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Phillip R. Gordon-weeks - One of the best experts on this subject based on the ideXlab platform.
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MAP1B enhances microtubule assembly rates and axon extension rates in developing neurons
Molecular and cellular neurosciences, 2011Co-Authors: Stephen R. Tymanskyj, Timothy M. E. Scales, Phillip R. Gordon-weeksAbstract:Abstract The microtubule-associated protein MAP1B is known to have important roles in neuronal development, particularly during neuronal migration and axonogenesis, but its precise molecular actions are unknown. We used RNA interference silencing of protein expression to specifically knock down MAP1B in cultured embryonic rat cortical neurons. Reduction of MAP1B in these neurons is associated with several abnormal morphological phenotypes including the production of more highly branched and slower growing axons than normal. MAP1B binds to dynamic microtubules and indirect evidence suggests that MAP1B regulates microtubule dynamics. We used the + TIP protein EB3 to assess the dynamic behaviour and orientation of microtubules in neurons in which MAP1B had been knocked down. This revealed a reduction in the speed of microtubule growth in the proximal and distal axon shaft, but not in growth cone filopodia. These observations suggest that the function of MAP1B is to suppress axon branching and enhance axon growth and that this is achieved by maintaining dynamic microtubule growth. To test this hypothesis we expressed MAP1B in a cell line that does not have endogenous MAP1B, this led to an increase in microtubule elongation rates. These findings show that MAP1B enhances microtubule assembly rates and axon extension rates in developing neurons by binding to dynamic microtubules.
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Evolution of the spatial distribution of MAP1B phosphorylation sites in vertebrate neurons
Journal of anatomy, 2010Co-Authors: Stephen R. Tymanskyj, Shen Lin, Phillip R. Gordon-weeksAbstract:The microtubule-associated protein MAP1B has important roles in neural development, particularly in migrating and differentiating neurons. MAP1B is phosphorylated by glycogen synthase kinase 3β (GSK-3β) at a site that requires prior phosphorylation by another kinase four amino acid residues downstream of the GSK-3β site, a so-called primed site, and at non-primed sites that have no such requirement. In developing mammalian neurons, MAP1B phosphorylated by GSK-3β at primed and non-primed sites is distributed in spatially distinct patterns. Non-primed GSK-3β-phosphorylated MAP1B sites are only expressed in axons and are present in the form of a gradient that is highest distally, towards the growth cone. In contrast, primed GSK-3β-phosphorylated MAP1B sites are present throughout the neuron including the somato-dendritic compartment and uniformly throughout the axon. To examine the function of these two sites, we explored the evolutionary conservation of the spatial distribution of GSK-3β primed and non-primed sites on MAP1B in vertebrate neurons. We immunostained spinal cord sections from embryonic or newly hatched representatives of all of the main vertebrate groups using phospho-specific antibodies to GSK-3β primed and non-primed sites on MAP1B. This revealed a remarkable evolutionary conservation of the distribution of primed and non-primed GSK-3β-phosphorylated MAP1B sites in developing vertebrate neurons. By analysing amino acid sequences of MAP1B we found that non-primed GSK-3β sites are more highly conserved than primed sites throughout the vertebrates, suggesting that the latter evolved later. Finally, distinct distribution patterns of GSK-3β primed and non-primed sites on MAP1B were preserved in cultured rat embryonic cortical neurons, opening up the possibility of studying the two sites in vitro.
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Nonprimed and DYRK1A-primed GSK3β-phosphorylation sites on MAP1B regulate microtubule dynamics in growing axons
Journal of Cell Science, 2009Co-Authors: Timothy M. E. Scales, Michaela Kraus, Robert G. Goold, Shen Lin, Phillip R. Gordon-weeksAbstract:MAP1B is a developmentally regulated microtubule-associated phosphoprotein that regulates microtubule dynamics in growing axons and growth cones. We used mass spectrometry to map 28 phosphorylation sites on MAP1B, and selected for further study a putative primed GSK3β site and compared it with two nonprimed GSK3β sites that we had previously characterised. We raised a panel of phosphospecific antibodies to these sites on MAP1B and used it to assess the distribution of phosphorylated MAP1B in the developing nervous system. This showed that the nonprimed sites are restricted to growing axons, whereas the primed sites are also expressed in the neuronal cell body. To identify kinases phosphorylating MAP1B, we added kinase inhibitors to cultured embryonic cortical neurons and monitored MAP1B phosphorylation with our panel of phosphospecific antibodies. These experiments identified dual-specificity tyrosine-phosphorylation-regulated kinase (DYRK1A) as the kinase that primes sites of GSK3β phosphorylation in MAP1B, and we confirmed this by knocking down DYRK1A in cultured embryonic cortical neurons by using shRNA. DYRK1A knockdown compromised neuritogenesis and was associated with alterations in microtubule stability. These experiments demonstrate that MAP1B has DYRK1A-primed and nonprimed GSK3β sites that are involved in the regulation of microtubule stability in growing axons.
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Nonprimed and DYRK1A-primed GSK3 beta-phosphorylation sites on MAP1B regulate microtubule dynamics in growing axons.
Journal of cell science, 2009Co-Authors: Timothy M. E. Scales, Michaela Kraus, Robert G. Goold, Shen Lin, Phillip R. Gordon-weeksAbstract:MAP1B is a developmentally regulated microtubule-associated phosphoprotein that regulates microtubule dynamics in growing axons and growth cones. We used mass spectrometry to map 28 phosphorylation sites on MAP1B, and selected for further study a putative primed GSK3 beta site and compared it with two nonprimed GSK3 beta sites that we had previously characterised. We raised a panel of phosphospecific antibodies to these sites on MAP1B and used it to assess the distribution of phosphorylated MAP1B in the developing nervous system. This showed that the nonprimed sites are restricted to growing axons, whereas the primed sites are also expressed in the neuronal cell body. To identify kinases phosphorylating MAP1B, we added kinase inhibitors to cultured embryonic cortical neurons and monitored MAP1B phosphorylation with our panel of phosphospecific antibodies. These experiments identified dual-specificity tyrosine-phosphorylation-regulated kinase (DYRK1A) as the kinase that primes sites of GSK3 beta phosphorylation in MAP1B, and we confirmed this by knocking down DYRK1A in cultured embryonic cortical neurons by using shRNA. DYRK1A knockdown compromised neuritogenesis and was associated with alterations in microtubule stability. These experiments demonstrate that MAP1B has DYRK1A-primed and nonprimed GSK3 beta sites that are involved in the regulation of microtubule stability in growing axons.
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DAPK-1 binding to a linear peptide motif in MAP1B stimulates autophagy and membrane blebbing
The Journal of biological chemistry, 2008Co-Authors: Ben Harrison, Phillip R. Gordon-weeks, Michaela Kraus, Lindsay Burch, Craig Stevens, Ashley L. Craig, Ted R. HuppAbstract:DAPK-1 (death-activated protein kinase) has wide ranging functions in cell growth control; however, DAPK-1 interacting proteins that mediate these effects are not well defined. Protein-protein interactions are driven in part by linear interaction motifs, and combinatorial peptide libraries were used to identify peptide interfaces for the kinase domain of DAPK-1. Peptides bound to DAPK-1core kinase domain fragments had homology to the N-terminal domain of the microtubule-associated protein MAP1B. Immunobinding assays demonstrated that DAPK-1 can bind to the full-length human MAP1B, a smaller N-terminal miniprotein containing amino acids 1-126 and the 12-amino acid polypeptides acquired by peptide selection. Amino acid starvation of cells induced a stable immune complex between MAP1B and DAPK-1, identifying a signal that forms the endogenous complex in cells. DAPK-1 and MAP1B co-expression form a synthetic lethal interaction as they cooperate to induce growth inhibition in a clonogenic assay. In cells, two co-localizing populations of DAPK-1 and MAP1B were observed using confocal microscopy; one pool co-localized with MAP1B plus tubulin, and a second pool co-localized with MAP1B plus cortical F-actin. Reduction of MAP1B protein using short interfering RNA attenuated DAPK-1-stimulated autophagy. Transfected MAP1B can synergize with DAPK-1 to stimulate membrane blebbing, whereas reduction of MAP1B using short interfering RNA attenuates DAPK-1 membrane blebbing activity. The autophagy inhibitor 3-methyladenine inhibits the DAPK-1 plus MAP1B-mediated membrane blebbing. These data highlight the utility of peptide aptamers to identify novel binding interfaces and highlight a role for MAP1B in DAPK-1-dependent signaling in autophagy and membrane blebbing.
Fatiha Nothias - One of the best experts on this subject based on the ideXlab platform.
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The GSK3-MAP1B pathway controls neurite branching and microtubule dynamics
Molecular and Cellular Neuroscience, 2016Co-Authors: Monia Barnat, Friedrich Propst, Sylvia Soares, Marie-noelle Benassy, Laetitia Vincensini, Coralie Fassier, Annie Andrieux, Ysander Boxberg, Fatiha NothiasAbstract:The microtubule-associated protein MAP1B plays a key role in axon regeneration. We investigated the role of GSK3-mediated MAP1B phosphorylation in local fine-tuning of neurite branching and the underlying microtubule (MT) dynamics. In wildtype adult dorsal root ganglia (DRG) neurons, MAP1B phosphorylation is locally reduced at branching points, and branching dynamics from growth cones and distal neurite shafts is increased upon GSK3 inhibition. While MAP1B-/- neurites, that display increased branching, are not affected by GSK3 inhibition, transfection of MAP1B-/- neurons with full-length MAP1B-cDNA restores the wildtype branching phenotype, demonstrating that MAP1B is a key effector downstream of GSK3. Experiments in mutant mice lacking tyrosinated MTs indicate a preferential association of phospho-MAP1B with tyrosinated MTs. Interestingly, inhibition of GSK3-mediated MAP1B phosphorylation in MAP1B-cDNA-transfected fibroblasts protects both tyrosinated and acetylated MTs from nocodazole-induced depolymerization, while detyrosinated MTs are less abundant in the presence of MAP1B. Our data thus provide new insight into the molecular link between GSK3, MAP1B, neurite branching and MT stability regulation. We suggest that, at branching points, MAP1B undergoes a fine regulation of both its phosphorylation and sub-cellular amounts, in order to modulate the local balance between acetylated, detyrosinated, and tyrosinated microtubule pools.
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Loss of MAP Function Leads to Hippocampal Synapse Loss and Deficits in the Morris Water Maze with Aging
Journal of Neuroscience, 2014Co-Authors: Xiaohong Zuo, Fatiha Nothias, Fusheng Yang, Oliver J. Ubeda, Dana J. Gant, Mher Alaverdyan, Nicolae C. Kiosea, Sean Nazari, Ping Ping Chen, Piu ChanAbstract:Hyperphosphorylation and accumulation of tau aggregates are prominent features in tauopathies, including Alzheimer's disease, but the impact of loss of tau function on synaptic and cognitive deficits remains poorly understood. We report that old (19 - 20 months; OKO) but not middle-aged (8 - 9 months; MKO) tau knock-out mice develop Morris Water Maze(MWM) deficits and loss of hippocampal acetylated alpha-tubulin and excitatory synaptic proteins. Mild motor deficits and reduction in tyrosine hydroxylase (TH) in the substantia nigra were present by middle age, but did not affect MWM performance, whereas OKO mice showed MWM deficits paralleling hippocampal deficits. Deletion of tau, a microtubule-associated protein (MAP), resulted in increased levels of MAP1A, MAP1B, and MAP2 in MKO, followed by loss of MAP2 and MAP1B in OKO. Hippocampal synaptic deficits in OKO mice were partially corrected with dietary supplementation with docosahexaenoic acid (DHA) and both MWM and synaptic deficits were fully corrected by combining DHA with alpha-lipoic acid (ALA), which also prevented TH loss. DHA or DHA/ALA restored phosphorylated and total GSK3 beta and attenuated hyperactivation of the tau C-Jun N-terminal kinases (JNKs) while increasing MAP1B, dephosphorylated (active) MAP2, and acetylated alpha-tubulin, suggesting improved microtubule stability and maintenance of active compensatory MAPs. Our results implicate the loss of MAP function in age-associated hippocampal deficits and identify a safe dietary intervention, rescuing both MAP function and TH in OKO mice. Therefore, in addition to microtubule-stabilizing therapeutic drugs, preserving or restoring compensatory MAP function may be a useful new prevention strategy.
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the light chains of microtubule associated proteins map1a and MAP1B interact with α1 syntrophin in the central and peripheral nervous system
PLOS ONE, 2012Co-Authors: Heike Fuhrmannstroissnigg, Rainer Noiges, Luise Descovich, Irmgard Fischer, Douglas E. Albrecht, Fatiha Nothias, Stanley C. Froehner, Friedrich PropstAbstract:Microtubule-associated proteins of the MAP1 family (MAP1A, MAP1B, and MAP1S) share, among other features, a highly conserved COOH-terminal domain approximately 125 amino acids in length. We conducted a yeast 2-hybrid screen to search for proteins interacting with this domain and identified α1-syntrophin, a member of a multigene family of adapter proteins involved in signal transduction. We further demonstrate that the interaction between the conserved COOH-terminal 125-amino acid domain (which is located in the light chains of MAP1A, MAP1B, and MAP1S) and α1-syntrophin is direct and occurs through the pleckstrin homology domain 2 (PH2) and the postsynaptic density protein 95/disk large/zonula occludens-1 protein homology domain (PDZ) of α1-syntrophin. We confirmed the interaction of MAP1B and α1-syntrophin by co-localization of the two proteins in transfected cells and by co-immunoprecipitation experiments from mouse brain. In addition, we show that MAP1B and α1-syntrophin partially co-localize in Schwann cells of the murine sciatic nerve during postnatal development and in the adult. However, intracellular localization of α1-syntrophin and other Schwann cell proteins such as ezrin and dystrophin-related protein 2 (DRP2) and the localization of the axonal node of Ranvier-associated protein Caspr1/paranodin were not affected in MAP1B null mice. Our findings add to a growing body of evidence that classical MAPs are likely to be involved in signal transduction not only by directly modulating microtubule function, but also through their interaction with signal transduction proteins.
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The Light Chains of Microtubule-Associated Proteins MAP1A and MAP1B Interact with alpha 1-Syntrophin in the Central and Peripheral Nervous System
PLoS ONE, 2012Co-Authors: Heike Fuhrmann-stroissnigg, Rainer Noiges, Luise Descovich, Irmgard Fischer, Douglas E. Albrecht, Fatiha Nothias, Stanley C. Froehner, Friedrich PropstAbstract:Microtubule-associated proteins of the MAP1 family (MAP1A, MAP1B, and MAP1S) share, among other features, a highly conserved COOH-terminal domain approximately 125 amino acids in length. We conducted a yeast 2-hybrid screen to search for proteins interacting with this domain and identified alpha 1-syntrophin, a member of a multigene family of adapter proteins involved in signal transduction. We further demonstrate that the interaction between the conserved COOH-terminal 125-amino acid domain (which is located in the light chains of MAP1A, MAP1B, and MAP1S) and alpha 1-syntrophin is direct and occurs through the pleckstrin homology domain 2 (PH2) and the postsynaptic density protein 95/disk large/zonula occludens-1 protein homology domain (PDZ) of alpha 1-syntrophin. We confirmed the interaction of MAP1B and alpha 1-syntrophin by co-localization of the two proteins in transfected cells and by co-immunoprecipitation experiments from mouse brain. In addition, we show that MAP1B and alpha 1-syntrophin partially co-localize in Schwann cells of the murine sciatic nerve during postnatal development and in the adult. However, intracellular localization of alpha 1-syntrophin and other Schwann cell proteins such as ezrin and dystrophin-related protein 2 (DRP2) and the localization of the axonal node of Ranvier-associated protein Caspr1/paranodin were not affected in MAP1B null mice. Our findings add to a growing body of evidence that classical MAPs are likely to be involved in signal transduction not only by directly modulating microtubule function, but also through their interaction with signal transduction proteins.
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Extensive structural remodeling of the injured spinal cord revealed by phosphorylated MAP1B in sprouting axons and degenerating neurons.
The European journal of neuroscience, 2007Co-Authors: Sylvia Soares, Michèle Ravaille-veron, Ysander Von Boxberg, Monia Barnat, Claudio Salim, Fatiha NothiasAbstract:Spinal cord injury (SCI) results in loss of sensory and motor function because injured axons do not regenerate and neurons that die are not replaced. Nevertheless, there is evidence for spontaneous reorganization of spared pathways (i.e. sprouting) that could be exploited to improve functional recovery. The extent of morphological remodeling after spinal cord injury is, however, not understood. We have previously shown that a phosphorylated form of microtubule-associated protein-1B, MAP1B-P, is expressed by growing axons, but is detected in intact adult SC in fibers exhibiting a somatotopic distribution of myelinated sensory fibers. We now demonstrate that after adult SCI, MAP1B-P is up-regulated in other classes of axons. We used immunohistochemistry to show changing levels and distributions of MAP1B-P after a right thoracic hemisection of adult rat spinal cord. MAP1B-P labeling suggests rearrangements of the axonal circuitry that go well beyond previous descriptions. MAP1B-P-positive fibers are present in ectopic locations in gray matter in both dorsal and ventral horns and around the central canal. Double staining reveals that primary sensory and descending serotonergic and corticospinal axons are MAP1B-P positive. In white matter, high MAP1B-P expression is found on terminal enlargements near the injury, reflecting retraction of transected axons. MAP1B-P also accumulates in pre-apoptotic neuronal somata axotomized by the lesion, indicating association of MAP1B-P not only with axon extension and retraction, but also with neuronal degeneration. Finally, we provide evidence that MAP1B phosphorylation is correlated with activation of JNK MAP-kinase, providing a step towards unraveling the mechanisms of regulation of this plasticity-related cytoskeletal protein.
Jesús Avila - One of the best experts on this subject based on the ideXlab platform.
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MAP1B dependent rac activation is required for ampa receptor endocytosis during long term depression
The EMBO Journal, 2013Co-Authors: Marion Benoist, Jesús Avila, Elena Tortosa, Christian Gonzalezbillault, Rocío Palenzuela, Carlos Rozas, Patricio Rojas, Bernardo Morales, José A. EstebanAbstract:The microtubule-associated protein 1B (MAP1B) plays critical roles in neurite growth and synapse maturation during brain development. This protein is well expressed in the adult brain. However, its function in mature neurons remains unknown. We have used a genetically modified mouse model and shRNA techniques to assess the role of MAP1B at established synapses, bypassing MAP1B functions during neuronal development. Under these conditions, we found that MAP1B deficiency alters synaptic plasticity by specifically impairing long-term depression (LTD) expression. Interestingly, this is due to a failure to trigger AMPA receptor endocytosis and spine shrinkage during LTD. These defects are accompanied by an impaired targeting of the Rac1 activator Tiam1 at synaptic compartments. Accordingly, LTD and AMPA receptor endocytosis are restored in MAP1B-deficient neurons by providing additional Rac1. Therefore, these results indicate that the MAP1B-Tiam1-Rac1 relay is essential for spine structural plasticity and removal of AMPA receptors from synapses during LTD. This work highlights the importance of MAPs as signalling hubs controlling the actin cytoskeleton and receptor trafficking during plasticity in mature neurons.
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MAP1B‐dependent Rac activation is required for AMPA receptor endocytosis during long‐term depression
The EMBO journal, 2013Co-Authors: Marion Benoist, Jesús Avila, Christian Gonzalez-billault, Elena Tortosa, Rocío Palenzuela, Carlos Rozas, Patricio Rojas, Bernardo Morales, José A. EstebanAbstract:The microtubule-associated protein 1B (MAP1B) plays critical roles in neurite growth and synapse maturation during brain development. This protein is well expressed in the adult brain. However, its function in mature neurons remains unknown. We have used a genetically modified mouse model and shRNA techniques to assess the role of MAP1B at established synapses, bypassing MAP1B functions during neuronal development. Under these conditions, we found that MAP1B deficiency alters synaptic plasticity by specifically impairing long-term depression (LTD) expression. Interestingly, this is due to a failure to trigger AMPA receptor endocytosis and spine shrinkage during LTD. These defects are accompanied by an impaired targeting of the Rac1 activator Tiam1 at synaptic compartments. Accordingly, LTD and AMPA receptor endocytosis are restored in MAP1B-deficient neurons by providing additional Rac1. Therefore, these results indicate that the MAP1B-Tiam1-Rac1 relay is essential for spine structural plasticity and removal of AMPA receptors from synapses during LTD. This work highlights the importance of MAPs as signalling hubs controlling the actin cytoskeleton and receptor trafficking during plasticity in mature neurons.
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MAP1B regulates microtubule dynamics by sequestering eb1 3 in the cytosol of developing neuronal cells
The EMBO Journal, 2013Co-Authors: Elena Tortosa, Jesús Avila, Niels Galjart, Carmen Laura SayasAbstract:MAP1B, a structural microtubule (MT)-associated protein highly expressed in developing neurons, plays a key role in neurite and axon extension. However, not all molecular mechanisms by which MAP1B controls MT dynamics during these processes have been revealed. Here, we show that MAP1B interacts directly with EB1 and EB3 (EBs), two core ‘microtubule plus-end tracking proteins' (+TIPs), and sequesters them in the cytosol of developing neuronal cells. MAP1B overexpression reduces EBs binding to plus-ends, whereas MAP1B downregulation increases binding of EBs to MTs. These alterations in EBs behaviour lead to changes in MT dynamics, in particular overstabilization and looping, in growth cones of MAP1B-deficient neurons. This contributes to growth cone remodelling and a delay in axon outgrowth. Together, our findings define a new and crucial role of MAP1B as a direct regulator of EBs function and MT dynamics during neurite and axon extension. Our data provide a new layer of MT regulation: a classical MAP, which binds to the MT lattice and not to the end, controls effective concentration of core +TIPs thereby regulating MTs at their plus-ends.
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MAP1B regulates microtubule dynamics by sequestering EB1/3 in the cytosol of developing neuronal cells
The EMBO journal, 2013Co-Authors: Elena Tortosa, Jesús Avila, Niels Galjart, Carmen Laura SayasAbstract:MAP1B, a structural microtubule (MT)-associated protein highly expressed in developing neurons, plays a key role in neurite and axon extension. However, not all molecular mechanisms by which MAP1B controls MT dynamics during these processes have been revealed. Here, we show that MAP1B interacts directly with EB1 and EB3 (EBs), two core ‘microtubule plus-end tracking proteins' (+TIPs), and sequesters them in the cytosol of developing neuronal cells. MAP1B overexpression reduces EBs binding to plus-ends, whereas MAP1B downregulation increases binding of EBs to MTs. These alterations in EBs behaviour lead to changes in MT dynamics, in particular overstabilization and looping, in growth cones of MAP1B-deficient neurons. This contributes to growth cone remodelling and a delay in axon outgrowth. Together, our findings define a new and crucial role of MAP1B as a direct regulator of EBs function and MT dynamics during neurite and axon extension. Our data provide a new layer of MT regulation: a classical MAP, which binds to the MT lattice and not to the end, controls effective concentration of core +TIPs thereby regulating MTs at their plus-ends.
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Microtubule-associated protein 1B (MAP1B) is required for dendritic spine development and synaptic maturation
The Journal of biological chemistry, 2011Co-Authors: Elena Tortosa, Christian Gonzalez-billault, Carolina Montenegro-venegas, Marion Benoist, Steffen Härtel, José A. Esteban, Jesús AvilaAbstract:Microtubule-associated protein 1B (MAP1B) is prominently expressed during early stages of neuronal development, and it has been implicated in axonal growth and guidance. MAP1B expression is also found in the adult brain in areas of significant synaptic plasticity. Here, we demonstrate that MAP1B is present in dendritic spines, and we describe a decrease in the density of mature dendritic spines in neurons of MAP1B-deficient mice that was accompanied by an increase in the number of immature filopodia-like protrusions. Although these neurons exhibited normal passive membrane properties and action potential firing, AMPA receptor-mediated synaptic currents were significantly diminished. Moreover, we observed a significant decrease in Rac1 activity and an increase in RhoA activity in the post-synaptic densities of adult MAP1B(+/-) mice when compared with wild type controls. MAP1B(+/-) fractions also exhibited a decrease in phosphorylated cofilin. Taken together, these results indicate a new and important role for MAP1B in the formation and maturation of dendritic spines, possibly through the regulation of the actin cytoskeleton. This activity of MAP1B could contribute to the regulation of synaptic activity and plasticity in the adult brain.
Kyung-hee Choi - One of the best experts on this subject based on the ideXlab platform.
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microtubule associated protein 1b light chain MAP1B lc1 negatively regulates the activity of tumor suppressor p53 in neuroblastoma cells
FEBS Letters, 2008Co-Authors: So-youn Lee, Jung-woong Kim, Mi-hee Jeong, Sang-min Jang, Ki-hyun Song, Kyung-hee ChoiAbstract:The tumor suppressor and transcription factor p53 is a key modulator of cellular stress responses and can trigger apoptosis in many cell types, including neurons. In this study, we have shown that the Microtubule-Associated Protein 1B (MAP1B) light chain can interact with the tumor suppressor p53. We also demonstrate that both p53 and the MAP1B light chain (MAP1B-LC1) alter their localization from the cytoplasm to the nucleus when neuroblastoma cells, SH-SY5Y, are treated with doxorubicin. Additionally, we demonstrate that the MAP1B-LC1 negatively regulates p53-dependent transcriptional activity of a reporter construct driven by the p21 promoter. Consequently, MAP1B-LC1 binds to p53 and this interaction leads to the inhibition of doxorubicin-induced apoptosis in SH-SY5Y cells.
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Microtubule‐associated Protein 1B Light Chain (MAP1B‐LC1) negatively regulates the activity of tumor suppressor p53 in neuroblastoma cells
FEBS letters, 2008Co-Authors: So-youn Lee, Jung-woong Kim, Mi-hee Jeong, Sang-min Jang, Ki-hyun Song, Kyung-hee ChoiAbstract:The tumor suppressor and transcription factor p53 is a key modulator of cellular stress responses and can trigger apoptosis in many cell types, including neurons. In this study, we have shown that the Microtubule-Associated Protein 1B (MAP1B) light chain can interact with the tumor suppressor p53. We also demonstrate that both p53 and the MAP1B light chain (MAP1B-LC1) alter their localization from the cytoplasm to the nucleus when neuroblastoma cells, SH-SY5Y, are treated with doxorubicin. Additionally, we demonstrate that the MAP1B-LC1 negatively regulates p53-dependent transcriptional activity of a reporter construct driven by the p21 promoter. Consequently, MAP1B-LC1 binds to p53 and this interaction leads to the inhibition of doxorubicin-induced apoptosis in SH-SY5Y cells.
Friedrich Propst - One of the best experts on this subject based on the ideXlab platform.
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The GSK3-MAP1B pathway controls neurite branching and microtubule dynamics
Molecular and Cellular Neuroscience, 2016Co-Authors: Monia Barnat, Friedrich Propst, Sylvia Soares, Marie-noelle Benassy, Laetitia Vincensini, Coralie Fassier, Annie Andrieux, Ysander Boxberg, Fatiha NothiasAbstract:The microtubule-associated protein MAP1B plays a key role in axon regeneration. We investigated the role of GSK3-mediated MAP1B phosphorylation in local fine-tuning of neurite branching and the underlying microtubule (MT) dynamics. In wildtype adult dorsal root ganglia (DRG) neurons, MAP1B phosphorylation is locally reduced at branching points, and branching dynamics from growth cones and distal neurite shafts is increased upon GSK3 inhibition. While MAP1B-/- neurites, that display increased branching, are not affected by GSK3 inhibition, transfection of MAP1B-/- neurons with full-length MAP1B-cDNA restores the wildtype branching phenotype, demonstrating that MAP1B is a key effector downstream of GSK3. Experiments in mutant mice lacking tyrosinated MTs indicate a preferential association of phospho-MAP1B with tyrosinated MTs. Interestingly, inhibition of GSK3-mediated MAP1B phosphorylation in MAP1B-cDNA-transfected fibroblasts protects both tyrosinated and acetylated MTs from nocodazole-induced depolymerization, while detyrosinated MTs are less abundant in the presence of MAP1B. Our data thus provide new insight into the molecular link between GSK3, MAP1B, neurite branching and MT stability regulation. We suggest that, at branching points, MAP1B undergoes a fine regulation of both its phosphorylation and sub-cellular amounts, in order to modulate the local balance between acetylated, detyrosinated, and tyrosinated microtubule pools.
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Microtubule Associated Protein 1b (MAP1B) Is a Marker of the Microtubular Cytoskeleton in Podocytes but Is Not Essential for the Function of the Kidney Filtration Barrier in Mice
PloS one, 2015Co-Authors: Markus Gödel, Friedrich Propst, Beat M. Riederer, Dunja Temerinac, Florian Grahammer, Björn Hartleben, Oliver Kretz, Stefan Kohl, Tobias B. HuberAbstract:Podocytes are essential for the function of the kidney glomerular filter. A highly differentiated cytoskeleton is requisite for their integrity. Although much knowledge has been gained on the organization of cortical actin networks in podocyte's foot processes, less is known about the molecular organization of the microtubular cytoskeleton in primary processes and the cell body. To gain an insight into the organization of the microtubular cytoskeleton of the podocyte, we systematically analyzed the expression of microtubule associated proteins (Maps), a family of microtubules interacting proteins with known functions as regulator, scaffold and guidance proteins. We identified microtubule associated protein 1b (MAP1B) to be specifically enriched in podocytes in human and rodent kidney. Using immunogold labeling in electron microscopy, we were able to demonstrate an enrichment of MAP1B in primary processes. A similar association of MAP1B with the microtubule cytoskeleton was detected in cultured podocytes. Subcellular distribution of MAP1B HC and LC1 was analyzed using a double fluorescent reporter MAP1B fusion protein. Subsequently we analyzed mice constitutively depleted of MAP1B. Interestingly, MAP1B KO was not associated with any functional or structural alterations pointing towards a redundancy of MAP proteins in podocytes. In summary, we established MAP1B as a specific marker protein of the podocyte microtubular cytoskeleton.
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the light chains of microtubule associated proteins map1a and MAP1B interact with α1 syntrophin in the central and peripheral nervous system
PLOS ONE, 2012Co-Authors: Heike Fuhrmannstroissnigg, Rainer Noiges, Luise Descovich, Irmgard Fischer, Douglas E. Albrecht, Fatiha Nothias, Stanley C. Froehner, Friedrich PropstAbstract:Microtubule-associated proteins of the MAP1 family (MAP1A, MAP1B, and MAP1S) share, among other features, a highly conserved COOH-terminal domain approximately 125 amino acids in length. We conducted a yeast 2-hybrid screen to search for proteins interacting with this domain and identified α1-syntrophin, a member of a multigene family of adapter proteins involved in signal transduction. We further demonstrate that the interaction between the conserved COOH-terminal 125-amino acid domain (which is located in the light chains of MAP1A, MAP1B, and MAP1S) and α1-syntrophin is direct and occurs through the pleckstrin homology domain 2 (PH2) and the postsynaptic density protein 95/disk large/zonula occludens-1 protein homology domain (PDZ) of α1-syntrophin. We confirmed the interaction of MAP1B and α1-syntrophin by co-localization of the two proteins in transfected cells and by co-immunoprecipitation experiments from mouse brain. In addition, we show that MAP1B and α1-syntrophin partially co-localize in Schwann cells of the murine sciatic nerve during postnatal development and in the adult. However, intracellular localization of α1-syntrophin and other Schwann cell proteins such as ezrin and dystrophin-related protein 2 (DRP2) and the localization of the axonal node of Ranvier-associated protein Caspr1/paranodin were not affected in MAP1B null mice. Our findings add to a growing body of evidence that classical MAPs are likely to be involved in signal transduction not only by directly modulating microtubule function, but also through their interaction with signal transduction proteins.
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The Light Chains of Microtubule-Associated Proteins MAP1A and MAP1B Interact with alpha 1-Syntrophin in the Central and Peripheral Nervous System
PLoS ONE, 2012Co-Authors: Heike Fuhrmann-stroissnigg, Rainer Noiges, Luise Descovich, Irmgard Fischer, Douglas E. Albrecht, Fatiha Nothias, Stanley C. Froehner, Friedrich PropstAbstract:Microtubule-associated proteins of the MAP1 family (MAP1A, MAP1B, and MAP1S) share, among other features, a highly conserved COOH-terminal domain approximately 125 amino acids in length. We conducted a yeast 2-hybrid screen to search for proteins interacting with this domain and identified alpha 1-syntrophin, a member of a multigene family of adapter proteins involved in signal transduction. We further demonstrate that the interaction between the conserved COOH-terminal 125-amino acid domain (which is located in the light chains of MAP1A, MAP1B, and MAP1S) and alpha 1-syntrophin is direct and occurs through the pleckstrin homology domain 2 (PH2) and the postsynaptic density protein 95/disk large/zonula occludens-1 protein homology domain (PDZ) of alpha 1-syntrophin. We confirmed the interaction of MAP1B and alpha 1-syntrophin by co-localization of the two proteins in transfected cells and by co-immunoprecipitation experiments from mouse brain. In addition, we show that MAP1B and alpha 1-syntrophin partially co-localize in Schwann cells of the murine sciatic nerve during postnatal development and in the adult. However, intracellular localization of alpha 1-syntrophin and other Schwann cell proteins such as ezrin and dystrophin-related protein 2 (DRP2) and the localization of the axonal node of Ranvier-associated protein Caspr1/paranodin were not affected in MAP1B null mice. Our findings add to a growing body of evidence that classical MAPs are likely to be involved in signal transduction not only by directly modulating microtubule function, but also through their interaction with signal transduction proteins.
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MAP1B coordinates microtubule and actin filament remodeling in adult mouse Schwann cell tips and DRG neuron growth cones.
Molecular and cellular neurosciences, 2007Co-Authors: Céline Bouquet, Friedrich Propst, Michèle Ravaille-veron, Fatiha NothiasAbstract:We previously described the function of MAP1B in both turning and branching of regenerating neurites. Our results suggested implication of MAP1B in coupling of actin and microtubule movements, a hypothesis investigated here using DRG neurons and Schwann cells (SCs), which also transiently express MAP1B. Cell motility and cytoskeletal rearrangements were assessed before and after addition of lysophosphatidic acid (LPA), an extracellular signaling phospholipid triggering changes in actin distribution and cell morphology. First, we show that MAP1B is required for SC migration in vitro, extending our previous work on its function in growth cone motility. Second, LPA stimulation induces drastic retraction of processes from MAP1B-expressing cells in a two-step process: actin contraction, which is followed by microtubule backfolding. More importantly, we provide evidence that MAP1B is required for microtubule backfolding, thereby unravelling an important molecular mechanism implicated in coupling the movements of actin and microtubules during process retraction of neural cells.