scholarly journals Tau Tubulin Kinase TTBK2 Sensitivity of Glutamate Receptor GluK2

2016 ◽  
Vol 39 (4) ◽  
pp. 1444-1452 ◽  
Author(s):  
Kristina Nieding ◽  
Veronika Matschke ◽  
Sven G. Meuth ◽  
Florian Lang ◽  
Guiscard Seebohm ◽  
...  
Keyword(s):  
Confocal Microscopy ◽  
Cell Membrane ◽  
Glutamate Receptor ◽  
Receptor Protein ◽  
Spinocerebellar Ataxia Type ◽  
Protein Abundance ◽  
Loss Of Function ◽  
Electrode Voltage ◽  
A Current ◽  
Autosomal Dominant Spinocerebellar Ataxia

Background/Aims: Inherited, autosomal dominant spinocerebellar ataxia type 11 (SCA11) is caused by loss of function mutations of TTBK2 (tau tubulin kinase 2). Mutations observed in patients with SCA11 include truncated TTBK2(450). The present study explored the possibility that TTBK2 influences the function of the glutamate receptor GluK2. Methods: GluK2 was expressed in Xenopus oocytes without and with additional expression of wild type TTBK2, the truncated mutant TTBK2(450), or the kinase dead mutants TTBK2(KD) and TTBK2(450/KD). GluK2 current was determined by dual electrode voltage clamp and GluK2 protein abundance in the cell membrane utilizing confocal microscopy. Results: Glutamate exposure of GluK2 expressing oocytes generated a current, which was significantly lower in oocytes expressing GluK2 together with TTBK2 wt or TTBK2(KD) than in oocytes expressing GluK2 alone or together with either TTBK2(450) or TTBK2(450/KD). According to confocal microscopy of EGFP-tagged GluK2, TTBK2 wt decreased the GluK2 protein abundance in the cell membrane. Overexpression of an inactive RAB5(N133I) mutant but not RAB5wt could reverse the TTBK2 effect on GluK2 suggesting that RAB5 function is required for the effect. Conclusions: TTBK2 down-regulates GluK2 activity by decreasing the receptor protein abundance in the cell membrane via RAB5-dependent endocytosis, an effect that may protect against neuroexcitotoxicity.

scholarly journals Atxn2-CAG100-knock-in affects mouse lifespan and vestibulo-cerebellar function via neural disconnection

2018 ◽  
Author(s):  
Melanie V. Halbach ◽  
Nesli-Ece Sen ◽  
Júlia Canet-Pons ◽  
Bram W. Kuppens ◽  
Mandy Segers ◽  
...  
Keyword(s):  
Alpha Synuclein ◽  
Myelin Proteins ◽  
Spinocerebellar Ataxia Type ◽  
Loss Of Function ◽  
Motor Neuron Diseases ◽  
Disease Biomarkers ◽  
Neuronal Soma ◽  
Neuroprotective Therapies ◽  
Autosomal Dominant Spinocerebellar Ataxia

AbstractUnstable expansions in the Q22-polyglutamine domain of human ATXN2 mediate risks for motor neuron diseases such as ALS/FTLD or cause the autosomal dominant Spinocerebellar Ataxia type 2 (SCA2), but the pathogenesis is not understood and models are unavailable.We generated a novel knock-in mouse line with CAG100 expansion in Atxn2, transmitted unstably. The mutant protein accumulated in neuronal cytosolic aggregates, with a characteristic pattern of multi-system-atrophy. Loss-of-function phenotypes included less mutant offspring, initial weight gain and motor hyperactivity. Progressive toxic aggregation effects started around 20 weeks in homozygous animals showing weight loss, reduced muscle strength and gait ataxia. Lifespan was decreased. In the cerebellum, neuronal soma and dendrites were remarkably spared. However, myelin proteins MBP, CNP, PLP1 and transcripts Mal, Mobp, Rtn4 decreased markedly, especially adhesion factors MAG and MOG. In neurons, strong reductions were found for mRNAs of perineuronal elements Haplnl, Hapln2, Hapln4, of axonal myelin interactors Prnp and Klk6. At protein level, the adhesion factor neuroplastin and neurofilaments were strongly reduced, while presynaptic alpha-synuclein increased two-fold.Overall, this authentic SCA2 mouse model elucidates how altered function and aggregation toxicity of ATXN2 conspire to trigger axon-myelin disconnection. This model will promote the development of neuroprotective therapies and disease biomarkers.

scholarly journals CIC missense variants contribute to susceptibility for spina bifida

2021 ◽  
Author(s):  
Xiao Han ◽  
Xuanye Cao ◽  
Vanessa Aguiar-Pulido ◽  
Wei Yang ◽  
Menuka Karki ◽  
...  
Keyword(s):  
Spina Bifida ◽  
Cell Line ◽  
Neural Tube ◽  
Folate Receptor ◽  
Spinocerebellar Ataxia Type ◽  
Loss Of Function ◽  
Missense Variants ◽  
Increased Risk ◽  
Cell Line Hela

Neural Tube Defects (NTDs) are congenital malformations resulting from abnormal embryonic development of the brain, spine, or spinal column. The genetic etiology of human NTDs remains poorly understood despite intensive investigation. CIC, homolog of the Capicua transcription repressor, has been reported to interact with ataxin-1 (ATXN1) and participate in the pathogenesis of spinocerebellar ataxia type 1. Our previous study demonstrated that CIC loss of function (LoF) variants contributed to cerebral folate deficiency by downregulating folate receptor 1 (FOLR1) expression. Given the importance of folate transport in neural tube formation, we hypothesized that CIC variants could contribute to increased risk for NTDs by depressing embryonic folate concentrations. In this study, we examined CIC variants from whole genome sequencing (WGS) data of 140 isolated spina bifida cases and identified 8 missense variants of CIC gene. We tested the pathogenicity of the observed variants through multiple in vitro experiments. We determined that CIC variants decreased FOLR1 protein level and planar cell polarity (PCP) pathway signaling in a human cell line (HeLa). In a murine cell line (NIH3T3), CIC loss of function variants down regulated PCP signaling. Taken together, this study provides evidence supporting CIC as a risk gene for human NTD.

scholarly journals Ataxin-1 regulates B cell function and the severity of autoimmune experimental encephalomyelitis

2020 ◽  
Vol 117 (38) ◽  
pp. 23742-23750 ◽  
Author(s):  
Alessandro Didonna ◽  
Ester Canto Puig ◽  
Qin Ma ◽  
Atsuko Matsunaga ◽  
Brenda Ho ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Function ◽  
Cell Activity ◽  
Cell Polarization ◽  
Spinocerebellar Ataxia Type ◽  
Loss Of Function ◽  
Th1 Cell ◽  
Aberrant Expression

Ataxin-1 (ATXN1) is a ubiquitous polyglutamine protein expressed primarily in the nucleus where it binds chromatin and functions as a transcriptional repressor. Mutant forms of ataxin-1 containing expanded glutamine stretches cause the movement disorder spinocerebellar ataxia type 1 (SCA1) through a toxic gain-of-function mechanism in the cerebellum. Conversely, ATXN1 loss-of-function is implicated in cancer development and Alzheimer’s disease (AD) pathogenesis.ATXN1was recently nominated as a susceptibility locus for multiple sclerosis (MS). Here, we show thatAtxn1-null mice develop a more severe experimental autoimmune encephalomyelitis (EAE) course compared to wildtype mice. The aggravated phenotype is mediated by increased T helper type 1 (Th1) cell polarization, which in turn results from the dysregulation of B cell activity. Ataxin-1 ablation in B cells leads to aberrant expression of key costimulatory molecules involved in proinflammatory T cell differentiation, including cluster of differentiation (CD)44 and CD80. In addition, comprehensive phosphoflow cytometry and transcriptional profiling link the exaggerated proliferation of ataxin-1 deficient B cells to the activation of extracellular signal-regulated kinase (ERK) and signal transducer and activator of transcription (STAT) pathways. Lastly, selective deletion of the physiological binding partner capicua (CIC) demonstrates the importance of ATXN1 native interactions for correct B cell functioning. Altogether, we report a immunomodulatory role for ataxin-1 and provide a functional description of theATXN1locus genetic association with MS risk.

scholarly journals Calcium Current Activated by Depletion of Calcium Stores in Xenopus Oocytes

1997 ◽  
Vol 109 (6) ◽  
pp. 703-715 ◽  
Author(s):  
Yong Yao ◽  
Roger Y. Tsien
Keyword(s):  
Xenopus Oocytes ◽  
Voltage Dependence ◽  
Calcium Stores ◽  
Kinase C ◽  
Electrode Voltage ◽  
Activation Mechanisms ◽  
Electrophysiological Characterization ◽  
Inwardly Rectifying ◽  
A Current

Ca2+ currents activated by depletion of Ca2+ stores in Xenopus oocytes were studied with a two-electrode voltage clamp. Buffering of cytosolic Ca2+ with EGTA and MeBAPTA abolished ICl(Ca) and unmasked a current in oocytes that was activated by InsP3 or ionomycin in minutes and by thapsigargin or the chelators themselves over hours. At −60 mV in 10 mM extracellular CaCl2, the current was typically around −90 or −160 nA in oocytes loaded with EGTA or MeBAPTA, respectively. This current was judged to be a Ca2+-selective current for the following reasons: (a) it was inwardly rectifying and reversed at membrane potentials usually more positive than +40 mV; (b) it was dependent on extracellular [CaCl2] with Km = 11.5 mM; (c) it was highly selective for Ca2+ against monovalent cations Na+ and K+, because replacing Na+ and K+ by N-methyl-d-glucammonium did not reduce the amplitude or voltage dependence of the current significantly; and (d) Ca2+, Sr2+, and Ba2+ currents had similar instantaneous conductances, but Sr2+ and Ba2+ currents appeared to inactivate more strongly than Ca2+. This Ca2+ current was blocked by metal ions with the following potency sequence: Mg2+ << Ni2+ ≈ Co2+ ≈ Mn2+ < Cd2+ << Zn2+ << La3+. It was also inhibited by niflumic acid, which is commonly used to block ICl(Ca). PMA partially inhibited the Ca2+ current, and this effect was mostly abolished by calphostin C, indicating that the Ca2+ current is sensitive to protein kinase C. These results are the first detailed electrophysiological characterization of depletion-activated Ca2+ current in nondialyzed cells. Because exogenous molecules and channels are easy to introduce into oocytes and the distortions in measuring ICl(Ca) can now be bypassed, oocytes are now a superior system in which to analyze the activation mechanisms of capacitative Ca2+ influx.

La dissolution du chlorure cuivreux formé par oxydation électrochimique du cuivre

1982 ◽  
Vol 60 (5) ◽  
pp. 616-623 ◽  
Author(s):  
Robert-Louis Brossard
Keyword(s):  
Copper Chloride ◽  
Ionic Species ◽  
Open Circuit ◽  
Complete Disappearance ◽  
Rotating Disc ◽  
Electrode Voltage ◽  
Stationary Electrode ◽  
Local Enrichment ◽  
Rapid Drop ◽  
A Current

We have studied the dissolution of copper chloride formed by the electrochemical oxidation of copper immersed in aqueous lithium chloride. The pH was maintained between 3 and 5 while the concentration of LiCl in solution was varied between 2.36 × 10−2 M to 16.5 × 10−2 M. The corrosion product accumulating on the electrode consists of crystals of nantokite (CuCl) formed by precipitation.The presence of this precipitate contributes to the local enrichment of the solution which is close to saturation near the electrode. This enrichment is revealed by an electrode voltage in a well characterized open circuit. This current is about −40 mV (/ECS) on a stationary electrode. The complete dissolution of CuCl coincides with a rapid drop in voltage which allows the transition time τ to be defined from which the speed of dissolution of CuCl has been calculated. For example, the speed of dissolution is 0.15 ± 0.01 mC s−1 cm2 in a current equivalent for a stationary electrode in the presence of 2.36 × 10−2 M of dissolved LiCl. This is also constant until the complete disappearance of the precipitate.In another study, the use of a rotating disc electrode shows that the dissolution is completely dominated by the diffusion of ionic species in the liquid phase. The experimental results are compatible with the presence of CuCl2− as the diffusing species. [Journal Translation]

Sign in / Sign up

Export Citation Format

Share Document