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Moran CM, Donnelly M, Ortiz D, Pant HC, Mandelkow EM, Shea TB. Cdk5 inhibits anterograde axonal transport of neurofilaments but not that of tau by inhibition of mitogen-activated protein kinase activity. ACTA ACUST UNITED AC 2005; 134:338-44. [PMID: 15836929 DOI: 10.1016/j.molbrainres.2004.10.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2004] [Revised: 10/29/2004] [Accepted: 10/29/2004] [Indexed: 11/19/2022]
Abstract
Cyclin-dependent kinase 5 (cdk5) inhibits neurofilament (NF) anterograde axonal transport while p42/44 mitogen-activated protein kinase (MAPk) promotes it. Since cdk5 is known to inhibit MAP kinase activity, we examined whether or not cdk5 inhibits anterograde NF transport via inhibition of MAPk activity. To accomplish this, we manipulated the activity of these kinases in differentiated NB2a/d1 cells, and monitored anterograde axonal transport of green fluorescent protein-conjugated-NF-M (GFP-M) and cyan fluorescent protein-conjugated (CFP)-tau. The cdk5 inhibitor roscovitine increased anterograde axonal transport of GFP-M and CFP-tau; transfection with cdk5/p25 inhibited transport of both. Inhibition of MAPk activity by PD98059 or expression of dominant-negative MAPk inhibited anterograde GFP-M transport, while expression of constitutively active MAPk enhanced it; these treatments did not affect CFP-tau transport. PD98059 prevented roscovitine-mediated enhancement of GFP-M transport, but did not prevent enhancement of CFP-tau transport. Co-transfection with constitutively activated MAPk prevented the inhibition of GFP-M transport that normally accompanied transfection with cdk5/p25, but did not prevent inhibition of tau transport by cdk5/p25. Finally, the extent of inhibition of GFP-M axonal transport by PD98059 was not additive to that derived from transfection with cdk5/p35, and the increase in NF transport that accompanies roscovitine treatment was not additive to that derived from transfection with constitutively activated MAPk, suggesting that the influence of these kinases on NF transport was within the same, rather than distinct, pathways. These findings suggest that axonal transport of tau and NFs is under the control of distinct kinase cascades, and that cdk5 inhibits NF transport at least in part by inhibiting MAPk.
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Affiliation(s)
- Catherine M Moran
- Center for Cell Neurobiology and Neurodegeneration Research, University of Massachusetts Lowell, Lowell, MA 01854, USA
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52
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Matas OB, Martínez-Menárguez JA, Egea G. Association of Cdc42/N-WASP/Arp2/3 Signaling Pathway with Golgi Membranes. Traffic 2004; 5:838-46. [PMID: 15479449 DOI: 10.1111/j.1600-0854.2004.00225.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Recent findings indicate that Cdc42 regulates Golgi-to-ER (endoplasmic reticulum) protein transport through N-WASP and Arp2/3 (Luna et al. 2002, Mol. Biol. Cell, 13:866-879). To analyse the components of the Cdc42-governed signaling pathway in the secretory pathway, we localized Cdc42, N-WASP and Arp2/3 in the Golgi complex by cryoimmunoelectron microscopy. Cdc42 is found throughout the Golgi stack, particularly in cis/middle cisternae, whereas N-WASP and Arp3 (a component of the Arp2/3 complex) are restricted to cis cisternae. Arp3 also colocalized in peri-Golgi tubulovesicular structures with either KDEL receptor or GM130. Even though Arp3 is not found in TGN46-positive cisternal elements, a small fraction of Arp3-labeled tubulo-vesicular elements showed TGN46 labeling. Active Cdc42 (GTP-bound form) induced relocation of N-WASP and Arp3 to the lateral rims of Golgi cisternae. These results show that the actin nucleation and polymerization signaling pathway governed by Cdc42/N-WASP/Arp operates in the Golgi complex of mammalian cells, further implicating actin dynamics in Golgi-associated membrane trafficking.
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Affiliation(s)
- Olga B Matas
- Departament de Biologia Cellular i Anatomia Patològica, Facultat de Medicina, Universitat de Barcelona-IDIBAPS, 08036 Barcelona, Spain
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53
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Kerokoski P, Suuronen T, Salminen A, Soininen H, Pirttilä T. Both N-methyl-d-aspartate (NMDA) and non-NMDA receptors mediate glutamate-induced cleavage of the cyclin-dependent kinase 5 (cdk5) activator p35 in cultured rat hippocampal neurons. Neurosci Lett 2004; 368:181-5. [PMID: 15351445 DOI: 10.1016/j.neulet.2004.07.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2004] [Revised: 07/02/2004] [Accepted: 07/05/2004] [Indexed: 11/17/2022]
Abstract
Cyclin-dependent kinase 5 (cdk5) regulates crucial neurobiological events, and deregulation of cdk5 has been implicated in several neurodegenerative disorders. The deregulation is suggested to occur due to cleavage of the cdk5 activator protein p35 to a smaller p25 fragment by the calcium-activated protease calpain. Here we have elucidated the role of different calcium-permeable ionotropic glutamate receptors in the induction of p35 cleavage in cultured rat hippocampal neurons. The glutamate receptor agonists glutamic acid, N-methyl-D-aspartate (NMDA), kainic acid, and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) were all able to induce p35 cleavage, in a manner depending on extracellular calcium. The effect of glutamate was mediated by NMDA receptors, as it was prevented by the NMDA antagonist MK-801. Cyclothiazide (CTZ), an inhibitor of AMPA receptor desensitization, enhanced glutamate-induced p35 cleavage. In immature 6-day-old cultures the non-NMDA agonist kainic acid provoked p35 cleavage, whereas glutamate and NMDA were ineffective. The data suggest that both NMDA and non-NMDA receptors are able to induce p35 cleavage. Different factors, such as maturation state of neurons or desensitization properties of non-NMDA receptors, may determine which receptor predominantly mediates the effect of glutamate on p35 cleavage.
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Affiliation(s)
- Petri Kerokoski
- Department of Neuroscience and Neurology, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland.
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54
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Chan WKH, Dickerson A, Ortiz D, Pimenta AF, Moran CM, Motil J, Snyder SJ, Malik K, Pant HC, Shea TB. Mitogen-activated protein kinase regulates neurofilament axonal transport. J Cell Sci 2004; 117:4629-42. [PMID: 15331628 DOI: 10.1242/jcs.01135] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Mitogen-activated protein kinase (MAP) kinase plays a pivotal role in the development of the nervous system by mediating both neurogenesis and neuronal differentiation. Here we examined whether p42/44 MAP kinase plays a role in axonal transport and the organization of neurofilaments (NFs) in axonal neurites. Dominant-negative p42/44 MAP kinase, anti-MAP kinase antisense oligonucleotides and the MAP kinase inhibitor PD98059 all reduced NF phospho-epitopes and inhibited anterograde NF axonal transport of GFP-tagged NF subunits in differentiated NB2a/d1 neuroblastoma cells. Expression of constitutively active MAP kinase and intracellular delivery of active enzyme increased NF phospho-epitopes and increased NF axonal transport. Longer treatment with PD98059 shifted NF transport from anterograde to retrograde. PD98059 did not inhibit overall axonal transport nor compromise overall axonal architecture or composition. The p38 MAP kinase inhibitor SB202190 did not inhibit NF transport whereas the kinase inhibitor olomoucine inhibited both NF and mitochondrial transport. Axonal transport of NFs containing NF-H whose C-terminal region was mutated to mimic extensive phosphorylation was substantially less affected by PD98059 compared to a wild-type construct. These data suggest that p42/44 MAP kinase regulates NF anterograde transport by NF C-terminal phosphorylation. MAP kinase may therefore stabilize developing axons by promoting the accumulation of NFs within growing axonal neurites.
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Affiliation(s)
- Walter Kong-Ho Chan
- Center Cell Neurobiology and Neurodegeneration Research, University of Massachusetts, Lowell, MA 01854, USA
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55
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Morfini G, Szebenyi G, Brown H, Pant HC, Pigino G, DeBoer S, Beffert U, Brady ST. A novel CDK5-dependent pathway for regulating GSK3 activity and kinesin-driven motility in neurons. EMBO J 2004; 23:2235-45. [PMID: 15152189 PMCID: PMC419914 DOI: 10.1038/sj.emboj.7600237] [Citation(s) in RCA: 221] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2003] [Accepted: 04/20/2004] [Indexed: 11/09/2022] Open
Abstract
Neuronal transmission of information requires polarized distribution of membrane proteins within axonal compartments. Membrane proteins are synthesized and packaged in membrane-bounded organelles (MBOs) in neuronal cell bodies and later transported to axons by microtubule-dependent motor proteins. Molecular mechanisms underlying targeted delivery of MBOs to discrete axonal subdomains (i.e. nodes of Ranvier or presynaptic terminals) are poorly understood, but regulatory pathways for microtubule motors may be an essential step. In this work, pharmacological, biochemical and in vivo experiments define a novel regulatory pathway for kinesin-driven motility in axons. This pathway involves enzymatic activities of cyclin-dependent kinase 5 (CDK5), protein phosphatase 1 (PP1) and glycogen synthase kinase-3 (GSK3). Inhibition of CDK5 activity in axons leads to activation of GSK3 by PP1, phosphorylation of kinesin light chains by GSK3 and detachment of kinesin from transported cargoes. We propose that regulating the activity and localization of components in this pathway allows nerve cells to target organelle delivery to specific subcellular compartments. Implications of these findings for pathogenesis of neurodegenerative diseases such as Alzheimer's disease are discussed.
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Affiliation(s)
- Gerardo Morfini
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, USA
- Marine Biological Laboratory, Woods Hole, MA, USA
| | - Györgyi Szebenyi
- Department of Cell Biology and Center for Basic Neuroscience, UT Southwestern, Dallas, TX, USA
| | - Hannah Brown
- Marine Biological Laboratory, Woods Hole, MA, USA
| | - Harish C Pant
- Marine Biological Laboratory, Woods Hole, MA, USA
- Laboratory of Neurochemistry, NINDS, Bethesda, MD, USA
| | - Gustavo Pigino
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, USA
| | - Scott DeBoer
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, USA
| | - Uwe Beffert
- Department of Molecular Genetics, UT Southwestern, Dallas, TX, USA
| | - Scott T Brady
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, IL, USA
- Marine Biological Laboratory, Woods Hole, MA, USA
- Anatomy and Cell Biology M/C 512, 808 S Wood St, University of Illinois at Chicago, Chicago, IL 60612, USA. Tel.: +1 312 996 6791; Fax: +1 312 413 0354; E-mail:
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56
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Rosso S, Bollati F, Bisbal M, Peretti D, Sumi T, Nakamura T, Quiroga S, Ferreira A, Cáceres A. LIMK1 regulates Golgi dynamics, traffic of Golgi-derived vesicles, and process extension in primary cultured neurons. Mol Biol Cell 2004; 15:3433-49. [PMID: 15090620 PMCID: PMC452595 DOI: 10.1091/mbc.e03-05-0328] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In this study, we examined the subcellular distribution and functions of LIMK1 in developing neurons. Confocal microscopy, subcellular fractionation, and expression of several epitope-tagged LIMK1 constructs revealed that LIMK1 is enriched in the Golgi apparatus and growth cones, with the LIM domain required for Golgi localization and the PDZ domain for its presence at neuritic tips. Overexpression of wild-type LIMK1 suppresses the formation of trans-Golgi derived tubules, and prevents cytochalasin D-induced Golgi fragmentation, whereas that of a kinase-defective mutant has the opposite effect. Transfection of wild-type LIMK1 accelerates axon formation and enhances the accumulation of Par3/Par6, insulin-like growth factor (IGF)1 receptors, and neural cell adhesion molecule (NCAM) at growth cones, while inhibiting the Golgi export of synaptophysin-containing vesicles. These effects were dependent on the Golgi localization of LIMK1, paralleled by an increase in cofilin phosphorylation and phalloidin staining in the region of the Golgi apparatus, and prevented by coexpression of constitutive active cofilin. The long-term overexpression of LIMK1 produces growth cone collapse and axon retraction, an effect that is dependent on its growth cone localization. Together, our results suggest an important role for LIMK1 in axon formation that is related with its ability to regulate Golgi dynamics, membrane traffic, and actin cytoskeletal organization.
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Affiliation(s)
- Silvana Rosso
- Instituto Investigacion Medica Mercedes y Martin Ferreya-CONICET-Consejo Nacional de Investigaciones Científicas y Técnicas, 5000 Cordoba, Argentina
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57
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Abstract
Cyclin-dependent kinase-5 (CDK5) is predominantly active in the nervous system and it is well established that CDK5 is essential in neuronal development. In addition to its recognized role in development, there is increasing evidence that CDK5 may be involved in the pathogenesis of several neurodegenerative disorders. Although studies have shown that CDK5 can modulate cell death and survival, controversy still exists as to the exact role CDK5 may play in neurodegenerative processes. This review will highlight recent data on the possible roles of CDK5 in neurodegeneration.
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Affiliation(s)
- Shirley B Shelton
- Department of Psychiatry, University of Alabama at Birmingham, Birmingham, Alabama, USA
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58
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Shea TB, Yabe JT, Ortiz D, Pimenta A, Loomis P, Goldman RD, Amin N, Pant HC. Cdk5 regulates axonal transport and phosphorylation of neurofilaments in cultured neurons. J Cell Sci 2004; 117:933-41. [PMID: 14762105 DOI: 10.1242/jcs.00785] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phosphorylation has long been considered to regulate neurofilament (NF) interaction and axonal transport, and, in turn, to influence axonal stability and their maturation to large-caliber axons. Cdk5, a serine/threonine kinase homologous to the mitotic cyclin-dependent kinases, phosphorylates NF subunits in intact cells. In this study, we used two different haptenized NF subunits and manipulated cdk5 activity by microinjection, transfection and pharmacological inhibition to monitor the effect of Cdk5-p35 on NF dynamics and transport. We demonstrate that overexpression of cdk5 increases NF phosphorylation and inhibits NF axonal transport, whereas inhibition both reduces NF phosphorylation and enhances NF axonal transport in cultured chicken dorsal-root-ganglion neurons. Large phosphorylated-NF `bundles' were prominent in perikarya following cdk5 overexpression. These findings suggest that Cdk5-p35 activity regulates normal NF distribution and that overexpression of Cdk5-p35 induces perikaryal accumulation of phosphorylated-NFs similar to those observed under pathological conditions.
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Affiliation(s)
- Thomas B Shea
- Center for Cellular Neurobiology and Neurodegeneration Research, Department of Biological Sciences, University of Massachusetts, Lowell, One University Avenue, Lowell, MA 01854, USA.
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59
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Smith PD, Crocker SJ, Jackson-Lewis V, Jordan-Sciutto KL, Hayley S, Mount MP, O'Hare MJ, Callaghan S, Slack RS, Przedborski S, Anisman H, Park DS. Cyclin-dependent kinase 5 is a mediator of dopaminergic neuron loss in a mouse model of Parkinson's disease. Proc Natl Acad Sci U S A 2003; 100:13650-5. [PMID: 14595022 PMCID: PMC263868 DOI: 10.1073/pnas.2232515100] [Citation(s) in RCA: 244] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recent evidence indicates that cyclin-dependent kinases (CDKs, cdks) may be inappropriately activated in several neurodegenerative conditions. Here, we report that cdk5 expression and activity are elevated after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a toxin that damages the nigrostriatal dopaminergic pathway. Supporting the pathogenic significance of the cdk5 alterations are the findings that the general cdk inhibitor, flavopiridol, or expression of dominant-negative cdk5, and to a lesser extent dominant-negative cdk2, attenuates the loss of dopaminergic neurons caused by MPTP. In addition, CDK inhibition strategies attenuate MPTP-induced hypolocomotion and markers of striatal function independent of striatal dopamine. We propose that cdk5 is a key regulator in the degeneration of dopaminergic neurons in Parkinson's disease.
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Affiliation(s)
- Patrice D Smith
- Neuroscience Group, Ottawa Health Research Institute, Ottawa, ON, Canada K1H 8M5
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60
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Identification of a novel, membrane-associated neuronal kinase, cyclin-dependent kinase 5/p35-regulated kinase. J Neurosci 2003. [PMID: 12832520 DOI: 10.1523/jneurosci.23-12-04975.2003] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Here we characterize a novel neuronal kinase, cyclin-dependent kinase 5 (cdk5)/p35-regulated kinase (cprk). Cprk is a member of a previously undescribed family of kinases that are predicted to contain two N-terminal membrane-spanning domains and a long C terminus, which harbors a dual-specificity serine/threonine/tyrosine kinase domain. Cprk was isolated in a yeast two-hybrid screen using the neuronal cdk5 activator p35 as "bait." Cprk interacts with p35 in the yeast-two hybrid system, binds to p35 in glutathione S-transferase fusion pull-down assays, and colocalizes with p35 in cultured neurons and transfected cells. In these cells, cprk is present with p35 in the Golgi apparatus. Cprk is expressed in a number of tissues but is enriched in brain and muscle and within the brain is found in a wide range of neuronal populations. Cprk displays catalytic activity in in vitro kinase assays and is itself phosphorylated by cdk5/p35. Cdk5/p35 inhibits cprk activity. Cdk5/p35 may therefore regulate cprk function in the brain.
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61
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Kesavapany S, Lau KF, Ackerley S, Banner SJ, Shemilt SJA, Cooper JD, Leigh PN, Shaw CE, McLoughlin DM, Miller CCJ. Identification of a novel, membrane-associated neuronal kinase, cyclin-dependent kinase 5/p35-regulated kinase. J Neurosci 2003; 23:4975-83. [PMID: 12832520 PMCID: PMC6741199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
Here we characterize a novel neuronal kinase, cyclin-dependent kinase 5 (cdk5)/p35-regulated kinase (cprk). Cprk is a member of a previously undescribed family of kinases that are predicted to contain two N-terminal membrane-spanning domains and a long C terminus, which harbors a dual-specificity serine/threonine/tyrosine kinase domain. Cprk was isolated in a yeast two-hybrid screen using the neuronal cdk5 activator p35 as "bait." Cprk interacts with p35 in the yeast-two hybrid system, binds to p35 in glutathione S-transferase fusion pull-down assays, and colocalizes with p35 in cultured neurons and transfected cells. In these cells, cprk is present with p35 in the Golgi apparatus. Cprk is expressed in a number of tissues but is enriched in brain and muscle and within the brain is found in a wide range of neuronal populations. Cprk displays catalytic activity in in vitro kinase assays and is itself phosphorylated by cdk5/p35. Cdk5/p35 inhibits cprk activity. Cdk5/p35 may therefore regulate cprk function in the brain.
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Affiliation(s)
- Sashi Kesavapany
- Departments of Neuroscience and Neurology, The Institute of Psychiatry, Kings College London, London SE5 8AF, United Kingdom
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62
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Fischer A, Sananbenesi F, Schrick C, Spiess J, Radulovic J. Regulation of contextual fear conditioning by baseline and inducible septo-hippocampal cyclin-dependent kinase 5. Neuropharmacology 2003; 44:1089-99. [PMID: 12763101 DOI: 10.1016/s0028-3908(03)00102-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this work, we confirm the novel role of cyclin-dependent kinase (Cdk) 5 in associative learning by demonstrating that injection of the Cdk5 inhibitor butyrolactone I into the lateral septum or hippocampus profoundly impaired context-dependent fear conditioning of C57BL/6J mice. However, unlike the inducible up-regulation of Cdk5 and its regulator p35 observed in Balb/c mice, high baseline levels, which were not affected by fear conditioning, were found in C57BL/6J mice. Surprisingly, microinjections of butyrolactone I into the lateral septum or hippocampus significantly decreased baseline Cdk5 activity within the entire septo-hippocampal circuitry, suggesting a functional link between septal and hippocampal Cdk5 activity. Significantly higher levels of the transcription factor Sp4 in the septo-hippocampal system of C57BL/6J mice may account for the high baseline Cdk5/p35 production. On the other hand, the stronger cFos production observed in the lateral septum of fear conditioned Balb/c mice may be responsible, at least in part, for the inducible up-regulation of Cdk5 in this strain. These results suggest that the role of Cdk5 in memory consolidation is strain independent and functionally related to the septo-hippocampal circuitry. However, the molecular regulation of baseline and inducible Cdk5 protein might be different among individual mouse strains and possibly other species.
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Affiliation(s)
- André Fischer
- Department of Molecular Neuroendocrinology, Max Planck Institute for Experimental Medicine, Hermann-Rein-Str. 3, 37075, Goettingen, Germany.
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63
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Pfenninger KH, Laurino L, Peretti D, Wang X, Rosso S, Morfini G, Cáceres A, Quiroga S. Regulation of membrane expansion at the nerve growth cone. J Cell Sci 2003; 116:1209-17. [PMID: 12615964 DOI: 10.1242/jcs.00285] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Exocytotic incorporation of plasmalemmal precursor vesicles (PPVs) into the cell surface is necessary for neurite extension and is known to occur mainly at the growth cone. This report examines whether this is a regulated event controlled by growth factors. The Golgi complex and nascent PPVs of hippocampal neurons in culture were pulse-labeled with fluorescent ceramide. We studied the dynamics of labeled PPVs upon arrival at the axonal growth cone. In controls and cultures stimulated with brain-derived neurotrophic factor (BDNF), PPV clusters persisted in growth cones with a half-life (t(1/2)) of >14 minutes. Upon challenge with IGF-1, however, fluorescent elements cleared from the growth cones with a t(1/2) of only 6 minutes. Plasmalemmal expansion was measured directly as externalization of membrane glycoconjugates in resealed growth cone particles (GCPs) isolated from fetal forebrain. These assays demonstrated that membrane expansion could be stimulated by IGF-1 in a dose-dependent manner but not by BDNF, even though intact, functional BDNF receptor was present on GCPs. Because both BDNF and IGF-1 are known to enhance neurite growth, but BDNF did not stimulate membrane expansion at the growth cone, we studied the effect of BDNF on the IGF-1 receptor. BDNF was found to cause the translocation of the growth-cone-specific IGF-1 receptor subunit beta(gc) to the distal axon, in a KIF2-dependent manner. We conclude that IGF-1 stimulates axonal assembly at the growth cone, and that this occurs via regulated exocytosis of PPVs. This mechanism is affected by BDNF only indirectly, by regulation of the beta(gc) level at the growth cone.
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Affiliation(s)
- Karl H Pfenninger
- Department of Cellular and Structural Biology, University of Colorado, School of Medicine and Cancer Center, Denver, CO 80262, USA
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64
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Nguyen MD, Mushynski WE, Julien JP. Cycling at the interface between neurodevelopment and neurodegeneration. Cell Death Differ 2002; 9:1294-306. [PMID: 12478466 DOI: 10.1038/sj.cdd.4401108] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2002] [Revised: 07/23/2002] [Accepted: 07/23/2002] [Indexed: 11/09/2022] Open
Abstract
The discovery of cell cycle regulators has directed cell research into uncharted territory. In dividing cells, cell cycle-associated protein kinases, which are referred to as cyclin-dependent-kinases (Cdks), regulate proliferation, differentiation, senescence and apoptosis. In contrast, all Cdks in post-mitotic neurons, with the notable exception of Cdk5, are silenced. Surprisingly, misregulation of Cdks occurs in neurons in a wide diversity of neurological disorders, including Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Ectopic expression of these proteins in neurons potently induces cell death with hallmarks of apoptosis. Deregulation of the unique, cell cycle-unrelated Cdk5 by its truncated co-activator, p25 and p29, contributes to neurodegeneration by altering the phosphorylation state of non-membrane-associated proteins and possibly through the induction of cell cycle proteins. On the other hand, cycling Cdks such as Cdk2, Cdk4 and Cdk6, initiate death pathways by derepressing E2F-1/Rb-dependent transcription at the neuronal G1/S checkpoint. Thus, Cdk5 and cycling Cdks may have little in common in the healthy CNS, but they likely conspire in leading neurons to their demise.
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Affiliation(s)
- M D Nguyen
- Centre for Research in Neurosciences, Research Institute of the McGill University Health Centre, Montreal General Hospital, 1650 Cedar Avenue, Montréal, Québec, H3G 1A4, Canada
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65
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Abstract
The p21 activated kinases (Paks), an evolutionarily conserved family of serine/threonine kinases, are important for a variety of cellular functions including cell morphogenesis, motility, survival, mitosis, and angiogenesis. Paks are widely expressed in numerous tissues and are activated by growth factors and extracellular signals through GTPase-dependent and -independent mechanisms. Overexpression of Paks in epithelial cancer cells has been shown to increase migration potential, increase anchorage independent growth, and cause abnormalities in mitosis. Dysregulation of Paks has been reported in several human tumors and neurodegenerative diseases. A growing list of novel Pak interacting proteins has opened up exciting avenues of investigation by which to understand the functions of Paks in tumorigenesis. In this review, we will summarize the current knowledge of the Paks family with respect to emerging cellular functions and possible contributions to cancer.
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Affiliation(s)
- Rakesh Kumar
- Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA.
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66
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Teng FYH, Tang BL. Neuritogenesis: polarization of constitutive exocytosis by effectors of Rho-family GTPases? Biochem Biophys Res Commun 2002; 294:923-5. [PMID: 12074564 DOI: 10.1016/s0006-291x(02)00609-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The sprouting of neurites from a neuron represents a highly specialized form of cellular morphogenesis that must involve coordinated changes in two major cellular processes at two membrane locations: reorganization of the cytoskeleton and redirection of membrane traffic from the trans-Golgi network to the plasma membrane of the growth tip. How exactly are these two processes linked and how is spatial and temporal coordination achieved at the first instance of neurite sprouting? Recent advances may have already revealed some, if not most of the pieces in the puzzle. We discuss below, with some extrapolations, of what has recently come to light, and what more is needed to construct a coherent picture.
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Affiliation(s)
- Felicia Y H Teng
- NCA lab, Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Singapore
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