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Sandouk A, Xu Z, Baruah S, Tremblay M, Hopkins JB, Chakravarthy S, Gakhar L, Schnicker NJ, Houtman JCD. GRB2 dimerization mediated by SH2 domain-swapping is critical for T cell signaling and cytokine production. Sci Rep 2023; 13:3505. [PMID: 36864087 PMCID: PMC9981690 DOI: 10.1038/s41598-023-30562-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 02/25/2023] [Indexed: 03/04/2023] Open
Abstract
GRB2 is an adaptor protein required for facilitating cytoplasmic signaling complexes from a wide array of binding partners. GRB2 has been reported to exist in either a monomeric or dimeric state in crystal and solution. GRB2 dimers are formed by the exchange of protein segments between domains, otherwise known as "domain-swapping". Swapping has been described between SH2 and C-terminal SH3 domains in the full-length structure of GRB2 (SH2/C-SH3 domain-swapped dimer), as well as between α-helixes in isolated GRB2 SH2 domains (SH2/SH2 domain-swapped dimer). Interestingly, SH2/SH2 domain-swapping has not been observed within the full-length protein, nor have the functional influences of this novel oligomeric conformation been explored. We herein generated a model of full-length GRB2 dimer with an SH2/SH2 domain-swapped conformation supported by in-line SEC-MALS-SAXS analyses. This conformation is consistent with the previously reported truncated GRB2 SH2/SH2 domain-swapped dimer but different from the previously reported, full-length SH2/C-terminal SH3 (C-SH3) domain-swapped dimer. Our model is also validated by several novel full-length GRB2 mutants that favor either a monomeric or a dimeric state through mutations within the SH2 domain that abrogate or promote SH2/SH2 domain-swapping. GRB2 knockdown and re-expression of selected monomeric and dimeric mutants in a T cell lymphoma cell line led to notable defects in clustering of the adaptor protein LAT and IL-2 release in response to TCR stimulation. These results mirrored similarly-impaired IL-2 release in GRB2-deficient cells. These studies show that a novel dimeric GRB2 conformation with domain-swapping between SH2 domains and monomer/dimer transitions are critical for GRB2 to facilitate early signaling complexes in human T cells.
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Affiliation(s)
- Aline Sandouk
- Interdisciplinary Graduate Program in Immunology, University of Iowa, Iowa City, IA, 52242, USA
| | - Zhen Xu
- Protein and Crystallography Facility, University of Iowa, Iowa City, IA, 52242, USA
| | - Sankar Baruah
- Protein and Crystallography Facility, University of Iowa, Iowa City, IA, 52242, USA
| | - Mikaela Tremblay
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, 52242, USA
| | - Jesse B Hopkins
- Biophysics Collaborative Access Team, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Srinivas Chakravarthy
- Biophysics Collaborative Access Team, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Lokesh Gakhar
- Protein and Crystallography Facility, University of Iowa, Iowa City, IA, 52242, USA
- Department of Biochemistry and Molecular Biology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Nicholas J Schnicker
- Protein and Crystallography Facility, University of Iowa, Iowa City, IA, 52242, USA
| | - Jon C D Houtman
- Interdisciplinary Graduate Program in Immunology, University of Iowa, Iowa City, IA, 52242, USA.
- Department of Microbiology and Immunology, University of Iowa, Iowa City, IA, 52242, USA.
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Podvin S, Rosenthal SB, Poon W, Wei E, Fisch KM, Hook V. Mutant Huntingtin Protein Interaction Map Implicates Dysregulation of Multiple Cellular Pathways in Neurodegeneration of Huntington's Disease. J Huntingtons Dis 2022; 11:243-267. [PMID: 35871359 PMCID: PMC9484122 DOI: 10.3233/jhd-220538] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Huntington's disease (HD) is a genetic neurodegenerative disease caused by trinucleotide repeat (CAG) expansions in the human HTT gene encoding the huntingtin protein (Htt) with an expanded polyglutamine tract. OBJECTIVE HD models from yeast to transgenic mice have investigated proteins interacting with mutant Htt that may initiate molecular pathways of cell death. There is a paucity of datasets of published Htt protein interactions that include the criteria of 1) defining fragments or full-length Htt forms, 2) indicating the number of poly-glutamines of the mutant and wild-type Htt forms, and 3) evaluating native Htt interaction complexes. This research evaluated such interactor data to gain understanding of Htt dysregulation of cellular pathways. METHODS Htt interacting proteins were compiled from the literature that meet our criteria and were subjected to network analysis via clustering, gene ontology, and KEGG pathways using rigorous statistical methods. RESULTS The compiled data of Htt interactors found that both mutant and wild-type Htt interact with more than 2,971 proteins. Application of a community detection algorithm to all known Htt interactors identified significant signal transduction, membrane trafficking, chromatin, and mitochondrial clusters, among others. Binomial analyses of a subset of reported protein interactor information determined that chromatin organization, signal transduction and endocytosis were diminished, while mitochondria, translation and membrane trafficking had enriched overall edge effects. CONCLUSION The data support the hypothesis that mutant Htt disrupts multiple cellular processes causing toxicity. This dataset is an open resource to aid researchers in formulating hypotheses of HD mechanisms of pathogenesis.
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Affiliation(s)
- Sonia Podvin
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Sara Brin Rosenthal
- Center for Computational Biology & Bioinformatics, University of California, San Diego, La Jolla, CA, USA
| | - William Poon
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Enlin Wei
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Kathleen M Fisch
- Center for Computational Biology & Bioinformatics, University of California, San Diego, La Jolla, CA, USA.,Department of Obstetrics, Gynecology & Reproductive Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Vivian Hook
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, USA.,Department of Neuroscience and Dept of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, CA, USA
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Zhang L, Kang H, Perez-Aguilar JM, Zhou R. Possible Co-Evolution of Polyglutamine and Polyproline in Huntingtin Protein: Proline-Rich Domain as Transient Folding Chaperone. J Phys Chem Lett 2022; 13:6331-6341. [PMID: 35796410 DOI: 10.1021/acs.jpclett.2c01184] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Huntington's disease is an inherited neurodegenerative disorder caused by the overduplication of CAG repeats in the Huntingtin gene. Recent findings revealed that among the orthologs, the expansion of CAG repeats (polyQ) in the Huntingtin gene occurs in tandem with the duplication of CCG repeats (polyP). However, the molecular mechanism of this possible co-evolution remains unknown. We examined the structures of Huntingtin exon 1 (HttEx1) from six species along with five designed mutants. We found that the polyP segments "chaperone" the rest of the HttEx1 by forming ad hoc polyP binding grooves. Such a process elongates the otherwise poorly solvated polyQ domain, while modulating its secondary structure propensity from β-strands to α-helices. This chaperoning effect is achieved mostly through transient hydrogen bond interactions between polyP and the rest of HttEx1, resulting in a striking golden ratio of ∼2:1 between the chain lengths of polyQ and polyP.
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Affiliation(s)
- Leili Zhang
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
| | - Hongsuk Kang
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
| | - Jose Manuel Perez-Aguilar
- School of Chemical Sciences, Meritorious Autonomous University of Puebla (BUAP), University City, Puebla 72570, Mexico
| | - Ruhong Zhou
- Computational Biology Center, IBM Thomas J. Watson Research Center, Yorktown Heights, New York 10598, United States
- Institute of Quantitative Biology, College of Life Sciences, Zhejiang University, Hangzhou 310027, China
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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4
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Nikolovska K, Seidler UE, Stock C. The Role of Plasma Membrane Sodium/Hydrogen Exchangers in Gastrointestinal Functions: Proliferation and Differentiation, Fluid/Electrolyte Transport and Barrier Integrity. Front Physiol 2022; 13:899286. [PMID: 35665228 PMCID: PMC9159811 DOI: 10.3389/fphys.2022.899286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 04/19/2022] [Indexed: 12/11/2022] Open
Abstract
The five plasma membrane Na+/H+ exchanger (NHE) isoforms in the gastrointestinal tract are characterized by distinct cellular localization, tissue distribution, inhibitor sensitivities, and physiological regulation. NHE1 (Slc9a1) is ubiquitously expressed along the gastrointestinal tract in the basolateral membrane of enterocytes, but so far, an exclusive role for NHE1 in enterocyte physiology has remained elusive. NHE2 (Slc9a2) and NHE8 (Slc9a8) are apically expressed isoforms with ubiquitous distribution along the colonic crypt axis. They are involved in pHi regulation of intestinal epithelial cells. Combined use of a knockout mouse model, intestinal organoid technology, and specific inhibitors revealed previously unrecognized actions of NHE2 and NHE8 in enterocyte proliferation and differentiation. NHE3 (Slc9a3), expressed in the apical membrane of differentiated intestinal epithelial cells, functions as the predominant nutrient-independent Na+ absorptive mechanism in the gut. The new selective NHE3 inhibitor (Tenapanor) allowed discovery of novel pathophysiological and drug-targetable NHE3 functions in cystic-fibrosis associated intestinal obstructions. NHE4, expressed in the basolateral membrane of parietal cells, is essential for parietal cell integrity and acid secretory function, through its role in cell volume regulation. This review focuses on the expression, regulation and activity of the five plasma membrane Na+/H+ exchangers in the gastrointestinal tract, emphasizing their role in maintaining intestinal homeostasis, or their impact on disease pathogenesis. We point to major open questions in identifying NHE interacting partners in central cellular pathways and processes and the necessity of determining their physiological role in a system where their endogenous expression/activity is maintained, such as organoids derived from different parts of the gastrointestinal tract.
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Pigazzini ML, Lawrenz M, Margineanu A, Kaminski Schierle GS, Kirstein J. An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging. Front Mol Neurosci 2021; 14:721749. [PMID: 34720872 PMCID: PMC8554126 DOI: 10.3389/fnmol.2021.721749] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 08/30/2021] [Indexed: 02/02/2023] Open
Abstract
Huntington's disease is a dominantly inherited neurodegenerative disorder caused by the expansion of a CAG repeat, encoding for the amino acid glutamine (Q), present in the first exon of the protein huntingtin. Over the threshold of Q39 HTT exon 1 (HTTEx1) tends to misfold and aggregate into large intracellular structures, but whether these end-stage aggregates or their on-pathway intermediates are responsible for cytotoxicity is still debated. HTTEx1 can be separated into three domains: an N-terminal 17 amino acid region, the polyglutamine (polyQ) expansion and a C-terminal proline rich domain (PRD). Alongside the expanded polyQ, these flanking domains influence the aggregation propensity of HTTEx1: with the N17 initiating and promoting aggregation, and the PRD modulating it. In this study we focus on the first 11 amino acids of the PRD, a stretch of pure prolines, which are an evolutionary recent addition to the expanding polyQ region. We hypothesize that this proline region is expanding alongside the polyQ to counteract its ability to misfold and cause toxicity, and that expanding this proline region would be overall beneficial. We generated HTTEx1 mutants lacking both flanking domains singularly, missing the first 11 prolines of the PRD, or with this stretch of prolines expanded. We then followed their aggregation landscape in vitro with a battery of biochemical assays, and in vivo in novel models of C. elegans expressing the HTTEx1 mutants pan-neuronally. Employing fluorescence lifetime imaging we could observe the aggregation propensity of all HTTEx1 mutants during aging and correlate this with toxicity via various phenotypic assays. We found that the presence of an expanded proline stretch is beneficial in maintaining HTTEx1 soluble over time, regardless of polyQ length. However, the expanded prolines were only advantageous in promoting the survival and fitness of an organism carrying a pathogenic stretch of Q48 but were extremely deleterious to the nematode expressing a physiological stretch of Q23. Our results reveal the unique importance of the prolines which have and still are evolving alongside expanding glutamines to promote the function of HTTEx1 and avoid pathology.
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Affiliation(s)
- Maria Lucia Pigazzini
- Department of Molecular Physiology and Cell Biology, Leibniz Research Institute for Molecular Pharmacology in the Forschungsverbund Berlin e.V. (FMP), Berlin, Germany,NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Mandy Lawrenz
- Department of Molecular Physiology and Cell Biology, Leibniz Research Institute for Molecular Pharmacology in the Forschungsverbund Berlin e.V. (FMP), Berlin, Germany
| | - Anca Margineanu
- Advanced Light Microscopy, Max-Delbrück Centrum for Molecular Medicine (MDC), Berlin, Germany
| | - Gabriele S. Kaminski Schierle
- Molecular Neuroscience Group, Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, United Kingdom
| | - Janine Kirstein
- Department of Molecular Physiology and Cell Biology, Leibniz Research Institute for Molecular Pharmacology in the Forschungsverbund Berlin e.V. (FMP), Berlin, Germany,Department of Cell Biology, University of Bremen, Bremen, Germany,*Correspondence: Janine Kirstein,
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6
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Ceccon A, Tugarinov V, Clore GM. Quantitative Exchange NMR-Based Analysis of Huntingtin-SH3 Interactions Suggests an Allosteric Mechanism of Inhibition of Huntingtin Aggregation. J Am Chem Soc 2021; 143:9672-9681. [PMID: 34137596 DOI: 10.1021/jacs.1c04786] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Huntingtin polypeptides (httex1), encoded by exon 1 of the htt gene and containing an expanded polyglutamine tract, form fibrils that accumulate within neuronal inclusion bodies, resulting in the fatal neurodegenerative condition known as Huntington's disease. Httex1 comprises three regions: a 16-residue N-terminal amphiphilic domain (NT), a polyglutamine tract of variable length (Qn), and a polyproline-rich domain containing two polyproline tracts. The NT region of httex1 undergoes prenucleation transient oligomerization on the sub-millisecond time scale, resulting in a productive tetramer that promotes self-association and nucleation of the polyglutamine tracts. Here we show that binding of Fyn SH3, a small intracellular proline-binding domain, to the first polyproline tract of httex1Q35 inhibits fibril formation by both NMR and a thioflavin T fluorescence assay. The interaction of Fyn SH3 with httex1Q7 was investigated using NMR experiments designed to probe kinetics and equilibria at atomic resolution, including relaxation dispersion, and concentration-dependent exchange-induced chemical shifts and transverse relaxation in the rotating frame. Sub-millisecond exchange between four species is demonstrated: two major states comprising free (P) and SH3-bound (PL) monomeric httex1Q7, and two sparsely populated dimers in which either both subunits (P2L2) or only a single subunit (P2L) is bound to SH3. Binding of SH3 increases the helical propensity of the NT domain, resulting in a 25-fold stabilization of the P2L2 dimer relative to the unliganded P2 dimer. The P2L2 dimer, in contrast to P2, does not undergo any detectable oligomerization to a tetramer, thereby explaining the allosteric inhibition of httex1 fibril formation by Fyn SH3.
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Affiliation(s)
- Alberto Ceccon
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - Vitali Tugarinov
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - G Marius Clore
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
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7
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Kastano K, Mier P, Andrade-Navarro MA. The Role of Low Complexity Regions in Protein Interaction Modes: An Illustration in Huntingtin. Int J Mol Sci 2021; 22:1727. [PMID: 33572172 PMCID: PMC7915032 DOI: 10.3390/ijms22041727] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 01/25/2021] [Accepted: 02/04/2021] [Indexed: 12/11/2022] Open
Abstract
Low complexity regions (LCRs) are very frequent in protein sequences, generally having a lower propensity to form structured domains and tending to be much less evolutionarily conserved than globular domains. Their higher abundance in eukaryotes and in species with more cellular types agrees with a growing number of reports on their function in protein interactions regulated by post-translational modifications. LCRs facilitate the increase of regulatory and network complexity required with the emergence of organisms with more complex tissue distribution and development. Although the low conservation and structural flexibility of LCRs complicate their study, evolutionary studies of proteins across species have been used to evaluate their significance and function. To investigate how to apply this evolutionary approach to the study of LCR function in protein-protein interactions, we performed a detailed analysis for Huntingtin (HTT), a large protein that is a hub for interaction with hundreds of proteins, has a variety of LCRs, and for which partial structural information (in complex with HAP40) is available. We hypothesize that proteins RASA1, SYN2, and KAT2B may compete with HAP40 for their attachment to the core of HTT using similar LCRs. Our results illustrate how evolution might favor the interplay of LCRs with domains, and the possibility of detecting multiple modes of LCR-mediated protein-protein interactions with a large hub such as HTT when enough protein interaction data is available.
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Affiliation(s)
| | | | - Miguel A. Andrade-Navarro
- Institute of Organismic and Molecular Evolution, Faculty of Biology, Johannes Gutenberg University of Mainz, 55128 Mainz, Germany; (K.K.); (P.M.)
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8
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Falk AS, Bravo-Arredondo JM, Varkey J, Pacheco S, Langen R, Siemer AB. Structural Model of the Proline-Rich Domain of Huntingtin Exon-1 Fibrils. Biophys J 2020; 119:2019-2028. [PMID: 33096080 PMCID: PMC7732765 DOI: 10.1016/j.bpj.2020.10.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 08/17/2020] [Accepted: 10/13/2020] [Indexed: 01/09/2023] Open
Abstract
Huntington's disease is a heritable neurodegenerative disease that is caused by a CAG expansion in the first exon of the huntingtin gene. This expansion results in an elongated polyglutamine domain that increases the propensity of huntingtin exon-1 to form cross-β fibrils. Although the polyglutamine domain is important for fibril formation, the dynamic, C-terminal proline-rich domain (PRD) of huntingtin exon-1 makes up a large fraction of the fibril surface. Because potential fibril toxicity has to be mediated by interactions of the fibril surface with its cellular environment, we wanted to model the conformational space adopted by the PRD. We ran 800-ns long molecular dynamics simulations of the PRD using an explicit water model optimized for intrinsically disordered proteins. These simulations accurately predicted our previous solid-state NMR data and newly acquired electron paramagnetic resonance double electron-electron resonance distances, lending confidence in their accuracy. The simulations show that the PRD generally forms an imperfect polyproline (polyP) II helical conformation. The two polyP regions within the PRD stay in a polyP II helix for most of the simulation, whereas occasional kinks in the proline-rich linker region cause an overall bend in the PRD structure. The dihedral angles of the glycine at the end of the second polyP region are very variable, effectively decoupling the highly dynamic 12 C-terminal residues from the rest of the PRD.
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Affiliation(s)
- Alexander S Falk
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - José M Bravo-Arredondo
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Jobin Varkey
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Sayuri Pacheco
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Ralf Langen
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California
| | - Ansgar B Siemer
- Department of Physiology & Neuroscience, Zilkha Neurogenetic Institute, Keck School of Medicine of USC, Los Angeles, California.
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Tousley A, Iuliano M, Weisman E, Sapp E, Zhang N, Vodicka P, Alexander J, Aviolat H, Gatune L, Reeves P, Li X, Khvorova A, Ellerby LM, Aronin N, DiFiglia M, Kegel-Gleason KB. Rac1 Activity Is Modulated by Huntingtin and Dysregulated in Models of Huntington's Disease. J Huntingtons Dis 2020; 8:53-69. [PMID: 30594931 PMCID: PMC6398565 DOI: 10.3233/jhd-180311] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Background: Previous studies suggest that Huntingtin, the protein mutated in Huntington’s disease (HD), is required for actin based changes in cell morphology, and undergoes stimulus induced targeting to plasma membranes where it interacts with phospholipids involved in cell signaling. The small GTPase Rac1 is a downstream target of growth factor stimulation and PI 3-kinase activity and is critical for actin dependent membrane remodeling. Objective: To determine if Rac1 activity is impaired in HD or regulated by normal Huntingtin. Methods: Analyses were performed in differentiated control and HD human stem cells and HD Q140/Q140 knock-in mice. Biochemical methods included SDS-PAGE, western blot, immunoprecipitation, affinity chromatography, and ELISA based Rac activity assays. Results: Basal Rac1 activity increased following depletion of Huntingtin with Huntingtin specific siRNA in human primary fibroblasts and in human control neuron cultures. Human cells (fibroblasts, neural stem cells, and neurons) with the HD mutation failed to increase Rac1 activity in response to growth factors. Rac1 activity levels were elevated in striatum of 1.5-month-old HD Q140/Q140 mice and in primary embryonic cortical neurons from HD mice. Affinity chromatography analysis of striatal lysates showed that Huntingtin is in a complex with Rac1, p85α subunit of PI 3-kinase, and the actin bundling protein α-actinin and interacts preferentially with the GTP bound form of Rac1. The HD mutation reduced Huntingtin interaction with p85α. Conclusions: These findings suggest that Huntingtin regulates Rac1 activity as part of a coordinated response to growth factor signaling and this function is impaired early in HD.
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Affiliation(s)
- Adelaide Tousley
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Maria Iuliano
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Elizabeth Weisman
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Ellen Sapp
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Ningzhe Zhang
- Buck Institute for Research on Aging, Novato, CA, USA
| | - Petr Vodicka
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Jonathan Alexander
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Hubert Aviolat
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Leah Gatune
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Patrick Reeves
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Xueyi Li
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Anastasia Khvorova
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA
| | | | - Neil Aronin
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, MA, USA.,Department of Medicine and Cell Biology, University of Massachusetts Medical School, Worcester, MA, USA
| | - Marian DiFiglia
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
| | - Kimberly B Kegel-Gleason
- Department of Neurology, Laboratory of Cellular Neurobiology, Massachusetts General Hospital, Charlestown, MA, USA
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Abstract
Huntingtin (HTT) is an essential protein during early embryogenesis and the development of the central nervous system (CNS). Conditional knock-out of mouse Huntingtin (Htt) expression in the CNS beginning during neural development, as well as reducing Htt expression only during embryonic and early postnatal stages, results in neurodegeneration in the adult brain. These findings suggest that HTT is important for the development and/or maintenance of the CNS, but they do not address the question of whether HTT is required specifically in the adult CNS for its normal functions and/or homeostasis. Recently, it was reported that although removing Htt expression in young adult mice causes lethality due to acute pancreatitis, loss of Htt expression in the adult brain is well tolerated and does not result in either motor deficits or neurodegeneration for up to 7 months after Htt inactivation. However, recent studies have also demonstrated that HTT participates in several cellular functions that are important for neuronal homeostasis and survival including sensing reactive oxygen species (ROS), DNA damage repair, and stress responses, in addition to its role in selective macroautophagy. In this review, HTT's functions in development and in the adult CNS will be discussed in the context of these recent discoveries, together with a discussion of their potential impact on the design of therapeutic strategies for Huntington's disease (HD) aimed at lowering total HTT expression.
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Affiliation(s)
| | - Scott O. Zeitlin
- Correspondence to: Scott O. Zeitlin, Ph.D., Department of Neuroscience, University of Virginia School of Medicine, 409 Lane Rd., Box 801392, MR4-5022, Charlottesville, VA 22908, USA. Tel.: +1 434 924 5011; Fax: +1 434 982 4380; E-mail:
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11
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André EA, Braatz EM, Liu JP, Zeitlin SO. Generation and Characterization of Knock-in Mouse Models Expressing Versions of Huntingtin with Either an N17 or a Combined PolyQ and Proline-Rich Region Deletion. J Huntingtons Dis 2017; 6:47-62. [PMID: 28211815 PMCID: PMC5389044 DOI: 10.3233/jhd-160231] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Background: The polyglutamine (polyQ) stretch of the Huntingtin protein (HTT) in mammals is flanked by a highly conserved 17 amino acid N-terminal domain (N17), and a proline-rich region (PRR). The PRR is a binding site for many HTT-interacting proteins, and the N17 domain regulates several normal HTT functions, including HTT’s ability to associate with membranes and organelles. Objective: This study investigates the consequence of deleting mouse Huntingtin’s (Htt’s) N17 domain or a combination of its polyQ stretch and PRR (QP) on normal Htt function in mice. Methods: Knock-in mice expressing versions of Htt lacking either the N17 domain (HttΔN17) or both the polyQ and PRR domains (HttΔQP) were generated, and their behavior, autophagy function, and neuropathology were evaluated. Results: Homozygous and hemizygous HttΔQP/ΔQP, HttΔN17/ΔN17, HttΔQP/–, and HttΔN17/– mice were generated at the expected Mendelian frequency. HttΔQP/ΔQP mutants exhibit improvements in motor coordination compared to controls (Htt+/+). In contrast, HttΔN17/ΔN17 mutants do not exhibit any changes in motor coordination, but they do display variable changes in spatial learning that are dependent on their age at testing. Neither mutant exhibited any changes in basal autophagy in comparison to controls, but thalamostriatal synapses in the dorsal striatum of 24-month-old HttΔN17/ΔN17 mice were decreased compared to controls. Conclusions: These findings support the hypothesis that Htt’s N17 and QP domains are dispensable for its critical functions during early embryonic development, but are likely more important for Htt functions in CNS development or maintenance.
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Affiliation(s)
| | | | | | - Scott O. Zeitlin
- Correspondence to: Scott O. Zeitlin, Ph.D., Department of Neuroscience, University of Virginia School of Medicine, 409 Lane Rd., Box 801392, MR4-5022, Charlottesville, VA 22908 USA. Tel.: +1 434 924 5011; Fax: +1 434 982 4380; E-mail:
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Akbergenova Y, Littleton JT. Pathogenic Huntington Alters BMP Signaling and Synaptic Growth through Local Disruptions of Endosomal Compartments. J Neurosci 2017; 37:3425-39. [PMID: 28235896 DOI: 10.1523/JNEUROSCI.2752-16.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 02/07/2017] [Accepted: 02/13/2017] [Indexed: 01/05/2023] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by expansion of a polyglutamine (polyQ) stretch within the Huntingtin (Htt) protein. Pathogenic Htt disrupts multiple neuronal processes, including gene expression, axonal trafficking, proteasome and mitochondrial activity, and intracellular vesicle trafficking. However, the primary pathogenic mechanism and subcellular site of action for mutant Htt are still unclear. Using a Drosophila HD model, we found that pathogenic Htt expression leads to a profound overgrowth of synaptic connections that correlates directly with the levels of Htt at nerve terminals. Branches of the same nerve containing different levels of Htt show distinct phenotypes, indicating that Htt acts locally to disrupt synaptic growth. The effects of pathogenic Htt on synaptic growth arise from defective synaptic endosomal trafficking, leading to expansion of a recycling endosomal signaling compartment containing Sorting Nexin 16 and a reduction in late endosomes containing Rab11. The disruption of endosomal compartments leads to elevated BMP signaling within nerve terminals, driving excessive synaptic growth. Blocking aberrant signaling from endosomes or reducing BMP activity ameliorates the severity of HD pathology and improves viability. Pathogenic Htt is present largely in a nonaggregated form at synapses, indicating that cytosolic forms of the protein are likely to be the toxic species that disrupt endosomal signaling. Our data indicate that pathogenic Htt acts locally at nerve terminals to alter trafficking between endosomal compartments, leading to defects in synaptic structure that correlate with pathogenesis and lethality in the Drosophila HD model.SIGNIFICANCE STATEMENT Huntington's disease (HD) is the most commonly inherited polyglutamine expansion disorder, but how mutant Huntingtin (Htt) disrupts neuronal function is unclear. In particular, it is unknown within what subcellular compartment pathogenic Htt acts and whether the pathogenesis is associated with aggregated or more soluble forms of the protein. Using a Drosophila HD model, we find that nonaggregated pathogenic Htt acts locally at synaptic terminals to disrupt endosomal compartments, leading to aberrant wiring defects. Genetic manipulations to increase endosomal trafficking of synaptic growth receptors from signaling endosomes or to reduce BMP signaling reduce pathology in this HD model. These data indicate that pathogenic Htt can act locally within nerve terminals to disrupt synaptic endosomal signaling and induce neuropathology.
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Neveklovska M, Clabough EBD, Steffan JS, Zeitlin SO. Deletion of the huntingtin proline-rich region does not significantly affect normal huntingtin function in mice. J Huntingtons Dis 2016; 1:71-87. [PMID: 22956985 DOI: 10.3233/jhd-2012-120016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The N-terminus of Huntingtin, the protein encoded by the Huntington's disease gene, contains a stretch of polyglutamine residues that is expanded in Huntington's disease. The polyglutamine stretch is flanked by two conserved protein domains in vertebrates: an N1-17 domain, and a proline-rich region (PRR). The PRR can modulate the structure of the adjacent polyglutamine stretch, and is a binding site for several interacting proteins. To determine the role of the PRR in Huntingtin function, we have generated a knock-in allele of the mouse Huntington's disease gene homolog that expresses full-length normal huntingtin lacking the PRR. Mice that are homozygous for the huntingtin PRR deletion are born at the normal Mendelian frequency, suggesting that the PRR is not required for essential huntingtin functions during embryonic development. Moreover, adult homozygous mutants did not exhibit any significant differences from wild-type controls in general motor function and motor learning. However, 18 month-old male, but not female, homozygous PRR deletion mutants exhibited deficits in the Morris water task, suggesting that age-dependent spatial learning and memory may be affected in a sex-specific fashion by the huntingtin PRR deletion.
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Affiliation(s)
- Michelle Neveklovska
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, Virginia, USA
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Choudhury KR, Bucha S, Baksi S, Mukhopadhyay D, Bhattacharyya NP. Chaperone-like protein HYPK and its interacting partners augment autophagy. Eur J Cell Biol 2016; 95:182-94. [PMID: 27067261 DOI: 10.1016/j.ejcb.2016.03.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 03/24/2016] [Accepted: 03/29/2016] [Indexed: 12/26/2022] Open
Abstract
To decipher the function(s) of HYPK, a huntingtin (HTT)-interacting protein with chaperone-like activity, we had previously identified 36 novel interacting partners of HYPK. Another 13 proteins were known earlier to be associated with HYPK. On the basis of analysis of the interacting partners of HYPK, it has been shown that HYPK may participate in diverse cellular functions relevant to Huntington's disease. In the present study, we identified additional 5 proteins by co-immunoprecipitation and co-localization. As of now we have 54 primary interactors of HYPK. From the database we collected 1026 unique proteins (secondary interactors) interacting with these 54 primary HYPK interacting partners. We observed that 10 primary and 91 secondary interacting proteins of HYPK are associated with two types of autophagy processes. We next tested the hypothesis that the hub, HYPK, might itself be involved in autophagy. Using mouse striatal STHdh(Q7)/Hdh(Q7) cell lines, we observed that over expression of HYPK significantly increased background cellular autophagy, while knock down of endogenous HYPK decreased the autophagy level as detected by altered LC3I conversion, BECN1 expression, cleavage of GFP from LC3-GFP, ATG5-ATG12 conjugate formation and expression of transcription factors like Tfeb, Srebp2 and Zkscan3. This result shows that HYPK, possibly with its interacting partners, induces autophagy. We further observed that N-terminal mutant HTT reduced the cellular levels of LC3II and BECN1, which could be recovered significantly upon over expression of HYPK in these cells. This result further confirms that HYPK could also be involved in clearing mutant HTT aggregates by augmenting autophagy pathway.
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Affiliation(s)
- Kamalika Roy Choudhury
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata 700 064, India.
| | - Sudha Bucha
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata 700 064, India.
| | - Shounak Baksi
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata 700 064, India.
| | - Debashis Mukhopadhyay
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata 700 064, India.
| | - Nitai P Bhattacharyya
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF, Bidhan Nagar, Kolkata 700 064, India.
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Chandrasekaran S, Bonchev D. Network analysis of human post-mortem microarrays reveals novel genes, microRNAs, and mechanistic scenarios of potential importance in fighting huntington's disease. Comput Struct Biotechnol J 2016; 14:117-130. [PMID: 27924190 PMCID: PMC5128196 DOI: 10.1016/j.csbj.2016.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 01/28/2016] [Accepted: 02/02/2016] [Indexed: 01/18/2023] Open
Abstract
Huntington's disease is a progressive neurodegenerative disorder characterized by motor disturbances, cognitive decline, and neuropsychiatric symptoms. In this study, we utilized network-based analysis in an attempt to explore and understand the underlying molecular mechanism and to identify critical molecular players of this disease condition. Using human post-mortem microarrays from three brain regions (cerebellum, frontal cortex and caudate nucleus) we selected in a four-step procedure a seed set of highly modulated genes. Several protein-protein interaction networks, as well as microRNA-mRNA networks were constructed for these gene sets with the Elsevier Pathway Studio software and its associated ResNet database. We applied a gene prioritizing procedure based on vital network topological measures, such as high node connectivity and centrality. Adding to these criteria the guilt-by-association rule and exploring their innate biomolecular functions, we propose 19 novel genes from the analyzed microarrays, from which CEBPA, CDK1, CX3CL1, EGR1, E2F1, ERBB2, LRP1, HSP90AA1 and ZNF148 might be of particular interest for experimental validation. A possibility is discussed for dual-level gene regulation by both transcription factors and microRNAs in Huntington's disease mechanism. We propose several possible scenarios for experimental studies initiated via the extra-cellular ligands TGFB1, FGF2 and TNF aiming at restoring the cellular homeostasis in Huntington's disease.
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Affiliation(s)
- Sreedevi Chandrasekaran
- Center for the Study of Biological Complexity, Virginia Commonwealth University, Richmond, VA, USA
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Bowles KR, Brooks SP, Dunnett SB, Jones L. Huntingtin Subcellular Localisation Is Regulated by Kinase Signalling Activity in the StHdhQ111 Model of HD. PLoS One 2015; 10:e0144864. [PMID: 26660732 PMCID: PMC4679340 DOI: 10.1371/journal.pone.0144864] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2015] [Accepted: 11/23/2015] [Indexed: 12/03/2022] Open
Abstract
Huntington's disease is a neurodegenerative disorder characterised primarily by motor abnormalities, and is caused by an expanded polyglutamine repeat in the huntingtin protein. Huntingtin dynamically shuttles between subcellular compartments, and the mutant huntingtin protein is mislocalised to cell nuclei, where it may interfere with nuclear functions, such as transcription. However, the mechanism by which mislocalisation of mutant huntingtin occurs is currently unknown. An immortalised embryonic striatal cell model of HD (StHdhQ111) was stimulated with epidermal growth factor in order to determine whether the subcellular localisation of huntingtin is dependent on kinase signalling pathway activation. Aberrant phosphorylation of AKT and MEK signalling pathways was identified in cells carrying mutant huntingtin. Activity within these pathways was found to contribute to the regulation of huntingtin and mutant huntingtin localisation, as well as to the expression of immediate-early genes. We propose that altered kinase signalling is a phenotype of Huntington's disease that occurs prior to cell death; specifically, that altered kinase signalling may influence huntingtin localisation, which in turn may impact upon nuclear processes such as transcriptional regulation. Aiming to restore the balance of activity between kinase signalling networks may therefore prove to be an effective approach to delaying Huntington's disease symptom development and progression.
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Affiliation(s)
- Kathryn R. Bowles
- Institute of Psychological Medicine and Clinical Neurosciences, MRC centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Hadyn Ellis building, Maindy Road, Cardiff University, Cardiff CF24 4HQ, Wales, United Kingdom
| | - Simon P. Brooks
- The Brain Repair Group, School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AX, Wales, United Kingdom
| | - Stephen B. Dunnett
- The Brain Repair Group, School of Biosciences, Cardiff University, Museum Avenue, Cardiff CF10 3AX, Wales, United Kingdom
| | - Lesley Jones
- Institute of Psychological Medicine and Clinical Neurosciences, MRC centre for Neuropsychiatric Genetics and Genomics, School of Medicine, Hadyn Ellis building, Maindy Road, Cardiff University, Cardiff CF24 4HQ, Wales, United Kingdom
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Liu Y, Liu T, Sun Q, Niu M, Jiang Y, Pang D. Downregulation of Ras GTPase‑activating protein 1 is associated with poor survival of breast invasive ductal carcinoma patients. Oncol Rep 2014; 33:119-24. [PMID: 25394563 DOI: 10.3892/or.2014.3604] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 09/15/2014] [Indexed: 11/05/2022] Open
Abstract
Ras GTPase‑activating protein 1 (RASA1) functions to inactivate Ras‑GTPase and inhibit the mitogenic signal. Reduction or loss of RASA1 expression occurs during human cancer development and progression. This study investigated RASA1 expression in normal and breast cancer tissue specimens to determine the association with prognosis of breast cancer patients. Two sets of patient samples (45 fresh tissues and 373 paraffin‑embedded tissues) were analyzed for RASA1 expression using RT‑qPCR and immunohisto-chemistry. The results showed that the expression of RASA1 mRNA was lower in breast cancer tissues than in the corresponding normal tissues (P<0.001). Additionally, RASA1 expression was reduced in 60.6% (226/373) of breast cancer tissues. The reduced RASA1 expression was significantly associated with tumor lymph node metastasis (P=0.002), advanced TNM stages (P=0.017), estrogen receptor (ER) expression (P=0.002), Ki‑67 (P=0.009), higher histological grade (P<0.001), and triple‑negative breast cancer (P=0.041). Moreover, the reduced RASA1 expression was associated with shorter disease‑free survival (P=0.036) and overall survival (P<0.001) of breast cancer patients. RASA1 expression, together with tumor lymph‑node metastasis, TNM stage, Her‑2 expression, and triple‑negative breast cancer were independent factors in predicting survival of breast cancer patients. In conclusion, RASA1 expression is frequently reduced in breast cancer tissues, and the reduced RASA1 expression is associated with breast cancer progression and poor survival and disease‑free survival of patients.
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Affiliation(s)
- Yang Liu
- Department of Breast Surgery, The Affiliated Cancer Hospital, Harbin Medical University, Nangang, Harbin, Heilongjiang, P.R. China
| | - Tong Liu
- Department of Breast Surgery, The Affiliated Cancer Hospital, Harbin Medical University, Nangang, Harbin, Heilongjiang, P.R. China
| | - Qian Sun
- Department of Breast Surgery, The Affiliated Cancer Hospital, Harbin Medical University, Nangang, Harbin, Heilongjiang, P.R. China
| | - Ming Niu
- Department of Breast Surgery, The Affiliated Cancer Hospital, Harbin Medical University, Nangang, Harbin, Heilongjiang, P.R. China
| | - Yang Jiang
- Department of Pathology, The Affiliated Cancer Hospital, Harbin Medical University, Nangang, Harbin, Heilongjiang, P.R. China
| | - Da Pang
- Department of Breast Surgery, The Affiliated Cancer Hospital, Harbin Medical University, Nangang, Harbin, Heilongjiang, P.R. China
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Baksi S, Basu S, Mukhopadhyay D. Mutant huntingtin replaces Gab1 and interacts with C-terminal SH3 domain of growth factor receptor binding protein 2 (Grb2). Neurosci Res 2014; 87:77-83. [DOI: 10.1016/j.neures.2014.06.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 06/18/2014] [Accepted: 06/25/2014] [Indexed: 10/25/2022]
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de Oliveira GP, Maximino JR, Maschietto M, Zanoteli E, Puga RD, Lima L, Carraro DM, Chadi G. Early gene expression changes in skeletal muscle from SOD1(G93A) amyotrophic lateral sclerosis animal model. Cell Mol Neurobiol 2014; 34:451-62. [PMID: 24442855 DOI: 10.1007/s10571-014-0029-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Accepted: 01/07/2014] [Indexed: 02/07/2023]
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by loss of motor neurons. Familial ALS is strongly associated to dominant mutations in the gene for Cu/Zn superoxide dismutase (SOD1). Recent evidences point to skeletal muscle as a primary target in the ALS mouse model. Wnt/PI3 K signaling pathways and epithelial-mesenchymal transition (EMT) have important roles in maintenance and repair of skeletal muscle. Wnt/PI3 K pathways and EMT gene expression profile were investigated in gastrocnemius muscle from SOD1(G93A) mouse model and age-paired wild-type control in the presymptomatic ages of 40 and 80 days aiming the early neuromuscular abnormalities that precede motor neuron death in ALS. A customized cDNA microarray platform containing 326 genes of Wnt/PI3 K and EMT was used and results revealed eight up-regulated (Loxl2, Pik4ca, Fzd9, Cul1, Ctnnd1, Snf1lk, Prkx, Dner) and nine down-regulated (Pik3c2a, Ripk4, Id2, C1qdc1, Eif2ak2, Rac3, Cds1, Inppl1, Tbl1x) genes at 40 days, and also one up-regulated (Pik3ca) and five down-regulated (Cd44, Eef2 k, Fzd2, Crebbp, Piki3r1) genes at 80 days. Also, protein-protein interaction networks grown from the differentially expressed genes of 40 and 80 days old mice have identified Grb2 and Src genes in both presymptomatic ages, thus playing a potential central role in the disease mechanisms. mRNA and protein levels for Grb2 and Src were found to be increased in 80 days old ALS mice. Gene expression changes in the skeletal muscle of transgenic ALS mice at presymptomatic periods of disease gave further evidence of early neuromuscular abnormalities that precede motor neuron death. The results were discussed in terms of initial triggering for neuronal degeneration and muscle adaptation to keep function before the onset of symptoms.
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Affiliation(s)
- Gabriela P de Oliveira
- Neuroregeneration Center, Department of Neurology, University of São Paulo School of Medicine, Av. Dr. Arnaldo, 455, 2nd Floor, Room 2119, São Paulo, 01246-903, Brazil
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Baksi S, Jana NR, Bhattacharyya NP, Mukhopadhyay D. Grb2 is regulated by foxd3 and has roles in preventing accumulation and aggregation of mutant huntingtin. PLoS One 2013; 8:e76792. [PMID: 24116161 PMCID: PMC3792889 DOI: 10.1371/journal.pone.0076792] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 09/03/2013] [Indexed: 11/18/2022] Open
Abstract
Growth factor receptor protein binding protein 2 (Grb2) is known to be associated with intracellular growth and proliferation related signaling cascades. Huntingtin (Htt), a ubiquitously expressed protein, when mutated, forms toxic intracellular aggregates - the hallmark of Huntington’s disease (HD). We observed an elevated expression of Grb2 in neuronal cells in animal and cell models of HD. Grb2 overexpression was predominantly regulated by the transcription factor Forkhead Box D3 (Foxd3). Exogenous expression of Grb2 also reduced aggregation of mutant Htt in Neuro2A cells. Grb2 is also known to interact with Htt, depending on epidermal growth factor receptor (EGFR) activation. Grb2- mutant Htt interaction in the contrary, took place in vesicular structures, independent of EGFR activation that eventually merged with autophagosomes and activated the autophagy machinery helping in autophagosome and lysosome fusion. Grb2, with its emerging dual role, holds promise for a survival mechanism for HD.
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Affiliation(s)
- Shounak Baksi
- Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India
| | - Nihar R. Jana
- Division of Cellular and Molecular Neuroscience, National Brain Research Centre, Manesar, Haryana, India
| | | | - Debashis Mukhopadhyay
- Structural Genomics Division, Saha Institute of Nuclear Physics, Kolkata, India
- * E-mail:
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Drost J, Nonis D, Eich F, Leske O, Damrath E, Brunt ER, Lastres-Becker I, Heumann R, Nowock J, Auburger G. Ataxin-2 modulates the levels of Grb2 and SRC but not ras signaling. J Mol Neurosci 2013; 51:68-81. [PMID: 23335000 PMCID: PMC3739869 DOI: 10.1007/s12031-012-9949-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 12/28/2012] [Indexed: 12/13/2022]
Abstract
Ataxin-2 (ATXN2) is implicated mainly in mRNA processing. Some ATXN2 associates with receptor tyrosine kinases (RTK), inhibiting their endocytic internalization through interaction of proline-rich domains (PRD) in ATXN2 with SH3 motifs in Src. Gain of function of ATXN2 leads to neuronal atrophy in the diseases spinocerebellar ataxia type 2 (SCA2) and amyotrophic lateral sclerosis (ALS). Conversely, ATXN2 knockout (KO) mice show hypertrophy and insulin resistance. To elucidate the influence of ATXN2 on trophic regulation, we surveyed interactions of ATXN2 with SH3 motifs from numerous proteins and observed a novel interaction with Grb2. Direct binding in glutathione S-transferase (GST) pull-down assays and coimmunoprecipitation of the endogenous proteins indicated a physiologically relevant association. In SCA2 patient fibroblasts, Grb2 more than Src protein levels were diminished, with an upregulation of both transcripts suggesting enhanced protein turnover. In KO mouse embryonal fibroblasts (MEF), the protein levels of Grb2 and Src were decreased. ATXN2 absence by itself was insufficient to significantly change Grb2-dependent signaling for endogenous Ras levels, Ras-GTP levels, and kinetics as well as MEK1 phosphorylation, suggesting that other factors compensate for proliferation control. In KO tissue with postmitotic neurons, a significant decrease of Src protein levels is prominent rather than Grb2. ATXN2 mutations modulate the levels of several components of the RTK endocytosis complex and may thus contribute to alter cell proliferation as well as translation and growth.
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Affiliation(s)
- Jessica Drost
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - David Nonis
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
- Present Address: Department of Reproductive Medicine, University of California at San Diego, School of Medicine, 9500 Gilman Dr., La Jolla, CA 92093-0633 USA
| | - Florian Eich
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - Oliver Leske
- Department Molecular Neurobiochemistry, Faculty for Chemistry and Biochemistry, Ruhr-University Bochum, Universitätsstraβe 150, 44780 Bochum, Germany
| | - Ewa Damrath
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - Ewout R. Brunt
- Department of Neurology, University Medical Centre Groningen, University of Groningen, Hanzeplein 1, 9713 RB Groningen, The Netherlands
| | - Isabel Lastres-Becker
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
- Present Address: Departamento de Bioquímica, Instituto de Investigaciones Biomédicas “Alberto Sols”, and Centro de Investigación en Red en Enfermedades Neurodegenerativas (CIBERNED), Madrid, Spain
| | - Rolf Heumann
- Department Molecular Neurobiochemistry, Faculty for Chemistry and Biochemistry, Ruhr-University Bochum, Universitätsstraβe 150, 44780 Bochum, Germany
| | - Joachim Nowock
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
| | - Georg Auburger
- Section Experimental Neurology, Department of Neurology, Goethe University Medical School, Building 89, 3rd Floor, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
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Nguyen GD, Gokhan S, Molero AE, Mehler MF. Selective roles of normal and mutant huntingtin in neural induction and early neurogenesis. PLoS One 2013; 8:e64368. [PMID: 23691206 PMCID: PMC3653864 DOI: 10.1371/journal.pone.0064368] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/12/2013] [Indexed: 01/08/2023] Open
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by abnormal polyglutamine expansion in the amino-terminal end of the huntingtin protein (Htt) and characterized by progressive striatal and cortical pathology. Previous reports have shown that Htt is essential for embryogenesis, and a recent study by our group revealed that the pathogenic form of Htt (mHtt) causes impairments in multiple stages of striatal development. In this study, we have examined whether HD-associated striatal developmental deficits are reflective of earlier maturational alterations occurring at the time of neurulation by assessing differential roles of Htt and mHtt during neural induction and early neurogenesis using an in vitro mouse embryonic stem cell (ESC) clonal assay system. We demonstrated that the loss of Htt in ESCs (KO ESCs) severely disrupts the specification of primitive and definitive neural stem cells (pNSCs, dNSCs, respectively) during the process of neural induction. In addition, clonally derived KO pNSCs and dNSCs displayed impaired proliferative potential, enhanced cell death and altered multi-lineage potential. Conversely, as observed in HD knock-in ESCs (Q111 ESCs), mHtt enhanced the number and size of pNSC clones, which exhibited enhanced proliferative potential and precocious neuronal differentiation. The transition from Q111 pNSCs to fibroblast growth factor 2 (FGF2)-responsive dNSCs was marked by potentiation in the number of dNSCs and altered proliferative potential. The multi-lineage potential of Q111 dNSCs was also enhanced with precocious neurogenesis and oligodendrocyte progenitor elaboration. The generation of Q111 epidermal growth factor (EGF)-responsive dNSCs was also compromised, whereas their multi-lineage potential was unaltered. These abnormalities in neural induction were associated with differential alterations in the expression profiles of Notch, Hes1 and Hes5. These cumulative observations indicate that Htt is required for multiple stages of neural induction, whereas mHtt enhances this process and promotes precocious neurogenesis and oligodendrocyte progenitor cell elaboration.
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Affiliation(s)
- Giang D. Nguyen
- Roslyn and Leslie Goldstein Laboratory for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Institute for Brain Disorders and Neural Regeneration, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Rose F. Kennedy Center for Research on Intellectual and Developmental Disabilities, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Solen Gokhan
- Roslyn and Leslie Goldstein Laboratory for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Institute for Brain Disorders and Neural Regeneration, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Neurology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Rose F. Kennedy Center for Research on Intellectual and Developmental Disabilities, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Aldrin E. Molero
- Roslyn and Leslie Goldstein Laboratory for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Institute for Brain Disorders and Neural Regeneration, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Neurology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Rose F. Kennedy Center for Research on Intellectual and Developmental Disabilities, Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Mark F. Mehler
- Roslyn and Leslie Goldstein Laboratory for Stem Cell Biology and Regenerative Medicine, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Institute for Brain Disorders and Neural Regeneration, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Neurology, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Department of Psychiatry and Behavioral Sciences, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Rose F. Kennedy Center for Research on Intellectual and Developmental Disabilities, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Einstein Cancer Center, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Ruth L. and David S. Gottesman Institute for Stem Cell and Regenerative Medicine Research, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Center for Epigenomics, Albert Einstein College of Medicine, Bronx, New York, United States of America
- Institute for Aging Research, Albert Einstein College of Medicine, Bronx, New York, United States of America
- * E-mail:
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Moreira Sousa C, McGuire JR, Thion MS, Gentien D, de la Grange P, Tezenas du Montcel S, Vincent-Salomon A, Durr A, Humbert S. The Huntington disease protein accelerates breast tumour development and metastasis through ErbB2/HER2 signalling. EMBO Mol Med 2013; 5:309-25. [PMID: 23300147 PMCID: PMC3569645 DOI: 10.1002/emmm.201201546] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2012] [Revised: 11/19/2012] [Accepted: 11/21/2012] [Indexed: 01/23/2023] Open
Abstract
In Huntington disease (HD), polyglutamine expansion in the huntingtin protein causes specific neuronal death. The consequences of the presence of mutant huntingtin in other tissues are less well understood. Here we propose that mutant huntingtin influences breast cancer progression. Indeed, we show that mammary tumours appear earlier in mouse breast cancer models expressing mutant huntingtin as compared to control mice expressing wild-type huntingtin. Tumours bearing mutant huntingtin have a modified gene expression pattern that reflects enhanced aggressiveness with the overexpression of genes favouring invasion and metastasis. In agreement, mutant huntingtin accelerates epithelial to mesenchymal transition and enhances cell motility and invasion. Also, lung metastasis is higher in HD conditions than in control mice. Finally, we report that in HD, the dynamin dependent endocytosis of the ErbB2/HER2 receptor tyrosine kinase is reduced. This leads to its accumulation and to subsequent increases in cell motility and proliferation. Our study may thus have important implications for both cancer and HD.
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Melone MA, Calarco A, Petillo O, Margarucci S, Colucci-D'Amato L, Galderisi U, Koverech G, Peluso G. Mutant huntingtin regulates EGF receptor fate in non-neuronal cells lacking wild-type protein. Biochim Biophys Acta Mol Basis Dis 2013; 1832:105-13. [DOI: 10.1016/j.bbadis.2012.09.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Revised: 08/10/2012] [Accepted: 09/04/2012] [Indexed: 12/30/2022]
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Kalathur RKR, Hernández-Prieto MA, Futschik ME. Huntington's disease and its therapeutic target genes: a global functional profile based on the HD Research Crossroads database. BMC Neurol 2012; 12:47. [PMID: 22741533 PMCID: PMC3492045 DOI: 10.1186/1471-2377-12-47] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 06/05/2012] [Indexed: 01/09/2023] Open
Abstract
Background Huntington’s disease (HD) is a fatal progressive neurodegenerative disorder caused by the expansion of the polyglutamine repeat region in the huntingtin gene. Although the disease is triggered by the mutation of a single gene, intensive research has linked numerous other genes to its pathogenesis. To obtain a systematic overview of these genes, which may serve as therapeutic targets, CHDI Foundation has recently established the HD Research Crossroads database. With currently over 800 cataloged genes, this web-based resource constitutes the most extensive curation of genes relevant to HD. It provides us with an unprecedented opportunity to survey molecular mechanisms involved in HD in a holistic manner. Methods To gain a synoptic view of therapeutic targets for HD, we have carried out a variety of bioinformatical and statistical analyses to scrutinize the functional association of genes curated in the HD Research Crossroads database. In particular, enrichment analyses were performed with respect to Gene Ontology categories, KEGG signaling pathways, and Pfam protein families. For selected processes, we also analyzed differential expression, using published microarray data. Additionally, we generated a candidate set of novel genetic modifiers of HD by combining information from the HD Research Crossroads database with previous genome-wide linkage studies. Results Our analyses led to a comprehensive identification of molecular mechanisms associated with HD. Remarkably, we not only recovered processes and pathways, which have frequently been linked to HD (such as cytotoxicity, apoptosis, and calcium signaling), but also found strong indications for other potentially disease-relevant mechanisms that have been less intensively studied in the context of HD (such as the cell cycle and RNA splicing, as well as Wnt and ErbB signaling). For follow-up studies, we provide a regularly updated compendium of molecular mechanism, that are associated with HD, at http://hdtt.sysbiolab.eu Additionally, we derived a candidate set of 24 novel genetic modifiers, including histone deacetylase 3 (HDAC3), metabotropic glutamate receptor 1 (GRM1), CDK5 regulatory subunit 2 (CDK5R2), and coactivator 1ß of the peroxisome proliferator-activated receptor gamma (PPARGC1B). Conclusions The results of our study give us an intriguing picture of the molecular complexity of HD. Our analyses can be seen as a first step towards a comprehensive list of biological processes, molecular functions, and pathways involved in HD, and may provide a basis for the development of more holistic disease models and new therapeutics.
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Affiliation(s)
- Ravi Kiran Reddy Kalathur
- Centro de Biomedicina Molecular e Estrutural, Campus de Gambelas, Universidade do Algarve, Faro, Portugal
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Abstract
The most well known effect of single amino acid repeat expansion, beyond a certain threshold, is the development of a specific disease, depending on the protein in which the expansion has occurred. For example, the expansion of the glutamine repeat in huntingtin leads to the debilitating neurodegenerative disease, Huntington's disease. Similarly, there are a range of other disorders caused by trinucleotide repeat expansions encoding polyglutamine or polyalanine tracts. The age of onset of the polyglutamine-induced neurodegenerative diseases is usually negatively correlated with the length of expanded CAG/glutamine repeat. However, recent studies have given evidence that single amino acid repeats may also play critical roles in normal protein function and that changes in the length of single amino acid repeats is likely to play a beneficial role in evolution. This chapter will look at the prevalence, function and possible role single amino acid repeats have in evolution and other biological processes.
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Affiliation(s)
- Noel Faux
- Mental Health Research Institute, The University of Melbourne, Parkville, Victoria, Australia.
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Boxall R, Porteous DJ, Thomson PA. DISC1 and Huntington's disease--overlapping pathways of vulnerability to neurological disorder? PLoS One 2011; 6:e16263. [PMID: 21298101 PMCID: PMC3027647 DOI: 10.1371/journal.pone.0016263] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 12/09/2010] [Indexed: 01/29/2023] Open
Abstract
We re-annotated the interacting partners of the neuronal scaffold protein DISC1 using a knowledge-based approach that incorporated recent protein interaction data and published literature to. This revealed two highly connected networks. These networks feature cellular function and maintenance, and cell signaling. Of potentially greatest interest was the novel finding of a high degree of connectivity between the DISC1 scaffold protein, linked to psychiatric illness, and huntingtin, the protein which is mutated in Huntington's disease. The potential link between DISC1, huntingtin and their interacting partners may open new areas of research into the effects of pathway dysregulation in severe neurological disorders.
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Affiliation(s)
- Ruth Boxall
- Medical Genetics Section, Molecular Medicine Centre, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
| | - David J. Porteous
- Medical Genetics Section, Molecular Medicine Centre, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
| | - Pippa A. Thomson
- Medical Genetics Section, Molecular Medicine Centre, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, United Kingdom
- * E-mail:
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Abstract
It has been more than 17 years since the causative mutation for Huntington's disease was discovered as the expansion of the triplet repeat in the N-terminal portion of the Huntingtin (HTT) gene. In the intervening time, researchers have discovered a great deal about Huntingtin's involvement in a number of cellular processes. However, the role of Huntingtin in the key pathogenic mechanism leading to neurodegeneration in the disease process has yet to be discovered. Here, we review the body of knowledge that has been uncovered since gene discovery and include discussions of the HTT gene, CAG triplet repeat expansion, HTT expression, protein features, posttranslational modifications, and many of its known protein functions and interactions. We also highlight potential pathogenic mechanisms that have come to light in recent years.
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Affiliation(s)
- Karen N McFarland
- Department of Neurology, University of Florida, Gainesville, FL 32610-0236, USA.
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Ginés S, Paoletti P, Alberch J. Impaired TrkB-mediated ERK1/2 activation in huntington disease knock-in striatal cells involves reduced p52/p46 Shc expression. J Biol Chem 2010; 285:21537-48. [PMID: 20442398 DOI: 10.1074/jbc.m109.084202] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Altered neurotrophic support as a result of reduced brain-derived neurotrophic factor (BDNF) expression and trafficking has been revealed as a key factor in Huntington disease (HD) pathology. BDNF binds to and activates the tyrosine kinase receptor TrkB, leading to activation of intracellular signaling pathways to promote differentiation and cell survival. In order to design new neuroprotective therapies based on BDNF delivery, it is important to define whether BDNF-mediated TrkB signaling is affected in HD. Here, we demonstrate reduced TrkB-mediated Ras/MAPK/ERK1/2 signaling but unchanged phosphatidylinositol 3-kinase/Akt and phospholipase Cgamma activation in knock-in HD striatal cells. Altered BDNF-mediated ERK1/2 activation in mutant huntingtin cells is associated with reduced expression of p52/p46 Shc docking proteins. Notably, reduced BDNF-induced ERK1/2 activation increases the sensitivity of mutant huntingtin striatal cells to oxidative damage. Accordingly, pharmacological activation of the MAPK pathway with PMA prevents cell death induced by oxidative stress. Taken together, our results suggest that in addition to reduced BDNF, diminished Ras/MAPK/ERK1/2 activation is involved in neurotrophic deficits associated with HD pathology. Therefore, pharmacological approaches aimed to directly modulate the MAPK/ERK1/2 pathway may represent a valuable therapeutic strategy in HD.
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Affiliation(s)
- Silvia Ginés
- Departament de Biologia Cel.lular, Facultat de Medicina, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, Casanova 143, E-08036 Barcelona, Spain.
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Túnez I, Tasset I, Pérez-De La Cruz V, Santamaría A. 3-Nitropropionic acid as a tool to study the mechanisms involved in Huntington's disease: past, present and future. Molecules 2010; 15:878-916. [PMID: 20335954 PMCID: PMC6263191 DOI: 10.3390/molecules15020878] [Citation(s) in RCA: 141] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 01/12/2010] [Accepted: 02/01/2010] [Indexed: 11/17/2022] Open
Abstract
Huntington's disease (HD) is an inheritable autosomal-dominant disorder whose causal mechanisms remain unknown. Experimental models have begun to uncover these pathways, thus helping to understand the mechanisms implicated and allowing for the characterization of potential targets for new therapeutic strategies. 3-Nitropropionic acid is known to produce in animals behavioural, biochemical and morphologic changes similar to those occurring in HD. For this reason, this phenotypic model is gaining attention as a valuable tool to mimick this disorder and further developing new therapies. In this review, we will focus on the past and present research of this molecule, to finally bring a perspective on what will be next in this promising field of study.
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Affiliation(s)
- Isaac Túnez
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Instituto Maimónides de Investigaciones Biomédicas de Córdoba, Universidad de Córdoba, Av. Menéndez Pidal s/n, 14004 Córdoba, Spain.
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Zheng S, Clabough EB, Sarkar S, Futter M, Rubinsztein DC, Zeitlin SO. Deletion of the huntingtin polyglutamine stretch enhances neuronal autophagy and longevity in mice. PLoS Genet 2010; 6:e1000838. [PMID: 20140187 DOI: 10.1371/journal.pgen.1000838] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 01/04/2010] [Indexed: 01/07/2023] Open
Abstract
Expansion of a stretch of polyglutamine in huntingtin (htt), the protein product of the IT15 gene, causes Huntington's disease (HD). Previous investigations into the role of the polyglutamine stretch (polyQ) in htt function have suggested that its length may modulate a normal htt function involved in regulating energy homeostasis. Here we show that expression of full-length htt lacking its polyglutamine stretch (DeltaQ-htt) in a knockin mouse model for HD (Hdh(140Q/DeltaQ)), reduces significantly neuropil mutant htt aggregates, ameliorates motor/behavioral deficits, and extends lifespan in comparison to the HD model mice (Hdh(140Q/+)). The rescue of HD model phenotypes is accompanied by the normalization of lipofuscin levels in the brain and an increase in the steady-state levels of the mammalian autophagy marker microtubule-associate protein 1 light chain 3-II (LC3-II). We also find that DeltaQ-htt expression in vitro increases autophagosome synthesis and stimulates the Atg5-dependent clearance of truncated N-terminal htt aggregates. DeltaQ-htt's effect on autophagy most likely represents a gain-of-function, as overexpression of full-length wild-type htt in vitro does not increase autophagosome synthesis. Moreover, Hdh(DeltaQ/DeltaQ) mice live significantly longer than wild-type mice, suggesting that autophagy upregulation may be beneficial both in diseases caused by toxic intracellular aggregate-prone proteins and also as a lifespan extender in normal mammals.
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Kegel KB, Sapp E, Alexander J, Valencia A, Reeves P, Li X, Masso N, Sobin L, Aronin N, DiFiglia M. Polyglutamine expansion in huntingtin alters its interaction with phospholipids. J Neurochem 2009; 110:1585-97. [PMID: 19566678 DOI: 10.1111/j.1471-4159.2009.06255.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Huntingtin has an expanded polyglutamine tract in patients with Huntington's disease. Huntingtin localizes to intracellular and plasma membranes but the function of huntingtin at membranes is unknown. Previously we reported that exogenously expressed huntingtin bound pure phospholipids using protein-lipid overlays. Here we show that endogenous huntingtin from normal (Hdh(7Q/7Q)) mouse brain and mutant huntingtin from Huntington's disease (Hdh(140Q/140Q)) mouse brain bound to large unilamellar vesicles containing phosphoinositol (PI) PI 3,4-bisphosphate, PI 3,5-bisphosphate, and PI 3,4,5-triphosphate [PI(3,4,5)P3]. Huntingtin interactions with multivalent phospholipids were similar to those of dynamin. Mutant huntingtin associated more with phosphatidylethanolamine and PI(3,4,5)P3 than did wild-type huntingtin, and associated with other phospholipids not recognized by wild-type huntingtin. Wild-type and mutant huntingtin also bound to large unilamellar vesicles containing cardiolipin, a phospholipid specific to mitochondrial membranes. Maximal huntingtin-phospholipid association required inclusion of huntingtin amino acids 171-287. Endogenous huntingtin recruited to the plasma membrane in cells that incorporated exogenous PI 3,4-bisphosphate and PI(3,4,5)P3 or were stimulated by platelet-derived growth factor or insulin growth factor 1, which both activate PI 3-kinase. These data suggest that huntingtin interacts with membranes through specific phospholipid associations and that mutant huntingtin may disrupt membrane trafficking and signaling at membranes.
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Affiliation(s)
- Kimberly B Kegel
- Laboratory of Cellular Neurobiology, Department of Neurology, Massachusetts General Hospital, 11416th Street, Room 2150, Charlestown, MA 02129, USA.
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Zhang S, Feany MB, Saraswati S, Littleton JT, Perrimon N. Inactivation of Drosophila Huntingtin affects long-term adult functioning and the pathogenesis of a Huntington's disease model. Dis Model Mech 2009; 2:247-66. [PMID: 19380309 PMCID: PMC2675792 DOI: 10.1242/dmm.000653] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2008] [Accepted: 01/14/2009] [Indexed: 11/20/2022] Open
Abstract
A polyglutamine expansion in the huntingtin (HTT) gene causes neurodegeneration in Huntington's disease (HD), but the in vivo function of the native protein (Htt) is largely unknown. Numerous biochemical and in vitro studies have suggested a role for Htt in neuronal development, synaptic function and axonal trafficking. To test these models, we generated a null mutant in the putative Drosophila HTT homolog (htt, hereafter referred to asdhtt) and, surprisingly, found that dhtt mutant animals are viable with no obvious developmental defects. Instead, dhtt is required for maintaining the mobility and long-term survival of adult animals, and for modulating axonal terminal complexity in the adult brain. Furthermore, removing endogenous dhtt significantly accelerates the neurodegenerative phenotype associated with a Drosophila model of polyglutamine Htt toxicity (HD-Q93), providing in vivo evidence that disrupting the normal function of Htt might contribute to HD pathogenesis.
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Affiliation(s)
- Sheng Zhang
- Department of Genetics
- Present address: Research Center for Neurodegenerative Diseases, The Brown Foundation Institute of Molecular Medicine, University of Texas Health Science Center at Houston, 1825 Pressler Street, Houston, TX 77030, USA
| | | | - Sudipta Saraswati
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - J. Troy Littleton
- The Picower Institute for Learning and Memory, Department of Biology and Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Norbert Perrimon
- Department of Genetics
- Howard Hughes Medical Institute, Brigham and Women’s Hospital, 77 Avenue Louis Pasteur, Harvard Medical School, Boston, MA 02115, USA
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Abstract
BACKGROUND Metastasis is the primary cause of death in most human cancers, and understanding the molecular mechanisms underpinning this multistep process is fundamental to identifying novel molecular targets and developing more effective therapies. OBJECTIVE/METHODS Here we review the role of growth factor receptor-bound protein 2 (Grb2) in cancer and specifically in metastasis-related processes, and summarize the development of anticancer therapeutics selectively targeting this adapter protein. RESULTS/CONCLUSION Grb2 is a key molecule in intracellular signal transduction, linking activated cell surface receptors to downstream targets by binding to specific phosphotyrosine-containing and proline-rich sequence motifs. Grb2 signaling is critical for cell cycle progression and actin-based cell motility, and, consequently, more complex processes such as epithelial morphogenesis, angiogenesis and vasculogenesis. These functions make Grb2 a therapeutic target for strategies designed to prevent the spread of solid tumors through local invasion and metastasis.
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Affiliation(s)
- Alessio Giubellino
- National Cancer Institute, Urologic Oncology Branch, CCR, Building 10, 10 Center Drive MSC 1107, Bethesda, MD 20892-1107, USA.
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Cavet ME, Pang J, Yin G, Berk BC. An epidermal growth factor (EGF) -dependent interaction between GIT1 and sorting nexin 6 promotes degradation of the EGF receptor. FASEB J 2008; 22:3607-16. [PMID: 18523162 DOI: 10.1096/fj.07-094086] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
G-protein coupled receptor (GPCR) kinase-2 interacting protein 1 (GIT1) is a multifunctional scaffolding protein that regulates epidermal growth factor receptor (EGFR) signaling pathways. We demonstrate that GIT1 interacts with sorting nexin 6 (SNX6), a member of the SNX family that increases EGFR trafficking between endosomes and lysosomes, thereby enhancing EGFR degradation. The GIT1-SNX6 interaction is increased 3-fold after treatment with EGF for 60 min. The second coiled-coil domain (CC2; aa 424-474) of GIT1 mediates binding to SNX6. Subcellular fractionation and confocal microscopy data indicate that GIT1 and SNX6 interact in endosomes. Knockdown of GIT1 expression by small interfering RNA decreased the rate of EGF-induced EGFR degradation. Expression of exogenous GIT1 or SNX6 alone did not alter EGFR degradation; however, coexpression of GIT1 and SNX6 decreased EGFR levels both basally and in response to EGF. In contrast, expression of GIT1(CC2 deleted) and SNX6 did not reduce EGFR levels, demonstrating that the interaction between GIT1 and SNX6 was required to regulate EGFR trafficking. Phosphorylation of the EGFR substrate phospholipase C-gamma was decreased by coexpression of GIT1 and SNX6. These data demonstrate an endosomal, EGF-regulated interaction between SNX6 and GIT1 that enhances degradation of the EGFR, and thereby alters EGFR signaling. Our findings suggest a new role for GIT1 in tyrosine kinase receptor trafficking.
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Affiliation(s)
- Megan E Cavet
- Aab Cardiovascular Research Institute and Department of Medicine, University of Rochester School of Medicine, Rochester, New York 14642, USA
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37
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Abstract
The DISC locus is located at the breakpoint of a balanced t(1;11) chromosomal translocation in a large and unique Scottish family. This translocation segregates in a highly statistically significant manner with a broad diagnosis of psychiatric illness, including schizophrenia, bipolar disorder and major depression, as well as with a narrow diagnosis of schizophrenia alone. Two novel genes were identified at this locus and due to the high prevalence of schizophrenia in this family, they were named Disrupted-in-Schizophrenia-1 (DISC1) and Disrupted-in-Schizophrenia-2 (DISC2). DISC1 encodes a novel multifunctional scaffold protein, whereas DISC2 is a putative noncoding RNA gene antisense to DISC1. A number of independent genetic linkage and association studies in diverse populations support the original linkage findings in the Scottish family and genetic evidence now implicates the DISC locus in susceptibility to schizophrenia, schizoaffective disorder, bipolar disorder and major depression as well as various cognitive traits. Despite this, with the exception of the t(1;11) translocation, robust evidence for a functional variant(s) is still lacking and genetic heterogeneity is likely. Of the two genes identified at this locus, DISC1 has been prioritized as the most probable candidate susceptibility gene for psychiatric illness, as its protein sequence is directly disrupted by the translocation. Much research has been undertaken in recent years to elucidate the biological functions of the DISC1 protein and to further our understanding of how it contributes to the pathogenesis of schizophrenia. These data are the main subject of this review; however, the potential involvement of DISC2 in the pathogenesis of psychiatric illness is also discussed. A detailed picture of DISC1 function is now emerging, which encompasses roles in neurodevelopment, cytoskeletal function and cAMP signalling, and several DISC1 interactors have also been defined as independent genetic susceptibility factors for psychiatric illness. DISC1 is a hub protein in a multidimensional risk pathway for major mental illness, and studies of this pathway are opening up opportunities for a better understanding of causality and possible mechanisms of intervention.
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Affiliation(s)
- J E Chubb
- Medical Genetics Section, The Centre for Molecular Medicine, Western General Hospital, The University of Edinburgh, Edinburgh, UK
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Abstract
Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a mutation in the gene huntingtin and characterized by motor, cognitive and psychiatric symptoms. Huntingtin contains a CAG repeat in exon 1. An expansion of this CAG repeat above 35 results in misfolding of Huntingtin, giving rise to protein aggregates and neuronal cell death. There are several transgenic HD mouse models that reproduce most of the features of the human disorder, for example protein inclusions, some neurodegeneration as well as motor and cognitive symptoms. At the same time, a subgroup of the HD transgenic mouse models exhibit dramatically reduced susceptibility to excitotoxicity. The mechanism behind this is unknown. Here, we review the literature regarding this phenomenon, attempt to explain what protein domains are crucial for this phenomenon and point toward a putative mechanism. We suggest, that the C-terminal domain of exon 1 Huntingtin, namely the proline rich domain, is responsible for mediating a neuroprotective effect against excitotoxicity. Furthermore, we point out the possible importance of this mechanism for future therapies in neurological disorders that have been suggested to be associated with excitotoxicity, for example Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.
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Affiliation(s)
- T Zuchner
- Neuronal Survival Unit, Department of Experimental Medical Science, Wallenberg Neuroscience Center, Lund University, BMC A10, Lund 22184, Sweden.
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Quilter CR, Blott SC, Wilson AE, Bagga MR, Sargent CA, Oliver GL, Southwood OI, Gilbert CL, Mileham A, Affara NA. Porcine maternal infanticide as a model for puerperal psychosis. Am J Med Genet B Neuropsychiatr Genet 2007; 144B:862-8. [PMID: 17503476 DOI: 10.1002/ajmg.b.30529] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Childbirth is a period of substantial rapid biological and psychological change and a wide range of psychotic disorders can occur ranging from mild 'baby blues' to severe episodes of psychotic illnesses. Puerperal psychosis is the most extreme form of postnatal psychosis, occurring in 1 in 1,000 births. In this study, we have used the pig as an animal model for human postnatal psychiatric illness. Our aim was to identify quantitative trait loci (QTL) associated with maternal (infanticide) sow aggression. This is defined by sows attacking and killing their own newborn offspring, within 24 hr of birth. An affected sib pair whole genome linkage analysis was carried out with 80 microsatellite markers covering the 18 porcine autosomes and the X chromosome, with the aim of identifying chromosomal regions responsible for this abnormal behavior. Analysis was carried out using the non-parametric linkage test of Whittemore and Halpern, as implemented in the Merlin software. The results identified 4 QTL mapping on Sus scrofa chromosomes 2 (SSC2), 10 (SSC10), and X (SSCX). The peak regions of these QTL are syntenic to HSA 5q14.3-15, 1q32, Xpter-Xp2.1, and Xq2.4-Xqter, respectively. Several potential candidate genes lie in these regions in addition to relevant abnormal behavioral QTL, found in humans and rodents.
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Affiliation(s)
- Claire R Quilter
- Human Molecular Genetics Group, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, UK.
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Gao YG, Yan XZ, Song AX, Chang YG, Gao XC, Jiang N, Zhang Q, Hu HY. Structural Insights into the Specific Binding of Huntingtin Proline-Rich Region with the SH3 and WW Domains. Structure 2006; 14:1755-65. [PMID: 17161366 DOI: 10.1016/j.str.2006.09.014] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Revised: 09/12/2006] [Accepted: 09/27/2006] [Indexed: 10/23/2022]
Abstract
The interactions of huntingtin (Htt) with the SH3 domain- or WW domain-containing proteins have been implicated in the pathogenesis of Huntington's disease (HD). We report the specific interactions of Htt proline-rich region (PRR) with the SH3GL3-SH3 domain and HYPA-WW1-2 domain pair by NMR. The results show that Htt PRR binds with the SH3 domain through nearly its entire chain, and that the binding region on the domain includes the canonical PxxP-binding site and the specificity pocket. The C terminus of PRR orients to the specificity pocket, whereas the N terminus orients to the PxxP-binding site. Htt PRR can also specifically bind to WW1-2; the N-terminal portion preferentially binds to WW1, while the C-terminal portion binds to WW2. This study provides structural insights into the specific interactions between Htt PRR and its binding partners as well as the alteration of these interactions that involve PRR, which may have implications for the understanding of HD.
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Affiliation(s)
- Yong-Guang Gao
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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Abstract
Nine neurodegenerative diseases, such as Huntington, are caused by a polyglutamine (poly(Q)) expansion in otherwise unrelated proteins. Although poly(Q) expansion causes aggregation of the affected proteins, the protein context might determine the selective neuronal vulnerability found in each disease. Here we have report that, although expression of Huntingtin derivatives with a pathological poly(Q) expansion are innocuous in yeast, deletion of the flanking proline-rich region alters the shape and number of poly(Q) inclusions and unmasks toxic properties. Strikingly, deletion of Hsp104 increases the size of inclusions formed by expanded poly(Q) lacking the proline-rich region and abolishes toxicity. Overexpression of the chaperones Hsp104 or Hsp70 rescues growth defects in affected cells without resolving inclusions. However, aggregates formed by nontoxic Huntingtin derivatives or by toxic derivatives cured by chaperones are physically distinct from aggregates formed by toxic proteins. This study identifies the proline-rich region in Huntingtin as a profound cis-acting modulator of expanded poly(Q) toxicity and distinguishes between aggregates of toxic or non-toxic proteins.
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Affiliation(s)
- Benjamin Dehay
- Laboratoire de Génétique Moléculaire, CNRS UMR8541, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris Cedex 05, France
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Abstract
Huntington's disease is an autosomal dominant neurodegenerative disorder that is characterized by motor, cognitive, and psychiatric alterations. The mutation responsible for this fatal disease is an abnormally expanded and unstable CAG repeat within the coding region of the gene encoding huntingtin. Numerous mouse models have been generated that constitute invaluable tools to examine the pathogenesis of the disease and to develop and evaluate novel therapies. Among those models, knock-in mice provide a genetically precise reproduction of the human condition. The slow progression and early development of behavioral, pathological, cellular, and molecular abnormalities in knock-in mice make these animals valuable to understand the early pathological events triggered by the mutation. This review describes the different knock-in models generated, the insight gained from them, and their value in the development and testing of prospective treatments of the disease.
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Apostol BL, Illes K, Pallos J, Bodai L, Wu J, Strand A, Schweitzer ES, Olson JM, Kazantsev A, Marsh JL, Thompson LM. Mutant huntingtin alters MAPK signaling pathways in PC12 and striatal cells: ERK1/2 protects against mutant huntingtin-associated toxicity. Hum Mol Genet 2005; 15:273-85. [PMID: 16330479 DOI: 10.1093/hmg/ddi443] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Huntington's disease (HD) is a devastating neurodegenerative disorder caused by an expanded polyglutamine (polyQ) tract within the huntingtin protein (Htt). Identifying the pathways that are altered in response to the mutant protein is crucial for understanding the cellular processes impacted by the disease as well as for the rational development of effective pharmacological interventions. Here, expression profiling of a cellular HD model identifies genes that implicate altered mitogen-activated protein kinase (MAPK) signaling. Targeted biochemical studies and pharmacological modulation of these MAPK pathways suggest that mutant Htt affects signaling at upstream points such that both ERK and JNK are activated. Modulation of the ERK pathway suggests that this pathway is associated with cell survival, whereas inhibition of JNK was found to effectively suppress pathogenesis. These studies suggest that pharmacological intervention in MAPK pathways, particularly at the level of ERK activation, may be an appropriate approach to HD therapy.
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Affiliation(s)
- Barbara L Apostol
- Department of Psychiatry and Human Behavior, University of California, Irvine, 92697, USA
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Brouillet E, Jacquard C, Bizat N, Blum D. 3-Nitropropionic acid: a mitochondrial toxin to uncover physiopathological mechanisms underlying striatal degeneration in Huntington's disease. J Neurochem 2005; 95:1521-40. [PMID: 16300642 DOI: 10.1111/j.1471-4159.2005.03515.x] [Citation(s) in RCA: 269] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Huntington's disease (HD) is a neurodegenerative disorder caused by a mutation in the gene encoding Huntingtin. The mechanisms underlying the preferential degeneration of the striatum, the most striking neuropathological change in HD, are unknown. Of those probably involved, mitochondrial defects might play an important role. The behavioural and anatomical similarities found between HD and models using the mitochondrial toxin 3-nitropropionic acid (3NP) in rats and primates support this hypothesis. Here, we discuss the recently identified mechanisms of 3NP-induced striatal degeneration. Two types of important factor have been identified. The first are the 'executioner' components that have direct roles in cell death, such as c-Jun N-terminal kinase and Ca2+-activated protease calpains. The second are 'environmental' factors, such as glutamate, dopamine and adenosine, which modulate the striatal degeneration induced by 3NP. Interestingly, these recent studies support the hypothesis that 3NP and mutated Huntingtin have certain mechanisms of toxicity in common, suggesting that the use of 3NP might give new insights into the pathogenesis of HD. Research on 3NP provides additional proof that the neurochemical environment of a given neurone can determine its preferential vulnerability in neurodegenerative diseases.
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Affiliation(s)
- Emmanuel Brouillet
- Centre Nationale de la Recherche Scientifique 2210, Service Hospitalier Frédéric Joliot, Départment de Recherches Médicales, Direction des Sciences du Vivant, CEA, Orsay France.
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Liévens JC, Rival T, Iché M, Chneiweiss H, Birman S. Expanded polyglutamine peptides disrupt EGF receptor signaling and glutamate transporter expression in Drosophila. Hum Mol Genet 2005; 14:713-24. [PMID: 15677486 DOI: 10.1093/hmg/ddi067] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Huntington's disease (HD) is a late onset heritable neurodegenerative disorder caused by expansion of a polyglutamine (polyQ) sequence in the protein huntingtin (Htt). Transgenic models in mice have suggested that the motor and cognitive deficits associated to this disease are triggered by extended neuronal and possibly glial dysfunction, whereas neuronal death occurs late and selectively. Here, we provide in vivo evidence that expanded polyQ peptides antagonize epidermal growth factor receptor (EGFR) signaling in Drosophila glia. We targeted the expression of the polyQ-containing domain of Htt or an extended polyQ peptide alone in a subset of Drosophila glial cells, where the only fly glutamate transporter, dEAAT1, is detected. This resulted in formation of nuclear inclusions, progressive decrease in dEAAT1 transcription and shortened adult lifespan, but no significant glial cell death. We observed that brain expression of dEAAT1 is normally sustained by the EGFR-Ras-extracellular signal-regulated kinase (ERK) signaling pathway, suggesting that polyQ could act by antagonizing this pathway. We found that the presence of polyQ peptides indeed abolished dEAAT1 upregulation by constitutively active EGFR and potently inhibited EGFR-mediated ERK activation in fly glial cells. Long polyQ also limited the effect of activated EGFR on Drosophila eye development. Our results further indicate that the polyQ acts at an upstream step in the pathway, situated between EGFR and ERK activation. This suggests that disruption of EGFR signaling and ensuing glial cell dysfunction could play a direct role in the pathogenesis of HD and other polyQ diseases in humans.
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Abstract
Huntington's disease results from a polyglutamine expansion in the N-terminal region of huntingtin (htt). This abnormality causes protein aggregation and leads to neurotoxicity. Despite its widespread expression in the brain and body, mutant htt causes selective neurodegeneration in Huntington's disease patient brains. However, Huntington's disease mouse models expressing mutant htt do not have obvious neurodegeneration despite significant neurological symptoms. Most Huntington's disease mouse models display the accumulation of toxic N-terminal mutant htt fragments in both the nucleus and neuronal processes, suggesting that these subcellular sites are hotspots for the early neuropathology of Huntington's disease. Intranuclear htt affects gene expression and may cause neuronal dysfunction. Mutant htt in neuronal processes affects axonal transport and induces degeneration, and these effects may be more relevant to the selective neurodegeneration in Huntington's disease. Growing evidence has also suggested that mutant htt mediates multiple pathological pathways. This review discusses the early pathological changes identified in Huntington's disease cellular and animal models. These changes may be the causes of neurode-generation.
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Affiliation(s)
- Shi-Hua Li
- Department of Human Genetics, School of Medicine, Emory University, Atlanta, GA 30322, USA
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Qin ZH, Wang Y, Sapp E, Cuiffo B, Wanker E, Hayden MR, Kegel KB, Aronin N, DiFiglia M. Huntingtin bodies sequester vesicle-associated proteins by a polyproline-dependent interaction. J Neurosci 2004; 24:269-81. [PMID: 14715959 PMCID: PMC6729557 DOI: 10.1523/jneurosci.1409-03.2004] [Citation(s) in RCA: 136] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Polyglutamine expansion in the N terminus of huntingtin (htt) causes selective neuronal dysfunction and cell death by unknown mechanisms. Truncated htt expressed in vitro produced htt immunoreactive cytoplasmic bodies (htt bodies). The fibrillar core of the mutant htt body resisted protease treatment and contained cathepsin D, ubiquitin, and heat shock protein (HSP) 40. The shell of the htt body was composed of globules 14-34 nm in diameter and was protease sensitive. HSP70, proteasome, dynamin, and the htt binding partners htt interacting protein 1 (HIP1), SH3-containing Grb2-like protein (SH3GL3), and 14.7K-interacting protein were reduced in their normal location and redistributed to the shell. Removal of a series of prolines adjacent to the polyglutamine region in htt blocked formation of the shell of the htt body and redistribution of dynamin, HIP1, SH3GL3, and proteasome to it. Internalization of transferrin was impaired in cells that formed htt bodies. In cortical neurons of Huntington's disease patients with early stage pathology, dynamin immunoreactivity accumulated in cytoplasmic bodies. Results suggest that accumulation of a nonfibrillar form of mutant htt in the cytoplasm contributes to neuronal dysfunction by sequestering proteins involved in vesicle trafficking.
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Affiliation(s)
- Zheng-Hong Qin
- Laboratory of Cellular Neurobiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
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48
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Abstract
The nematode C. elegans is an established model for developmental biology. Since the early 90's, this simple model organism has been increasingly used for studying human disease pathogenesis. C. elegans models based either on the mutagenesis of human disease genes conserved in this nematode or transgenesis with disease genes not conserved in C. elegans show several features that are observed in mammalian models. These observations suggest that the genetic dissection and pharmacological manipulation of disease-like phenotypes in C. elegans will shed light on the cellular mechanisms that are altered in human diseases, and the compounds that may be used as drugs. This review illustrates these aspects by commenting on two inherited degenerative diseases, Duchenne's muscular dystrophy and Huntington's neurodegenerative disease.
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Affiliation(s)
- Laurent Ségalat
- Cnrs-CGMC, Université Lyon-1 Claude Bernard, 43, boulevard du 11 Novembre, 69622 Villeurbanne, France
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Luthi-Carter R, Apostol BL, Dunah AW, DeJohn MM, Farrell LA, Bates GP, Young AB, Standaert DG, Thompson LM, Cha JHJ. Complex alteration of NMDA receptors in transgenic Huntington's disease mouse brain: analysis of mRNA and protein expression, plasma membrane association, interacting proteins, and phosphorylation. Neurobiol Dis 2003; 14:624-36. [PMID: 14678777 DOI: 10.1016/j.nbd.2003.08.024] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
We analyzed NMDA receptor subunit mRNAs, proteins, and anchoring proteins in mice transgenic for exon 1 of the HD gene. R6/2 mice had decreased levels of mRNAs encoding epsilon1 and epsilon2 NMDA receptor subunits (mouse orthologs of rat NR2A and NR2B subunits), but not the zeta1 subunit (mouse ortholog of NR1), as assessed by gene expression profiling and Northern blotting. In situ hybridization resolved mRNA decreases spatially to the CA1 field of hippocampus. Western blotting revealed decreases in plasma membrane-associated epsilon1 and epsilon2 subunits in hippocampus, and decreases in plasma membrane-associated zeta1 subunit in cortex and hippocampus. In addition, PSD-95 and alpha-actinin-2, proteins essential for anchoring NMDA receptors, were decreased. Finally, we found a decreased level of tyrosine-phosphorylated epsilon1 subunit, another determinant of NMDA receptor trafficking, in R6/2 hippocampus. Taken together, these data demonstrate multiple levels of NMDA receptor dysregulation, including abnormalities in mRNA expression levels, receptor stoichiometry, protein phosphorylation, and receptor trafficking.
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Affiliation(s)
- Ruth Luthi-Carter
- MassGeneral Institute for Neurodegenerative Diseases, B114-2000, 114 16th Street, Charlestown, MA 02129-4404, USA
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Humbert S, Saudou F. Huntingtin phosphorylation and signaling pathways that regulate toxicity in Huntington's disease. ACTA ACUST UNITED AC 2003; 3:149-55. [DOI: 10.1016/s1566-2772(03)00057-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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