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52
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Prieto AL, Weber JL, Lai C. Expression of the receptor protein-tyrosine kinases Tyro-3, Axl, and Mer in the developing rat central nervous system. J Comp Neurol 2000. [DOI: 10.1002/1096-9861(20000918)425:2<295::aid-cne11>3.0.co;2-g] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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53
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54
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Ruan W, Pang P, Rao Y. The SH2/SH3 adaptor protein dock interacts with the Ste20-like kinase misshapen in controlling growth cone motility. Neuron 1999; 24:595-605. [PMID: 10595512 DOI: 10.1016/s0896-6273(00)81115-0] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent studies suggest that the SH2/SH3 adaptor Dock/Nck transduces tyrosine phosphorylation signals to the actin cytoskeleton in regulating growth cone motility. The signaling cascade linking the action of Dock/Nck to the reorganization of cytoskeleton is poorly understood. We now demonstrate that Dock interacts with the Ste20-like kinase Misshapen (Msn) in the Drosophila photoreceptor (R cell) growth cones. Loss of msn causes a failure of growth cones to stop at the target, a phenotype similar to loss of dock, whereas overexpression of msn induces pretarget growth cone termination. Physical and genetic interactions between Msn and Dock indicate a role for Msn in the Dock signaling pathway. We propose that Msn functions as a key controller of growth cone cytoskeleton in response to Dock-mediated signals.
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Affiliation(s)
- W Ruan
- Department of Neurology and Neurosurgery, Centre for Research in Neuroscience, McGill University and The Montreal General Hospital, Québec, Canada
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55
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Ledig MM, Haj F, Bixby JL, Stoker AW, Mueller BK. The receptor tyrosine phosphatase CRYPalpha promotes intraretinal axon growth. J Cell Biol 1999; 147:375-88. [PMID: 10525542 PMCID: PMC2174224 DOI: 10.1083/jcb.147.2.375] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/1999] [Accepted: 09/01/1999] [Indexed: 01/06/2023] Open
Abstract
Retinal ganglion cell axons grow towards the optic fissure in close contact with the basal membrane, an excellent growth substratum. One of the ligands of receptor tyrosine phosphatase CRYPalpha is located on the retinal and tectal basal membranes. To analyze the role of this RPTP and its ligand in intraretinal growth and guidance of ganglion cell axons, we disrupted ligand- receptor interactions on the retinal basal membrane in culture. Antibodies against CRYPalpha strongly reduced retinal axon growth on the basal membrane, and induced a dramatic change in morphology of retinal growth cones, reducing the size of growth cone lamellipodia. A similar effect was observed by blocking the ligand with a CRYPalpha ectodomain fusion protein. These effects did not occur, or were much reduced, when axons were grown either on laminin-1, on matrigel or on basal membranes with glial endfeet removed. This indicates that a ligand for CRYPalpha is located on glial endfeet. These results show for the first time in vertebrates that the interaction of a receptor tyrosine phosphatase with its ligand is crucial not only for promotion of retinal axon growth but also for maintenance of retinal growth cone lamellipodia on basal membranes.
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Affiliation(s)
- Matthias M. Ledig
- Max-Planck-Institut für Entwicklungsbiologie, Physikalische Biologie, D-72076 Tübingen, Germany
| | - Fawaz Haj
- Institute of Child Health, Neural Development Unit, University College London, London WC1N 1EH, United Kingdom
| | - John L. Bixby
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami School of Medicine, Miami, Florida 33101
| | - Andrew W. Stoker
- Institute of Child Health, Neural Development Unit, University College London, London WC1N 1EH, United Kingdom
| | - Bernhard K. Mueller
- Max-Planck-Institut für Entwicklungsbiologie, Physikalische Biologie, D-72076 Tübingen, Germany
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56
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Haj F, McKinnell I, Stoker A. Retinotectal ligands for the receptor tyrosine phosphatase CRYPalpha. Mol Cell Neurosci 1999; 14:225-40. [PMID: 10493824 DOI: 10.1006/mcne.1999.0785] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The cell adhesion molecule-like tyrosine phosphatase CRYPalpha is localized on retinal axons and their growth cones. We present evidence that two isoforms of this type IIa phosphatase, CRYPalpha1 and CRYPalpha2, have extracellular ligands along the developing retinotectal pathway. Using alkaline phosphatase fusion proteins containing the CRYPalpha1 ectodomain, we detect a prominent ligand on basement membranes of the early retina, optic stalk, and chiasm. A second ligand is observed in the endfeet region of radial processes in the developing stratum opticum, the site of initial retinal axon invasion. This latter ligand binds CRYPalpha2 preferentially. Further ligand interactions are detected for both CRYPalpha protein isoforms in retinorecipient tectal laminae and on retinal fibers themselves. CRYPalpha thus has cell- and matrix-associated ligands along the entire retinotectal projection. Moreover, these ligands appear to be heterotypic and interact with CRYPalpha through both its immunoglobulin and fibronectin type III regions. The anteroposterior levels of the ligands are relatively uniform within the retina and tectum, suggesting that the CRYPalpha protein within retinal axons does not directly recognise topographically graded guidance cues. We propose that CRYPalpha may have a permissive role in promoting retinal axon growth across the eye and tectum and that its functions are modulated temporally and spatially by isoform-specific interactions with cell- and matrix-associated ligands.
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Affiliation(s)
- F Haj
- Institute of Child Health, University College London, 30 Guilford Street, London, WC1N 1EH, United Kingdom
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57
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Yu SP, Yeh CH, Gottron F, Wang X, Grabb MC, Choi DW. Role of the outward delayed rectifier K+ current in ceramide-induced caspase activation and apoptosis in cultured cortical neurons. J Neurochem 1999; 73:933-41. [PMID: 10461882 DOI: 10.1046/j.1471-4159.1999.0730933.x] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We studied the novel hypothesis that an up-modulation of channels for outward delayed rectifier K+ current (I(K)) plays a key role in ceramide-induced neuronal apoptosis. Exposure for 6-10 h to the membrane-permeable C2-ceramide (25 microM) or to sphingomyelinase (0.2 unit/ml), but not to the inactive ceramide analogue C2-dihydroceramide (25 microM), enhanced the whole-cell I(K) current without affecting the transient A-type K+ current and increased caspase activity, followed by neuronal apoptosis 24 h after exposure onset. Tetraethylammonium (TEA) or 4-chloro-N,N-diethyl-N-heptylbenzenebutanaminium tosylate (clofilium), at concentrations inhibiting I(K), attenuated the C2-ceramide-induced caspase-3-like activation as well as neuronal apoptosis. Raising extracellular K+ to 25 mM similarly blocked the C2-ceramide-induced cell death; the neuroprotection by 25 mM K+ or TEA was not eliminated by blocking voltage-gated Ca2+ channels. An inhibitor of tyrosine kinases, herbimycin A (10 nM) or lavendustin A (0.1-1 microM), suppressed I(K) enhancement and/or apoptosis induced by C2-ceramide. It is suggested that ceramide-induced I(K) current enhancement is mediated by tyrosine phosphorylation and plays a critical role in neuronal apoptosis.
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Affiliation(s)
- S P Yu
- Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St. Louis, Missouri, USA
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58
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Abstract
One of the most important mechanisms of eukaryotic signalling is protein phosphorylation on tyrosine residues, which plays a pivotal role in development by regulating cell proliferation, differentiation and migration. Cellular phosphotyrosine (P.Tyr) levels are regulated by the antagonistic activities of the protein-tyrosine kinases (PTKs) and protein-tyrosine phosphatases (PTPs). We have good insight into the function of PTKs at the molecular level and into the role of PTK-mediated signalling in development. Intuitively, PTPs and PTKs are equally important in development. Over the past decade, much emphasis has been placed on elucidation of the function of PTPs, which has led to good insights into the mechanism of PTP-mediated dephosphorylation. Although still relatively little is known about the role of PTPs in cell signalling and development, evidence is now emerging that several PTPs are crucial for proper development. Here I will introduce PTP-mediated signalling and discuss recent findings regarding the function of PTPs in development.
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Affiliation(s)
- J den Hertog
- Hubrecht Laboratory, Netherlands Institute for Developmental Biology, Uppsalalaan 8, 3584 CT, Utrecht, The Netherlands.
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59
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A single growth cone is capable of integrating simultaneously presented and functionally distinct molecular cues during target recognition. J Neurosci 1999. [PMID: 10366624 DOI: 10.1523/jneurosci.19-12-04899.1999] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A variety of cell recognition pathways affect neuronal target recognition. However, whether such pathways can converge at the level of a single growth cone is not well known. The RP3 motoneuron in Drosophila has previously been shown to respond to the muscle cell surface molecules TOLL and fasciclin III (FAS3), which are normally encountered during RP3 pathfinding in a sequential manner. TOLL and FAS3, putative "negative" and "positive" recognition molecules, respectively, affect RP3 antagonistically. Under normal conditions, TOLL and FAS3 together improve the accuracy of its target recognition. Here, we show that, when presented with concurrent TOLL and FAS3 expression, RP3 responds to both, integrating their effects. This was demonstrated most succinctly by single cell visualization methods. When a balance in relative expression levels between the two antagonistic cues is achieved, the RP3 growth cone exhibits a phenotype virtually identical to that seen when neither TOLL nor FAS3 is misexpressed. Thus, growth cones are capable of quantitatively evaluating distinct recognition cues and integrating them to attain a net result, in effect responding to the "balance of power" between positive and negative influences. We suggest that the ability to integrate multiple recognition pathways in real-time is one important way in which an individual growth cone interprets and navigates complex molecular environments.
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60
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Wills Z, Bateman J, Korey CA, Comer A, Van Vactor D. The tyrosine kinase Abl and its substrate enabled collaborate with the receptor phosphatase Dlar to control motor axon guidance. Neuron 1999; 22:301-12. [PMID: 10069336 DOI: 10.1016/s0896-6273(00)81091-0] [Citation(s) in RCA: 256] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Genetic analysis of growth cone guidance choice points in Drosophila identified neuronal receptor protein tyrosine phosphatases (RPTPs) as key determinants of axon pathfinding behavior. We now demonstrate that the Drosophila Abl tyrosine kinase functions in the intersegmental nerve b (ISNb) motor choice point pathway as an antagonist of the RPTP Dlar. The function of Abl in this pathway is dependent on an intact catalytic domain. We also show that the Abl phosphoprotein substrate Enabled (Ena) is required for choice point navigation. Both Abl and Ena proteins associate with the Dlar cytoplasmic domain and serve as substrates for Dlar in vitro, suggesting that they play a direct role in the Dlar pathway. These data suggest that Dlar, Abl, and Ena define a phosphorylation state-dependent switch that controls growth cone behavior by transmitting signals at the cell surface to the actin cytoskeleton.
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Affiliation(s)
- Z Wills
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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61
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Honkaniemi J, Zhang JS, Yang T, Zhang C, Tisi MA, Longo FM. LAR tyrosine phosphatase receptor: proximal membrane alternative splicing is coordinated with regional expression and intraneuronal localization. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 1998; 60:1-12. [PMID: 9748473 DOI: 10.1016/s0169-328x(98)00151-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Examination of null-mutant Drosophila and Leukocyte Common Antigen-Related (LAR)-deficient transgenic mice has demonstrated that the LAR protein tyrosine phosphatase (PTP) receptor promotes neurite outgrowth. In the absence of known ligands, the mechanisms by which LAR-type PTP receptors are regulated are unknown. We hypothesized that an alternatively spliced eleven amino acid proximal membrane segment of LAR (LAR alternatively spliced element-a; LASE-a) contributes to regulation of LAR function. Human, rat and mouse LAR cDNA sequences demonstrated that the predicted eleven amino acid inserts in rat and mouse are identical and share nine of eleven residues with the human insert. LASE-a splicing led to the introduction of a Ser residue into LAR at a position analogous to Ser residues undergoing regulated phosphorylation in other PTPs. In-situ studies revealed increasingly region-specific expression of LASE-a containing LAR transcripts during postnatal development. RT-PCR analysis of cortical and hippocampal tissue confirmed that the proportion of LAR transcripts containing LASE-a decreases during development. Immunostaining of cultured PC12 cells, cerebellar granule neurons, dorsal root ganglia and sciatic nerve sections with antibody directed against the LASE-a insert demonstrated signal in cell bodies but little if any along neurites. In contrast, staining with antibody directed to a separate domain of LAR showed accumulation of LAR along neurites. The findings that LASE-a splicing is conserved across human, rat and mouse, that the LASE-a insert introduces a Ser at a site likely to be targeted for regulated phosphorylation and that developmentally regulated splicing is coordinated with specific regional and intraneuronal localization point to important novel potential mechanisms regulating LAR-type tyrosine phosphatase receptor function in the nervous system.
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MESH Headings
- Alternative Splicing/physiology
- Amino Acid Sequence
- Animals
- Antibodies
- Cerebellum/chemistry
- Cerebellum/cytology
- Cerebellum/enzymology
- Cerebral Cortex/chemistry
- Cerebral Cortex/cytology
- Cerebral Cortex/enzymology
- Child, Preschool
- Cloning, Molecular
- DNA, Complementary
- Female
- Ganglia, Spinal/chemistry
- Ganglia, Spinal/cytology
- Ganglia, Spinal/enzymology
- Gene Expression
- Gene Library
- Hippocampus/chemistry
- Humans
- Mice
- Molecular Sequence Data
- Nerve Tissue Proteins
- Neurons/chemistry
- Neurons/enzymology
- Neurons/physiology
- PC12 Cells
- Protein Tyrosine Phosphatases
- RNA, Messenger/analysis
- Rats
- Rats, Sprague-Dawley
- Receptor-Like Protein Tyrosine Phosphatases, Class 2
- Receptors, Cell Surface/analysis
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/immunology
- Reverse Transcriptase Polymerase Chain Reaction
- Sciatic Nerve/chemistry
- Sciatic Nerve/cytology
- Sciatic Nerve/enzymology
- Spinal Cord/chemistry
- Spinal Cord/cytology
- Spinal Cord/enzymology
- Transcription, Genetic/physiology
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Affiliation(s)
- J Honkaniemi
- Neurology Service, VA Medical Center, San Francisco, CA 94121, USA
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62
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Abstract
Numerous in vitro assays and in vivo perturbation studies have led to a model of neural development in which selective fasciculation helps to define accurate axonal projections. Genetic analysis in vivo confirms the hypothesis that axonal fasciculation and defasciculation are controlled by adhesion mechanisms, but also suggests that, in many cases, adhesion and guidance are separable phenomena. In addition, receptors that control the level of tyrosine phosphorylation may play an important role in fasciculation, suggesting that complex intracellular pathways lie just beneath the surface.
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Affiliation(s)
- D Van Vactor
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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63
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Abstract
Genetic analysis has enhanced our understanding of the biological roles of many protein tyrosine kinases (PTKs). More recently, studies utilizing both spontaneous mutants and mutants induced by homologous recombination techniques have begun to yield key insights into the role of specific protein tyrosine phosphatases (PTPs) and to suggest how PTKs and PTPs interact. Specific PTPs in Saccharomyces cerevesiae and Schizomyces pombe regulate MAP kinase pathways. Several Drosophila receptor PTPs control axonal targeting pathways, whereas the non-receptor PTP Corkscrew (Csw), plays an essential positive signaling role in multiple developmental pathways directed by receptor PTKs. The vertebrate homolog of Csw, SHP-2, also is required for growth factor signaling and normal development. Finally, very recent studies of other mammalian PTPs suggest that they have critical roles in processes as diverse as hematopoiesis and liver and pituitary development.
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Affiliation(s)
- D Van Vactor
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
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