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Arceneaux JS, Brockman AA, Khurana R, Chalkley MBL, Geben LC, Krbanjevic A, Vestal M, Zafar M, Weatherspoon S, Mobley BC, Ess KC, Ihrie RA. Multiparameter quantitative analyses of diagnostic cells in brain tissues from tuberous sclerosis complex. CYTOMETRY. PART B, CLINICAL CYTOMETRY 2024. [PMID: 38953209 DOI: 10.1002/cyto.b.22194] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 06/05/2024] [Accepted: 06/11/2024] [Indexed: 07/03/2024]
Abstract
The advent of high-dimensional imaging offers new opportunities to molecularly characterize diagnostic cells in disorders that have previously relied on histopathological definitions. One example case is found in tuberous sclerosis complex (TSC), a developmental disorder characterized by systemic growth of benign tumors. Within resected brain tissues from patients with TSC, detection of abnormally enlarged balloon cells (BCs) is pathognomonic for this disorder. Though BCs can be identified by an expert neuropathologist, little is known about the specificity and broad applicability of protein markers for these cells, complicating classification of proposed BCs identified in experimental models of this disorder. Here, we report the development of a customized machine learning pipeline (BAlloon IDENtifier; BAIDEN) that was trained to prospectively identify BCs in tissue sections using a histological stain compatible with high-dimensional cytometry. This approach was coupled to a custom 36-antibody panel and imaging mass cytometry (IMC) to explore the expression of multiple previously proposed BC marker proteins and develop a descriptor of BC features conserved across multiple tissue samples from patients with TSC. Here, we present a modular workflow encompassing BAIDEN, a custom antibody panel, a control sample microarray, and analysis pipelines-both open-source and in-house-and apply this workflow to understand the abundance, structure, and signaling activity of BCs as an example case of how high-dimensional imaging can be applied within human tissues.
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Affiliation(s)
- Jerome S Arceneaux
- Department of Biochemistry, Cancer Biology, Neuroscience, and Pharmacology, Meharry Medical College, Nashville, Tennessee, USA
| | - Asa A Brockman
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Rohit Khurana
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Mary-Bronwen L Chalkley
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
| | - Laura C Geben
- Department of Pharmacology, Vanderbilt University, Nashville, Tennessee, USA
| | - Aleksandar Krbanjevic
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Matthew Vestal
- Duke University Children's Hospital and Health Center, Durham, North Carolina, USA
| | - Muhammad Zafar
- Duke University Children's Hospital and Health Center, Durham, North Carolina, USA
| | - Sarah Weatherspoon
- Neuroscience Institute, Le Bonheur Children's Hospital, Memphis, Tennessee, USA
- Department of Pediatrics, University of Tennessee Health Science Center, Memphis, Tennessee, USA
| | - Bret C Mobley
- Department of Pathology, Microbiology, & Immunology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Kevin C Ess
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Department of Neurology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Section of Child Neurology, University of Colorado Anschutz Medical Center, Aurora, Colorado, USA
| | - Rebecca A Ihrie
- Department of Cell & Developmental Biology, Vanderbilt University, Nashville, Tennessee, USA
- Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
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2
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Vicente M, Addo-Osafo K, Vossel K. Latest advances in mechanisms of epileptic activity in Alzheimer's disease and dementia with Lewy Bodies. Front Neurol 2024; 15:1277613. [PMID: 38390593 PMCID: PMC10882721 DOI: 10.3389/fneur.2024.1277613] [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: 08/14/2023] [Accepted: 01/12/2024] [Indexed: 02/24/2024] Open
Abstract
Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) stand as the prevailing sources of neurodegenerative dementia, impacting over 55 million individuals across the globe. Patients with AD and DLB exhibit a higher prevalence of epileptic activity compared to those with other forms of dementia. Seizures can accompany AD and DLB in early stages, and the associated epileptic activity can contribute to cognitive symptoms and exacerbate cognitive decline. Aberrant neuronal activity in AD and DLB may be caused by several mechanisms that are not yet understood. Hyperexcitability could be a biomarker for early detection of AD or DLB before the onset of dementia. In this review, we compare and contrast mechanisms of network hyperexcitability in AD and DLB. We examine the contributions of genetic risk factors, Ca2+ dysregulation, glutamate, AMPA and NMDA receptors, mTOR, pathological amyloid beta, tau and α-synuclein, altered microglial and astrocytic activity, and impaired inhibitory interneuron function. By gaining a deeper understanding of the molecular mechanisms that cause neuronal hyperexcitability, we might uncover therapeutic approaches to effectively ease symptoms and slow down the advancement of AD and DLB.
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Affiliation(s)
- Mariane Vicente
- Mary S. Easton Center for Alzheimer's Research and Care, Department of Neurology, David Geffen School of Medicine at University of California, Los Angeles, CA, United States
| | - Kwaku Addo-Osafo
- Mary S. Easton Center for Alzheimer's Research and Care, Department of Neurology, David Geffen School of Medicine at University of California, Los Angeles, CA, United States
| | - Keith Vossel
- Mary S. Easton Center for Alzheimer's Research and Care, Department of Neurology, David Geffen School of Medicine at University of California, Los Angeles, CA, United States
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Suslova M, Kortzak D, Machtens JP, Kovermann P, Fahlke C. Apo state pore opening as functional basis of increased EAAT anion channel activity in episodic ataxia 6. Front Physiol 2023; 14:1147216. [PMID: 37538371 PMCID: PMC10394623 DOI: 10.3389/fphys.2023.1147216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 07/07/2023] [Indexed: 08/05/2023] Open
Abstract
SLC1A2 and SLC1A3 encode the glial glutamate transporters EAAT2 and EAAT1, which are not only the predominant glutamate uptake carriers in our brain, but also function as anion channels. Two homologous mutations, which predict substitutions of prolines in the center of the fifth transmembrane helix by arginine (P289R EAAT2, P290R EAAT1), have been identified in patients with epileptic encephalopathy (SLC1A2) or with episodic ataxia type 6 (SLC1A3). Both mutations have been shown to impair glutamate uptake and to increase anion conduction. The molecular processes that link the disease-causing mutations to two major alterations of glutamate transporter function remain insufficiently understood. The mutated proline is conserved in every EAAT. Since the pathogenic changes mainly affect the anion channel function, we here study the functional consequences of the homologous P312R mutation in the neuronal glutamate transporter EAAT4, a low capacity glutamate transporter with predominant anion channel function. To assess the impact of charge and structure of the inserted amino acid for the observed functional changes, we generated and functionally evaluated not only P312R, but also substitutions of P312 with all other amino acids. However, only exchange of proline by arginine, lysine, histidine and asparagine were functionally tolerated. We compared WT, P312R and P312N EAAT4 using a combination of cellular electrophysiology, fast substrate application and kinetic modelling. We found that WT and mutant EAAT4 anion currents can be described with a 11-state model of the transport cycle, in which several states are connected to branching anion channel states to account for the EAAT anion channel function. Substitutions of P312 modify various transitions describing substrate binding/unbinding, translocation or anion channel opening. Most importantly, P312R generates a new anion conducting state that is accessible in the outward facing apo state and that is the main determinant of the increased anion conduction of EAAT transporters carrying this mutation. Our work provides a quantitative description how a naturally occurring mutation changes glutamate uptake and anion currents in two genetic diseases.
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Kolen B, Borghans B, Kortzak D, Lugo V, Hannack C, Guzman RE, Ullah G, Fahlke C. Vesicular glutamate transporters are H +-anion exchangers that operate at variable stoichiometry. Nat Commun 2023; 14:2723. [PMID: 37169755 PMCID: PMC10175566 DOI: 10.1038/s41467-023-38340-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 04/26/2023] [Indexed: 05/13/2023] Open
Abstract
Vesicular glutamate transporters accumulate glutamate in synaptic vesicles, where they also function as a major Cl- efflux pathway. Here we combine heterologous expression and cellular electrophysiology with mathematical modeling to understand the mechanisms underlying this dual function of rat VGLUT1. When glutamate is the main cytoplasmic anion, VGLUT1 functions as H+-glutamate exchanger, with a transport rate of around 600 s-1 at -160 mV. Transport of other large anions, including aspartate, is not stoichiometrically coupled to H+ transport, and Cl- permeates VGLUT1 through an aqueous anion channel with unitary transport rates of 1.5 × 105 s-1 at -160 mV. Mathematical modeling reveals that H+ coupling is sufficient for selective glutamate accumulation in model vesicles and that VGLUT Cl- channel function increases the transport efficiency by accelerating glutamate accumulation and reducing ATP-driven H+ transport. In summary, we provide evidence that VGLUT1 functions as H+-glutamate exchanger that is partially or fully uncoupled by other anions.
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Affiliation(s)
- Bettina Kolen
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Bart Borghans
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Daniel Kortzak
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Victor Lugo
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Cora Hannack
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Raul E Guzman
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL, 33620, USA
| | - Christoph Fahlke
- Institute of Biological Information Processing, Molekular- und Zellphysiologie (IBI-1), Forschungszentrum Jülich, 52428, Jülich, Germany.
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Alijanpour S, Miryounesi M, Ghafouri-Fard S. The role of excitatory amino acid transporter 2 (EAAT2) in epilepsy and other neurological disorders. Metab Brain Dis 2023; 38:1-16. [PMID: 36173507 DOI: 10.1007/s11011-022-01091-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 09/15/2022] [Indexed: 02/03/2023]
Abstract
Glutamate is the major excitatory neurotransmitter in the central nervous system (CNS). Excitatory amino acid transporters (EAATs) have important roles in the uptake of glutamate and termination of glutamatergic transmission. Up to now, five EAAT isoforms (EAAT1-5) have been identified in mammals. The main focus of this review is EAAT2. This protein has an important role in the pathoetiology of epilepsy. De novo dominant mutations, as well as inherited recessive mutation in this gene, have been associated with epilepsy. Moreover, dysregulation of this protein is implicated in a range of neurological diseases, namely amyotrophic lateral sclerosis, alzheimer's disease, parkinson's disease, schizophrenia, epilepsy, and autism. In this review, we summarize the role of EAAT2 in epilepsy and other neurological disorders, then provide an overview of the therapeutic modulation of this protein.
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Affiliation(s)
- Sahar Alijanpour
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Miryounesi
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Soudeh Ghafouri-Fard
- Department of Medical Genetics, Faculty of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Fahlke C. Membrane physiology and biophysics-Another milestone. Front Physiol 2022; 13:1081004. [PMID: 36505083 PMCID: PMC9733666 DOI: 10.3389/fphys.2022.1081004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 11/14/2022] [Indexed: 11/27/2022] Open
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Sha L, Li G, Zhang X, Lin Y, Qiu Y, Deng Y, Zhu W, Xu Q. Pharmacological induction of AMFR increases functional EAAT2 oligomer levels and reduces epileptic seizures in mice. JCI Insight 2022; 7:160247. [PMID: 35938532 PMCID: PMC9462477 DOI: 10.1172/jci.insight.160247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Accepted: 06/24/2022] [Indexed: 11/29/2022] Open
Abstract
Dysregulation of excitatory amino acid transporter 2 (EAAT2) contributes to the development of temporal lobe epilepsy (TLE). Several strategies for increasing total EAAT2 levels have been proposed. However, the mechanism underlying the oligomeric assembly of EAAT2, impairment of which inhibits the formation of functional oligomers by EAAT2 monomers, is still poorly understood. In the present study, we identified E3 ubiquitin ligase AMFR as an EAAT2-interacting protein. AMFR specifically increased the level of EAAT2 oligomers rather than inducing protein degradation through K542-specific ubiquitination. By using tissues from humans with TLE and epilepsy model mice, we observed that AMFR and EAAT2 oligomer levels were simultaneously decreased in the hippocampus. Screening of 2386 FDA-approved drugs revealed that the most common analgesic/antipyretic medicine, acetaminophen (APAP), can induce AMFR transcriptional activation via transcription factor SP1. Administration of APAP protected against pentylenetetrazol-induced epileptogenesis. In mice with chronic epilepsy, APAP treatment partially reduced the occurrence of spontaneous seizures and greatly enhanced the antiepileptic effects of 17AAG, an Hsp90 inhibitor that upregulates total EAAT2 levels, when the 2 compounds were administered together. In summary, our studies reveal an essential role for AMFR in regulating the oligomeric state of EAAT2 and suggest that APAP can improve the efficacy of EAAT2-targeted antiepileptic treatments.
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Affiliation(s)
- Longze Sha
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
- Neuroscience Center, Chinese Academy of Medical Sciences, Beijing, China
| | - Guanjun Li
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Xiuneng Zhang
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Yarong Lin
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Yunjie Qiu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Yu Deng
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
| | - Wanwan Zhu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
- Neuroscience Center, Chinese Academy of Medical Sciences, Beijing, China
| | - Qi Xu
- State Key Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Beijing, China
- Neuroscience Center, Chinese Academy of Medical Sciences, Beijing, China
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8
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Chen I, Wu Q, Font J, Ryan RM. The twisting elevator mechanism of glutamate transporters reveals the structural basis for the dual transport-channel functions. Curr Opin Struct Biol 2022; 75:102405. [PMID: 35709614 DOI: 10.1016/j.sbi.2022.102405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2022] [Revised: 05/10/2022] [Accepted: 05/12/2022] [Indexed: 11/16/2022]
Abstract
Glutamate transporters facilitate the removal of this excitatory neurotransmitter from the synapse. Increasing evidence indicates that this process is linked to intrinsic chloride channel activity that is thermodynamically uncoupled from substrate transport. A recent cryo-EM structure of GltPh - an archaeal homolog of the glutamate transporters - in an open channel state has shed light on the structural basis for channel opening formed at the interface of two domains within the transporter which is gated by two clusters of hydrophobic residues. These transporters cycle through several conformational states during the transport process, including the chloride conducting state, which appears to be stabilised by protein-membrane interactions and membrane deformation. Several point mutations that perturb the chloride conductance can have detrimental effects and are linked to the pathogenesis of the neurological disorder, episodic ataxia type 6.
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Affiliation(s)
- Ichia Chen
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Qianyi Wu
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Josep Font
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia
| | - Renae M Ryan
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, NSW, Australia.
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Guzman RE, Sierra-Marquez J, Bungert-Plümke S, Franzen A, Fahlke C. Functional Characterization of CLCN4 Variants Associated With X-Linked Intellectual Disability and Epilepsy. Front Mol Neurosci 2022; 15:872407. [PMID: 35721313 PMCID: PMC9198718 DOI: 10.3389/fnmol.2022.872407] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 04/27/2022] [Indexed: 11/13/2022] Open
Abstract
Early/late endosomes, recycling endosomes, and lysosomes together form the endo-lysosomal recycling pathway. This system plays a crucial role in cell differentiation and survival, and dysregulation of the endo-lysosomal system appears to be important in the pathogenesis of neurodevelopmental and neurodegenerative diseases. Each endo-lysosomal compartment fulfils a specific function, which is supported by ion transporters and channels that modify ion concentrations and electrical gradients across endo-lysosomal membranes. CLC-type Cl–/H+ exchangers are a group of endo-lysosomal transporters that are assumed to regulate luminal acidification and chloride concentration in multiple endosomal compartments. Heterodimers of ClC-3 and ClC-4 localize to various internal membranes, from the endoplasmic reticulum and Golgi to recycling endosomes and late endosomes/lysosomes. The importance of ClC-4-mediated ion transport is illustrated by the association of naturally occurring CLCN4 mutations with epileptic encephalopathy, intellectual disability, and behavioral disorders in human patients. However, how these mutations affect the expression, subcellular localization, and function of ClC-4 is insufficiently understood. We here studied 12 CLCN4 variants that were identified in patients with X-linked intellectual disability and epilepsy and were already characterized to some extent in earlier work. We analyzed the consequences of these mutations on ClC-4 ion transport, subcellular trafficking, and heterodimerization with ClC-3 using heterologous expression in mammalian cells, biochemistry, confocal imaging, and whole-cell patch-clamp recordings. The mutations led to a variety of changes in ClC-4 function, ranging from gain/loss of function and impaired heterodimerization with ClC-3 to subtle impairments in transport functions. Our results suggest that even slight functional changes to the endosomal Cl–/H+ exchangers can cause serious neurological symptoms.
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