23 research outputs found
Characterization of the Bafilomycin Biosynthetic Gene Cluster from Streptomyces lohii
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96305/1/301_ftp.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/96305/2/cbic_201200743_sm_miscellaneous_information.pd
Tailoring of polar and nonpolar ZnO planes on MgO (001) substrates through molecular beam epitaxy
Polar and nonpolar ZnO thin films were deposited on MgO (001) substrates under different deposition parameters using oxygen plasma-assisted molecular beam epitaxy (MBE). The orientations of ZnO thin films were investigated by in situ reflection high-energy electron diffraction and ex situ X-ray diffraction (XRD). The film roughness measured by atomic force microscopy evolved as a function of substrate temperature and was correlated with the grain sizes determined by XRD. Synchrotron-based X-ray absorption spectroscopy (XAS) was performed to study the conduction band structures of the ZnO films. The fine structures of the XAS spectra, which were consistent with the results of density functional theory calculation, indicated that the polar and nonpolar ZnO films had different electronic structures. Our work suggests that it is possible to vary ZnO film structures from polar to nonpolar using the MBE growth technique and hence tailoring the electronic structures of the ZnO films
Regulation von MembrantransportvorgÀngen durch Lipide und Proteine
Title and directory
Abstract
Introduction
Aims of the studies
Materials and methods
Results
Discussion
Conclusions
Bibliography
Appendix
List of publicationsSpecific membrane lipids have been proposed to regulate protein sorting during
the exo- and endocytic pathways at multiple stages. This includes the
formation of membrane microdomains, and membrane shape changes induced by
recruitment of peripheral proteins. Here we have addressed both mechanisms in
two distinct experimental systems: (1) the recycling of synaptic vesicles
(SVs) at nerve terminals and (2) membrane deformation at the Golgi/endosomal
boundary. SVs in the central nervous system upon stimulation undergo rapid
calcium-triggered exo-endocytic cycling within the nerve terminal which at
least in part depends on components of the clathrin- and dynamin-dependent
endocytosis machinery. How exocytic SV fusion and endocytic retrieval are
temporally and spatially coordinated is still an open question. One
possibility is that specialized membrane microdomains characterized by their
high content in membrane cholesterol may assist in the spatial coordination of
synaptic membrane protein recycling. Quantitative proteomic analysis of
detergent-resistant lipid microdomains (DRMs) isolated from rat brain synapses
or cholesterol-depleted control samples by liquid chromatography tandem mass
spectrometry identified a total of 159 proteins. Among these 122 proteins were
classified as cholesterol-dependent DRM or DRM-associated proteins, many of
which with proven or hypothesized functions in exo-endocytic vesicle cycling
including clathrin, the clathrin adaptor complex AP-2, and a variety of SV
proteins. In agreement with this SV membrane and endocytic proteins display a
partial resistance to extraction with cold Triton X-100 in cultured rat
hippocampal neurons where they co-localize with labeled cholera toxin B, a
marker for cholesterol-enriched DRMs. Moreover, SV proteins form cholesterol-
dependent complexes in CHAPS-extracted synaptic membrane lysates. Membrane
traffic at the Golgi/endosomal boundary requires the action of Arfs (ADP
ribosylation factors), NH2-terminal myristoylated proteins that belong to the
Ras superfamily of small GTP binding proteins. We demonstrate that bothwild
type myristoylated and non-myristoylated recombinant Arf1 and Arf6 can bind to
liposomes and bend them into tubular structures as observed by electron and
video microscopy. Mutations of hydrophobic residues within the amphipathic
helices abolish their liposome binding or tubulation capacity. Co-
overexpression of Arf1-EGFP and FAPP-PH domain, a PI4P-binding protein module,
in COS7 cells produces enormous tubules from a perinuclear compartment. In
comparison, Arf1 NH2-terminal hydrophobic residue mutants show a cytosolic
localization similar to GDP-locked Arf1 T31N. The NH2-terminal amphipathic
helix itself is sufficient to drive membrane curvature generation when
overexpressed in COS7 cells. These data identify a novel GTP-controlled switch
that regulates membrane deformation during budding of coated vesicles and
tubules at the Golgi/endosomal boundary.Möglicherweise können bestimmte Membranlipide die Proteinsortierung wÀhrend
der Exo- und Endocytose auf verschiedenen Ebenen regulieren. Dies könnte z.B.
durch die Formierung sog. MembranmikrodomÀnen aber auch durch VerÀnderung in
der Membrangestalt, induziert durch die Bindung peripherer Proteine,
geschehen. In dieser Arbeit wurden beide Mechanismen durch zwei verschiedene
experimentelle Systeme untersucht: 1) Recycling synaptischer Vesikel an
Nervenendigung und 2) MembranverÀnderungen an der Golgi/Endosomen-Grenze.
Synaptische Vesikel im zentralen Nervensystem werden nach Stimulierung einem
schnellen, Calcium-induzierten, exo- und endocytischen Zyklus unterworfen.
Dieser hÀngt zumindest teilweise von Komponenten der Clathrin und Dynamin-
abhÀngigen Endocytose-Maschinerie ab. Wie die Vesikelfusion und die Aufnahme
zeitlich und rÀumlich koordiniert werden ist ungewiss. Eine Möglichkeit ist,
dass spezialisierte MembrandomÀnen, die durch einen hohen Gehalt an
Cholesterin charakterisiert sind, die rÀumliche Voraussetzung schaffen, um
synaptische Membranproteine aufzunehmen. Quantitative Proteinanalysen von
Detergenz-resistenten LipidmikrodomÀnen (DRMs) aus Rattengehirnsynapsen oder
aus Cholesterin depletierten Kontrollen, ergaben nach massenspektroskopischen
Untersuchungen 159 Proteine. Darunter waren 122 Proteine als Cholesterin-
abhĂ€ngige DRM oder DRM-assoziierte Proteine aufgefĂŒhrt, viele davon mit
bewiesener Funktion im exo-und endocytischen Vesikelkreislauf. Darunter waren
Clathrin, der Clathrin Adaptor Komplex AP-2 und verschiedene synaptische
Vesikelproteine. In Ăbereinstimmung damit sind Vesikelmembranproteine und
endocytierte Proteine gegenĂŒber einer Extraktion mit kaltem Triton in
kultivierten Rattenhippocampus-Neuronen resistent. Hier kolokalisieren sie mit
markiertem Choleratoxin B, einem Protein das spezifisch fĂŒr cholesterinhaltige
DRMs ist. DarĂŒberhinaus formen Vesikelproteine Cholesterin abhĂ€ngige Komplexe
in CHAPS extrahierten Membranlysaten. Membranverkehr an der Golgi/endosomalen
Grenze benötigt ARFs (ADP ribosylation factors), NH2- terminal myristoylierte
Proteine, die zur Ras Superfamilie kleiner GTP-bindender Proteine gehören. Wir
zeigen Normales und nicht myristoyliertes rekombinantes Arf1 und Arf6 können
an Liposomen binden und sie zu tubulĂ€ren Strukuren krĂŒmmen, wie man im
Elektronen und Videomikroskop sehen konnte. Mutationen hydrophober
Bestandteile der amphipathischen Helix zerstörten die FÀhigkeit Liposomen zu
krĂŒmmen. Ăberexpression von Arf1-EGFP und FAPP-PH, einem PI(4)P bindenden
Proteinbaustein, in COS7 Zellen ergab enorme tubulÀre Strukturen aus einem
perinukleÀrem Kompartiment. Dagegen zeigten Arf1 Mutanten deren NH2 terminale
hydrophobische Bestandteile verÀndert wurden, eine zytosolische Lokalisation,
die Àhnlich der GDP-gesperrten Arf1 Mutante T31N war. Die NH2 terminale
amphipathische Helix selbst genĂŒgt, um bei Ăberexpression in Cos7 Zellen
MembrankrĂŒmmung zu erreichen. Diese Daten identifizieren einen neuen GTP-
kontrollierten Schalter, der die Membrandeformation wÀhrend der
Vesikelausknospung an der Golgi/endosomalen Grenze regulieren kann
Prevalence and factors associated with different pathogens of acute diarrhea in adults in Beijing, China
Activated hepatic stellate cells promote hepatocellular carcinoma development in immunocompetent mice
National Key Sci-Tech Special Project of China [2008ZX10002-019]; National Natural Science Foundation of China [30872484]Activated hepatic stellate cells (HSCs) play a central role in the hepatic fibrosis and cirrhosis. Recently, HSCs were reported to have strong immune modulatory activities. However, the role of HSCs in hepatocellular carcinoma (HCC) remains unclear. In this study, we showed that HSCs could promote HCC growth both in vitro and in vivo. We examined the HSC-mediated inhibition of T-cell proliferation and the ability of conditioned medium from activated HSCs to promote the growth of murine HCC cell lines in vitro. We also assessed the immune suppression by HSCs during the development of HCC in immunocompetent mice. Cotransplantation of HSCs promoted HCC growth and progression by enhancing tumor angiogenesis and tumor cell proliferation and by creating an immunosuppressed microenvironment. Cotransplanted HSCs inhibited the lymphocyte infiltration in tumors and the spleens of mice bearing tumors, induced apoptosis of infiltrating mononuclear cells, and enhanced the expression of B7H1 and CD4(+)CD25(+) Treg cells. The immune modulation by HSCs seemed to be systemic. In conclusion, our data provide new information to support an integral role for HSCs in promoting HCC progression in part via their immune regulatory activities, and suggest that HSCs may serve as a therapeutic target in HCC