GSK3 and β-catenin determines functional expression of sodium channels at the axon initial segment

Neuronal action potentials are generated through voltage-gated sodium channels, which are tethered by ankyrinG at the membrane of the axon initial segment (AIS). Despite the importance of the AIS in the control of neuronal excitability, the cellular and molecular mechanisms regulating sodium channel expression at the AIS remain elusive. Our results show that GSK3α/β and β-catenin phosphorylated by GSK3 (S33/37/T41) are localized at the AIS and are new components of this essential neuronal domain. Pharmacological inhibition of GSK3 or β-catenin knockdown with shRNAs decreased the levels of phosphorylated-β-catenin, ankyrinG, and voltage-gated sodium channels at the AIS, both “in vitro” and “in vivo”, therefore diminishing neuronal excitability as evaluated via sodium current amplitude and action potential number. Thus, our results suggest a mechanism for the modulation of neuronal excitability through the control of sodium channel density by GSK3 and β-catenin at the AIS.     

Localisation of acetylcholinesterase in rat myotubes in the presence of β-endorphin and β-endorphin-(1-27)

Summary In rat embryo skeletal myotubes, acetylcholinesterase is present, as multiple forms, and can be detected in deposits at the cell surface. Myotubes cultured in the presence of -endorphin, exhibit an increased predominance of the globular (precursor) forms of the enzyme, which are largely restricted to intracellular sites associated with nuclei. In the presence of -endorphin-(1-27), the relative proportions of the different forms of acetylcholinesterase is similar to that seen in the controls, but the enzyme is intracellular and has a characteristic focal localisation in the myotube.     

Cadherin 22 participates in the self-renewal of mouse female germ line stem cells via interaction with JAK2 and β-catenin

The self-renewal capacity of the stem cell pool determines tissue function and health. Cadherin-22 (Cdh22), a member of the cadherin superfamily, has two splicing patterns in rats, and the short type that lacks a catenin binding domain is closely related to spermatogonial stem cell self-renewal. Previously, we reported that CDH22 was highly expressed in mouse ovary germ cells, especially in female germ line stem cells (FGSCs). However, its underlying function in FGSCs is still not clear. Here, we found that Cdh22 encodes only one type of protein product in mice and demonstrated that CDH22 was required for FGSC self-renewal. In addition, JAK2 and β-catenin were found to interact with CDH22 and be involved in CDH22 signaling in mouse FGSCs. Moreover, extrinsic CDH22 was identified as a potential molecule that participates in FGSC adhesion and is pivotal for FGSC maintenance and self-renewal. These results reveal that CDH22 functions as an essential molecule in FGSC maintenance and self-renewal via different mechanisms, including interaction with the JAK-STAT signaling pathway and β-catenin.     

Comparison of the effects of β-palmitoyl lysolecithin and cardiac glycosides in two mammalian tissues

Zusammenfassung 1957 sind vonHajdu et al. Versuche veröffentlicht worden, wonach sich aus verschiedenen Geweben eine Substanz mit Herzglykosid-ähnlicher Wirkung auf Kaltblüterherzen extrahieren lässt, welche als -Palmitoyl-lysolecithin interpretiert wurde. In unseren Versuchen wurde aus Hefe Dipalmitoleyl-lecithin isoliert und daraus durch enzymatische Abspaltung der -ständigen Fettsäure und anschliessende katalytische Hydrierung reines, hämolytisch wirksames -Palmitoyl-lysolecithin hergestellt. Diese Verbindung zeigte jedoch keine den Effekten der Herzglykoside verwandte Wirkung am isolierten Meerschweinchenventrikel sowie an menschlichen Erythrocyten.     

Folding and assembly defects of pyruvate dehydrogenase deficiency-related variants in the E1α subunit of the pyruvate dehydrogenase complex

The pyruvate dehydrogenase complex (PDC) bridges glycolysis and the citric acid cycle. In human, PDC deficiency leads to severe neurodevelopmental delay and progressive neurodegeneration. The majority of cases are caused by variants in the gene encoding the PDC subunit E1α. The molecular effects of the variants, however, remain poorly understood. Using yeast as a eukaryotic model system, we have studied the substitutions A189V, M230V, and R322C in yeast E1α (corresponding to the pathogenic variants A169V, M210V, and R302C in human E1α) and evaluated how substitutions of single amino acid residues within different functional E1α regions affect PDC structure and activity. The E1α A189V substitution located in the heterodimer interface showed a more compact conformation with significant underrepresentation of E1 in PDC and impaired overall PDC activity. The E1α M230V substitution located in the tetramer and heterodimer interface showed a relatively more open conformation and was particularly affected by low thiamin pyrophosphate concentrations. The E1α R322C substitution located in the phosphorylation loop of E1α resulted in PDC lacking E3 subunits and abolished overall functional activity. Furthermore, we show for the E1α variant A189V that variant E1α accumulates in the Hsp60 chaperonin, but can be released upon ATP supplementation. Our studies suggest that pathogenic E1α variants may be associated with structural changes of PDC and impaired folding of E1α.     

The role of ‘complex’ empiricism in the debates about satellite data and climate models

Climate scientists have been engaged in a decades-long debate over the standing of satellite measurements of the temperature trends of the atmosphere above the surface of the earth. This is especially significant because skeptics of global warming and the greenhouse effect have utilized this debate to spread doubt about global climate models used to predict future states of climate. I use this case from an understudied science to illustrate two distinct philosophical approaches to the relations among data, scientist, measurement, models, and theory. I argue that distinguishing between ‘direct’ empiricist and ‘complex’ empiricist approaches helps us understand and analyze this important scientific episode. I also introduce a complex empiricist account of testing and evaluation, and contrast it with the basic Hypothetico-Deductive approach to the climate models used by the direct empiricists. This more developed complex empiricist approach will serve philosophy of science well, as computational models become more widespread in the sciences.     

Characterization of the role of the antioxidant proteins metallothioneins 1 and 2 in an animal model of Alzheimer’s disease

Alzheimer’s disease (AD) is by far the most commonly diagnosed dementia, and despite multiple efforts, there are still no effective drugs available for its treatment. One strategy that deserves to be pursued is to alter the expression and/or physiological action of endogenous proteins instead of administering exogenous factors. In this study, we intend to characterize the roles of the antioxidant, anti-inflammatory, and heavy-metal binding proteins, metallothionein-1?+?2 (MT1?+?2), in a mouse model of Alzheimer’s disease, Tg2576 mice. Contrary to expectations, MT1?+?2-deficiency rescued partially the human amyloid precursor protein-induced changes in mortality and body weight in a gender-dependent manner. On the other hand, amyloid plaque burden was decreased in the cortex and hippocampus in both sexes, while the amyloid cascade, neuroinflammation, and behavior were affected in the absence of MT1?+?2 in a complex manner. These results highlight that the control of the endogenous production and/or action of MT1?+?2 could represent a powerful therapeutic target in AD.     

Induction of IgG1 and IgE responses to protein-conjugated and unconjugated β-lactam antibiotics in the mouse-efficacy of Freund's complete adjuvant

Summary One or two injections two weeks apart of protein-conjugated penicillin G, cephalothin or cefmetazole emulsified with Freund's complete adjuvant were quite effective in producing anti-antibiotic antibodies of the IgE as well as of the IgG₁ class in mice. Long-lasting and boostable production of both antibody classes was also obtained against unconjugated cephalothin or cefmetazole, though the positivity depended on the mouse strain.     

Short- and medium-chain carnitine acyltransferases and acyl-CoA thioesterases in mouse provide complementary systems for transport of β-oxidation products out of peroxisomes

Peroxisomes metabolize a variety of lipids, acting as a chain-shortening system that produces acyl-CoAs of varying chain lengths, including acetyl-CoA and propionyl-CoA. It is, however, still largely unknown how β-oxidation products exit peroxisomes and where they are further metabolized. Peroxisomes contain carnitine acetyltransferase (CRAT) and carnitine octanoyltransferase (CROT) that produce carnitine esters for transport out of peroxisomes, together with recently characterized acyl-CoA thioesterases (ACOTs) that produce free fatty acids. Here we have performed tissue expression profiling of the short- and medium-chain carnitine acyltransferases Crat, Crot and the short- and medium-chain thioesterases (Acot12) and (Acot5), and show that they are largely expressed in different tissues, suggesting that they do not compete for the same substrates but rather provide complementary systems for transport of metabolites across the peroxisomal membrane. These data also explain earlier observed tissue differences in peroxisomal production of acetyl-CoA/acetyl-carnitine/acetate and underscores the differences in peroxisome function in various organs. Received 18 December 2007; received after revision 18 January 2008; accepted 22 January 2008     

Effect of acute administration of Δ1-tetrahydrocannabinol on β-endorphin levels in plasma and brain tissue of the rat

Summary Acute treatment with ¹-tetrahydrocannabinol (¹-THC) elevated the concentration of -endorphin-like immunoreactivity (-ELIR) in plasma and in the hypothalamus, but not in the hippocampus of rats habituated to the injection procedure. These effects were not obtained with the psychotropically inert analog of (¹-THC), cannabidiol. In animals that had not been habituated to the injection procedure, placebo treatment induced a decrease in hippocampal -ELIR.The authors acknowledge the skillful technical assistance of Mrs Willeke Logtenberg.     

Can the binding of GABA,glycine and β-alanine to synaptic receptors be determined in the presence of a physiological concentration of Na+?

Summary Bicuculline- and strychnine-sensitive components of the binding of GABA, glycine and -alanine, which can be demonstrated in the presence of a physiological concentration of Na⁺, might be related to synaptic receptors.     

The presence of β-phenylethylamine,p-tyramine,m-tyramine and tryptamine in ganglia and foot muscle of the garden snail (Helix aspersa)

Summary The concentrations of -phenylethylamine,p-tyramine,m-tyramine,m-octopamine and tryptamine in the ganglia or foot muscle ofHelix aspersa range from <0.6 to 11 ng/g.p-Octopamine levels are higher in ganglia (327 ng/g) than in foot muscle (4.1 ng/g). Dopamine and 5-hydroxytryptamine range from 840 to 2710 ng/g while their acid metabolites, 3,4-dihydroxyphenylacetic acid, 3-methoxy-4-hydroxyphenylacetic acid and 5-hydroxyindoleacetic acid range from <20 to 130 ng/g.Acknowledgments. We thank Dr A.A. Boulton for helpful discus sion, Dr D.A. Durden for supervising the mass spectrometric analyses, Dr B.A. Davis for the synthesis of the deuterated standards, G.H. Wheatley, E.P. Zarycki and M. Mizuno for expert technical assistance, and Saskatchewan Health and the MRC of Canada for providing financial support.     

Epigenetic identification of receptor tyrosine kinase-like orphan receptor 2 as a functional tumor suppressor inhibiting β-catenin and AKT signaling but frequently methylated in common carcinomas

Through subtraction of tumor-specific CpG methylation, we identified receptor tyrosine kinase-like orphan receptor 2 (ROR2) as a candidate tumor suppressor gene (TSG). ROR2 is a specific receptor or co-receptor for WNT5A, involved in canonical and non-canonical WNT signaling, with its role in tumorigenesis controversial. We characterized its functions and related cell signaling in common carcinomas. ROR2 was frequently silenced by promoter CpG methylation in multiple carcinomas including nasopharyngeal, esophageal, gastric, colorectal, hepatocellular, lung, and breast cancers, while no direct correlation of ROR2 and WNT5A expression was observed. Ectopic expression of ROR2 resulted in tumor suppression independent of WNT5A status, through inhibiting tumor cell growth and inducing cell cycle arrest and apoptosis. ROR2 further suppressed epithelial-mesenchymal transition and tumor cell stemness through repressing β-catenin and AKT signaling, leading to further inhibition of tumor cell migration/invasion and increased chemo-sensitivity. Thus ROR2, as an epigenetically inactivated TSG, antagonizes both β-catenin and AKT signaling in multiple tumorigenesis. Its epigenetic silencing could be a potential tumor biomarker and therapeutic target for carcinomas.     

To envision a new particle or change an existing law? Hypothesis formation and anomaly resolution for the curious case of the β decay spectrum

This paper addresses the question of how scientists determine which type of hypothesis is most suitable for tackling a particular problem by examining the historical case of the anomalous β spectrum in early nuclear physics (1927–1934), a puzzle that occasioned the most diverse hypotheses amongst physicists at the time. It is shown that such determinations are most often implicitly informed by scientists' individual perspectives on the structural relations between the various elements of the theory and the problem at hand. In addition to this main result, it is suggested that Wolfgang Pauli's neutrino idea may well have been an adaptation of Ernst Rutherford's original and older neutron idea, which would provide evidence that the adaptation of older ideas is a more common practice than is often thought.     

A dialyzable factor from plasma responsible for the “viscous metamorphosis” of the blood platelets. Its role in clot retraction and haemostasis

Zusammenfassung Die visköse Metamorphose der Blutplättchen ist ein von der Fibrinbildung unabhängiger Prozess, der durch Thrombin und einen thermostabilen, dialysierbaren Faktor aus Plasma oder Serum ausgelöst wird. Das unter diesen Bedingungen aus den zerfallenden Plättchen austretende Material kontrahiert sich spontan. Dies erklärt die Gerinnselretraktion, bei der dem Fibrin folglich eine völlig passive Rolle zukommt.

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Supported by grants from the Swiss National Foundation for Scientific Research and the F. Hoffmann-La Roche Foundation.