Publications by authors named "Matthew B Phillips"

8 Publications

  • Page 1 of 1

Interplay between Gating and Block of Ligand-Gated Ion Channels.

Brain Sci 2020 Dec 1;10(12). Epub 2020 Dec 1.

Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA.

Drugs that inhibit ion channel function by binding in the channel and preventing current flow, known as channel blockers, can be used as powerful tools for analysis of channel properties. Channel blockers are used to probe both the sophisticated structure and basic biophysical properties of ion channels. Gating, the mechanism that controls the opening and closing of ion channels, can be profoundly influenced by channel blocking drugs. Channel block and gating are reciprocally connected; gating controls access of channel blockers to their binding sites, and channel-blocking drugs can have profound and diverse effects on the rates of gating transitions and on the stability of channel open and closed states. This review synthesizes knowledge of the inherent intertwining of block and gating of excitatory ligand-gated ion channels, with a focus on the utility of channel blockers as analytic probes of ionotropic glutamate receptor channel function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/brainsci10120928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7760600PMC
December 2020

Lymphatic Type 1 Interferon Responses Are Critical for Control of Systemic Reovirus Dissemination.

J Virol 2021 Jan 28;95(4). Epub 2021 Jan 28.

Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA

Mammalian orthoreovirus (reovirus) spreads from the site of infection to every organ system in the body via the blood. However, mechanisms that underlie reovirus hematogenous spread remain undefined. Nonstructural protein σ1s is a critical determinant of reovirus bloodstream dissemination that is required for efficient viral replication in many types of cultured cells. Here, we used the specificity of the σ1s protein for promoting hematogenous spread as a platform to uncover a role for lymphatic type 1 interferon (IFN-1) responses in limiting reovirus systemic dissemination. We found that replication of a σ1s-deficient reovirus was restored to wild-type levels in cells with defective interferon-α receptor (IFNAR1) signaling. Reovirus spreads systemically following oral inoculation of neonatal mice, whereas the σ1s-null virus remains localized to the intestine. We found that σ1s enables reovirus spread in the presence of a functional IFN-1 response, as the σ1s-deficient reovirus disseminated comparably to wild-type virus in IFNAR1 mice. Lymphatics are hypothesized to mediate reovirus spread from the intestine to the bloodstream. IFNAR1 deletion from cells expressing lymphatic vessel endothelium receptor 1 (LYVE-1), a marker for lymphatic endothelial cells, enabled the σ1s-deficient reovirus to disseminate systemically. Together, our findings indicate that IFN-1 responses in lymphatics limit reovirus dissemination. Our data further suggest that the lymphatics are an important conduit for reovirus hematogenous spread. Type 1 interferons (IFN-1) are critical host responses to viral infection. However, the contribution of IFN-1 responses to control of viruses in specific cell and tissue types is not fully defined. Here, we identify IFN-1 responses in lymphatics as important for limiting reovirus dissemination. We found that nonstructural protein σ1s enhances reovirus resistance to IFN-1 responses, as a reovirus mutant lacking σ1s was more sensitive to IFN-1 than wild-type virus. In neonatal mice, σ1s is required for reovirus systemic spread. We used tissue-specific IFNAR1 deletion in combination with the IFN-1-sensitive σ1s-null reovirus as a tool to test how IFN-1 responses in lymphatics affect reovirus systemic spread. Deletion of IFNAR1 in lymphatic cells using Cre- technology enabled dissemination of the IFN-1-sensitive σ1s-deficient reovirus. Together, our results indicate that IFN-1 responses in lymphatics are critical for controlling reovirus systemic spread.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.02167-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7851543PMC
January 2021

Synaptic zinc inhibition of NMDA receptors depends on the association of GluN2A with the zinc transporter ZnT1.

Sci Adv 2020 Jul 3;6(27). Epub 2020 Jul 3.

Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.

The NMDA receptor (NMDAR) is inhibited by synaptically released zinc. This inhibition is thought to be the result of zinc diffusion across the synaptic cleft and subsequent binding to the extracellular domain of the NMDAR. However, this model fails to incorporate the observed association of the highly zinc-sensitive NMDAR subunit GluN2A with the postsynaptic zinc transporter ZnT1, which moves intracellular zinc to the extracellular space. Here, we report that disruption of ZnT1-GluN2A association by a cell-permeant peptide strongly reduced NMDAR inhibition by synaptic zinc in mouse dorsal cochlear nucleus synapses. Moreover, synaptic zinc inhibition of NMDARs required postsynaptic intracellular zinc, suggesting that cytoplasmic zinc is transported by ZnT1 to the extracellular space in close proximity to the NMDAR. These results challenge a decades-old dogma on how zinc inhibits synaptic NMDARs and demonstrate that presynaptic release and a postsynaptic transporter organize zinc into distinct microdomains to modulate NMDAR neurotransmission.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/sciadv.abb1515DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7458442PMC
July 2020

Heat Generation Changes with Electrically Heated Pluggers after Multiple Autoclave Cycles at Different Operating Temperatures.

J Endod 2019 Dec;45(12):1529-1534

Department of Clinical Investigations, Dwight D. Eisenhower Army Medical Center, Fort Gordon, Georgia.

Introduction: Electrically heated pluggers are the most commonly used instruments during warm obturation techniques. This study aimed to evaluate the effect of sterilization and operating temperature settings on the heat generation of pluggers of various taper sizes.

Methods: Fifty pluggers were sterilized at 132°C for 25 minutes for a total of 150 cycles. One group (Autoclave200) consisted of 25 pluggers tested at an operating temperature setting of 200°C, whereas another group (Autoclave400) consisted of 25 pluggers tested at 400°C. The heat generation at their tip surface was measured with T-type thermocouples at 0, 50, 100, and 150 autoclave cycles. An unpaired t test was used to compare the time it took the pluggers to reach 60°C and the mean maximum temperature change.

Results: After 50 autoclave cycles, all of the 0.04 taper pluggers in Autoclave200 failed to reach 60°C. After 100 autoclave cycles, one of the 0.10 taper pluggers in Autoclave200 did not reach 60°C, and after 150 autoclave cycles, one of the 0.04 taper pluggers failed to generate any heat. The mean increase in the time to reach 60°C ranged from 1071-4004 milliseconds and 510-2074 milliseconds for Autoclave200 and Autoclave400, respectively. The mean maximum temperature change decreased by 13-29°C and 24-116°C for Autoclave200 and Autoclave400, respectively.

Conclusions: After multiple autoclave cycles and higher operating temperature use, the electrically heated pluggers transferred less heat to the tip surface, potentially making them less effective.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.joen.2019.09.008DOI Listing
December 2019

Current understanding of reovirus oncolysis mechanisms.

Oncolytic Virother 2018 14;7:53-63. Epub 2018 Jun 14.

Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Atlanta, GA, USA.

Mammalian orthoreovirus (reovirus) is under development as a cancer virotherapy. Clinical trials demonstrate that reovirus-based therapies are safe and tolerated in patients with a wide variety of cancers. Although reovirus monotherapy has proven largely ineffective, reovirus sensitizes cancer cells to existing chemotherapeutic agents and radiation. Clinical trials are underway to test the efficacy of reovirus in combination with chemotherapeutic and radiation regimens and to evaluate the effectiveness of reovirus in conjunction with immunotherapies. Central to the use of reovirus to treat cancer is its capacity to directly kill cancer cells and alter the cellular environment to augment other therapies. Apoptotic cell death is a prominent mechanism of reovirus cancer cell killing. However, reoviruses can also kill cancer cells through nonapoptotic mechanisms. Here, we describe mechanisms of reovirus cancer cell killing, highlight how reovirus is used in combination with existing cancer treatments, and discuss what is known as to how reovirus modulates cancer immunotherapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2147/OV.S143808DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6005300PMC
June 2018

Pharmacological and Electrophysiological Characterization of Novel NMDA Receptor Antagonists.

ACS Chem Neurosci 2018 11 1;9(11):2722-2730. Epub 2018 Jun 1.

Laboratori de Química Farmacèutica (Unitat Associada al CSIC), Facultat de Farmàcia i Ciències de l'Alimentació i Institut de Biomedicina (IBUB) , Universitat de Barcelona , Av. Joan XXIII, 27-31 , 08028 Barcelona , Spain.

This work reports the synthesis and pharmacological and electrophysiological evaluation of new N-methyl-d-aspartic acid receptor (NMDAR) channel blocking antagonists featuring polycyclic scaffolds. Changes in the chemical structure modulate the potency and voltage dependence of inhibition. Two of the new antagonists display properties comparable to those of memantine, a clinically approved NMDAR antagonist.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acschemneuro.8b00154DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6249113PMC
November 2018

Nonstructural Protein σ1s Is Required for Optimal Reovirus Protein Expression.

J Virol 2018 04 14;92(7). Epub 2018 Mar 14.

Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA

Reovirus nonstructural protein σ1s is required for the establishment of viremia and hematogenous viral dissemination. However, the function of σ1s during the reovirus replication cycle is not known. In this study, we found that σ1s was required for efficient reovirus replication in simian virus 40 (SV40)-immortalized endothelial cells (SVECs), mouse embryonic fibroblasts, human umbilical vein endothelial cells (HUVECs), and T84 human colonic epithelial cells. In each of these cell lines, wild-type reovirus produced substantially higher viral titers than a σ1s-deficient mutant. The σ1s protein was not required for early events in reovirus infection, as evidenced by the fact that no difference in infectivity between the wild-type and σ1s-null viruses was observed. However, the wild-type virus produced markedly higher viral protein levels than the σ1s-deficient strain. The disparity in viral replication did not result from differences in viral transcription or protein stability. We further found that the σ1s protein was dispensable for cell killing and the induction of type I interferon responses. In the absence of σ1s, viral factory (VF) maturation was impaired but sufficient to support low levels of reovirus replication. Together, our results indicate that σ1s is not absolutely essential for viral protein production but rather potentiates reovirus protein expression to facilitate reovirus replication. Our findings suggest that σ1s enables hematogenous reovirus dissemination by promoting efficient viral protein synthesis, and thereby reovirus replication, in cells that are required for reovirus spread to the blood. Hematogenous dissemination is a critical step in the pathogenesis of many viruses. For reovirus, nonstructural protein σ1s is required for viral spread via the blood. However, the mechanism by which σ1s promotes reovirus dissemination is unknown. In this study, we identified σ1s as a viral mediator of reovirus protein expression. We found several cultured cell lines in which σ1s is required for efficient reovirus replication. In these cells, wild-type virus produced substantially higher levels of viral protein than a σ1s-deficient mutant. The σ1s protein was not required for viral mRNA transcription or viral protein stability. Since reduced levels of viral protein were synthesized in the absence of σ1s, the maturation of viral factories was impaired, and significantly fewer viral progeny were produced. Taken together, our findings indicate that σ1s is required for optimal reovirus protein production, and thereby viral replication, in cells required for hematogenous reovirus dissemination.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.02259-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5972882PMC
April 2018

Reverse Genetics for Mammalian Orthoreovirus.

Methods Mol Biol 2017 ;1602:1-10

Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA.

Reverse genetics allows introduction of specific alterations into a viral genome. Studies performed with mutant viruses generated using reverse genetics approaches have contributed immeasurably to our understanding of viral replication and pathogenesis, and also have led to development of novel vaccines and virus-based vectors. Here, we describe the reverse genetics system that allows for production and recovery of mammalian orthoreovirus, a double-stranded (ds) RNA virus, from plasmids that encode the viral genome.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/978-1-4939-6964-7_1DOI Listing
March 2018