scholarly journals Evolution of a neuroprotective function of central nervous system myelin

2006 ◽  
Vol 172 (3) ◽  
pp. 469-478 ◽  
Author(s):  
Xinghua Yin ◽  
Rena C. Baek ◽  
Daniel A. Kirschner ◽  
Alan Peterson ◽  
Yasuhisa Fujii ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Membrane Protein ◽  
Genetically Engineered ◽  
Major Protein ◽  
Type I ◽  
Structural Protein ◽  
Terrestrial Vertebrates ◽  
Genetically Engineered Mice ◽  
Neuroprotective Function

The central nervous system (CNS) of terrestrial vertebrates underwent a prominent molecular change when a tetraspan membrane protein, myelin proteolipid protein (PLP), replaced the type I integral membrane protein, P0, as the major protein of myelin. To investigate possible reasons for this molecular switch, we genetically engineered mice to express P0 instead of PLP in CNS myelin. In the absence of PLP, the ancestral P0 provided a periodicity to mouse compact CNS myelin that was identical to mouse PNS myelin, where P0 is the major structural protein today. The PLP–P0 shift resulted in reduced myelin internode length, degeneration of myelinated axons, severe neurological disability, and a 50% reduction in lifespan. Mice with equal amounts of P0 and PLP in CNS myelin had a normal lifespan and no axonal degeneration. These data support the hypothesis that the P0–PLP shift during vertebrate evolution provided a vital neuroprotective function to myelin-forming CNS glia.

scholarly journals Differential Effects of Three CanonicalToxoplasmaStrains on Gene Expression in Human Neuroepithelial Cells

2010 ◽  
Vol 79 (3) ◽  
pp. 1363-1373 ◽  
Author(s):  
Jianchun Xiao ◽  
Lorraine Jones-Brando ◽  
C. Conover Talbot ◽  
Robert H. Yolken
Keyword(s):  
Gene Expression ◽  
Central Nervous System ◽  
Nervous System ◽  
Nucleotide Metabolism ◽  
Neural Cells ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Neuroepithelial Cells ◽  
The Central Nervous System

ABSTRACTStrain type is one of the key factors suspected to play a role in determining the outcome ofToxoplasmainfection. In this study, we examined the transcriptional profile of human neuroepithelioma cells in response to representative strains ofToxoplasmaby using microarray analysis to characterize the strain-specific host cell response. The study of neural cells is of interest in light of the ability ofToxoplasmato infect the brain and to establish persistent infection within the central nervous system. We found that the extents of the expression changes varied considerably among the three strains. Neuroepithelial cells infected withToxoplasmatype I exhibited the highest level of differential gene expression, whereas type II-infected cells had a substantially smaller number of genes which were differentially expressed. Cells infected with type III exhibited intermediate effects on gene expression. The three strains also differed in the individual genes and gene pathways which were altered following cellular infection. For example, gene ontology (GO) analysis indicated that type I infection largely affects genes related to the central nervous system, while type III infection largely alters genes which affect nucleotide metabolism; type II infection does not alter the expression of a clearly defined set of genes. Moreover, Ingenuity Pathways Analysis (IPA) suggests that the three lineages differ in the ability to manipulate their host; e.g., they employ different strategies to avoid, deflect, or subvert host defense mechanisms. These observed differences may explain some of the variation in the neurobiological effects of different strains ofToxoplasmaon infected individuals.

scholarly journals Encephalitic Alphaviruses Exploit Caveola-Mediated Transcytosis at the Blood-Brain Barrier for Central Nervous System Entry

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Hamid Salimi ◽  
Matthew D. Cain ◽  
Xiaoping Jiang ◽  
Robyn A. Roth ◽  
Wandy L. Beatty ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Endothelial Cells ◽  
Nervous System ◽  
Viral Replication ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Type I ◽  
Brain Endothelial Cells ◽  
Blood Brain ◽  
Deficient Mice

ABSTRACT Venezuelan and western equine encephalitis viruses (VEEV and WEEV, respectively) invade the central nervous system (CNS) early during infection, via neuronal and hematogenous routes. While viral replication mediates host shutoff, including expression of type I interferons (IFN), few studies have addressed how alphaviruses gain access to the CNS during established infection or the mechanisms of viral crossing at the blood-brain barrier (BBB). Here, we show that hematogenous dissemination of VEEV and WEEV into the CNS occurs via caveolin-1 (Cav-1)-mediated transcytosis (Cav-MT) across an intact BBB, which is impeded by IFN and inhibitors of RhoA GTPase. Use of reporter and nonreplicative strains also demonstrates that IFN signaling mediates viral restriction within cells comprising the neurovascular unit (NVU), differentially rendering brain endothelial cells, pericytes, and astrocytes permissive to viral replication. Transmission and immunoelectron microscopy revealed early events in virus internalization and Cav-1 association within brain endothelial cells. Cav-1-deficient mice exhibit diminished CNS VEEV and WEEV titers during early infection, whereas viral burdens in peripheral tissues remained unchanged. Our findings show that alphaviruses exploit Cav-MT to enter the CNS and that IFN differentially restricts this process at the BBB. IMPORTANCE VEEV, WEEV, and eastern equine encephalitis virus (EEEV) are emerging infectious diseases in the Americas, and they have caused several major outbreaks in the human and horse population during the past few decades. Shortly after infection, these viruses can infect the CNS, resulting in severe long-term neurological deficits or death. Neuroinvasion has been associated with virus entry into the CNS directly from the bloodstream; however, the underlying molecular mechanisms have remained largely unknown. Here, we demonstrate that following peripheral infection alphavirus augments vesicular formation/trafficking at the BBB and utilizes Cav-MT to cross an intact BBB, a process regulated by activators of Rho GTPases within brain endothelium. In vivo examination of early viral entry in Cav-1-deficient mice revealed significantly lower viral burdens in the brain than in similarly infected wild-type animals. These studies identify a potentially targetable pathway to limit neuroinvasion by alphaviruses.

scholarly journals Lysosomal integral membrane protein 2 is a novel component of the cardiac intercalated disc and vital for load-induced cardiac myocyte hypertrophy

2007 ◽  
Vol 204 (5) ◽  
pp. 1227-1235 ◽  
Author(s):  
Blanche Schroen ◽  
Joost J. Leenders ◽  
Arie van Erk ◽  
Anne T. Bertrand ◽  
Mirjam van Loon ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Cardiac Myocyte ◽  
Cardiac Development ◽  
Integral Membrane Protein ◽  
Genetically Engineered ◽  
Intercalated Disc ◽  
Hypertrophic Response ◽  
Id Proteins ◽  
Genetically Engineered Mice ◽  
Cardiac Myocyte Hypertrophy

The intercalated disc (ID) of cardiac myocytes is emerging as a crucial structure in the heart. Loss of ID proteins like N-cadherin causes lethal cardiac abnormalities, and mutations in ID proteins cause human cardiomyopathy. A comprehensive screen for novel mechanisms in failing hearts demonstrated that expression of the lysosomal integral membrane protein 2 (LIMP-2) is increased in cardiac hypertrophy and heart failure in both rat and human myocardium. Complete loss of LIMP-2 in genetically engineered mice did not affect cardiac development; however, these LIMP-2 null mice failed to mount a hypertrophic response to increased blood pressure but developed cardiomyopathy. Disturbed cadherin localization in these hearts suggested that LIMP-2 has important functions outside lysosomes. Indeed, we also find LIMP-2 in the ID, where it associates with cadherin. RNAi-mediated knockdown of LIMP-2 decreases the binding of phosphorylated β-catenin to cadherin, whereas overexpression of LIMP-2 has the opposite effect. Collectively, our data show that LIMP-2 is crucial to mount the adaptive hypertrophic response to cardiac loading. We demonstrate a novel role for LIMP-2 as an important mediator of the ID.

scholarly journals Osteopontin ImpactsWest Nile virusPathogenesis and Resistance by Regulating Inflammasome Components and Cell Death in the Central Nervous System at Early Time Points

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Nikki Bortell ◽  
Claudia Flynn ◽  
Bruno Conti ◽  
Howard S. Fox ◽  
Maria Cecilia G. Marcondes
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Viral Infections ◽  
Early Time ◽  
Cns Infection ◽  
Critical Threshold ◽  
Type I ◽  
Time Points ◽  
Viral Spread ◽  
The Impact

Osteopontin (OPN) is a molecule that is common in central nervous system (CNS) pathologies, which participates in the activation, migration, and survival of inflammatory cells. However, the mechanisms by which OPN modulates inflammatory pathways are not clear. To understand the role of OPN in CNS viral infections, we used a lethal mouse model ofWest Nile virus(WNV), characterized by the injection of high doses of the Eg101 strain of WNV, causing the increase of OPN levels in the brain since early time points. To measure the impact of OPN in neuropathogenesis and resistance, we compared C57BI/6 WT with mice lacking the OPN gene (OPN KO). OPN KO presented a significantly higher mortality compared to WT mice, detectable since day 5 pi. Our data suggests that OPN expression at early time points may provide protection against viral spread in the CNS by negatively controlling the type I IFN-sensitive, caspase 1-dependent inflammasome, while promoting an alternative caspase 8-associated pathway, to control the apoptosis of infected cells during WNV infection in the CNS. Overall, we conclude that the expression of OPN maintains a critical threshold in the innate immune response that controls apoptosis and lethal viral spread in early CNS infection.

Cellular mechanisms of muscle fatigue

1994 ◽  
Vol 74 (1) ◽  
pp. 49-94 ◽  
Author(s):  
R. H. Fitts
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Muscle Fatigue ◽  
Fiber Type ◽  
Type I ◽  
Fiber Types ◽  
Force Frequency ◽  
Frequency Curve ◽  
Tension Development ◽  
The Central Nervous System

Fatigue, defined as the failure to maintain the required or expected power output, is a complex problem, since multiple factors are clearly involved, with the relative importance of each dependent on the fiber type composition of the contracting muscles(s), and the intensity, type, and duration of the contractile activity. The primary sites of fatigue appear to be within the muscle cell itself and for the most part do not involve the central nervous system or the neuromuscular junction. The major hypotheses of fatigue center on disturbances in the surface membrane, E-C coupling, or metabolic events. The cell sites most frequently linked to the etiology of skeletal muscle fatigue are shown in Figure 1. Skeletal muscles are composed of at least four distinct fiber types (3 fast twitch and 1 slow twitch), with the slow type I and fast type IIa fibers containing the highest mitochondrial content and fatigue resistance. Despite fiber type differences in the degree of fatigability, the contractile properties undergo characteristic changes with the development of fatigue that can be observed in whole muscles, single motor units, and single fibers. The Po declines, and the contraction and relaxation times are prolonged. Additionally, there is a decrease in the peak rate of tension development and decline and a reduced Vo. Changes in Vo are more resistant to fatigue than Po and are not observed until Po has declined by at least 10% of its initial prefatigued value. However, the reduced peak power by which fatigue is defined results from both a reduction in Vo and Po. In the absence of muscle fiber damage, the prolonged relaxation time associated with fatigue causes the force-frequency curve to shift to the left, such that peak tensions are obtained at lower frequencies of stimulation. In a mechanism not clearly understood, the central nervous system senses this condition and reduces the alpha-motor nerve activation frequency as fatigue develops. In some cases, selective LFF develops that displaces the force-frequency curve to the right. Although not proven, it appears likely that this condition is associated with and likely caused by muscle injury, such that the SR releases less Ca2+ at low frequencies of activation. Alternatively, LFF could result from a reduced membrane excitability, such that the sarcolemma action potential frequency is considerably less than the stimulation frequency.(ABSTRACT TRUNCATED AT 400 WORDS)

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