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Baliova M, Jursky F. Correlation of calpain sensitivity, Bradford assay instability, and electrophoretic mobility in phosphomimetic mutants of GlyT2 N-terminus. Biochem Biophys Rep 2024; 38:101734. [PMID: 38799113 PMCID: PMC11127470 DOI: 10.1016/j.bbrep.2024.101734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2024] [Revised: 05/02/2024] [Accepted: 05/13/2024] [Indexed: 05/29/2024] Open
Abstract
The glycine transporter GlyT2 plays an important role in glycine-inhibitory neurotransmission of the hindbrain and spinal cord. Its special feature is the extended N-terminus, which contains a large number of potentially phosphorylated serine and threonine residues. Due to its unstructured nature, it is difficult to address the changes introduced by potential phosphorylation. Here, we used relatively simple methods such as calpain sensitivity, Bradford instability, and SDS electrophoretic mobility shift to investigate the effect of multiple phosphomimetic mutations versus neutral mutations on GlyT2N properties. The replacement of several serines or threonines with neutral alanines did not have a significant effect on the studied GlyT2N properties. Replacement of the same residues with phosphomimetic aspartate resulted in significant alterations in calpain cleavage patterns, Bradford instability, and SDS gel protein mobility. Interestingly, a correlation between the relative intensity of the measured effects was observed, indicating that they all reflect similar structural changes introduced by potential phosphorylation in vivo. Results indicate that a potential single or multiple phosphorylation significantly alters the proteomic properties of the glycine transporter GlyT2 N-terminus. Assays can be helpful in the first screening of structurally significant and possibly phosphorylated residues in the N-terminus of GlyT2.
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Affiliation(s)
- Martina Baliova
- Laboratory of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, 845 51, Bratislava, Slovakia
| | - Frantisek Jursky
- Laboratory of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, 845 51, Bratislava, Slovakia
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2
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Marques BL, Oliveira-Lima OC, Carvalho GA, de Almeida Chiarelli R, Ribeiro RI, Parreira RC, da Madeira Freitas EM, Resende RR, Klempin F, Ulrich H, Gomez RS, Pinto MCX. Neurobiology of glycine transporters: From molecules to behavior. Neurosci Biobehav Rev 2020; 118:97-110. [PMID: 32712279 DOI: 10.1016/j.neubiorev.2020.07.025] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/07/2020] [Accepted: 07/17/2020] [Indexed: 12/16/2022]
Abstract
Glycine transporters (GlyTs) are Na+/Cl--dependent neurotransmitter transporters, responsible for l-glycine uptake into the central nervous system. GlyTs are members of the solute carrier family 6 (SLC6) and comprise glycine transporter type 1 (SLC6A9; GlyT1) and glycine transporter type 2 (SLC6A5; Glyt2). GlyT1 and GlyT2 are expressed on both astrocytes and neurons, but their expression pattern in brain tissue is foremost related to neurotransmission. GlyT2 is markedly expressed in brainstem, spinal cord and cerebellum, where it is responsible for glycine uptake into glycinergic and GABAergic terminals. GlyT1 is abundant in neocortex, thalamus and hippocampus, where it is expressed in astrocytes, and involved in glutamatergic neurotransmission. Consequently, inhibition of GlyT1 transporters can modulate glutamatergic neurotransmission through NMDA receptors, suggesting an alternative therapeutic strategy. In this review, we focus on recent progress in the understanding of GlyTs role in brain function and in various diseases, such as epilepsy, hyperekplexia, neuropathic pain, drug addiction, schizophrenia and stroke, as well as in neurodegenerative disorders.
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Affiliation(s)
- Bruno Lemes Marques
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Onésia Cristina Oliveira-Lima
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Gustavo Almeida Carvalho
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raphaela de Almeida Chiarelli
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Raul Izidoro Ribeiro
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Ricardo Cambraia Parreira
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Elis Marra da Madeira Freitas
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil
| | - Rodrigo Ribeiro Resende
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | | | - Henning Ulrich
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Renato Santiago Gomez
- Departamento de Cirurgia, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Mauro Cunha Xavier Pinto
- Laboratório de Neuroquímica e Neurofarmacologia - Neurolab, Instituto de Ciências Biológicas, Universidade Federal de Goiás, Goiânia, GO, Brazil.
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3
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Baliova M, Jursky F. Comparison of SynCAM1/CADM1 PDZ interactions with MUPP1 using mammalian and bacterial pull-down systems. Brain Behav 2020; 10:e01587. [PMID: 32108449 PMCID: PMC7177587 DOI: 10.1002/brb3.1587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 01/20/2020] [Accepted: 02/15/2020] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Synaptic cell adhesion molecule 1 (SynCAM1) also known as cell adhesion molecule 1 (CADM1) is a transmembrane cell adhesion protein that operates in a variety of physiological and pathological cellular contexts, and its interaction with the PDZ signalling protein MUPP1 have been previously implicated in autism spectrum disorder (ASD). METHODS We used in vitro pull-down systems based on the bacterial and mammalian extracts to study SynCAM1/CADM1 PDZ interactions with MUPP1 at various conditions. RESULTS So far, the investigated interaction of SynCAM1/CADM1 with MUPP1 has been mostly attributed to an unspecified region of MUPP1 PDZ domains 1-5 or exclusively to domain 2, using a yeast two-hybrid system. We also confirmed the single interaction of native synaptosomal CADM1 with PDZ domain 2. However, in this work, using recombinant proteins overexpressed in bacteria, we found an in vitro pull-down conditions in which all first five domains and, to a much lesser extent, MUPP1 domains 7 and 11 significantly interacted with the whole C-terminal domain of SynCAM1/CADM1. These PDZ interactions were confirmed by a pull-down assay using the last seven amino acids of the SynCAM1/CADM1 PDZ motif and using two fusion partners. Multiple interactions were additionally replicated using the continuous N-terminal MUPP1 protein fragment, which included first five PDZ domains, containing either intact or mutated domain 2. CONCLUSIONS We hypothesize that multiple interactions might exist in vivo, representing transient low-affinity interactions or alternative binding sites on MUPP1 when domain 2 is occupied or occluded by the interaction with other ligands. This newly identified interactions extend the potential genetic mutations, possibly affecting SynCAM1/CADM1/MUPP1 function. Possible reasons for the absence of some of the identified CADM1 PDZ interactions in mammalian extracts are discussed.
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Affiliation(s)
- Martina Baliova
- Laboratory of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
| | - Frantisek Jursky
- Laboratory of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia
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Phosphorylation of Serine 157 Protects the Rat Glycine Transporter GlyT2 from Calpain Cleavage. J Mol Neurosci 2020; 70:1216-1224. [PMID: 32172509 DOI: 10.1007/s12031-020-01529-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Accepted: 03/03/2020] [Indexed: 11/25/2022]
Abstract
The N-terminal region of the rat glycine transporter 2 (rGlyT2, SLC6A5) is cleaved by calpain protease in vitro, which raises the question of its protection against calpain in vivo. Here, we used a phosphomimetic and orthogonal phosphoserine translation approach to investigate the possible role of phosphorylation in the protection of two calpain cleavage sites, M156/S157 and G164/T165, previously identified in the N-terminus region of the rat GlyT2. Replacement of serine 157 with phosphomimetic aspartate or with orthogonal phosphoserine blocked both calpain cleavage sites and caused an electrophoretic mobility shift of rGlyT2N fusion proteins. Both effects can be reversed by dephosphorylation, suggesting that phosphorylation might induce structural changes in the rGlyT2 N-terminus, preventing the accessibility of the M156/S157 and G164/T165 cleavage sites to calpain in vivo. In comparison with the wild type, the phosphomimetic mutation S157D increased the total immunoreactivity of the transporter expressed in neuroblastoma cells, suggesting that serine 157 phosphorylation or phosphorylation-regulated calpain cleavage might contribute to the turnover of the glycine transporter GlyT2.
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Baliova M, Jursky F. Phosphomimetic Mutation of Glycine Transporter GlyT1 C-Terminal PDZ Binding Motif Inhibits its Interactions with PSD95. J Mol Neurosci 2019; 70:488-493. [DOI: 10.1007/s12031-019-01435-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 11/04/2019] [Indexed: 12/11/2022]
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Tien WS, Chen JH, Wu KP. SheddomeDB: the ectodomain shedding database for membrane-bound shed markers. BMC Bioinformatics 2017; 18:42. [PMID: 28361715 PMCID: PMC5374707 DOI: 10.1186/s12859-017-1465-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND A number of membrane-anchored proteins are known to be released from cell surface via ectodomain shedding. The cleavage and release of membrane proteins has been shown to modulate various cellular processes and disease pathologies. Numerous studies revealed that cell membrane molecules of diverse functional groups are subjected to proteolytic cleavage, and the released soluble form of proteins may modulate various signaling processes. Therefore, in addition to the secreted protein markers that undergo secretion through the secretory pathway, the shed membrane proteins may comprise an additional resource of noninvasive and accessible biomarkers. In this context, identifying the membrane-bound proteins that will be shed has become important in the discovery of clinically noninvasive biomarkers. Nevertheless, a data repository for biological and clinical researchers to review the shedding information, which is experimentally validated, for membrane-bound protein shed markers is still lacking. RESULTS In this study, the database SheddomeDB was developed to integrate publicly available data of the shed membrane proteins. A comprehensive literature survey was performed to collect the membrane proteins that were verified to be cleaved or released in the supernatant by immunological-based validation experiments. From 436 studies on shedding, 401 validated shed membrane proteins were included, among which 199 shed membrane proteins have not been annotated or validated yet by existing cleavage databases. SheddomeDB attempted to provide a comprehensive shedding report, including the regulation of shedding machinery and the related function or diseases involved in the shedding events. In addition, our published tool ShedP was embedded into SheddomeDB to support researchers for predicting the shedding event on unknown or unrecorded membrane proteins. CONCLUSIONS To the best of our knowledge, SheddomeDB is the first database for the identification of experimentally validated shed membrane proteins and currently may provide the most number of membrane proteins for reviewing the shedding information. The database included membrane-bound shed markers associated with numerous cellular processes and diseases, and some of these markers are potential novel markers because they are not annotated or validated yet in other databases. SheddomeDB may provide a useful resource for discovering membrane-bound shed markers. The interactive web of SheddomeDB is publicly available at http://bal.ym.edu.tw/SheddomeDB/ .
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Affiliation(s)
- Wei-Sheng Tien
- Institute of Biomedical Informatics, National Yang Ming University, Taipei, 112, Taiwan.,Bioinformatics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 115, Taiwan
| | - Jun-Hong Chen
- Department of Computer Science, National Taipei University of Education, Taipei, 106, Taiwan
| | - Kun-Pin Wu
- Institute of Biomedical Informatics, National Yang Ming University, Taipei, 112, Taiwan.
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Juhasova A, Baliova M, Jursky F. A Dynamic Interaction of Coomassie Dye with the Glycine Transporters N-termini. Protein J 2016; 35:371-378. [DOI: 10.1007/s10930-016-9682-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Bali KK, Venkataramani V, Satagopam VP, Gupta P, Schneider R, Kuner R. Transcriptional mechanisms underlying sensitization of peripheral sensory neurons by granulocyte-/granulocyte-macrophage colony stimulating factors. Mol Pain 2013; 9:48. [PMID: 24067145 PMCID: PMC3852053 DOI: 10.1186/1744-8069-9-48] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 08/25/2013] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Cancer-associated pain is a major cause of poor quality of life in cancer patients and is frequently resistant to conventional therapy. Recent studies indicate that some hematopoietic growth factors, namely granulocyte macrophage colony stimulating factor (GMCSF) and granulocyte colony stimulating factor (GCSF), are abundantly released in the tumor microenvironment and play a key role in regulating tumor-nerve interactions and tumor-associated pain by activating receptors on dorsal root ganglion (DRG) neurons. Moreover, these hematopoietic factors have been highly implicated in postsurgical pain, inflammatory pain and osteoarthritic pain. However, the molecular mechanisms via which G-/GMCSF bring about nociceptive sensitization and elicit pain are not known. RESULTS In order to elucidate G-/GMCSF mediated transcriptional changes in the sensory neurons, we performed a comprehensive, genome-wide analysis of changes in the transcriptome of DRG neurons brought about by exposure to GMCSF or GCSF. We present complete information on regulated genes and validated profiling analyses and report novel regulatory networks and interaction maps revealed by detailed bioinformatics analyses. Amongst these, we validate calpain 2, matrix metalloproteinase 9 (MMP9) and a RhoGTPase Rac1 as well as Tumor necrosis factor alpha (TNFα) as transcriptional targets of G-/GMCSF and demonstrate the importance of MMP9 and Rac1 in GMCSF-induced nociceptor sensitization. CONCLUSION With integrative approach of bioinformatics, in vivo pharmacology and behavioral analyses, our results not only indicate that transcriptional control by G-/GMCSF signaling regulates a variety of established pain modulators, but also uncover a large number of novel targets, paving the way for translational analyses in the context of pain disorders.
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Affiliation(s)
- Kiran Kumar Bali
- Institute for Pharmacology and Molecular Medicine Partnership Unit, Heidelberg University, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany
| | - Varun Venkataramani
- Institute for Pharmacology and Molecular Medicine Partnership Unit, Heidelberg University, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany
| | - Venkata P Satagopam
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Campus Belval, House of Biomedicine, 7 avenue des Hauts-Fourneaux, L-4362 Esch-sur-Alzette, Luxembourg
- European Molecular Biology Laboratory, Meyerhofstrasse. 1, D-69117 Heidelberg, Germany
| | - Pooja Gupta
- Institute for Pharmacology and Molecular Medicine Partnership Unit, Heidelberg University, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany
| | - Reinhard Schneider
- Luxembourg Centre for Systems Biomedicine (LCSB), University of Luxembourg, Campus Belval, House of Biomedicine, 7 avenue des Hauts-Fourneaux, L-4362 Esch-sur-Alzette, Luxembourg
- European Molecular Biology Laboratory, Meyerhofstrasse. 1, D-69117 Heidelberg, Germany
| | - Rohini Kuner
- Institute for Pharmacology and Molecular Medicine Partnership Unit, Heidelberg University, Im Neuenheimer Feld 366, D-69120 Heidelberg, Germany
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Jursky F, Baliova M. Expression and purification of recombinant calpain-derived N-terminal peptides from glycine transporter GlyT2. Protein Expr Purif 2013; 88:143-9. [DOI: 10.1016/j.pep.2012.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Revised: 12/17/2012] [Accepted: 12/18/2012] [Indexed: 11/15/2022]
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10
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Puskarjov M, Ahmad F, Kaila K, Blaesse P. Activity-dependent cleavage of the K-Cl cotransporter KCC2 mediated by calcium-activated protease calpain. J Neurosci 2012; 32:11356-64. [PMID: 22895718 PMCID: PMC6621186 DOI: 10.1523/jneurosci.6265-11.2012] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 06/29/2012] [Accepted: 07/03/2012] [Indexed: 11/21/2022] Open
Abstract
The K-Cl cotransporter KCC2 plays a crucial role in neuronal chloride regulation. In mature central neurons, KCC2 is responsible for the low intracellular Cl(-) concentration ([Cl(-)](i)) that forms the basis for hyperpolarizing GABA(A) receptor-mediated responses. Fast changes in KCC2 function and expression have been observed under various physiological and pathophysiological conditions. Here, we show that the application of protein synthesis inhibitors cycloheximide and emetine to acute rat hippocampal slices have no effect on total KCC2 protein level and K-Cl cotransporter function. Furthermore, blocking constitutive lysosomal degradation with leupeptin did not induce significant changes in KCC2 protein levels. These findings indicate a low basal turnover rate of the total KCC2 protein pool. In the presence of the glutamate receptor agonist NMDA, the total KCC2 protein level decreased to about 30% within 4 h, and this effect was blocked by calpeptin and MDL-28170, inhibitors of the calcium-activated protease calpain. Interictal-like activity induced by incubation of hippocampal slices in an Mg(2+)-free solution led to a fast reduction in KCC2-mediated Cl(-) transport efficacy in CA1 pyramidal neurons, which was paralleled by a decrease in both total and plasmalemmal KCC2 protein. These effects were blocked by the calpain inhibitor MDL-28170. Taken together, these findings show that calpain activation leads to cleavage of KCC2, thereby modulating GABAergic signaling.
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Affiliation(s)
- Martin Puskarjov
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland and
| | - Faraz Ahmad
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland and
| | - Kai Kaila
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland and
| | - Peter Blaesse
- Department of Biosciences and Neuroscience Center, University of Helsinki, FI-00014 Helsinki, Finland and
- Institute of Physiology I, Westfälische Wilhelms-University Münster, D-48149 Münster, Germany
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Differential effect of the benzophenanthridine alkaloids sanguinarine and chelerythrine on glycine transporters. Neurochem Int 2011; 58:641-7. [DOI: 10.1016/j.neuint.2011.02.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Revised: 01/29/2011] [Accepted: 02/01/2011] [Indexed: 11/30/2022]
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Baliova M, Knab A, Franekova V, Jursky F. Modification of the cytosolic regions of GABA transporter GAT1 by calpain. Neurochem Int 2009; 55:288-94. [PMID: 19576516 DOI: 10.1016/j.neuint.2009.03.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 02/20/2009] [Accepted: 03/18/2009] [Indexed: 11/18/2022]
Abstract
Cytosolic regions of sodium dependent neurotransmitter transporters regulate their surface density and transporting function by interconnecting themselves with intracellular signaling pathways. Here we show that calpain activation in rat brain synaptosomes leads to cleavage of both N- and C-terminal regions of GABA transporter GAT1. In the C-terminal region, calpain removes a short segment of amino acids involved in binding of GAT1 to a high-density PDZ anchoring matrix. Using a protein pull-down assay, we found that C-terminal truncation of GAT1 results in modification of its interacting proteome in vitro. Results indicate that calpain activation/inhibition in GABAergic terminals may influence the scaffolding and surface expression of GABA transporter GAT1 under normal conditions or imbalance GAT1-mediated GABAergic transmission under pathological states.
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Affiliation(s)
- Martina Baliova
- Laboratory of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, 84251 Bratislava, Slovakia
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13
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Franekova V, Baliova M, Jursky F. Truncation of human dopamine transporter by protease calpain. Neurochem Int 2008; 52:1436-41. [PMID: 18468730 DOI: 10.1016/j.neuint.2008.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2007] [Revised: 02/17/2008] [Accepted: 04/01/2008] [Indexed: 01/13/2023]
Abstract
It has been shown recently that the N-terminal domain of the dopamine transporter (DAT) plays a role in several transporter functions. Here we provide evidence for a possible cellular mechanism of how the N-terminus of dopamine transporter might be removed in vivo. We isolated a recombinant N-terminal protein region of human dopamine transporter and cleaved it with calpain protease. Peptide fragment analysis revealed the existence of two calpain cleavage sites at positions Thr43/Ser44 and Leu71/Ser72 of the DATN-terminus. We show that calpain activation in rat striatal synaptosomes leads to a rapid decrease of dopamine transporter N-terminal epitopes corresponding to the protein sequences removed by a calpain cleavage at Thr43/Ser44 and that the process is totally blocked by a calpain inhibitor. Calpain truncation of the DATN-terminus abolishes its interaction with the receptor of activated protein kinase C, RACK1 and removes protein sequences previously implicated in amphetamine-induced dopamine release, PKC-dependent endocytosis and the interaction of DAT with the dopamine D2 receptor. The above suggests that cleavage of DAT by calpain may significantly modify dopamine homeostasis under pathological or physiological conditions.
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Affiliation(s)
- Veronika Franekova
- Laboratory of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Dubravska cesta 21, Bratislava, Slovakia
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14
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Mercado A, Broumand V, Zandi-Nejad K, Enck AH, Mount DB. A C-terminal domain in KCC2 confers constitutive K+-Cl- cotransport. J Biol Chem 2006; 281:1016-26. [PMID: 16291749 DOI: 10.1074/jbc.m509972200] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The neuron-specific K(+)-Cl(-) cotransporter KCC2 plays a crucial role in determining intracellular chloride activity and thus the neuronal response to gamma-aminobutyric acid and glycine. Of the four KCCs, KCC2 is unique in mediating constitutive K(+)-Cl(-) cotransport under isotonic conditions; the other three KCCs are exclusively swelling-activated, with no isotonic activity. We have utilized a series of chimeric cDNAs to localize the determinant of isotonic transport in KCC2. Two generations of chimeric KCC4-KCC2 cDNAs initially localized this characteristic to within a KCC2-specific expansion of the cytoplasmic C terminus, between residues 929 and 1043. This region of KCC2 is rich in prolines, serines, and charged residues and encompasses two predicted PEST sequences. Substitution of this region in KCC2 with the equivalent sequence of KCC4 resulted in a chimeric KCC that was devoid of isotonic activity, with intact swelling-activated transport. A third generation of chimeras demonstrated that a domain just distal to the PEST sequences confers isotonic transport on KCC4. Mutagenesis of this region revealed that residues 1021-1035 of KCC2 are sufficient for isotonic transport. Swelling-activated K(+)-Cl(-) cotransport is abrogated by calyculin A, whereas isotonic transport mediated by KCC chimeras and KCC2 is completely resistant to this serine-threonine phosphatase inhibitor. In summary, a 15-residue C-terminal domain in KCC2 is both necessary and sufficient for constitutive K(+)-Cl(-) cotransport under isotonic conditions. Furthermore, unlike swelling-activated transport, constitutive K(+)-Cl(-) cotransport mediated by KCC2 is completely independent of serine-threonine phosphatase activity, suggesting that these two modes of transport are activated by distinct mechanisms.
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Affiliation(s)
- Adriana Mercado
- Renal Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
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15
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Baliova M, Jursky F. Calpain Sensitive Regions in the N-terminal Cytoplasmic Domains of Glycine Transporters GlyT1A and GlyT1B. Neurochem Res 2005; 30:1093-100. [PMID: 16292501 DOI: 10.1007/s11064-005-7520-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/18/2005] [Indexed: 10/25/2022]
Abstract
Glycine transporters are members of the Na+/Cl- dependent transporter gene family and play crucial roles in regulating inhibitory as well as excitatory neurotransmission. In this report we show that calcium elevation in spinal cord synaptosomes decreases the levels of glycine transporter, GlyT1, N-terminal immunoreactivity, and that this decrease can be blocked by calpain inhibitor. Sequencing of GST fusion proteins containing the N-terminal domains of GlyT1A and B splice variants cleaved with rat recombinant calpain identified calpain cleavage sites after glycine 17 in GlyT1B and N-terminally of the first conserved arginine residue in both GlyT1A and GlyT1B. Expression in HEK293 cells revealed that truncation of the N-terminus of GlyT1 results in significant inhibition of glycine uptake. A syntaxin1A GST fusion protein was able to pull-down N-terminally deleted GlyT1, indicating that calpain cleavage does not eliminate syntaxin1A binding. These results suggest that calpain cleavage may regulate the transport activity/turnover of GlyT1 in vivo by cleaving its N-terminal domain.
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Affiliation(s)
- Martina Baliova
- Department of Neurobiology, Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava, Slovakia.
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16
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Horiuchi M, Loebrich S, Brandstaetter JH, Kneussel M, Betz H. Cellular localization and subcellular distribution of Unc-33-like protein 6, a brain-specific protein of the collapsin response mediator protein family that interacts with the neuronal glycine transporter 2. J Neurochem 2005; 94:307-15. [PMID: 15998282 DOI: 10.1111/j.1471-4159.2005.03198.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Unc-33-like protein (Ulip)6, a brain-specific phosphoprotein of the Ulip/collapsin response mediator protein family, was originally identified in our laboratory by yeast two-hybrid screening using the cytoplasmic N-terminal domain of the neuronal glycine transporter, glycine transporter (GlyT) 2, as a bait. Here, the interaction of Ulip6 with the N-terminal domain of GlyT2 was found to be specific for this member of the Ulip/collapsin response mediator protein family and to involve amino acids 135-184 of GlyT2. In pull-down assays and coimmunoprecipitation experiments with rat spinal cord extract, the presence of phosphatase inhibitors significantly enhanced binding of Ulip6 to GlyT2. Subcellular fractionation of spinal cord and retina homogenates at different developmental stages showed Ulip6 immunoreactivity to be associated with light vesicles that were distinct from GlyT2-containing and synaptic vesicles. Immunocytochemistry revealed punctate Ulip6 immunoreactivity in both somatic regions and processes of cultured spinal neurones; no colocalization with GlyT2 or other synaptic marker proteins was found. In retina, which expresses only GlyT1 but not GlyT2, Ulip6 was detected in the inner plexiform layer and along the somata and processes of selected bipolar, amacrine and ganglion cells. Our data support a model in which Ulip6 transiently interacts with GlyT2 in a phosphorylation-dependent manner.
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Affiliation(s)
- Masahisa Horiuchi
- Abteilung Neurochemie, Max-Planck-Institut für Hirnforschung, Frankfurt am Main, Germany
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17
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Susarla BTS, Seal RP, Zelenaia O, Watson DJ, Wolfe JH, Amara SG, Robinson MB. Differential regulation of GLAST immunoreactivity and activity by protein kinase C: evidence for modification of amino and carboxyl termini. J Neurochem 2005; 91:1151-63. [PMID: 15569258 DOI: 10.1111/j.1471-4159.2004.02791.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Many neurotransmitter transporters, including the GLT-1 and EAAC1 subtypes of the glutamate transporter, are regulated by protein kinase C (PKC) and these effects are associated with changes in cell surface expression. In the present study, the effects of PKC activation on the glutamate aspartate transporter (GLAST) subtype of glutamate transporter were examined in primary astrocyte cultures. Acute (30 min) exposure to the phorbol 12-myristate 13-acetate (PMA) increased (approximately 20%) transport activity but had the opposite effect on both total and cell surface immunoreactivity. Chronic treatment (6 or 24 h) with PMA had no effect on transport activity but caused an even larger decrease in total and cell surface immunoreactivity. This loss of immunoreactivity was observed using antibodies directed against three different cytoplasmic epitopes, and was blocked by the PKC antagonist, bisindolylmaleimide II. We provide biochemical and pharmacological evidence that the activity observed after treatment with PMA is mediated by GLAST. Two different flag-tagged variants of the human homolog of GLAST were introduced into astrocytes using lentiviral vectors. Although treatment with PMA caused a loss of transporter immunoreactivity, flag immunoreactivity did not change in amount or size. Together, these studies suggest that activation of PKC acutely up-regulates GLAST activity, but also results in modification of several different intracellular epitopes so that they are no longer recognized by anti-GLAST antibodies. We found that exposure of primary cultures of neurons/astrocytes to transient hypoxia/glucose deprivation also caused a loss of GLAST immunoreactivity that was attenuated by the PKC antagonist, bisindolylmaleimide II, suggesting that some acute insults previously thought to cause a loss of GLAST protein may mimic the phenomenon observed in the present study.
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Affiliation(s)
- Bala T S Susarla
- Department of Pediatrics, University of Pennsylvania and Children's Hospital of Philadelphia, Philadelphia, Pennsylvania, USA
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18
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Kunz S, Niederberger E, Ehnert C, Coste O, Pfenninger A, Kruip J, Wendrich TM, Schmidtko A, Tegeder I, Geisslinger G. The calpain inhibitor MDL 28170 prevents inflammation-induced neurofilament light chain breakdown in the spinal cord and reduces thermal hyperalgesia. Pain 2004; 110:409-18. [PMID: 15275793 DOI: 10.1016/j.pain.2004.04.031] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2003] [Revised: 02/18/2004] [Accepted: 04/13/2004] [Indexed: 02/01/2023]
Abstract
Since long-term hyperexcitability of nociceptive neurons in the spinal cord has been suggested to be caused and maintained by changes of protein expression we assessed protein patterns in lumbar spinal cord during a zymosan induced paw inflammation employing two-dimensional (2D) gel electrophoresis. 2D PAGE revealed a time-dependent breakdown of scaffolding proteins one of which was neurofilament light chain (NFL) protein, which has been previously found to be important for axonal architecture and transport. Nociception induced breakdown of NFL in the spinal cord and dorsal root ganglias was prevented by pretreatment of the animals with a single dose of the specific inhibitor of the protease calpain (MDL-28170) which has been shown to be the primary protease involved in neurofilament degradation in neurodegenerative diseases. Treatment with the calpain inhibitor also provided anti-inflammatory and anti-hyperalgesic effects in the zymosan-induced paw inflammation model irrespective of whether the drug was administered systemically (i.p.) or delivered onto the lumbar spinal cord. This suggests that the activation of calpain is involved in the sensitization of nociceptive neurons what is partly due to neurofilament breakdown but cleavage of other calpain substrates may also be involved. Our results indicate that inhibition of pathological calpain activity may present an interesting novel drug target in the treatment of pain and inflammation.
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Affiliation(s)
- Susanne Kunz
- pharmazentrum frankfurt, Institut für Klinische Pharmakologie, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany
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