The immunoproteasome β5i subunit is a key contributor to ictogenesis in a rat model of chronic epilepsy

Mishto, Michele; Raza, Muhammad Liaquat; Biase, Dario de; Ravizza, Teresa; Vasuri, Francesco; Martucci, Morena; Keller, Christin; Bellavista, Elena; Buchholz, Tonia J.; Kloetzel, Peter M.; Pession, Annalisa; Vezzani, Annamaria; Heinemann, Uwe

doi:10.1016/j.bbi.2015.05.007

Cited by 32 publications

(42 citation statements)

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“…TLR4 was not detectable in sham controls ( not shown ; see Refs 33,58). Rad, stratum radiatum ( d,e ).…”

Section: Figurementioning

confidence: 87%

“…Their convergent IL-1R1 and TLR4 signaling activation in neurons has been previously reported to modulate neuronal functions, for example by inducing post-translational changes in glutamate or GABAA receptor-gated channels [43, 44, 57]. Notably, TLR4 expression was undetectable by immunohistochemistry in sham rats [33, 58]. However, basal level of TLR4 expression were measured using RTqPCR [59, 60].…”

Section: Discussionmentioning

confidence: 99%

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Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells

et al. 2018

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Neuroinflammation is consistently found in many neurological disorders, but whether or not the inflammatory response independently affects neuronal network properties is poorly understood. Here, we report that intracerebroventricular injection of the prototypical inflammatory molecule lipopolysaccharide (LPS) in rats triggered a strong and long lasting inflammatory response in hippocampal microglia associated with a concomitant up-regulation of Toll-like receptor (TLR4) in pyramidal and hilar neurons. This, in turn, was associated with a significant reduction of the dendritic hyperpolarization-activated cyclic-AMP gated channel type 1 (HCN1) protein level while Kv4.2 channels were unaltered as assessed by western blot. Immunohistochemistry confirmed the HCN1 decrease in CA1 pyramidal neurons and showed that these changes were associated with a reduction of TRIP8b, an auxiliary subunit for HCN channels implicated in channel subcellular localization and trafficking. At the physiological level, this effect translated into a 50% decrease in HCN1-mediated currents (Ih) measured in the distal dendrites of hippocampal CA1 pyramidal cells. At the functional level, the band-pass filtering properties of dendrites in the theta frequency range (4-12 Hz) and their temporal summation properties were compromised. We conclude that neuroinflammation can independently trigger an acquired channelopathy in CA1 pyramidal cell dendrites that alters their integrative properties. By directly changing cellular function, this phenomenon may participate in the phenotypic expression of various brain diseases.

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“…TLR4 was not detectable in sham controls ( not shown ; see Refs 33,58). Rad, stratum radiatum ( d,e ).…”

Section: Figurementioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells

et al. 2018

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“…Thus, we may speculate about the existence of a reinforcing feedback loop between NF-kB pathway and the immunoproteasome system, which may play a crucial role in perpetuating the pro-epileptogenic inflammatory response in epilepsy. Interestingly, Mishto et al [18] provide additional experimental evidence of the regulation of β5i subunit by TLR4 signaling in epileptogenic tissue.…”

Section: Discussionmentioning

confidence: 99%

“…An example of the possible use of inhibition of the immunoproteasome as therapeutic strategy in epilepsy is represented by the study of Mishto and colleagues [18] in which specific inhibition of the β5i subunit by ONX-0914 [64] resulted in prevention, or significant delay, of 4-aminopyridine-induced seizure-like events in acute rat hippocampal/entorhinal cortex slices, particularly in slices of epileptic rats. Clinically approved proteasome inhibitors targeting the catalytic activity of both the constitutive proteasome and the immunoproteasome have been already used in hematological malignancies [65–67].…”

Section: Discussionmentioning

confidence: 99%

“…Interestingly, induction of β1i and β5i subunits has been also observed in specimens of patients with pharmaco-resistent mesial temporal lobe epilepsy (MTLE; [17]). Moreover, recent experimental data support a role for the β5i subunit in modulating seizure generation in epileptic tissue, and interestingly, this subunit was not upregulated in rats exposed to pilocarpine but not developing SE and spontaneous seizures [18]. …”

Section: Introductionmentioning

confidence: 99%

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Dysregulation of the (immuno)proteasome pathway in malformations of cortical development

Scheppingen

Broekaart

Scholl

et al. 2016

J Neuroinflammation

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BackgroundThe proteasome is a multisubunit enzyme complex involved in protein degradation, which is essential for many cellular processes. During inflammation, the constitutive subunits are replaced by their inducible counterparts, resulting in the formation of the immunoproteasome.MethodsWe investigated the expression pattern of constitutive (β1, β5) and immunoproteasome (β1i, β5i) subunits using immunohistochemistry in malformations of cortical development (MCD; focal cortical dysplasia (FCD) IIa and b, cortical tubers from patients with tuberous sclerosis complex (TSC), and mild MCD (mMCD)). Glial cells in culture were used to elucidate the mechanisms regulating immunoproteasome subunit expression.ResultsIncreased expression was observed in both FCD II and TSC; β1, β1i, β5, and β5i were detected (within cytosol and nucleus) in dysmorphic neurons, balloon/giant cells, and reactive astrocytes. Glial and neuronal nuclear expression positively correlated with seizure frequency. Positive correlation was also observed between the glial expression of constitutive and immunoproteasome subunits and IL-1β. Accordingly, the proteasome subunit expression was modulated by IL-1β in human astrocytes in vitro. Expression of both constitutive and immunoproteasome subunits in FCD II-derived astroglial cultures was negatively regulated by treatment with the immunomodulatory drug rapamycin (inhibitor of the mammalian target of rapamycin (mTOR) pathway, which is activated in both TSC and FCD II).ConclusionsThese observations support the dysregulation of the proteasome system in both FCD and TSC and provide new insights on the mechanism of regulation the (immuno)proteasome in astrocytes and the molecular links between inflammation, mTOR activation, and epilepsy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0662-z) contains supplementary material, which is available to authorized users.

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CD8⁺ T cells of Listeria monocytogenes‐infected mice recognize both linear and spliced proteasome products

et al. 2016

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CD8+ T cells responding to infection recognize pathogen-derived epitopes presented by MHC class-I molecules. While most of such epitopes are generated by proteasomemediated antigen cleavage, analysis of tumor antigen processing has revealed that epitopes may also derive from proteasome-catalyzed peptide splicing (PCPS). To determine whether PCPS contributes to epitope processing during infection, we analyzed the fragments produced by purified proteasomes from a Listeria monocytogenes polypeptide. Mass spectrometry identified a known H-2K b -presented linear epitope (LLO 296-304 ) in the digests, as well as four spliced peptides that were trimmed by ERAP into peptides with in silico predicted H-2K b binding affinity. These spliced peptides, which displayed sequence similarity with LLO 296-304 , bound to H-2K b molecules in cellular assays and one of the peptides was recognized by CD8 + T cells of infected mice. This spliced epitope differed by one amino acid from LLO 296-304 and double staining with LLO 296-304 -and spliced peptidefolded MHC multimers showed that LLO 296-304 and its spliced variant were recognized by the same CD8 + T cells. Thus, PCPS multiplies the variety of peptides that is processed from an antigen and leads to the production of epitope variants that can be recognized by cross-reacting pathogen-specific CD8 + T cells. Such mechanism may reduce the chances for pathogen immune evasion. Eur. J. Immunol. 2016Immunol. . 46: 1109Immunol. -1118 Although proteasomes are present in all eukaryotic cells, their subunit composition may vary. Proteasomes consist of four stacked rings, formed of seven subunits each. The two inner rings are composed of β-subunits, of which the three subunits β1, β2, and β5 are constitutively expressed and display catalytic activity. Exposure of cells to inflammatory cytokines, such as IFN-γ, induces the expression of the facultative subunits β1i/LMP2, β2i/MECL-1, and β5i/LMP7 that are preferentially incorporated by newly assembled proteasome complexes, leading to the formation of immunoproteasomes [4]. Cells of the immune system express different combinations of the facultative subunits in a constitutive manner. Keywords: CD8Proteasomes generate epitopes by simple peptide-bond cleavage as well as by proteasome-catalyzed peptide splicing (PCPS), which involves the linkage of fragments originally distant in the parental protein [5][6][7][8][9]. Cleavage by the proteasome is the result of a nucleophilic attack on peptide bonds by the catalytic threonines of the β1, β2, and β5 subunits in constitutive proteasomes, or of the β1i, β2i, and β5i subunits in immunoproteasomes. This attack results in the formation of an acyl-enzyme intermediate. These peptides are released from the proteasome by rapid hydrolysis, giving rise to linear proteasome-generated products. However, when the acyl-enzyme intermediate is stabilized at the active site for an extended time span, the N-termini of released peptide fragments may outcompete hydrolysis and make a nucleophilic attack on the ester bon...

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The immunoproteasome β5i subunit is a key contributor to ictogenesis in a rat model of chronic epilepsy

Cited by 32 publications

References 56 publications

Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells

Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells

Dysregulation of the (immuno)proteasome pathway in malformations of cortical development

CD8⁺ T cells of Listeria monocytogenes‐infected mice recognize both linear and spliced proteasome products

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The immunoproteasome β5i subunit is a key contributor to ictogenesis in a rat model of chronic epilepsy

Cited by 32 publications

References 56 publications

Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells

Neuroinflammation Alters Integrative Properties of Rat Hippocampal Pyramidal Cells

Dysregulation of the (immuno)proteasome pathway in malformations of cortical development

CD8+ T cells of Listeria monocytogenes‐infected mice recognize both linear and spliced proteasome products

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CD8⁺ T cells of Listeria monocytogenes‐infected mice recognize both linear and spliced proteasome products