128 research outputs found

    Hrs Promotes Ubiquitination and Mediates Endosomal Trafficking of Smoothened in Drosophila Hedgehog Signaling

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    In Hedgehog (Hh) signaling, the seven-transmembrane protein Smoothened (Smo) acts as a signal transducer that is regulated by phosphorylation, ubiquitination, and cell surface accumulation. However, it is not clear how Smo cell surface accumulation and intracellular trafficking are regulated. Here, we demonstrate that inactivation of Hrs by deletion or RNAi accumulates Smo in the late endosome that is marked by late endosome markers. Inactivation of Hrs enhances the wing defects caused by dominant-negative Smo. We show that Hrs promotes Smo ubiquitination, deleting the ubiquitin-interacting-motif (UIM) in Hrs abolishes the ability of Hrs to regulate Smo ubiquitination. However, the UIM domain neither recognizes the ubiquitinated Smo nor directly interacts with Smo. Hrs lacking UIM domain still downregulates Smo activity even though to a less extent. We have characterized that the N-terminus of Hrs directly interacts with the PKA/CK1 phosphorylation clusters to prevent Smo phosphorylation and activation, indicating an ubiquitin-independent regulation of Smo by Hrs. Finally, we found that knockdown of Tsg101 accumulates Smo that is co-localized with Hrs and other late endosome markers. Taken together, our data indicate that Hrs mediates Smo trafficking in the late endosome by not only promoting Smo ubiquitination but also blocking Smo phosphorylation

    Magic angle in thermal conductivity of twisted bilayer graphene

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    We report a local minimum in thermal conductivity in twisted bilayer graphene (TBG) at the angle of 1.08^\circ, which corresponds to the 'magic angle' in the transition of several other reported properties. Within the supercell of a moir\'e lattice, different stacking modes generate phonon scattering sites which reduce the thermal conductivity of TBG. The thermal magic angle arises from the competition between the delocalization of atomic vibrational amplitudes and stresses on one hand, and the increased AA stacking density on the other hand. The former effect weakens the scattering strength of a single scatterer while the latter one increases the density of scatterers. The combination of these two effects eventually leads to the apparition of the highlighted irregularity in heat conduction. The manifestation of a magic angle, disclosing new thermal mechanisms at nanoscale, further uncovers the unique physics of two-dimensional materials.Comment: 15 pages, 5 figure

    The emission positions of kHz QPOs and Kerr spacetime influence

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    Based the Alfven wave oscillation model (AWOM) and relativistic precession model (RPM) for twin kHz QPOs, we estimate the emission positions of most detected kHz QPOs to be at r=18+-3 km (R/15km) except Cir X-1 at r = 30\+-5 km (R/15km). For the proposed Keplerian frequency as an upper limit to kHz QPO, the spin effects in Kerr Spacetime are discussed, which have about a 5% (2%) modification for that of the Schwarzchild case for the spin frequency of 1000 (400) Hz.The application to the four typical QPO sources, Cir X-1, Sco X-1, SAX J1808.4-3658 and XTE 1807-294, is mentioned.Comment: Science China, Physics, Mechanics & Astronomy, 2010, 53, NO.

    Uber die Welch-Fraenkelschen Bazillen und ihre Verwandten im Darmkanal

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    Der Welch-Fraenkelsche Bazillus, der sich als ein Bodenbakterium weit im Boden verbreitet, ist obligater Anaerobier, und bekannt als Erreger des Gasoedems, welches eine chirurgisch und insbesonders kriegschirurgisch wichtige Wundinfektionskrankheit ist. Die Tatsache, dass dieses Stabchen nicht nur aus dem Boden, sondern auch aus menschlichem Darm gezuchtet wird, hat viele Autoren schon bisweilen beschaftigt. Dieser Bazillus ist Gram-positiv, gross und kraftig, abgerundet, unbeweglich und sporuliert nicht im gewohnlichen Nahrboden. Die Milch wurde sturmisch mit Gasbildung vergoren. Schon nach 20 Stunden schwamm das Kasein deutlich geschieden in truber, immer klarer werdender Molke. Die Kaseingerinnsel wurden ferner nicht wieder durch Peptonisierung gelost, noch kam es nach dem leicht sauerlich bleibenden Geruch zu Eiweissfaulniss. Die oben beschriebene Eigenschaft, die sog. Sturmische Gerinnung , ist charakteristisches Merkmal zur Diagnose-stellung des Welch-Fraenkelschen Bazillus. Der Verfasser hat aus 172 Faeces der Menschen 244 Stamme der Welch-Fraenkelschen Bazillen und 39 ahnliche Stamme, die von erstem Bazillus deutlich voneinander in Eigenstumlichkeit abweicht gezuchtet; d. h. dem Letzteren fehlt die sturmische Gerinnung. Diesen Bazillus nennt der Verfasser einen Verwandten der Welch-Fraenkelschen Bazillen , und vergleicht dieses Stabchen morphologisch und biologisch mit den Welch-Fraenkelschen Bazillen, welche er aus menschlichen Faeces und klassischem Gasoedem isoliert hat. Morphologie: Die Verwandten sind ebenso mit abgerundetem Ende 0.8-1.0μ breit, 4.0-1.0μ, nicht haufig 15μ in der Lange, zuweilen leicht gekrummt, und werden zarter als Welch-Fraenkelche Bazillen beobachtet. Sporen und Kapseln: Nicht nur in gewohnlichen Nahrboden, sondern auch in den alkalischen-, natriumphosphathaltigen Nahrsubstraten und im Hirnbrei nahm der Verfasser keine Sporen oder Kapseln wahr. Aber nur bei aus Gasoedem gezuchtetem Stamm beobachtete er beide im spezifischen antiserumhaltigen Nahrboden. Kolonientypen: Auf d

    USP8 Promotes Smoothened Signaling by Preventing Its Ubiquitination and Changing Its Subcellular Localization

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    The seven transmembrane protein Smoothened (Smo) is a critical component of the Hedgehog (Hh) signaling pathway and is regulated by phosphorylation, dimerization, and cell-surface accumulation upon Hh stimulation. However, it is not clear how Hh regulates Smo accumulation on the cell surface or how Hh regulates the intracellular trafficking of Smo. In addition, little is known about whether ubiquitination is involved in Smo regulation. In this study, we demonstrate that Smo is multimonoubiquitinated and that Smo ubiquitination is inhibited by Hh and by phosphorylation. Using an in vivo RNAi screen, we identified ubiquitin-specific protease 8 (USP8) as a deubiquitinase that down-regulates Smo ubiquitination. Inactivation of USP8 increases Smo ubiquitination and attenuates Hh-induced Smo accumulation, leading to decreased Hh signaling activity. Moreover, overexpression of USP8 prevents Smo ubiquitination and elevates Smo accumulation, leading to increased Hh signaling activity. Mechanistically, we show that Hh promotes the interaction of USP8 with Smo aa625–753, which covers the three PKA and CK1 phosphorylation clusters. Finally, USP8 promotes the accumulation of Smo at the cell surface and prevents localization to the early endosomes, presumably by deubiquitinating Smo. Our studies identify USP8 as a positive regulator in Hh signaling by down-regulating Smo ubiquitination and thereby mediating Smo intracellula

    An Improved Genetic Algorithm Based Robust Approach for Stochastic Dynamic Facility Layout Problem

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    This paper deals with stochastic dynamic facility layout problem under demand uncertainty in terms of material flow between facilities. A robust approach suggests a robust layout in each period as the most frequent one falling within a prespecified percentage of the optimal solution for multiple scenarios. Mont Carlo simulation method is used to randomly generate different scenarios. A mathematical model is established to describe the dynamic facility layout problem with the consideration of transport device assignment. As a solution procedure for the proposed model, an improved adaptive genetic algorithm with population initialization strategy is developed to reduce the search space and improve the solving efficiency. Different sized instances are compared with Particle Swarm Optimization (PSO) algorithm to verify the effectiveness of the proposed genetic algorithm. The experiments calculating the cost deviation ratio under different fluctuation level show the good performance of the robust layout compared to the expected layout
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