttetanic potentiation (PTP), long-term potentiation (LTP), and long-term depression (LTD) were similar to wild-type controls in abl-/- and arg-/- slices and in STI571-treated wild-type slices. These results indicate that an important function of Abl and Arg is to modulate synaptic efficacy via a presynaptic mechanism during repetitive activation.
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Affiliation(s)
- Eva Marie Yang Moresco
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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110
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Abstract
To construct the intricate network of connections that supports the functions of an adult nervous system, neurons must form highly elaborate processes, extending in the appropriate direction across long distances to form synapses with their partners. As the nervous system takes shape, the process of neuronal morphogenesis is controlled by a broad repertoire of cellular signals. These extracellular cues and cellular interactions are translated by receptors at the cell surface into physical forces that control the dynamic architecture of the neuron as it explores the surrounding terrain. The interpretation of these cues involves a large set of intracellular proteins, whose functional logic we are just beginning to appreciate. We shall consider the basic mechanics of neuronal morphogenesis and some of the emerging pathways that seem to link the outer and inner worlds of the neuron.
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Affiliation(s)
- Haeryun Lee
- Department of Cell Biology, Program in Neuroscience, and Harvard Center for Neurodegeneration and Repair, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
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111
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Renfranz PJ, Siegrist SE, Stronach BE, Macalma T, Beckerle MC. Molecular and phylogenetic characterization of Zyx102, a Drosophila orthologue of the zyxin family that interacts with Drosophila Enabled. Gene 2003; 305:13-26. [PMID: 12594038 DOI: 10.1016/s0378-1119(02)01173-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Adherens junctions, which are cadherin-mediated junctions between cells, and focal adhesions, which are integrin-mediated junctions between cells and the extracellular matrix, are protein complexes that link the actin cytoskeleton to the plasma membrane and, in turn, to the extracellular environment. Zyxin is a LIM domain protein that is found in vertebrate adherens junctions and focal adhesions. Zyxin's molecular architecture and binding partner repertoire suggest roles in actin assembly and dynamics, cell motility, and nuclear-cytoplasmic communication. In order to study the function of zyxin in development, we have identified a zyxin orthologue in Drosophila melanogaster that we have termed Zyx102. Like its vertebrate counterparts, Zyx102 displays three carboxy-terminal LIM domains, a potential nuclear export signal, and three proline-rich motifs, one of which matches the consensus for mediating an interaction with Ena/VASP (Drosophila Enabled/Vasodilator-stimulated phosphoprotein) proteins. Here we show that Zyx102 and Enabled (Ena), the Drosophila member of the Ena/VASP family, can interact specifically in vitro and that this interaction does not occur when a particular mutant form of Ena, encoded by the lethal ena210 allele, is used. Lastly, we show that the zyx102 gene and Drosophila Ena are co-expressed during oogenesis and early embryogenesis, indicating that the two proteins may be able to interact during the development of the Drosophila egg chamber and early embryo.
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MESH Headings
- Alternative Splicing
- Amino Acid Sequence
- Animals
- Base Sequence
- Chromosome Mapping
- Cloning, Molecular
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Drosophila Proteins
- Drosophila melanogaster/embryology
- Drosophila melanogaster/genetics
- Drosophila melanogaster/metabolism
- Embryo, Nonmammalian/metabolism
- Embryonic Development
- Gene Expression Regulation, Developmental
- Homeodomain Proteins/genetics
- Homeodomain Proteins/metabolism
- In Situ Hybridization
- Molecular Sequence Data
- Mutation
- Phylogeny
- Protein Binding
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Zyxin
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Affiliation(s)
- Patricia J Renfranz
- Department of Biology, Huntsman Cancer Institute, University of Utah, 2000 E. Circle of Hope, Salt Lake City, UT 84112-5550, USA
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112
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Gitai Z, Yu TW, Lundquist EA, Tessier-Lavigne M, Bargmann CI. The netrin receptor UNC-40/DCC stimulates axon attraction and outgrowth through enabled and, in parallel, Rac and UNC-115/AbLIM. Neuron 2003; 37:53-65. [PMID: 12526772 DOI: 10.1016/s0896-6273(02)01149-2] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Netrins promote axon outgrowth and turning through DCC/UNC-40 receptors. To characterize Netrin signaling, we generated a gain-of-function UNC-40 molecule, MYR::UNC-40. MYR::UNC-40 causes axon guidance defects, excess axon branching, and excessive axon and cell body outgrowth. These defects are suppressed by loss-of-function mutations in ced-10 (a Rac GTPase), unc-34 (an Enabled homolog), and unc-115 (a putative actin binding protein). ced-10, unc-34, and unc-115 also function in endogenous unc-40 signaling. Our results indicate that Enabled functions in axonal attraction as well as axon repulsion. UNC-40 has two conserved cytoplasmic motifs that mediate distinct downstream pathways: CED-10, UNC-115, and the UNC-40 P2 motif act in one pathway, and UNC-34 and the UNC-40 P1 motif act in the other. Thus, UNC-40 might act as a scaffold to deliver several independent signals to the actin cytoskeleton.
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Affiliation(s)
- Zemer Gitai
- Howard Hughes Medical Institute, Department of Anatomy, University of California, San Francisco, San Francisco, CA 94143, USA
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113
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Abstract
Receptor protein tyrosine phosphatases (RPTPs) are key regulators of neuronal morphogenesis in a variety of different vertebrate and invertebrate systems, yet the mechanisms by which these proteins regulate central nervous system development are poorly understood. In the past few years, studies have begun to outline possible models for RPTP function by demonstrating in vivo roles for RPTPs in axon outgrowth, guidance, and synaptogenesis. In addition, the crystal structures of several RPTPs have been solved, numerous downstream effectors of RPTP signaling have been identified, and a small number of RPTP ligands have been described. In this review, we focus on how RPTPs transduce signals from the extracellular environment to the cytoplasm, using a detailed comparative analysis of the different RPTP subfamilies. Focusing on the roles RPTPs play in the development of the central nervous system, we discuss how the elucidation of RPTP crystal structures, the biochemical analysis of phosphatase enzyme catalysis, and the characterization of complex signal transduction cascades downstream of RPTPs have generated testable models of RPTP structure and function.
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Affiliation(s)
- Karl G Johnson
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02446, USA
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114
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Abstract
Ena/VASP proteins are actin-binding proteins that localize to actin stress fibres, the tips of filopodia and the lamellipodial leading edge. In the past few years, a number of seemingly conflicting studies have confused the Ena/VASP field, pointing to roles for these proteins in both promotion and inhibition of actin-dependent processes. Recent discoveries resolve these contradictions and suggest a novel mechanism of Ena/VASP function, in which the proteins function as 'anti-capping' proteins that antagonize capping proteins at the barbed end of actin filaments.
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Affiliation(s)
- Matthias Krause
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA
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115
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Godenschwege TA, Hu H, Shan-Crofts X, Goodman CS, Murphey RK. Bi-directional signaling by Semaphorin 1a during central synapse formation in Drosophila. Nat Neurosci 2002; 5:1294-301. [PMID: 12436113 DOI: 10.1038/nn976] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2002] [Accepted: 10/22/2002] [Indexed: 11/09/2022]
Abstract
Semaphorins have been intensively studied for their role in dendritic and axonal pathfinding, but less is known about their potential role in synapse formation. In the adult giant fiber (GF) system of fruit flies (Drosophila melanogaster), we show that transmembrane Semaphorin 1a (Sema-1a) is involved in synapse formation in addition to its role in guidance during pathfinding. Cell-autonomous rescue experiments showed that Sema-1a is involved in assembly of a central synapse and that it is required both pre- and postsynaptically. We also found that pre- but not postsynaptic gain-of-function Sema-1a was able to disrupt the GF-motor neuron synapse and that the phenotype depended on a proline-rich intracellular domain that contains a putative Enabled binding site. We suggest that transmembrane Sema-1a is part of a bi-directional signaling system that leads to the formation of the GF synapse and possibly acts as both a ligand and a receptor.
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Affiliation(s)
- Tanja A Godenschwege
- University of Massachusetts, Department of Biology, Morrill Science Center, Amherst, Massachusetts 01003, USA
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116
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Biswas SC, Dutt A, Baker MW, Macagno ER. Association of LAR-like receptor protein tyrosine phosphatases with an enabled homolog in Hirudo medicinalis. Mol Cell Neurosci 2002; 21:657-70. [PMID: 12504598 DOI: 10.1006/mcne.2002.1209] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Receptor protein tyrosine phosphatases (RPTPs) are thought to play important functions in pathfinding and target recognition by growing neuronal processes. The leech RPTPs HmLAR1 and HmLAR2 are expressed selectively by central neurons, Comb cells, and peripheral muscle tissues in the Hirudo medicinalis embryo. To explore the functions of HmLARs, we have sought to determine their physiological substrates. We report here the cloning and embryonic expression of Lena, the leech homolog of Enabled, a cytosolic protein implicated in actin-based cell motility. Lena is expressed in embryonic central neurons and in the Comb cell. We present experimental evidences indicating that Lena associates selectively with the intracellular domain of HmLAR1 and HmLAR2. Additionally, RNA interference (RNAi) of HmLAR1 in intact leech embryos leads to the hyperphosphorylation of Lena. We propose, therefore, that Lena is an in vivo substrate of HmLAR1 in neurons and perhaps of HmLAR2 in the Comb cells.
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MESH Headings
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cell Differentiation/genetics
- Cells, Cultured
- Central Nervous System/cytology
- Central Nervous System/embryology
- Central Nervous System/enzymology
- Cytoskeletal Proteins
- DNA, Complementary/analysis
- DNA, Complementary/genetics
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/isolation & purification
- DNA-Binding Proteins/metabolism
- Embryo, Nonmammalian/cytology
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/enzymology
- Ganglia, Invertebrate/cytology
- Ganglia, Invertebrate/embryology
- Ganglia, Invertebrate/enzymology
- Gene Expression Regulation, Developmental/genetics
- Immunohistochemistry
- Leeches/cytology
- Leeches/enzymology
- Leeches/genetics
- Microfilament Proteins
- Molecular Sequence Data
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neurons/cytology
- Neurons/enzymology
- Protein Structure, Tertiary/genetics
- Protein Tyrosine Phosphatases
- Receptor-Like Protein Tyrosine Phosphatases, Class 2
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
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Affiliation(s)
- Subhas C Biswas
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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117
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Abstract
The low-density-lipoprotein (LDL) receptor family is an evolutionarily ancient gene family of structurally closely related cell-surface receptors. Members of the family are involved in the cellular uptake of extracellular ligands and regulate diverse biological processes including lipid and vitamin metabolism and cell-surface protease activity. Some members of the family also participate in cellular signaling and regulate the development and functional maintenance of the nervous system. Here we review the roles of this family of multifunctional receptors in the nervous system and focus on recent advances toward the understanding of the mechanisms by which lipoprotein receptors and their ligands transmit and modulate signals in the brain.
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Affiliation(s)
- Joachim Herz
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, Texas 75390, USA.
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118
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Wills Z, Emerson M, Rusch J, Bikoff J, Baum B, Perrimon N, Van Vactor D. A Drosophila homolog of cyclase-associated proteins collaborates with the Abl tyrosine kinase to control midline axon pathfinding. Neuron 2002; 36:611-22. [PMID: 12441051 DOI: 10.1016/s0896-6273(02)01022-x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We demonstrate that Drosophila capulet (capt), a homolog of the adenylyl cyclase-associated protein that binds and regulates actin in yeast, associates with Abl in Drosophila cells, suggesting a functional relationship in vivo. We find a robust and specific genetic interaction between capt and Abl at the midline choice point where the growth cone repellent Slit functions to restrict axon crossing. Genetic interactions between capt and slit support a model where Capt and Abl collaborate as part of the repellent response. Further support for this model is provided by genetic interactions that both capt and Abl display with multiple members of the Roundabout receptor family. These studies identify Capulet as part of an emerging pathway linking guidance signals to regulation of cytoskeletal dynamics and suggest that the Abl pathway mediates signals downstream of multiple Roundabout receptors.
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Affiliation(s)
- Zachary Wills
- Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
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119
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Yu TW, Hao JC, Lim W, Tessier-Lavigne M, Bargmann CI. Shared receptors in axon guidance: SAX-3/Robo signals via UNC-34/Enabled and a Netrin-independent UNC-40/DCC function. Nat Neurosci 2002; 5:1147-54. [PMID: 12379860 DOI: 10.1038/nn956] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2002] [Accepted: 11/09/2002] [Indexed: 11/09/2022]
Abstract
The C. elegans SAX-3/Robo receptor acts in anterior-posterior, dorsal-ventral and midline guidance decisions. Here we show that SAX-3 signaling involves the C. elegans Enabled protein UNC-34 and an unexpected Netrin-independent function of the Netrin receptor UNC-40/DCC. Genetic interactions with gain- and loss-of-function mutations suggest that unc-34 and unc-40 act together with sax-3 in several guidance decisions, but the C. elegans Netrin gene unc-6 does not act in the same genetic pathways. Within the migrating axon, sax-3, unc-34 and unc-40 all act cell-autonomously. Our results support a role for UNC-34/Enabled proteins in SAX-3-mediated repulsion, and show that UNC-40/DCC can potentiate SAX-3/Robo signaling via a mechanism that may involve direct binding of the two guidance receptors. A combinatorial logic dictates alternative functions for UNC-40/DCC, which can act in attraction to UNC-6/Netrin, repulsion from Netrin (with UNC-5), or repulsion from Slit (with SAX-3).
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Affiliation(s)
- Timothy W Yu
- Howard Hughes Medical Institute, Program in Neuroscience, Department of Anatomy and of Biochemistry and Biophysics, The University of California, San Francisco, California 94143, USA
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120
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Howe AK, Hogan BP, Juliano RL. Regulation of vasodilator-stimulated phosphoprotein phosphorylation and interaction with Abl by protein kinase A and cell adhesion. J Biol Chem 2002; 277:38121-6. [PMID: 12087107 DOI: 10.1074/jbc.m205379200] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the vasodilator-stimulated phosphoprotein (VASP) family are important regulators of actin cytoskeletal dynamics whose functions and protein-protein interactions are regulated by phosphorylation by the cAMP-dependent protein kinase (PKA). Herein, we show that phosphorylation of VASP is dynamically regulated by cellular adhesion to extracellular matrix. Detachment of cells stimulated PKA activity and induced PKA-dependent phosphorylation of VASP and the related murine-Enabled (Mena) protein. VASP and Mena were rapidly dephosphorylated immediately following reattachment but showed an intermediate level of phosphorylation during active cell spreading. This pattern correlated closely with adhesion-dependent changes in PKA activity. The in vivo interaction of VASP with the Abl tyrosine kinase, shown here for the first time, was readily apparent in adherent cells, lost following cellular detachment, and induced upon reattachment to matrix. Importantly, inhibition of PKA activity prevented phosphorylation of VASP and dissociation of VASP-Abl complexes after cellular detachment, whereas activation of PKA completely eliminated the co-immunoprecipitation of Abl activity with VASP. These data establish a new biochemical link between cell adhesion and regulation of VASP proteins and provide the first demonstration of a regulated interaction between VASP and Abl in mammalian cells.
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Affiliation(s)
- Alan K Howe
- Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599-7365, USA.
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121
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Kalirin Dbl-homology guanine nucleotide exchange factor 1 domain initiates new axon outgrowths via RhoG-mediated mechanisms. J Neurosci 2002. [PMID: 12177196 DOI: 10.1523/jneurosci.22-16-06980.2002] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The large multidomain Kalirin and Trio proteins containing dual Rho GTPase guanine nucleotide exchange factor (GEF) domains have been implicated in the regulation of neuronal fiber extension and pathfinding during development. In mammals, Kalirin is expressed predominantly in the nervous system, whereas Trio, broadly expressed throughout the body, is expressed at a lower level in the nervous system. To evaluate the role of Kalirin in fiber initiation and outgrowth, we microinjected cultured sympathetic neurons with vectors encoding Kalirin or with Kalirin antisense oligonucleotides, and we assessed neuronal fiber growth in a serum-free, satellite cell-free environment. Kalirin antisense oligonucleotides blocked the continued extension of preexisting axons. Kalirin overexpression induced the prolific sprouting of new axonal fibers that grew at the normal rate; the activity of Kalirin was entirely dependent on the activity of the first GEF domain. KalGEF1-induced sprouting of new fibers from lamellipodial structures was accompanied by extensive actin cytoskeleton reorganization. The kalGEF1 phenotype was mimicked by constitutively active RhoG and was blocked by RhoG inhibitors. Constitutively active Rac1, RhoA, and Cdc42 were unable to initiate new axons, whereas dominant-negative Rac1, RhoA, and Cdc42 failed to block axon sprouting. Thus Kalirin, acting via RhoG in a novel manner, plays a central role in establishing the morphological phenotypic diversity that is essential to the connectivity of the developing nervous system.
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122
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Loureiro JJ, Rubinson DA, Bear JE, Baltus GA, Kwiatkowski AV, Gertler FB. Critical roles of phosphorylation and actin binding motifs, but not the central proline-rich region, for Ena/vasodilator-stimulated phosphoprotein (VASP) function during cell migration. Mol Biol Cell 2002; 13:2533-46. [PMID: 12134088 PMCID: PMC117332 DOI: 10.1091/mbc.e01-10-0102] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The Ena/vasodilator-stimulated phosphoprotein (VASP) protein family is implicated in the regulation of a number of actin-based cellular processes, including lamellipodial protrusion necessary for whole cell translocation. A growing body of evidence derived largely from in vitro biochemical experiments using purified proteins, cell-free extracts, and pathogen motility has begun to suggest various mechanistic roles for Ena/VASP proteins in the control of actin dynamics. Using complementation of phenotypes in Ena/VASP-deficient cells and overexpression in normal fibroblasts, we have assayed the function of a panel of mutants in one member of this family, Mena, by mutating highly conserved sequence elements found in this protein family. Surprisingly, deletion of sites required for binding of the actin monomer-binding protein profilin, a known ligand of Ena/VASP proteins, has no effect on the ability of Mena to regulate random cell motility. Our analysis revealed two features essential for Ena/VASP function in cell movement, cyclic nucleotide-dependent kinase phosphorylation sites and an F-actin binding motif. Interestingly, expression of the C-terminal EVH2 domain alone is sufficient to complement loss of Ena/VASP function in random cell motility.
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Affiliation(s)
- Joseph J Loureiro
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
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123
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Sabo SL, Ikin AF. Cytosolic protein-protein interactions that regulate the amyloid precursor protein. Drug Dev Res 2002. [DOI: 10.1002/ddr.10078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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124
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Kurakin A, Bredesen D. Target-assisted iterative screening reveals novel interactors for PSD95, Nedd4, Src, Abl and Crk proteins. J Biomol Struct Dyn 2002; 19:1015-29. [PMID: 12023804 DOI: 10.1080/07391102.2002.10506805] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
A new in vitro screening method has been developed and applied to a commercial phage-displayed cDNA library to search for novel protein-protein interactions. PDZ, WW and SH3 domains from PSD95, Nedd4, Src, Abl and Crk proteins were used as targets. 12 novel putative and 2 previously reported interactions were identified in test screens. The novel screening format, dubbed TAIS (target-assisted iterative screening), is discussed as an alternative platform to existing technologies for a pair-wise characterization of protein-protein interactions.
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Affiliation(s)
- Alexei Kurakin
- Buck Institute for Age Research, 8001 Redwood Blvd., Novato, CA 94945, USA.
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125
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Lawrence DW, Comerford KM, Colgan SP. Role of VASP in reestablishment of epithelial tight junction assembly after Ca2+ switch. Am J Physiol Cell Physiol 2002; 282:C1235-45. [PMID: 11997237 DOI: 10.1152/ajpcell.00288.2001] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epithelial permeability is tightly regulated by intracellular messengers. Critical to maintaining barrier integrity is the formation of tight junction complexes. A number of signaling pathways have been implicated in tight junction biogenesis; however, the precise molecular mechanisms are not fully understood. A growing body of evidence suggests a role for intracellular cAMP in tight junction assembly. Using an epithelial model, we investigated the role of cAMP signal transduction in barrier recovery after Ca2+ switch. Our data demonstrate that elevation of intracellular cAMP levels significantly enhanced barrier recovery after Ca2+ switch. Parallel experiments revealed that epithelial barrier recovery is diminished by H-89, a specific and potent inhibitor of cAMP-dependent protein kinase (protein kinase A) activity. Of the possible PKA effector proteins, the vasodilator-stimulated phosphoprotein (VASP) is an attractive candidate, since it has been implicated in actin-binding and cross-linking functions. We therefore hypothesized that VASP may play a role in the cAMP-mediated regulation of epithelial junctional reassembly after Ca2+ switch. We demonstrate here that VASP is phosphorylated via a PKA-dependent process under conditions that enhance barrier recovery. Confocal laser scanning microscopy studies revealed that VASP localizes with ZO-1 at the tight junction and at cell-cell borders and that phospho-VASP appears at the junction after Ca2+ switch. Subsequent transfection studies utilizing epithelial cells expressing truncated forms of VASP abnormal in oligomerization or actin-binding activity revealed a functional diminution of barrier recovery after Ca2+ chelation. Our present studies suggest that VASP may provide a link between cAMP signal transduction and epithelial permeability.
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Affiliation(s)
- Donald W Lawrence
- Center for Experimental Therapeutics and Reperfusion Injury, Brigham and Women's Hospital, and Harvard Medical School, Boston, Massachusetts 02115, USA
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126
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Zambrano N, Bimonte M, Arbucci S, Gianni D, Russo T, Bazzicalupo P. feh-1 and apl-1, the Caenorhabditis elegansorthologues of mammalian Fe65 and β-amyloid precursor protein genes, are involved in the same pathway that controls nematode pharyngeal pumping. J Cell Sci 2002; 115:1411-22. [PMID: 11896189 DOI: 10.1242/jcs.115.7.1411] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The multigenic family of mammalian Fe65s encodes three highly similar proteins with the same modular organisation: a WW domain and two phosphotyrosine-binding domains. The PTB2 domain of these proteins binds to the cytosolic domains of the Alzheimer's β-amyloid precursor protein APP and related proteins APLP1 and APLP2, generating a highly redundant system that is hard to dissect by reverse genetics. By searching potential Fe65-like genes in the nematode Caenorhabditis elegans, we identified a single gene, feh-1 (Fe65 homolog-1), encoding a protein with a high sequence similarity to mammalian Fe65s. FEH-1 is also functionally related to mammalian orthologues;in fact its PTB2 domain binds to APL-1, the product of the C. elegansorthologue of APP. Staining with specific antibodies show that the neuromuscular structures of the pharynx are the sites in which FEH-1 is present at highest levels. Expression studies with reporters indicate that the feh-1 gene is also expressed by a subset of the worm neurons.
We generated and isolated a deletion allele of feh-1, and the corresponding homozygous mutants arrest as late embryos or as L1 larvae,demonstrating for the first time an essential role for a Fe65-like gene in vivo. The pharynx of homozygous larvae does not contract and the worms cannot feed. Analysis of pharyngeal pumping in heterozygous worms and in feh-1 RNA-interfered worms indicates that dosage of feh-1function affects the rate of pharyngeal contraction in C. elegans. Interference with apl-1 double-stranded RNA showed a similar effect on pharyngeal pumping, suggesting that FEH-1 and APL-1 are involved in the same pathway. The non-redundant system of the nematode will prove useful for studying the basic biology of the Fe65-APP interaction and the molecular events regulated by this evolutionarily conserved system of interacting proteins.
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Affiliation(s)
- Nicola Zambrano
- Dipartimento di Biochimica e Biotecnologie Mediche, Università degli Studi di Napoli Federico II, Via S. Pansini, 5, I-80131, Napoli, Italy.
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127
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Hubberstey AV, Mottillo EP. Cyclase-associated proteins: CAPacity for linking signal transduction and actin polymerization. FASEB J 2002; 16:487-99. [PMID: 11919151 DOI: 10.1096/fj.01-0659rev] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Many extracellular signals elicit changes in the actin cytoskeleton, which are mediated through an array of signaling proteins and pathways. One family of proteins that plays a role in regulating actin remodeling in response to cellular signals are the cyclase-associated proteins (CAPs). CAPs are highly conserved monomeric actin binding proteins present in a wide range of organisms including yeast, fly, plants, and mammals. The original CAP was isolated as a component of the Saccharomyces cerevisiae adenylyl cyclase complex that serves as an effector of Ras during nutritional signaling. CAPs are multifunctional molecules that contain domains involved in actin binding, adenylyl cyclase association in yeast, SH3 binding, and oligomerization. Genetic studies in yeast have implicated CAPs in vesicle trafficking and endocytosis. CAPs play a developmental role in multicellular organisms, and studies of Drosophila have illuminated the importance of the actin cytoskeleton during eye development and in establishing oocyte polarity. This review will highlight the critical structural and functional domains of CAPs, describe recent studies that have implied important roles for these proteins in linking cell signaling with actin polymerization, and highlight their roles in vesicle trafficking and development.
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Affiliation(s)
- Andrew V Hubberstey
- Department of Biological Sciences, University of Windsor, Windsor, Ontario, Canada.
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128
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Comerford KM, Lawrence DW, Synnestvedt K, Levi BP, Colgan SP. Role of vasodilator-stimulated phosphoprotein in PKA-induced changes in endothelial junctional permeability. FASEB J 2002; 16:583-5. [PMID: 11919161 DOI: 10.1096/fj.01-0739fje] [Citation(s) in RCA: 148] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
At sites of ongoing inflammation, polymorphonuclear leukocytes (PMN, neutrophils) migrate across vascular endothelia, and such transmigration has the potential to disturb barrier properties and can result in intravascular fluid loss and edema. It was recently appreciated that endogenous pathways exist to dampen barrier disruption during such episodes and may provide an important anti-inflammatory link. For example, during transmigration, PMN-derived adenosine activates endothelial adenosine receptors and induces a cAMP-dependent resealing of endothelial barrier function. In our study reported here, we sought to understand the link between cyclic nucleotide elevation and increased endothelial barrier function. Initial studies revealed that adenosine-induced barrier function is tightly linked to activation of protein kinase A (PKA). Because PKA selectively phosphorylates serine and threonine residues, we screened zonula occludens-1 (ZO-1) immunoprecipitates for the existence of such phosphorylated proteins as targets for barrier regulation. This analysis revealed a dominantly phosphorylated band at 50 kDa. Microsequencing identified this protein as vasodilator-stimulated phosphoprotein (VASP), an actin binding protein with multiple serine/threonine phosphorylation sites. Immunofluorescent microscopy revealed that VASP localizes to endothelial junctional complexes and colocalizes with ZO-1, occludin, and junctional adhesion molecule-1 (JAM-1). To address the role of phospho-VASP in regulation of barrier function, we generated a phosphospecific VASP antibody targeting the Ser157 residue phosphorylation site, the site preferred by PKA. Immunolocalization studies with this antibody revealed that upon PKA activation, phospho-VASP appears at cell-cell junctions. Transient transfection of truncated VASP fragments revealed a parallel increase in barrier function. Taken together, these studies reveal a central role for phospho-VASP in the coordination of PKA-regulated barrier function, such as occurs during episodes of inflammation.
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Affiliation(s)
- Katrina M Comerford
- Center for Experimental Therapeutics and Reperfusion Injury, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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129
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Woodring PJ, Litwack ED, O'Leary DDM, Lucero GR, Wang JYJ, Hunter T. Modulation of the F-actin cytoskeleton by c-Abl tyrosine kinase in cell spreading and neurite extension. J Cell Biol 2002; 156:879-92. [PMID: 11864995 PMCID: PMC2173320 DOI: 10.1083/jcb.200110014] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nonreceptor tyrosine kinase encoded by the c-Abl gene has the unique feature of an F-actin binding domain (FABD). Purified c-Abl tyrosine kinase is inhibited by F-actin, and this inhibition can be relieved through mutation of its FABD. The c-Abl kinase is activated by physiological signals that also regulate the actin cytoskeleton. We show here that c-Abl stimulated the formation of actin microspikes in fibroblasts spreading on fibronectin. This function of c-Abl is dependent on kinase activity and is not shared by c-Src tyrosine kinase. The Abl-dependent F-actin microspikes occurred under conditions where the Rho-family GTPases were inhibited. The FABD-mutated c-Abl, which is active in detached fibroblasts, stimulated F-actin microspikes independent of cell attachment. Moreover, FABD-mutated c-Abl stimulated the formation of F-actin branches in neurites of rat embryonic cortical neurons. The reciprocal regulation between F-actin and the c-Abl tyrosine kinase may provide a self-limiting mechanism in the control of actin cytoskeleton dynamics.
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130
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Fischer DD, Cai R, Bhatia U, Asselbergs FAM, Song C, Terry R, Trogani N, Widmer R, Atadja P, Cohen D. Isolation and characterization of a novel class II histone deacetylase, HDAC10. J Biol Chem 2002; 277:6656-66. [PMID: 11739383 DOI: 10.1074/jbc.m108055200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel histone deacetylase, HDAC10, was isolated from a mixed tissue human cDNA library. HDAC10 was classified as a class II subfamily member based upon similarity to HDAC6. The genomic structure of HDAC10 was found to consist of 20 exons. HDAC10 has two sequence variants, HDAC10v1 and HDAC10v2, and two transcripts were detectable by Northern blot analysis. HDAC10v1 and HDAC10v2 were found to be identical through exon 17 but diverged after this exon. HDAC10v2 has an 82-bp alternate exon that generates a frameshift and shortens the sequence by 11 amino acids. In this study, the characterization of HDAC10v1 was performed. HDAC10v1 has an N-terminal catalytic domain, two putative C-terminal retinoblastoma protein binding domains, and a nuclear hormone receptor binding motif. The HDAC10v1 enzyme was found to be catalytically active based upon its ability to deacetylate a (3)H-acetylated histone H4 N-terminal peptide. Immunofluorescence detection of transfected HDAC10v1-FLAG indicated that the enzyme is a nuclear protein. Furthermore, coimmunoprecipitation experiments indicated that HDAC10v1 associated with HDAC2 and SMRT (silencing mediator for retinoid and thyroid hormone receptors). In addition, based upon the public data base, a single nucleotide polymorphism was found in the C terminus of HDAC10 which changes a Gly residue to Cys, suggesting that HDAC10 molecules containing these single nucleotide polymorphisms may be folded improperly. HDAC10 extends the HDAC superfamily and adds to a growing number of HDACs that have been found to have splice variants, suggesting that RNA processing may play a role in mediating the activity of HDACs.
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Affiliation(s)
- Denise D Fischer
- Department of Functional Genomics, Novartis Pharmaceuticals, Summit, New Jersey 07901, USA
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131
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Abstract
Although actin-based motility drives cell crawling and intracellular locomotion of organelles and certain pathogens, the underlying mechanism of force generation remains a mystery. Recent experiments demonstrated that Listeria exhibit episodes of 5.4-nm stepwise motion corresponding to the periodicity of the actin filament subunits, and extremely small positional fluctuations during the intermittent pauses [S. C. Kuo and J. L. McGrath. 2000. Nature. 407:1026-1029]. These findings suggest that motile bacteria remain firmly bound to actin filament ends as they elongate, a behavior that appears to rule out previous models for actin-based motility. We propose and analyze a new mechanochemical model (called the "Lock, Load & Fire" mechanism) for force generation by means of affinity-modulated, clamped-filament elongation. During the locking step, the filament's terminal ATP-containing subunit binds tightly to a clamp situated on the surface of a motile object; in the loading step, actin.ATP monomer(s) bind to the filament end, an event that triggers the firing step, wherein ATP hydrolysis on the clamped subunit attenuates the filament's affinity for the clamp. This last step initiates translocation of the new ATP-containing terminus to the clamp, whereupon another cycle begins anew. This model explains how surface-tethered filaments can grow while exerting flexural or tensile force on the motile surface. Moreover, stochastic simulations of the model reproduce the signature motions of Listeria. This elongation motor, which we term actoclampin, exploits actin's intrinsic ATPase activity to provide a simple, high-fidelity enzymatic reaction cycle for force production that does not require elongating filaments to dissociate from the motile surface. This mechanism may operate whenever actin polymerization is called upon to generate the forces that drive cell crawling or intracellular organelle motility.
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Affiliation(s)
- Richard B Dickinson
- Department of Chemical Engineering, University of Florida College of Engineering, Gainesville, Florida 32610-0245 USA
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132
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Renfranz PJ, Beckerle MC. Doing (F/L)PPPPs: EVH1 domains and their proline-rich partners in cell polarity and migration. Curr Opin Cell Biol 2002; 14:88-103. [PMID: 11792550 DOI: 10.1016/s0955-0674(01)00299-x] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Actin filament assembly is a tightly regulated process that functions in many aspects of cell physiology. Members of the Ena/VASP (Drosophila Enabled/vasodilator-stimulated phosphoprotein) family are key players in regulating actin filament assembly, in many cases through their association with binding partners that display a particular proline-rich motif, FPPPP. Ena/VASP proteins interact with these partners via the highly conserved Ena/VASP homology 1 (EVH1) domain. The diverse array of binding partners for EVH1 domains, including cytoskeletal proteins such as zyxin, transmembrane guidance receptors such as Roundabout, and the T-cell signaling protein Fyb/SLAP, shows that these interactions are likely to be important in a number of cellular processes that require regulated actin filament assembly.
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Affiliation(s)
- Patricia J Renfranz
- Department of Biology and Huntsman Cancer Institute, 2000 East Circle of Hope, University of Utah, Salt Lake City, UT 84112-5550, USA
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133
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Abstract
The human blood platelet circulates in the blood as a non-adherent disk. Upon receiving signals of blood vessel damage, the platelet reorganizes its actin cytoskeleton which transforms it into a spiky dynamic adherent glue. This transformation involves a temporal sequence of four morphologically distinct steps which is reproducible in vitro. The actin dynamics underlying these shape changes depend on a large number of actin-binding proteins. Maintenance of the discoid shape requires actin-binding proteins that inhibit these reorganizations, whereas transformation involves other proteins, some to disassemble old filaments and others to polymerize new ones. F-Actin-affinity chromatography identified a large set of actin-binding proteins including VASP, Arp2 and 2E4/kaptin. Recent discoveries show that VASP inhibits filament disassembly and Arp2/3 is required to polymerize new filaments. Morphological analysis of the distribution of these actin-binding proteins in spread platelets together with biochemical measurements of their interactions with actin lead to a model of interactions with actin that mediate shape change.
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Affiliation(s)
- E L Bearer
- Department of Pathology and Laboratory Medicine, Brown University, Providence, Rhode Island 02912, USA
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134
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Grevengoed EE, Loureiro JJ, Jesse TL, Peifer M. Abelson kinase regulates epithelial morphogenesis in Drosophila. J Cell Biol 2001; 155:1185-98. [PMID: 11756472 PMCID: PMC2199330 DOI: 10.1083/jcb.200105102] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2001] [Revised: 11/05/2001] [Accepted: 11/06/2001] [Indexed: 11/22/2022] Open
Abstract
Activation of the nonreceptor tyrosine kinase Abelson (Abl) contributes to the development of leukemia, but the complex roles of Abl in normal development are not fully understood. Drosophila Abl links neural axon guidance receptors to the cytoskeleton. Here we report a novel role for Drosophila Abl in epithelial cells, where it is critical for morphogenesis. Embryos completely lacking both maternal and zygotic Abl die with defects in several morphogenetic processes requiring cell shape changes and cell migration. We describe the cellular defects that underlie these problems, focusing on dorsal closure as an example. Further, we show that the Abl target Enabled (Ena), a modulator of actin dynamics, is involved with Abl in morphogenesis. We find that Ena localizes to adherens junctions of most epithelial cells, and that it genetically interacts with the adherens junction protein Armadillo (Arm) during morphogenesis. The defects of abl mutants are strongly enhanced by heterozygosity for shotgun, which encodes DE-cadherin. Finally, loss of Abl reduces Arm and alpha-catenin accumulation in adherens junctions, while having little or no effect on other components of the cytoskeleton or cell polarity machinery. We discuss possible models for Abl function during epithelial morphogenesis in light of these data.
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Affiliation(s)
- E E Grevengoed
- Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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135
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Wang Y, Miller AL, Mooseker MS, Koleske AJ. The Abl-related gene (Arg) nonreceptor tyrosine kinase uses two F-actin-binding domains to bundle F-actin. Proc Natl Acad Sci U S A 2001; 98:14865-70. [PMID: 11752434 PMCID: PMC64950 DOI: 10.1073/pnas.251249298] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Abl family nonreceptor tyrosine kinases regulate cellular morphogenesis and motility through functional interactions with the actin cytoskeleton. Although Abl family kinases are known to contain filamentous (F)-actin-binding domains at their C termini, it is unclear how Abl family kinases regulate the structure and/or function of the actin cytoskeleton. We show here that the Abl-related kinase Arg binds with positive cooperativity to F-actin in vitro with binding saturating at a ratio of one Arg/two actin molecules. Measurements of the F-actin-binding properties of Arg deletion mutants led to the identification of a second, previously uncharacterized internal F-actin-binding domain in Arg. Purified Arg can bundle F-actin in vitro, and this bundling activity requires both F-actin-binding domains. An Arg-yellow fluorescent protein fusion protein can induce the formation of actin-rich structures at the lamellipodia of Swiss 3T3 fibroblasts. Both of Arg's F-actin-binding domains are necessary and sufficient for the formation of these actin-rich structures. Together, our data suggest that Arg can use its F-actin-bundling activity to directly regulate actin cytoskeletal structure in vivo.
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Affiliation(s)
- Y Wang
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520, USA
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136
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Shim K, Blake KJ, Jack J, Krasnow MA. TheDrosophila ribbongene encodes a nuclear BTB domain protein that promotes epithelial migration and morphogenesis. Development 2001; 128:4923-33. [PMID: 11731471 DOI: 10.1242/dev.128.23.4923] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During development of the Drosophila tracheal (respiratory) system, the cell bodies and apical and basal surfaces of the tracheal epithelium normally move in concert as new branches bud and grow out to form tubes. We show that mutations in the Drosophila ribbon (rib) gene disrupt this coupling: the basal surface continues to extend towards its normal targets, but movement and morphogenesis of the tracheal cell bodies and apical surface is severely impaired, resulting in long basal membrane protrusions but little net movement or branch formation. rib mutant tracheal cells are still responsive to the Branchless fibroblast growth factor (FGF) that guides branch outgrowth, and they express apical membrane markers normally. This suggests that the defect lies either in transmission of the FGF signal from the basal surface to the rest of the cell or in the apical cell migration and tubulogenesis machinery. rib encodes a nuclear protein with a BTB/POZ domain and Pipsqueak DNA-binding motif. It is expressed in the developing tracheal system and other morphogenetically active epithelia, many of which are also affected in rib mutants. We propose that Rib is a key regulator of epithelial morphogenesis that promotes migration and morphogenesis of the tracheal cell bodies and apical surface and other morphogenetic movements.
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Affiliation(s)
- K Shim
- Howard Hughes Medical Institute and Department of Biochemistry, Stanford University, Stanford, CA 94305-5307, USA
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137
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Goldberg MB. Actin-based motility of intracellular microbial pathogens. Microbiol Mol Biol Rev 2001; 65:595-626, table of contents. [PMID: 11729265 PMCID: PMC99042 DOI: 10.1128/mmbr.65.4.595-626.2001] [Citation(s) in RCA: 175] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
A diverse group of intracellular microorganisms, including Listeria monocytogenes, Shigella spp., Rickettsia spp., and vaccinia virus, utilize actin-based motility to move within and spread between mammalian host cells. These organisms have in common a pathogenic life cycle that involves a stage within the cytoplasm of mammalian host cells. Within the cytoplasm of host cells, these organisms activate components of the cellular actin assembly machinery to induce the formation of actin tails on the microbial surface. The assembly of these actin tails provides force that propels the organisms through the cell cytoplasm to the cell periphery or into adjacent cells. Each of these organisms utilizes preexisting mammalian pathways of actin rearrangement to induce its own actin-based motility. Particularly remarkable is that while all of these microbes use the same or overlapping pathways, each intercepts the pathway at a different step. In addition, the microbial molecules involved are each distinctly different from the others. Taken together, these observations suggest that each of these microbes separately and convergently evolved a mechanism to utilize the cellular actin assembly machinery. The current understanding of the molecular mechanisms of microbial actin-based motility is the subject of this review.
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Affiliation(s)
- M B Goldberg
- Infectious Disease Division, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
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138
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Maurel-Zaffran C, Suzuki T, Gahmon G, Treisman JE, Dickson BJ. Cell-autonomous and -nonautonomous functions of LAR in R7 photoreceptor axon targeting. Neuron 2001; 32:225-35. [PMID: 11683993 DOI: 10.1016/s0896-6273(01)00471-8] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
During Drosophila visual system development, photoreceptors R7 and R8 project axons to targets in distinct layers of the optic lobe. We show here that the LAR receptor tyrosine phosphatase is required in the eye for correct targeting of R7 axons. In LAR mutants, R7 axons initially project to their correct target layer, but then retract to the R8 target layer. This targeting defect can be fully rescued by transgenic expression of LAR in R7, and partially rescued by expression of LAR in R8. The phosphatase domains of LAR are required for its activity in R7, but not in R8. These data suggest that LAR can act both as a receptor in R7, and as a ligand provided by R8. Genetic interactions implicate both Enabled and Trio in LAR signal transduction.
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Affiliation(s)
- C Maurel-Zaffran
- Skirball Institute for Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
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139
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Baum B, Perrimon N. Spatial control of the actin cytoskeleton in Drosophila epithelial cells. Nat Cell Biol 2001; 3:883-90. [PMID: 11584269 DOI: 10.1038/ncb1001-883] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The actin cytoskeleton orders cellular space and transduces many of the forces required for morphogenesis. Here we combine genetics and cell biology to identify genes that control the polarized distribution of actin filaments within the Drosophila follicular epithelium. We find that profilin and cofilin regulate actin-filament formation throughout the cell cortex. In contrast, CAP-a Drosophila homologue of Adenylyl Cyclase Associated Proteins-functions specifically to limit actin-filament formation catalysed by Ena at apical cell junctions. The Abl tyrosine kinase also collaborates in this process. We therefore propose that CAP, Ena and Abl act in concert to modulate the subcellular distribution of actin filaments in Drosophila.
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Affiliation(s)
- B Baum
- Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, 200 Longwood Avenue, Boston, Massachusetts 02115, USA.
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140
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Buckles GR, Rauskolb C, Villano JL, Katz FN. four-jointed interacts with dachs, abelson and enabled and feeds back onto the Notch pathway to affect growth and segmentation in the Drosophila leg. Development 2001; 128:3533-42. [PMID: 11566858 DOI: 10.1242/dev.128.18.3533] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The molecular basis of segmentation and regional growth during morphogenesis of Drosophila legs is poorly understood. We show that four-jointed is not only required for these processes, but also can direct ectopic growth and joint initiation when its normal pattern of expression is disturbed. These effects are non-autonomous, consistent with our demonstration of both transmembrane and secreted forms of the protein in vivo. The similarities between four-jointed and Notch phenotypes led us to further investigate the relationships between these pathways. Surprisingly, we find that although four-jointed expression is regulated downstream of Notch activation, four-jointed can induce expression of the Notch ligands, Serrate and Delta, and may thereby participate in a feedback loop with the Notch signaling pathway. We also show that four-jointed interacts with abelson, enabled and dachs, which leads us to suggest that one target of four-jointed signaling is the actin cytoskeleton. Thus, four-jointed may bridge the gap between the signals that direct morphogenesis and those that carry it out.
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Affiliation(s)
- G R Buckles
- Department of Biology, Texas A&M University, College Station, TX 77843-3258, USA
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141
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Bradley PL, Andrew DJ. ribbon encodes a novel BTB/POZ protein required for directed cell migration in Drosophila melanogaster. Development 2001; 128:3001-15. [PMID: 11532922 DOI: 10.1242/dev.128.15.3001] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During development, directed cell migration is crucial for achieving proper shape and function of organs. One well-studied example is the embryonic development of the larval tracheal system of Drosophila, in which at least four signaling pathways coordinate cell migration to form an elaborate branched network essential for oxygen delivery throughout the larva. FGF signaling is required for guided migration of all tracheal branches, whereas the DPP, EGF receptor, and Wingless/WNT signaling pathways each mediate the formation of specific subsets of branches. Here, we characterize ribbon, which encodes a BTB/POZ-containing protein required for specific tracheal branch migration. In ribbon mutant tracheae, the dorsal trunk fails to form, and ventral branches are stunted; however, directed migrations of the dorsal and visceral branches are largely unaffected. The dorsal trunk also fails to form when FGF or Wingless/WNT signaling is lost, and we show that ribbon functions downstream of, or parallel to, these pathways to promote anterior-posterior migration. Directed cell migration of the salivary gland and dorsal epidermis are also affected in ribbon mutants, suggesting that conserved mechanisms may be employed to orient cell migrations in multiple tissues during development.
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Affiliation(s)
- P L Bradley
- Department of Cell Biology and Anatomy, The Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, Maryland 21205-2196, USA
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142
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Sabo SL, Ikin AF, Buxbaum JD, Greengard P. The Alzheimer amyloid precursor protein (APP) and FE65, an APP-binding protein, regulate cell movement. J Cell Biol 2001; 153:1403-14. [PMID: 11425871 PMCID: PMC2150733 DOI: 10.1083/jcb.153.7.1403] [Citation(s) in RCA: 172] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
FE65 binds to the Alzheimer amyloid precursor protein (APP), but the function of this interaction has not been identified. Here, we report that APP and FE65 are involved in regulation of cell movement. APP and FE65 colocalize with actin and Mena, an Abl-associated signaling protein thought to regulate actin dynamics, in lamellipodia. APP and FE65 specifically concentrate with beta 1-integrin in dynamic adhesion sites known as focal complexes, but not in more static adhesion sites known as focal adhesions. Overexpression of APP accelerates cell migration in an MDCK cell wound--healing assay. Coexpression of APP and FE65 dramatically enhances the effect of APP on cell movement, probably by regulating the amount of APP at the cell surface. These data are consistent with a role for FE65 and APP, possibly in a Mena-containing macromolecular complex, in regulation of actin-based motility.
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Affiliation(s)
- S L Sabo
- Laboratory of Molecular and Cellular Neuroscience and the Zachary and Elizabeth M. Fisher Center, The Rockefeller University, New York, New York 10021, USA.
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143
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Zambrano N, Bruni P, Minopoli G, Mosca R, Molino D, Russo C, Schettini G, Sudol M, Russo T. The beta-amyloid precursor protein APP is tyrosine-phosphorylated in cells expressing a constitutively active form of the Abl protoncogene. J Biol Chem 2001; 276:19787-92. [PMID: 11279131 DOI: 10.1074/jbc.m100792200] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cytosolic domain of the beta-amyloid precursor protein APP interacts with three PTB (phosphotyrosine binding domain)-containing adaptor proteins, Fe65, X11, and mDab1. Through these adaptors, other molecules can be recruited at the cytodomain of APP; one of them is Mena, that binds to the WW domain (a protein module with two conserved tryptophans) of Fe65. The enabled and disabled genes of Drosophila, homologues of the mammalian Mena and mDab1 genes, respectively, are genetic modulators of the phenotype observed in flies null for the Abl tyrosine kinase gene. The involvement of Mena and mDab1 in the APP-centered protein-protein interaction network suggests the possibility that Abl plays a role in APP biology. We show that Fe65, through its WW domain, binds in vitro and in vivo the active form of Abl. Furthermore, in cells expressing the active form of Abl, APP is tyrosine-phosphorylated. Phosphopeptide analysis and site-directed mutagenesis support the hypothesis that Tyr(682) of APP(695) is the target of this phosphorylation. Co-immunoprecipitation experiments demonstrate that active Abl and tyrosine-phosphorylated APP also form a stable complex, which could result from the interaction of the pYENP motif of the APP cytodomain with the SH2 domain of Abl. These results suggest that Abl, Mena, and mDab1 are involved in a common molecular machinery and that APP can play a role in tyrosine kinase-mediated signaling.
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Affiliation(s)
- N Zambrano
- Dipartimento di Biochimica e Biotecnologie Mediche, Università di Napoli Federico II, I-80131 Napoli, Italy
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144
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Yamabhai M, Kay BK. Mapping protein-protein interactions with alkaline phosphatase fusion proteins. Methods Enzymol 2001; 332:88-102. [PMID: 11305120 DOI: 10.1016/s0076-6879(01)32194-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- M Yamabhai
- School of Biotechnology, Suranaree University of Technology, Institute of Agricultural Technology, Nakhon Ratchasima 30000, Thailand
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145
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Zhao WM, Jiang C, Kroll TT, Huber PW. A proline-rich protein binds to the localization element of Xenopus Vg1 mRNA and to ligands involved in actin polymerization. EMBO J 2001; 20:2315-25. [PMID: 11331596 PMCID: PMC125447 DOI: 10.1093/emboj/20.9.2315] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A 340 nucleotide element within the 3' untranslated region of Vg1 mRNA determines its localization to the vegetal cortex of Xenopus oocytes. To identify protein factors that bind to this region, we screened a cDNA expression library with an RNA probe containing this sequence. Five independent isolates encoded a protein (designated Prrp for proline-rich RNA binding protein) having two RNP domains followed by multiple polyproline segments. Prrp and Vg1 mRNAs are co-localized to the vegetal cortex of stage IV oocytes, substantiating an interaction between the two in vivo. Prrp also associates with VegT mRNA, which like Vg1 mRNA uses the late localization pathway, but not with Xcat-2 or Xwnt-11 mRNAs, which use the early pathway. The proline-rich domain of Prrp interacts with profilin, a protein that promotes actin polymerization. Prrp can also associate with the EVH1 domain of Mena, another microfilament-associated protein. Since the anchoring of Vg1 mRNA to the vegetal cortex is actin dependent, one function of Prrp may be to facilitate local actin polymerization, representing a novel function for an RNA binding protein.
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Affiliation(s)
| | | | | | - Paul W. Huber
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
Corresponding author e-mail:
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146
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Abstract
Recent technical advances have made possible the visualization and genetic manipulation of individual dendritic trees. These studies have led to the identification and characterization of molecules that are important for different aspects of dendritic development. Although much remains to be learned, the existing knowledge has allowed us to take initial steps toward a comprehensive understanding of how complex dendritic trees are built. In this review, we describe recent advances in our understanding of the molecular mechanisms underlying dendritic morphogenesis, and discuss their cell-biological implications.
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Affiliation(s)
- E K Scott
- Department of Biological Sciences, Stanford University, Stanford, California 94305, USA
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147
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Gibbs SM. Regulation of Drosophila Visual System Development by Nitric Oxide and Cyclic GMP1. ACTA ACUST UNITED AC 2001. [DOI: 10.1668/0003-1569(2001)041[0268:rodvsd]2.0.co;2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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148
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Kim YS, Furman S, Sink H, VanBerkum MF. Calmodulin and profilin coregulate axon outgrowth in Drosophila. JOURNAL OF NEUROBIOLOGY 2001; 47:26-38. [PMID: 11257611 DOI: 10.1002/neu.1013] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Coordinated regulation of actin cytoskeletal dynamics is critical to growth cone movement. The intracellular molecules calmodulin and profilin actively regulate actin-based motility and participate in the signaling pathways used to steer growth cones. Here we show that in the developing Drosophila embryo, calmodulin and profilin convey complimentary information that is necessary for appropriate growth cone advance. Reducing calmodulin activity by expression of a dominant inhibitor (KA) stalls axon extension of pioneer neurons within the CNS, while a partial loss of profilin function decreases extension of motor axons in the periphery. Yet, surprisingly, when calmodulin and profilin are simultaneously reduced, the ability of both CNS pioneer axons and motor axons to extend beyond the choice points is restored. In the CNS, at the time when growth cones must decide whether to cross or not to cross the midline, a reduction in calmodulin and/or roundabout signaling causes axons to cross the midline inappropriately. These inappropriate crossings are suppressed when profilin activity is simultaneously reduced. Interestingly, the mutual suppression of calmodulin and profilin activity requires a minimal level of profilin. In KA combinations with profilin null alleles, defects in axon extension and midline guidance are synergistically enhanced rather than suppressed. Together, our data indicate that the growth cone must coordinate the activity of both calmodulin and profilin in order to advance past selected choice points, including those dictating midline crossovers.
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Affiliation(s)
- Y S Kim
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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149
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Abstract
The WW domain is a protein module found in a wide range of signaling proteins. It is one of the smallest protein modules that folds as a monomer without disulfide bridges or cofactors. WW domains bind proteins containing short linear peptide motifs that are proline-rich or contain at least one proline. Although the WW domain was initially considered a 'cytoplasmic module', the proteins containing WW domains have also been localized in the cell nucleus. Moreover, these proteins have been documented to participate in co-activation of transcription and modulation of RNA polymerase II activity. The carboxy-terminal domain (CTD) of RNA polymerase II acts as an assembly platform for distinct WW domain-containing proteins that affect the function of the RNA polymerase II. The formation of complexes between CTD and WW domain-containing proteins is regulated by phosphorylation of the CTD. Since the CTD sequence is highly repetitive and a target of several post-translational modifications and conformational changes, it presents a unique structure capable of enormous molecular diversity. The WW domain has been implicated in several human diseases including Alzheimer's disease. The WW domain-containing iso-prolyl isomerase named Pin1, a protein known to be essential for cell cycle progression, was shown to be active in restoration of the microtubule-binding activity of Tau, a protein of neurofibrillar tangles found in the brains of Alzheimer's patients. It is the WW domain of Pin1 that interacts directly with Tau protein. In addition, the WW domain-containing adapter protein FE65 was shown to regulate processing of Alzheimer's amyloid precursor protein. It is expected that by understanding the details of the WW domain-mediated protein-protein interactions, we will be able to illuminate numerous signaling pathways which control certain aspects of transcription and cell cycle.
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Affiliation(s)
- M Sudol
- Department of Medicine, Mount Sinai Medical Center, New York, NY 10029, USA.
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150
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Lee DF, Chen CC, Hsu TA, Juang JL. A baculovirus superinfection system: efficient vehicle for gene transfer into Drosophila S2 cells. J Virol 2000; 74:11873-80. [PMID: 11090187 PMCID: PMC112470 DOI: 10.1128/jvi.74.24.11873-11880.2000] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2000] [Accepted: 09/18/2000] [Indexed: 11/20/2022] Open
Abstract
The baculovirus expression vector system is considered to be a safe, powerful, but cell-lytic heterologous protein expression system in insect cells. We show here that there is a new baculovirus system for efficient gene transfer and expression using the popular and genetically well-understood Drosophila S2 cells. The recombinant baculovirus was constructed to carry an enhanced green fluorescent protein under the control of polyhedrin promoter as a fluorescent selection marker in the Sf21 cell line. Recombinant baculoviruses were then used to transduce S2 cells with target gene expression cassettes containing a Drosophila heat shock protein 70, an actin 5C, or a metallothionein promoter. Nearly 100% of the S2 cells showed evidence of gene expression after infection. The time course for the optimal protein expression peaked at 24 to 36 h postinfection, which is significantly earlier than a polyhedrin-driven protein expression in Sf21 cells. Importantly, S2 cells did not appear to be lysed after infection, and the protein expression levels are comparable to those of proteins under the control of polyhedrin promoter in several lepidopteran cell lines. Most surprisingly, S2 cells permit repetitive infections of multiple baculoviruses over time. These findings clearly suggest that this baculovirus-S2 system may effect the efficient gene transfer and expression system of the well-characterized Drosophila S2 cells.
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Affiliation(s)
- D F Lee
- Division of Molecular and Genomic Medicine, National Health Research Institutes, Taipei 11529, Taiwan
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