The autophagosomal SNARE Syntaxin17 (Syx17) forms a complex with Snap29 and Vamp7/8 to promote autophagosome-lysosome fusion via multiple interactions with the tethering complex HOPS. Here we ...demonstrate that, unexpectedly, one more SNARE (Ykt6) is also required for autophagosome clearance in Drosophila. We find that loss of Ykt6 leads to large-scale accumulation of autophagosomes that are unable to fuse with lysosomes to form autolysosomes. Of note, loss of Syx5, the partner of Ykt6 in ER-Golgi trafficking does not prevent autolysosome formation, pointing to a more direct role of Ykt6 in fusion. Indeed, Ykt6 localizes to lysosomes and autolysosomes, and forms a SNARE complex with Syx17 and Snap29. Interestingly, Ykt6 can be outcompeted from this SNARE complex by Vamp7, and we demonstrate that overexpression of Vamp7 rescues the fusion defect of ykt6 loss of function cells. Finally, a point mutant form with an RQ amino acid change in the zero ionic layer of Ykt6 protein that is thought to be important for fusion-competent SNARE complex assembly retains normal autophagic activity and restores full viability in mutant animals, unlike palmitoylation or farnesylation site mutant Ykt6 forms. As Ykt6 and Vamp7 are both required for autophagosome-lysosome fusion and are mutually exclusive subunits in a Syx17-Snap29 complex, these data suggest that Vamp7 is directly involved in membrane fusion and Ykt6 acts as a non-conventional, regulatory SNARE in this process.
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•The heptadentate derivatives of the octadentate bispa2 ligand can form somewhat stronger complexes with trivalent metals than the parent ligand.•In solution, the complexes with ...trivalent p-block metals (In, Bi) are significantly more stable than with trivalent f elements (La, Lu, Ac).•While the major bonding interaction is generally ionic in the studied complexes, the covalent contributions is particularly significant in the In and Bi complexes.•The efficient encapsulation of the metals by the bispidine ligands does not allow any significant effect of the solvent water molecules in the first coordination sphere.
The complexes of radiopharmaceutically relevant trivalent metals (MIII = InIII, BiIII, LaIII, LuIII, AcIII) with two heptadentate bispidine-based ligands (L) have been investigated by DFT calculations. The main questions included the encapsulation efficiency of the ligands for the different-size metals, the differences in bonding, the possibility and characteristics of octa- and nonacoordination achieved by attachment of H2O ligands to the ML complexes as well as the thermodynamic stabilities under isolated and aqueous solution conditions. The results supported high efficiencies of the ligands resulting in very good stabilities of the complexes. The bonding analysis revealed small differences based on a gentle interplay of the sizes and electronic structures of the MIII ions as well as on the difference in two donor groups of the ligands. The present heptadentate ligands form tighter interactions with the metals as compared to the octadentate derivative, and leave less space for coordination of additional ligands.
A quantitative classification of carbonate aquifers based on hydrodynamic behaviour is introduced. This type of classification is necessary to understand the physical functioning of carbonate ...hydrogeological systems and to provide a realistic interpretation of field data. Carbonate aquifers are generally considered as karst systems; however, geomorphology and aquifer geology alone are insufficient for determining hydrodynamic behaviour. Analysis of spring and well hydrographs based on analytical solutions is applied to establishing a quantitative classification. A base-flow recession coefficient is used as an indicator of hydrodynamic behaviour. Detailed numerical analyses suggest that carbonate systems can be classified into two distinct groups based on hydrodynamic behaviour. The physical processes depend on a combination of hydraulic and geometric parameters, and their functional relationships can be quantitatively determined. The proposed classification methodology involves making an assumption about aquifer type, estimating aquifer properties from hydrograph data, and comparing the results with field observations. The proposed classification methodology was applied to aquifers representing the two groups of carbonate systems. In both cases, the applied methods revealed crucial information about hydrodynamic functioning of the investigated systems. While the studied limestone aquifer showed karstic hydrodynamic behaviour, the investigation of a dolomite aquifer disproves a priori assumptions on karstic flow conditions. Dolomite aquifers represent an ambiguous group of carbonates and require caution in the selection of investigation tools and interpretation of hydrogeological data. The introduced methodology provides a reliable means of determining the hydrodynamic functioning of an aquifer and supports the quantitative classification of carbonate hydrogeological systems.
PtdIns(3)P plays critical roles in the autophagy pathway. However, little is known about how PtdIns(3)P effectors act with autophagy proteins in autophagosome formation. Here we identified an ...essential autophagy gene in C. elegans, epg-6, which encodes a WD40 repeat-containing protein with PtdIns(3)P-binding activity. EPG-6 directly interacts with ATG-2. epg-6 and atg-2 regulate progression of omegasomes to autophagosomes, and their loss of function causes accumulation of enlarged early autophagic structures. Another WD40 repeat PtdIns(3)P effector, ATG-18, plays a distinct role in autophagosome formation. We also established the hierarchical relationship of autophagy genes in degradation of protein aggregates and revealed that the UNC-51/Atg1 complex, EPG-8/Atg14, and binding of lipidated LGG-1 to protein aggregates are required for omegasome formation. Our study demonstrates that autophagic PtdIns(3)P effectors play distinct roles in autophagosome formation and also provides a framework for understanding the concerted action of autophagy genes in protein aggregate degradation.
► C. elegans PtdIns(3)P effector EPG-6 regulates omegasome-to-autophagosome progression ► Early autophagic structures accumulate upon mammalian homolog WIPI-4 depletion ► Binding of lipidated LGG-1/Atg8 to protein aggregates regulates omegasome formation ► PtdIns(3)P effectors play distinct roles in autophagosome formation
The complexes of selected radionuclides relevant for nuclear medicine (In
III
, Bi
III
, Lu
III
, Ac
III
and in addition La
III
for comparative purposes) with the octadentate ...(6,6′-((9-hydroxy-1,5-bis(methoxycarbonyl)-2,4-di(pyridin-2-yl)-3,7-diazabicyclo3.3.1nonane-3,7-diyl)bis(methylene))dipicolinic acid) ligand, H
2
bispa
2
, have been studied by density functional theory calculations modelling both isolated and aqueous solution conditions. The properties in focus are the encapsulation efficiency of the ligand for the different-size metals (M), the differences in bonding with the various M
III
ions analysed using Bader’s atoms in molecules theory and the possibility and characteristics of nona- and decacoordination by H
2
O ligands. The computed results confirmed strong steric effects in the case of the In complex excluding higher than octacoordination. The studied properties depend strongly on the interplay of the sizes and electronic structures of the M
III
ions. The computations support high stability of the complexes in aqueous solution, where also the solvation energies of the M
III
ions (as dissociation products) play a significant role.
The small GTPase Rab5 promotes recruitment of the Ccz1-Mon1 guanosine exchange complex to endosomes to activate Rab7, which facilitates endosome maturation and fusion with lysosomes. How these ...factors function during autophagy is incompletely understood. Here we show that autophagosomes accumulate due to impaired fusion with lysosomes upon loss of the Ccz1-Mon1-Rab7 module in starved Drosophila fat cells. In contrast, autophagosomes generated in Rab5-null mutant cells normally fuse with lysosomes during the starvation response. Consistent with that, Rab5 is dispensable for the Ccz1-Mon1-dependent recruitment of Rab7 to PI3P-positive autophagosomes, which are generated by the action of the Atg14-containing Vps34 PI3 kinase complex. Finally, we find that Rab5 is required for proper lysosomal function. Thus the Ccz1-Mon1-Rab7 module is required for autophagosome-lysosome fusion, whereas Rab5 loss interferes with a later step of autophagy: the breakdown of autophagic cargo within lysosomes.
Lanthanide dinitrogen complexes, Ln(N2)
x (x = 1‐8), were investigated by Density Functional Theory computations using the B3LYP exchange‐correlation functional in conjunction with quasirelativistic ...pseudopotentials for Ln. After a recent study on the lanthanum complexes (A. Kovács, Structural Chemistry 2018, 29, 1825), the present study aimed to probe the changes upon variously filled 4f subshells of Ln on the structures, stabilities, and bonding properties in related complexes of Nd, Ho, and Lu. The bonding properties were assessed on the basis of natural atomic charges, Ln valence orbital populations, and analysis of bonding molecular orbitals.
The structures, stabilities, and bonding properties of Ln(N2)
x (Ln = La, Nd, Ho, Lu; x = 1‐8) complexes were assessed using quantum chemical computations. The differences due to the variously filled 4f subshells of Ln were interpreted on the basis of the computed electronic structures.
The past decade has been very productive in the field of actinide (An) oxides containing high-valent An. Novel gas-phase experimental and an impressive number of theoretical studies have been ...performed, mostly on pure oxides or oxides extended with other ligands. The review covers the structural properties of molecular An oxides with high (An
≥V
) oxidation states. The presented compounds include the actinide dioxide cations AnO
2
+
and AnO
2
2+
, neutral and ionic AnO
x
(
x
= 3–6), oxides with more than one An atom like neutral dimers, trimers and dimers from cation–cation interactions, as well as large U-oxide clusters observed very recently in the gaseous phase.
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