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  • Ca2+ channel antagonists  (1)
  • Endosomes/*metabolism  (1)
  • 1
    Publication Date: 2015-02-18
    Description: Autophagy, an important catabolic pathway implicated in a broad spectrum of human diseases, begins by forming double membrane autophagosomes that engulf cytosolic cargo and ends by fusing autophagosomes with lysosomes for degradation. Membrane fusion activity is required for early biogenesis of autophagosomes and late degradation in lysosomes. However, the key regulatory mechanisms of autophagic membrane tethering and fusion remain largely unknown. Here we report that ATG14 (also known as beclin-1-associated autophagy-related key regulator (Barkor) or ATG14L), an essential autophagy-specific regulator of the class III phosphatidylinositol 3-kinase complex, promotes membrane tethering of protein-free liposomes, and enhances hemifusion and full fusion of proteoliposomes reconstituted with the target (t)-SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) syntaxin 17 (STX17) and SNAP29, and the vesicle (v)-SNARE VAMP8 (vesicle-associated membrane protein 8). ATG14 binds to the SNARE core domain of STX17 through its coiled-coil domain, and stabilizes the STX17-SNAP29 binary t-SNARE complex on autophagosomes. The STX17 binding, membrane tethering and fusion-enhancing activities of ATG14 require its homo-oligomerization by cysteine repeats. In ATG14 homo-oligomerization-defective cells, autophagosomes still efficiently form but their fusion with endolysosomes is blocked. Recombinant ATG14 homo-oligomerization mutants also completely lose their ability to promote membrane tethering and to enhance SNARE-mediated fusion in vitro. Taken together, our data suggest an autophagy-specific membrane fusion mechanism in which oligomeric ATG14 directly binds to STX17-SNAP29 binary t-SNARE complex on autophagosomes and primes it for VAMP8 interaction to promote autophagosome-endolysosome fusion.〈br /〉〈br /〉〈a href="" target="_blank"〉〈img src="" border="0"〉〈/a〉   〈a href="" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Diao, Jiajie -- Liu, Rong -- Rong, Yueguang -- Zhao, Minglei -- Zhang, Jing -- Lai, Ying -- Zhou, Qiangjun -- Wilz, Livia M -- Li, Jianxu -- Vivona, Sandro -- Pfuetzner, Richard A -- Brunger, Axel T -- Zhong, Qing -- 5P30CA142543/CA/NCI NIH HHS/ -- P41 GM103403/GM/NIGMS NIH HHS/ -- R01 CA133228/CA/NCI NIH HHS/ -- R01 R37-MH63105/MH/NIMH NIH HHS/ -- R37 MH063105/MH/NIMH NIH HHS/ -- T32 GM007232/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2015 Apr 23;520(7548):563-6. doi: 10.1038/nature14147. Epub 2015 Feb 9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305, USA [2] Department of Structural Biology, Stanford University, Stanford, California 94305, USA [3] Department of Photon Science, Stanford University, Stanford, California 94305, USA [4] Department of Neurology and Neurological Sciences, Stanford University, Stanford, California 94305, USA [5] Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA. ; 1] Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2] Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [3] College of Food Science &Nutritional Engineering, China Agricultural University, Beijing 100083, China. ; 1] Center for Autophagy Research, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA [2] Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA. ; Division of Biochemistry, Biophysics and Structural Biology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California 94720, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="" target="_blank"〉PubMed〈/a〉
    Keywords: Adaptor Proteins, Vesicular Transport/*chemistry/*metabolism ; *Autophagy ; Endosomes/*metabolism ; HEK293 Cells ; HeLa Cells ; Humans ; Lysosomes/*metabolism ; *Membrane Fusion ; Phagosomes/chemistry/*metabolism ; Protein Binding ; Protein Multimerization ; Protein Structure, Tertiary ; Qa-SNARE Proteins/metabolism ; Qb-SNARE Proteins/metabolism ; Qc-SNARE Proteins/metabolism ; R-SNARE Proteins/metabolism ; SNARE Proteins/chemistry/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    ISSN: 1432-1912
    Keywords: Ca2+ ; Ca2+ channels ; Ca2+ channel antagonists ; 1,4-Dihydropyridines ; [3H]PN 200-110
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The Ca2+ channel antagonistic potencies of tiamdipine [2-(2-aminoethylthio)methyl-3-carboethoxy-5-carbomethoxy-6-methyl-4-(3-nitrophenyl)-1,4-dihydropyridine] and nifedipine [2,6-dimethyl-3,5-dicarbomethoxy-4-(2nitrophenyl)-1,4-dihydropyridine] analogs bearing phenyl ring substituents were studied using pharmacologic and radioligand binding techniques. Additionally, analogs of tiamdipine possessing (2-aminoethylthio)methyl-, (2-acetamidoethylthio)methyl-and (2-pyrrolidinylmethylthio)methyl-groups at the C2 position of the 1,4-dihydropyridine ring have been studied. Tiamdipine and nifedipine analogs inhibited K+-induced contractile responses in rat tail artery. IC50 values of 4-phenyl ring substituted 2-(2-aminoethylthio)methyl tiamdipine analogs ranged from 10−7 mol/l to 10−8 mol/l. However, the corresponding 4-phenyl ring substituted nifedipine analogs covered a wider range of potency from 10−6 mol/l to 10−9 mol/l. K, values of the corresponding tiamdipine analogs for the inhibition of specific [3H]PN 200-110 [( I- ) [3H]isopropyl-4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-5-methoxycarbonyl-2,6-dimethyl-3-pyridinecarboxylate] binding-ranged from 10−7 mol/l to 10−9 mol/l in guinea pig ileal and rat heart membranes and rat brain synaptosomes. The two stereoisomers of tiamdipine and its analog 2-(2acetamidoethylthio)methyl-3-carboethoxy-5-carbomethoxy-6-methyl-4-(3-nitrophenyl)-1,4-dihydropyridine, and the four stereoisomers of 2-(2-pyrrolidinylmethylthio)methyl-3carboethoxy-5-carbomethoxy-6-methyl-4-(3-nitrophenyl)1,4-dihydropyridine showed high stereoselectivity ratios of approximately (−)/(+) = 100 and 1000 in pharmacologic and binding experiments, respectively. The inhibitory actions of 2-(2-aminoethylthio)methyltiamdipine analogs against K+-induced contractile responses in rat tail artery developed very slowly requiring at least 2 h for maximum effect. The recoveries of response to K+ depolarization were also correspondingly slow. However, recovery was greatly accelerated by the presence of the 1,4-dihydropyridine activator Bay K 8644 [2,6-dimethyl-3carbomethoxy-5-nitro-4-(2-trifluoromethyl)-1,4-dihydropyridine, 5 × 10−6 mol/l] immediately prior to the K+ challenge. The 2-(2-acetamidoethylthio)methyl tiamdipine derivative and nifedipine produced maximum inhibitory effects within 10 min, and responses recovered rapidly upon washing. The slow kinetics of onset and offset of action of the tiamdipine analogs and the reduced effects of 4-phenyl substitution relative to agents of the nifedipine series suggest that these two series of 1,4-dihydropyridines exhibit different modes of interaction with the Ca2+ channel. At least part of this difference is to be attributed to the presence of a charged group in the basic tiamdipine series. Trapping of these agents within the membrane phase likely contributes to their observed slow kinetics of action.
    Type of Medium: Electronic Resource
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