Mitchell Center for Neurodegenerative Diseases

Mitchell, United States

Mitchell Center for Neurodegenerative Diseases

Mitchell, United States
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James T.F.,University of Texas Medical Branch | Nenov M.N.,University of Texas Medical Branch | Tapia C.M.,University of Texas Medical Branch | Lecchi M.,University of Milan Bicocca | And 4 more authors.
NeuroToxicology | Year: 2017

Background Pyrethroid insecticides are the most popular class of insecticides in the world, despite their near-ubiquity, their effects of delaying the onset of inactivation of voltage-gated sodium (Nav) channels have not been well-evaluated in all the mammalian Nav isoforms. Objective Here we compare the well-studied Nav1.6 isoforms to the less-understood Nav1.1 in their responses to acute deltamethrin exposure. Methods We used patch-clamp electrophysiology to record sodium currents encoded by either Nav1.1 or Nav1.6 channels stably expressed in HEK293 cells. Protocols evaluating both resting and use-dependent modification were employed. Results We found that exposure of both isoforms to 10 μM deltamethrin significantly potentiated persistent and tail current densities without affecting peak transient current densities, and only Nav1.1 maintained these significant effects at 1 μM deltamethrin. Window currents increased for both as well, and while only Nav1.6 displayed changes in activation slope and V1/2 of steady-state inactivation for peak currents, V1/2 of persistent current activation was hyperpolarized of ∼10 mV by deltamethrin in Nav1.1 cells. Evaluating use-dependence, we found that deltamethrin again potentiated persistent and tail current densities in both isoforms, but only Nav1.6 demonstrated use-dependent enhancement, indicating the primary deltamethrin-induced effects on Nav1.1 channels are not use-dependent. Conclusion Collectively, these data provide evidence that Nav1.1 is indeed vulnerable to deltamethrin modification at lower concentrations than Nav1.6, and this effect is primarily mediated during the resting state. General significance These findings identify Nav1.1 as a novel target of pyrethroid exposure, which has major implications for the etiology of neuropsychiatric disorders associated with loss of Nav1.1-expressing inhibitory neurons. © 2016 Elsevier B.V.

Bodani R.U.,Mitchell Center for Neurodegenerative Diseases | Sengupta U.,Mitchell Center for Neurodegenerative Diseases | Castillo-Carranza D.L.,Mitchell Center for Neurodegenerative Diseases | Guerrero-Munoz M.J.,Mitchell Center for Neurodegenerative Diseases | And 5 more authors.
ACS Chemical Neuroscience | Year: 2015

Amyloid-beta (Aβ) oligomers have emerged as the most toxic species in Alzheimer's disease (AD) and other amyloid pathologies. Also, Aβ-42 peptide is more aggregation-prone compared to other Aβ isoforms. Thus, we synthesized a small peptide of repeated sequence containing the last three amino acids, Val-40, Ile-41, and Ala-42 of Aβ-42 that was subsequently aggregated and used to generate a novel antibody, VIA. In this study, we examined human AD and Tg2576 mouse brain samples using VIA in combination with other amyloid-specific antibodies and confirmed the specificity of VIA to oligomeric Aβ-42. Moreover, we found that VIA does not recognize classic amyloid plaques composed of fibrillar Aβ or Aβ-40 ex vivo. Since VIA recognizes a distinct epitope specific to Aβ-42 oligomers, it may have broad use for examining the accumulation of these oligomers in AD and other neurodegenerative diseases. VIA may also be used in immunotherapy studies to prevent neurodegenerative effects associated with Aβ-42 oligomers. © 2015 American Chemical Society.

Green T.A.,Center for Addiction Research | Labate D.,University of Houston | Laezza F.,Center for Addiction Research | Laezza F.,Center for Biomedical Engineering | And 2 more authors.
Biochimica et Biophysica Acta - General Subjects | Year: 2015

Background Phosphorylation plays an essential role in regulating voltage-gated sodium (Nav) channels and excitability. Yet, a surprisingly limited number of kinases have been identified as regulators of Nav channels. We posited that glycogen synthase kinase 3 (GSK3), a critical kinase found associated with numerous brain disorders, might directly regulate neuronal Nav channels. Methods We used patch-clamp electrophysiology to record sodium currents from Nav1.2 channels stably expressed in HEK-293 cells. mRNA and protein levels were quantified with RT-PCR, Western blot, or confocal microscopy, and in vitro phosphorylation and mass spectrometry to identify phosphorylated residues. Results We found that exposure of cells to GSK3 inhibitor XIII significantly potentiates the peak current density of Nav1.2, a phenotype reproduced by silencing GSK3 with siRNA. Contrarily, overexpression of GSK3β suppressed Nav1.2-encoded currents. Neither mRNA nor total protein expression was changed upon GSK3 inhibition. Cell surface labeling of CD4-chimeric constructs expressing intracellular domains of the Nav1.2 channel indicates that cell surface expression of CD4-Nav1.2 C-tail was up-regulated upon pharmacological inhibition of GSK3, resulting in an increase of surface puncta at the plasma membrane. Finally, using in vitro phosphorylation in combination with high resolution mass spectrometry, we further demonstrate that GSK3β phosphorylates T1966 at the C-terminal tail of Nav1.2. Conclusion These findings provide evidence for a new mechanism by which GSK3 modulates Nav channel function via its C-terminal tail. General significance These findings provide fundamental knowledge in understanding signaling dysfunction common in several neuropsychiatric disorders. © 2015 Published by Elsevier B.V.

PubMed | Washington University in St. Louis, Graduate School for Biomedical science, Institute for Translational science, University of Texas Medical Branch and 4 more.
Type: Journal Article | Journal: FASEB journal : official publication of the Federation of American Societies for Experimental Biology | Year: 2016

Recent data shows that fibroblast growth factor 14 (FGF14) binds to and controls the function of the voltage-gated sodium (Nav) channel with phenotypic outcomes on neuronal excitability. Mutations in the FGF14 gene in humans have been associated with brain disorders that are partially recapitulated in Fgf14(-/-) mice. Thus, signaling pathways that modulate the FGF14:Nav channel interaction may be important therapeutic targets. Bioluminescence-based screening of small molecule modulators of the FGF14:Nav1.6 complex identified 4,5,6,7 -: tetrabromobenzotriazole (TBB), a potent casein kinase 2 (CK2) inhibitor, as a strong suppressor of FGF14:Nav1.6 interaction. Inhibition of CK2 through TBB reduces the interaction of FGF14 with Nav1.6 and Nav1.2 channels. Mass spectrometry confirmed direct phosphorylation of FGF14 by CK2 at S228 and S230, and mutation to alanine at these sites modified FGF14 modulation of Nav1.6-mediated currents. In 1 d in vitro hippocampal neurons, TBB induced a reduction in FGF14 expression, a decrease in transient Na(+) current amplitude, and a hyperpolarizing shift in the voltage dependence of Nav channel steady-state inactivation. In mature neurons, TBB reduces the axodendritic polarity of FGF14. In cornu ammonis area 1 hippocampal slices from wild-type mice, TBB impairs neuronal excitability by increasing action potential threshold and lowering firing frequency. Importantly, these changes in excitability are recapitulated in Fgf14(-/-) mice, and deletion of Fgf14 occludes TBB-dependent phenotypes observed in wild-type mice. These results suggest that a CK2-FGF14 axis may regulate Nav channels and neuronal excitability.-Hsu, W.-C. J., Scala, F., Nenov, M. N., Wildburger, N. C., Elferink, H., Singh, A. K., Chesson, C. B., Buzhdygan, T., Sohail, M., Shavkunov, A. S., Panova, N. I., Nilsson, C. L., Rudra, J. S., Lichti, C. F., Laezza, F. CK2 activity is required for the interaction of FGF14 with voltage-gated sodium channels and neuronal excitability.

PubMed | University of Texas Medical Branch and Mitchell Center for Neurodegenerative Diseases
Type: Journal Article | Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience | Year: 2015

In Alzheimers disease (AD), the pathological accumulation of tau appears to be a downstream effect of amyloid protein (A). However, the relationship between these two proteins and memory loss is unclear. In this study, we evaluated the specific removal of pathological tau oligomers in aged Tg2576 mice by passive immunotherapy using tau oligomer-specific monoclonal antibody. Removal of tau oligomers reversed memory deficits and accelerated plaque deposition in the brain. Surprisingly, A*56 levels decreased, suggesting a link between tau and A oligomers in the promotion of cognitive decline. The results suggest that tau oligomerization is not only a consequence of A pathology but also a critical mediator of the toxic effects observed afterward in AD. Overall, these findings support the potential of tau oligomers as a therapeutic target for AD.

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