Cryo-EM structure of the Ustilago maydis kinesin-5 motor domain bound to microtubules

In many eukaryotes, kinesin-5 motors are essential for mitosis, and small molecules that inhibit human kinesin-5 disrupt cell division. To investigate whether fungal kinesin-5s could be targets for novel fungicides, we studied kinesin-5 from the pathogenic fungus Ustilago maydis. We used cryo-electron microscopy to determine the microtubule-bound structure of its motor domain with and without the N-terminal extension. The ATP-like conformations of the motor in the presence or absence of this N-terminus are very similar, suggesting this region is structurally disordered and does not directly influence the motor ATPase. The Ustilago maydis kinesin-5 motor domain adopts a canonical ATP-like conformation, thereby allowing the neck linker to bind along the motor domain towards the microtubule plus end. However, several insertions within this motor domain are structurally distinct. Loop2 forms a non-canonical interaction with α-tubulin, while loop8 may bridge between two adjacent protofilaments. Furthermore, loop5 - which in human kinesin-5 is involved in binding allosteric inhibitors - protrudes above the nucleotide binding site, revealing a distinct binding pocket for potential inhibitors. This work highlights fungal-specific elaborations of the kinesin-5 motor domain and provides the structural basis for future investigations of kinesins as targets for novel fungicides

Cryo-EM Structure (4.5-angstrom) of Yeast Kinesin-5-Microtubule Complex Reveals a Distinct Binding Footprint and Mechanism of Drug Resistance

Kinesin-5s are microtubule-dependent motors that drive spindle pole separation during mitosis. We used cryo-electron microscopy to determine the 4.5-Å resolution structure of the motor domain of the fission yeast kinesin-5 Cut7 bound to fission yeast microtubules and explored the topology of the motor–microtubule interface and the susceptibility of the complex to drug binding. Despite their non-canonical architecture and mechanochemistry, Schizosaccharomyces pombe microtubules were stabilized by epothilone at the taxane binding pocket. The overall Cut7 footprint on the S. pombe microtubule surface is altered compared to mammalian tubulin microtubules because of their different polymer architectures. However, the core motor–microtubule interaction is tightly conserved, reflected in similar Cut7 ATPase activities on each microtubule type. AMPPNP-bound Cut7 adopts a kinesin-conserved ATP-like conformation including cover neck bundle formation. However, the Cut7 ATPase is not blocked by a mammalian-specific kinesin-5 inhibitor, consistent with the non-conserved sequence and structure of its loop5 insertion

Circulating vaspin is unrelated to insulin sensitivity in a cohort of nondiabetic humans

Objective: To study the association of vaspin with glucose metabolism. Design: Cross-sectional and intervention study. Subjects and methods: The association of serum vaspin with metabolic and anthropometric characteristics was investigated in 108 volunteers. Euglycemic–hyperinsulinemic clamps (EHC) were performed in 83 of the participants. Changes of circulating vaspin levels were additionally studied in a crossover study using 300 min EHC with lipid versus saline infusion (n=10). Results: Neither glucose tolerance status nor insulin sensitivity, both as measured using EHCs and using homeostasis model assessment for insulin resistance (HOMA-IR), was significantly associated with serum vaspin in the cross-sectional study. Furthermore, there was no effect of short-term lipid-induced insulin resistance due to a 300 min intravenous lipid challenge on circulating vaspin. However, circulating vaspin levels were significantly elevated in women using oral contraceptives (OC), both compared to women without OC intake (1.17±0.26 vs 0.52±0.09 ng/ml, P=0.02) and males (1.17±0.26 vs 0.29±0.04 ng/ml, P=0.01). After exclusion of OC using females and stratification according to body mass index (BMI), a significant sexual dimorphism in subjects with a BMI <25 kg/m2 was observed (males 0.21±0.04 ng/ml versus females 0.70±0.16 ng/ml, P=0.009). Conclusion: Our results support the existence of a sexual dimorphism regarding circulating vaspin. The lack of an association of serum vaspin with HOMA-IR and M value indicates, however, no major role for vaspin concerning insulin sensitivity in nondiabetic humans

Cryo-EM structure (4.5-Å) of Yeast Kinesin-5–Microtubule Complex reveals a distinct binding footprint and mechanism of drug resistance

Kinesin-5s are microtubule-dependent motors that drive spindle pole separation during mitosis. We used cryo-electron microscopy to determine the 4.5 Å resolution structure of the motor domain of the fission yeast kinesin-5 Cut7 bound to fission yeast microtubules, and explored the topology of the motor-microtubule interface and the susceptibility of the complex to drug binding. Despite their non-canonical architecture and mechanochemistry, S. pombe microtubules were stabilized by epothilone at the taxane binding pocket. The overall Cut7 footprint on the S. pombe microtubule surface is altered compared to mammalian tubulin microtubules because of their different polymer architectures. However, the core motor-microtubule interaction is tightly conserved, reflected in similar Cut7 ATPase activities on each microtubule type. AMPPNP-bound Cut7 adopts a kinesin-conserved ATP-like conformation including cover neck bundle formation. However, the Cut7 ATPase is not blocked by a mammalian-specific kinesin-5 inhibitor, consistent with the non-conserved sequence and structure of its loop5 insertion

Endoplasmic reticulum stress and the unfolded protein response in skeletal muscle of subjects suffering from peritoneal sepsis

We provide a descriptive characterization of the unfolded protein response (UPR) in skeletal muscle of human patients with peritoneal sepsis and a sepsis model of C57BL/6J mice. Patients undergoing open surgery were included in a cross-sectional study and blood and skeletal muscle samples were taken. Key markers of the UPR and cluster of differentiation 68 (CD68) as surrogate of inflammatory injury were evaluated by real-time PCR and histochemical staining. CD68 mRNA increased with sepsis in skeletal muscle of patients and animals (p < 0.05). Mainly the inositol-requiring enzyme 1α branch of the UPR was upregulated as shown by elevated X-box binding-protein 1 (XBP1u) and its spliced isoform (XBP1s) mRNA (p < 0.05, respectively). Increased expression of Gadd34 indicated activation of PRKR-Like Endoplasmic Reticulum Kinase (PERK) branch of the UPR, and was only observed in mice (p < 0.001) but not human study subjects. Selected cell death signals were upregulated in human and murine muscle, demonstrated by increased bcl-2 associated X protein mRNA and TUNEL staining (p < 0.05). In conclusion we provide a first characterization of the UPR in skeletal muscle in human sepsis

Deletion of the diabetes candidate gene Slc16a13 in mice attenuates diet-induced ectopic lipid accumulation and insulin resistance

Abstract Genome-wide association studies have identified SLC16A13 as a novel susceptibility gene for type 2 diabetes. The SLC16A13 gene encodes SLC16A13/MCT13, a member of the solute carrier 16 family of monocarboxylate transporters. Despite its potential importance to diabetes development, the physiological function of SLC16A13 is unknown. Here, we validate Slc16a13 as a lactate transporter expressed at the plasma membrane and report on the effect of Slc16a13 deletion in a mouse model. We show that loss of Slc16a13 increases mitochondrial respiration in the liver, leading to reduced hepatic lipid accumulation and increased hepatic insulin sensitivity in high-fat diet fed Slc16a13 knockout mice. We propose a mechanism for improved hepatic insulin sensitivity in the context of Slc16a13 deficiency in which reduced intrahepatocellular lactate availability drives increased AMPK activation and increased mitochondrial respiration, while reducing hepatic lipid content. Slc16a13 deficiency thereby attenuates hepatic diacylglycerol-PKCε mediated insulin resistance in obese mice. Together, these data suggest that SLC16A13 is a potential target for the treatment of type 2 diabetes and non-alcoholic fatty liver disease

Determinants of Integration and Its Impact on the Economic Success of Immigrants: A Case Study of the Turkish Community in Berlin

Using a new data on 590 Turkish households in Berlin, we investigate the determinants and impact of integration on economic performance. We find that usual suspects such as time spent in Germany and education have positive impact, while networks have no impact on integration. There is strong evidence that political integration and the degree of full integration promote income. Using endogenous switching regression models, we show that local familial networks increase the income of unintegrated migrant groups only, while transnational networks decrease it. We also find that education is more welfare improving for integrated than non-integrated immigrants

Blutglukoseziele in der operativen Intensivmedizin.

Hintergrund: Bei 30–80&nbsp;% der Patienten auf Intensivstationen kommt es perioperativ zu einer Hyperglykämie. Diese Stresshyperglykämie wird über inflammatorisch-endokrine sowie iatrogene Stimuli ausgelöst beziehungsweise unterhalten und bedarf regelmäßig therapeutischer Interventionen. Dabei bestehen Unsicherheiten, welche Blutglukoseziele für Patienten mit Diabetes mellitus anzustreben sind.Methode: Es erfolgte eine selektive Literaturrecherche in PubMed und über GoogleScholar.Ergebnisse: Intensivmedizinisch versorgte Patienten mit vorbestehendem Diabetes mellitus profitieren nicht im selben Ausmaß von einer Blutglukosesenkung wie stoffwechselgesunde, werden aber gleichermaßen einem relevanten Hypoglykämierisiko ausgesetzt. Ein Therapiekorridor zwischen 4,4–6,1&nbsp;mmol/L (79–110&nbsp;mg/dL) ist für Patienten mit Diabetes mellitus nicht zu rechtfertigen. Perioperativ besteht das wichtigste Therapieziel darin, Hypoglykämien in jedem Fall strikt zu vermeiden. Negativfolgen der Hyperglykämie sind unter anderem neurotoxische Effekte und die Begünstigung von Wundheilungsstörungen. Metaanalysen belegen, dass eine obere Blutglukosegrenze von 10&nbsp;mmol/L (180&nbsp;mg/dL) mit einem günstigeren Ergebnis für Patienten mit Diabetes mellitus verbunden ist als eine niedrigere Schwelle. Der von Fachgesellschaften für hospitalisierte Menschen mit Diabetes mellitus vorgeschlagene Zielbereich von 7,8–10&nbsp;mmol/L (140–180&nbsp;mg/dL) scheint der Gratwanderung, einerseits eine Hypoglykämie zu vermeiden und andererseits die klinischen Resultate zu optimieren, derzeit am ehesten gerecht zu werden. Mittel der Wahl zur Therapie in der Intensivmedizin ist die kontinuierliche intravenöse Insulingabe, deren Anwendung es erfordert, dezidierte Rahmenbedingungen einzuhalten.Schlussfolgerung: In der Intensivmedizin ist eine optimale Blutglukosekontrolle für Patienten mit Diabetes mellitus darauf ausgerichtet, sowohl eine Hypoglykämie zu vermeiden als auch einen Zielbereich bis 10&nbsp;mmol/L (180&nbsp;mg/dL) zu erreichen. Die leitliniengerechte Steuerung der Ernährungstherapie ist hierbei eine unabdingbare Voraussetzung

Associations of betatrophin/ANGPTL8 with septic dyslipidemia in human peritonitis: An explorative analysis.

Sepsis is defined by life-threatening organ dysfunction mediated by the host’s response to infection. This can result in septic dyslipidemia, which is involved in the neutralization of pathogen-related lipids. Knowledge of the regulatory mechanisms of septic dyslipidemia is incomplete. The cytokine betatrophin/Angiopoietin-like protein 8 (ANGPTL8) plays a role in the regulation of triacylglyceride metabolism, though its function in septic dyslipidemia remains unknown. Sixty-six patients were enrolled in a cross-sectional study. Circulating concentrations and adipose tissue (AT) mRNA expression of betatrophin/ANGPTL8 were studied in patients suffering from peritoneal sepsis. Insulin-resistant individuals and subjects without metabolic derangement/systemic inflammation were enrolled as controls. All underwent open abdominal surgery. Circulating betatrophin/ANGPTL8 was analyzed by an enzyme-linked immunosorbent assay and AT mRNA expression levels were assessed by real-time PCR. Standard laboratory analyses including lipid electrophoresis were evaluated. Sepsis patients showed pronounced septic dyslipidemia (p &lt; 0.05 for all major lipid classes). Despite comparable betatrophin/ANGPTL8 mRNA expression in AT (p = 0.24), we found significantly increased circulating betatrophin/ANGPTL8 with septic dyslipidemia (p = 0.009). Expression levels of betatrophin/ANGPTL8 in AT correlated with circulating concentrations in both control groups (r = 0.61; p = 0.008 and r = 0.43; p = 0.034), while this association was undetectable in sepsis. After stratification, betatrophin/ANGPTL8 remained associated with hypertriacylglyceridemia (p &lt; 0.05)