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Maurer M, Lazaridis T. Transmembrane β-Barrel Models of α-Synuclein Oligomers. J Chem Inf Model 2023; 63:7171-7179. [PMID: 37963823 DOI: 10.1021/acs.jcim.3c00997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
The aggregation of α-synuclein is implicated in a number of neurodegenerative diseases, such as Parkinson's and Multiple System Atrophy, but the role of these aggregates in disease development is not clear. One possible mechanism of cytotoxicity is the disturbance or permeabilization of cell membranes by certain types of oligomers. However, no high-resolution structure of such membrane-embedded complexes has ever been determined. Here we construct and evaluate putative transmembrane β-barrels formed by this protein. Examination of the α-synuclein sequence reveals two regions that could form membrane-embedded β-hairpins: 64-92 (the NAC), and 35-56, which harbors many familial Parkinson's mutations. The stability of β-barrels formed by these hairpins is examined first in implicit membrane pores and then by multimicrosecond all-atom simulations. We find that a NAC region barrel remains stably inserted and hydrated for at least 10 μs. A 35-56 barrel remains stably inserted in the membrane but dehydrates and collapses if all His50 are neutral or if His50 is replaced by Q. If half of the His50 are doubly protonated, the barrel takes an oval shape but remains hydrated for at least 10 μs. Possible implications of these findings for α-synuclein pathology are discussed.
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Affiliation(s)
- Manuela Maurer
- Department of Chemistry & Biochemistry, City College of New York/CUNY, 160 Convent Ave, New York, New York 10031, United States
| | - Themis Lazaridis
- Department of Chemistry & Biochemistry, City College of New York/CUNY, 160 Convent Ave, New York, New York 10031, United States
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Jin X, Zhou M, Chen S, Li D, Cao X, Liu B. Effects of pH alterations on stress- and aging-induced protein phase separation. Cell Mol Life Sci 2022; 79:380. [PMID: 35750966 PMCID: PMC9232405 DOI: 10.1007/s00018-022-04393-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/26/2022] [Accepted: 05/21/2022] [Indexed: 01/18/2023]
Abstract
Upon stress challenges, proteins/RNAs undergo liquid–liquid phase separation (LLPS) to fine-tune cell physiology and metabolism to help cells adapt to adverse environments. The formation of LLPS has been recently linked with intracellular pH, and maintaining proper intracellular pH homeostasis is known to be essential for the survival of organisms. However, organisms are constantly exposed to diverse stresses, which are accompanied by alterations in the intracellular pH. Aging processes and human diseases are also intimately linked with intracellular pH alterations. In this review, we summarize stress-, aging-, and cancer-associated pH changes together with the mechanisms by which cells regulate cytosolic pH homeostasis. How critical cell components undergo LLPS in response to pH alterations is also discussed, along with the functional roles of intracellular pH fluctuation in the regulation of LLPS. Further studies investigating the interplay of pH with other stressors in LLPS regulation and identifying protein responses to different pH levels will provide an in-depth understanding of the mechanisms underlying pH-driven LLPS in cell adaptation. Moreover, deciphering aging and disease-associated pH changes that influence LLPS condensate formation could lead to a deeper understanding of the functional roles of biomolecular condensates in aging and aging-related diseases.
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Affiliation(s)
- Xuejiao Jin
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Min Zhou
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Shuxin Chen
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Danqi Li
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Xiuling Cao
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China.
| | - Beidong Liu
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China. .,Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan 9C, 413 90, Goteborg, Sweden. .,Center for Large-Scale Cell-Based Screening, Faculty of Science, University of Gothenburg, Medicinaregatan 9C, 413 90, Goteborg, Sweden.
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Zefirov AL, Mukhametzyanov RD, Zakharov AV, Mukhutdinova KA, Odnoshivkina UG, Petrov AM. Intracellular Acidification Suppresses Synaptic Vesicle Mobilization in the Motor Nerve Terminals. Acta Naturae 2020; 12:105-113. [PMID: 33456982 PMCID: PMC7800596 DOI: 10.32607/actanaturae.11054] [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] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 09/07/2020] [Indexed: 01/27/2023] Open
Abstract
Intracellular protons play a special role in the regulation of presynaptic processes, since the functioning of synaptic vesicles and endosomes depends on their acidification by the H+-pump. Furthermore, transient acidification of the intraterminal space occurs during synaptic activity. Using microelectrode recording of postsynaptic responses (an indicator of neurotransmitter release) and exo-endocytic marker FM1-43, we studied the effects of intracellular acidification with propionate on the presynaptic events underlying neurotransmitter release. Cytoplasmic acidification led to a marked decrease in neurotransmitter release during the first minute of a 20-Hz stimulation in the neuromuscular junctions of mouse diaphragm and frog cutaneous pectoris muscle. This was accompanied by a reduction in the FM1-43 loss during synaptic vesicle exocytosis in response to the stimulation. Estimation of the endocytic uptake of FM1-43 showed no disruption in synaptic vesicle endocytosis. Acidification completely prevented the action of the cell-membrane permeable compound 24-hydroxycholesterol, which can enhance synaptic vesicle mobilization. Thus, the obtained results suggest that an increase in [H+]in negatively regulates neurotransmission due to the suppression of synaptic vesicle delivery to the sites of exocytosis at high activity. This mechanism can be a part of the negative feedback loop in regulating neurotransmitter release.
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Affiliation(s)
- A. L. Zefirov
- Kazan State Medical University, Department of Normal Physiology, Kazan, 420012 Russia
- Institute of Neuroscience, Kazan State Medical University, Kazan, 420012 Russia
| | - R. D. Mukhametzyanov
- Kazan State Medical University, Department of Normal Physiology, Kazan, 420012 Russia
| | - A. V. Zakharov
- Kazan State Medical University, Department of Normal Physiology, Kazan, 420012 Russia
- Kazan Federal University, Kazan, 420008 Russia
| | - K. A. Mukhutdinova
- Institute of Neuroscience, Kazan State Medical University, Kazan, 420012 Russia
| | - U. G. Odnoshivkina
- Kazan State Medical University, Department of Normal Physiology, Kazan, 420012 Russia
| | - A. M. Petrov
- Kazan State Medical University, Department of Normal Physiology, Kazan, 420012 Russia
- Institute of Neuroscience, Kazan State Medical University, Kazan, 420012 Russia
- Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center “Kazan Scientific Center of RAS”, Kazan, 420111 Russia
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Traub RD, Moeller F, Rosch R, Baldeweg T, Whittington MA, Hall SP. Seizure initiation in infantile spasms vs. focal seizures: proposed common cellular mechanisms. Rev Neurosci 2020; 31:181-200. [PMID: 31525161 DOI: 10.1515/revneuro-2019-0030] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Accepted: 06/01/2019] [Indexed: 11/15/2022]
Abstract
Infantile spasms (IS) and seizures with focal onset have different clinical expressions, even when electroencephalography (EEG) associated with IS has some degree of focality. Oddly, identical pathology (with, however, age-dependent expression) can lead to IS in one patient vs. focal seizures in another or even in the same, albeit older, patient. We therefore investigated whether the cellular mechanisms underlying seizure initiation are similar in the two instances: spasms vs. focal. We noted that in-common EEG features can include (i) a background of waves at alpha to delta frequencies; (ii) a period of flattening, lasting about a second or more - the electrodecrement (ED); and (iii) often an interval of very fast oscillations (VFO; ~70 Hz or faster) preceding, or at the beginning of, the ED. With IS, VFO temporally coincides with the motor spasm. What is different between the two conditions is this: with IS, the ED reverts to recurring slow waves, as occurring before the ED, whereas with focal seizures the ED instead evolves into an electrographic seizure, containing high-amplitude synchronized bursts, having superimposed VFO. We used in vitro data to help understand these patterns, as such data suggest cellular mechanisms for delta waves, for VFO, for seizure-related burst complexes containing VFO, and, more recently, for the ED. We propose a unifying mechanistic hypothesis - emphasizing the importance of brain pH - to explain the commonalities and differences of EEG signals in IS versus focal seizures.
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Affiliation(s)
- Roger D Traub
- IBM Thomas J. Watson Research Center, Yorktown Heights, NY 10598, USA
- Department of Neurology, Columbia University, New York, NY 10032, USA
| | - Friederike Moeller
- Department of Clinical Neurophysiology, Great Ormond Street Hospital, London WC1N 3JH, UK
| | - Richard Rosch
- MRC Centre for Neurodevelopmental Disorders, King's College London, New Hunt's House, London SE1 1UL, UK
| | - Torsten Baldeweg
- Institute of Child Health, University College London, 30 Guildford Street, London WC1N 1EH, UK
| | | | - Stephen P Hall
- Hull York Medical School, University of York, Heslington YO10 5DD, UK
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Ponto LLB, Magnotta VA, Menda Y, Moser DJ, Oleson JJ, Harlynn EL, DeVries SD, Wemmie JA, Schultz SK. Comparison of T 1Rho MRI, Glucose Metabolism, and Amyloid Burden Across the Cognitive Spectrum: A Pilot Study. J Neuropsychiatry Clin Neurosci 2020; 32:352-361. [PMID: 32283991 PMCID: PMC8717916 DOI: 10.1176/appi.neuropsych.19100221] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE The pathological cascades associated with the development of Alzheimer's disease (AD) have a common element: acidosis. T1rho MRI is a pH-sensitive measure, with higher values associated with greater neuropathological burden. The authors investigated the relationship between T1rho imaging and AD-associated pathologies as determined by available diagnostic imaging techniques. METHODS Twenty-seven participants (men, N=13, women, N=14; ages 55-90) across the cognitive spectrum (healthy control subjects [HCs] with normal cognition, N=17; participants with mild cognitive impairment [MCI], N=7; participants with mild AD, N=3) underwent neuropsychological testing, MRI (T1-weighted and T1rho [spin-lattice relaxation time in the rotating frame]), and positron emission tomography imaging ([11C]Pittsburg compound B for amyloid burden [N=26] and [18F]fluorodeoxyglucose for cerebral glucose metabolism [N=12]). The relationships between global T1rho values and neuropsychological, demographic, and imaging measures were explored. RESULTS Global mean and median T1rho were positively associated with age. After controlling for age, higher global T1rho was associated with poorer cognitive function, poorer memory function (immediate and delayed memory scores), higher amyloid burden, and more abnormal cerebral glucose metabolism. Regional T1rho values, when controlling for age, significantly differed between HCs and participants with MCI or AD in select frontal, cingulate, and parietal regions. CONCLUSIONS Higher T1rho values were associated with greater cognitive impairment and pathological burden. T1rho, a biomarker that varies according to a feature common to each cascade rather than one that is unique to a particular pathology, has the potential to serve as a metric of neuropathology, theoretically providing a measure for assessing pathological status and for monitoring the neurodegeneration trajectory.
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Affiliation(s)
| | - Vincent A. Magnotta
- Department of Radiology, Carver College of Medicine, University of Iowa,Department of Psychiatry, Carver College of Medicine, University of Iowa
| | - Yusuf Menda
- Department of Radiology, Carver College of Medicine, University of Iowa
| | - David J. Moser
- Department of Psychiatry, Carver College of Medicine, University of Iowa
| | - Jacob J. Oleson
- Department of Biostatistics, College of Public Health, University of Iowa
| | - Emily L. Harlynn
- Department of Radiology, Carver College of Medicine, University of Iowa
| | - Sean D. DeVries
- Department of Biostatistics, College of Public Health, University of Iowa
| | - John A. Wemmie
- Department of Psychiatry, Carver College of Medicine, University of Iowa
| | - Susan K. Schultz
- Department of Psychiatry, Carver College of Medicine, University of Iowa
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Bonnet U, Bingmann D, Speckmann EJ, Wiemann M. Levetiracetam mediates subtle pH-shifts in adult human neocortical pyramidal cells via an inhibition of the bicarbonate-driven neuronal pH-regulation - Implications for excitability and plasticity modulation. Brain Res 2019; 1710:146-156. [PMID: 30590026 DOI: 10.1016/j.brainres.2018.12.039] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 11/24/2018] [Accepted: 12/23/2018] [Indexed: 01/20/2023]
Abstract
The intracellular pH (pHi) of mammalian central neurons is tightly regulated and small pHi-fluctuations can fine-tune inter-/intracellular signaling, excitability, and synaptic plasticity. The research-gap about the pHi-regulation of human brain neurons is addressed here by testing possible influences of the anticonvulsant levetiracetam (LEV). BCECF-AM-loaded neocortical pyramidal cells were fluorometrically investigated in slice-preparations of tissue resected from the middle temporal gyrus of five adults with intractable temporal-lobe epilepsy. Recovery-slope from intracellular acidification following an ammonium prepulse (APP) was used to measure the pHi-regulation. Among twenty pyramidal cells exposed to 50 μM LEV, the resting pHi (7.09 ± 0.14) was lowered in eight (40%) neurons, on average by 0.02 ± 0.011 pH-units. In three (15%) and nine (45%) neurons, a minimal alkaline shift (0.017 ± 0.004 pH-units) and no pHi-shift occurred, respectively. The LEV-induced pHi-shifts were positively correlated with the resting pHi (r = 0.6, p = 0.006, n = 20). In five neurons, which all had responded on LEV with an acidification before, the recovery from APP-acidification was significantly delayed during LEV (p < 0.001). This inhibitory LEV-effect on pHi-regulation i) was similar to that of 200 μM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (n = 2) and ii) did not occur under nominal bicarbonate-free conditions (n = 2). Thus, LEV lowered the pHi of human neocortical pyramidal cells most likely by a weakening of the transmembrane HCO3(-)-mediated acid-extrusion. This might contribute to LEV's anticonvulsive potency. Neurons with more acidic resting pHi-values showed a minimal alkalization upon LEV providing a mechanism for paradoxical proconvulsive LEV-effects rarely observed in epilepsy patients. The significance of these subtle pHi-shifts for cortical excitability and plasticity is discussed.
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Affiliation(s)
- Udo Bonnet
- Department of Psychiatry, Psychotherapy, and Psychosomatic Medicine, Evangelisches Krankenhaus Castrop-Rauxel, Academic Teaching Hospital of the University Duisburg-Essen, Castrop-Rauxel, Germany; Department of Psychiatry and Psychotherapy, Faculty of Medicine, LVR-Hospital Essen, University of Duisburg-Essen, Essen, Germany.
| | - Dieter Bingmann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany
| | | | - Martin Wiemann
- Institute of Physiology, University of Duisburg-Essen, Essen, Germany; IBE R&D gGmbH, Institute for Lung Health, D-48149 Münster, Germany
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