FMP Publications

Our publications are recorded in a searchable database since 2010, updates will be added regularly.

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References
A Non-canonical Voltage-Sensing Mechanism Controls Gating in K2P K(+) Channels
Schewe(*), M., Nematian-Ardestani(*), E., Sun, H., Musinszki(*), M., Cordeiro(*), S., Bucci(*), G., de Groot(*), B. L., Tucker(*), S. J., Rapedius(*), M.; Baukrowitz(*), T.
Cell, 164:937-949
(2016)

Tags: Computational Chemistry and Protein Design (Kühne)

Abstract: Two-pore domain (K2P) K(+) channels are major regulators of excitability that endow cells with an outwardly rectifying background "leak" conductance. In some K2P channels, strong voltage-dependent activation has been observed, but the mechanism remains unresolved because they lack a canonical voltage-sensing domain. Here, we show voltage-dependent gating is common to most K2P channels and that this voltage sensitivity originates from the movement of three to four ions into the high electric field of an inactive selectivity filter. Overall, this ion-flux gating mechanism generates a one-way "check valve" within the filter because outward movement of K(+) induces filter opening, whereas inward movement promotes inactivation. Furthermore, many physiological stimuli switch off this flux gating mode to convert K2P channels into a leak conductance. These findings provide insight into the functional plasticity of a K(+)-selective filter and also refine our understanding of K2P channels and the mechanisms by which ion channels can sense voltage.

Lysosomal Dysfunction Caused by Cellular Accumulation of Silica Nanoparticles
Schütz, I., Lopez-Hernandez, T., Gao(*), Q., Puchkov, D., Jabs, S., Nordmeyer(*), D., Schmudde(*), M., Rühl(*), E., Graf(*), C. M.; Haucke, V.
J Biol Chem, 291:14170-14184
(2016)

Tags: Molecular Pharmacology and Cell Biology (Haucke), Physiology and Pathology of Ion Transport (Jentsch), Cellular Imaging (Wiesner, Puchkov)

Abstract: Nanoparticles (NPs) are widely used as components of drugs or cosmetics and hold great promise for biomedicine, yet their effects on cell physiology remain poorly understood. Here we demonstrate that clathrin-independent dynamin 2-mediated caveolar uptake of surface-functionalized silica nanoparticles (SiNPs) impairs cell viability due to lysosomal dysfunction. We show that internalized SiNPs accumulate in lysosomes resulting in inhibition of autophagy-mediated protein turnover and impaired degradation of internalized epidermal growth factor, whereas endosomal recycling proceeds unperturbed. This phenotype is caused by perturbed delivery of cargo via autophagosomes and late endosomes to SiNP-filled cathepsin B/L-containing lysosomes rather than elevated lysosomal pH or altered mTOR activity. Given the importance of autophagy and lysosomal protein degradation for cellular proteostasis and clearance of aggregated proteins, these results raise the question of beneficial use of NPs in biomedicine and beyond.

Septins As Modulators of Endo-Lysosomal Membrane Traffic
Song, K., Russo, G.; Krauss, M.
Frontiers in cell and developmental biology, 4:124
(2016)

Tags: Molecular Pharmacology and Cell Biology (Haucke)

Abstract: Septins constitute a family of GTP-binding proteins, which assemble into non-polar filaments in a nucleotide-dependent manner. These filaments can be recruited to negatively charged membrane surfaces. When associated with membranes septin filaments can act as diffusion barriers, which confine subdomains of distinct biological functions. In addition, they serve scaffolding roles by recruiting cytosolic proteins and other cytoskeletal elements. Septins have been implicated in a large variety of membrane-dependent processes, including cytokinesis, signaling, cell migration, and membrane traffic, and several family members have been implicated in disease. However, surprisingly little is known about the molecular mechanisms underlying their biological functions. This review summarizes evidence in support of regulatory roles of septins during endo-lysosomal sorting, with a particular focus on phosphoinositides, which serve as spatial landmarks guiding septin recruitment to distinct subcellular localizations.

Cannabinoid Type 2 Receptors Mediate a Cell Type-Specific Plasticity in the Hippocampus
Stempel(*), A. V., Stumpf(*), A., Zhang(*), H. Y., Ozdogan(*), T., Pannasch(*), U., Theis(*), A. K., Otte(*), D. M., Wojtalla(*), A., Racz(*), I., Ponomarenko, A., Xi(*), Z. X., Zimmer(*), A.; Schmitz(*), D.
Neuron, 90:795-809
(2016)

Tags: Behavioral Neurodynamics (Korotkova/Ponomarenko)

Abstract: Endocannabinoids (eCBs) exert major control over neuronal activity by activating cannabinoid receptors (CBRs). The functionality of the eCB system is primarily ascribed to the well-documented retrograde activation of presynaptic CB1Rs. We find that action potential-driven eCB release leads to a long-lasting membrane potential hyperpolarization in hippocampal principal cells that is independent of CB1Rs. The hyperpolarization, which is specific to CA3 and CA2 pyramidal cells (PCs), depends on the activation of neuronal CB2Rs, as shown by a combined pharmacogenetic and immunohistochemical approach. Upon activation, they modulate the activity of the sodium-bicarbonate co-transporter, leading to a hyperpolarization of the neuron. CB2R activation occurred in a purely self-regulatory manner, robustly altered the input/output function of CA3 PCs, and modulated gamma oscillations in vivo. To conclude, we describe a cell type-specific plasticity mechanism in the hippocampus that provides evidence for the neuronal expression of CB2Rs and emphasizes their importance in basic neuronal transmission.

Inositol polyphosphates intersect with signaling and metabolic networks via two distinct mechanisms
Wu(*), M., Chong, L. S., Perlman(*), D. H., Resnick(*), A. C.; Fiedler, D.
Proc Natl Acad Sci U S A, 113:E6757-E6765
(2016)

Tags: Chemical Biology I (Fiedler)

Abstract: Inositol-based signaling molecules are central eukaryotic messengers and include the highly phosphorylated, diffusible inositol polyphosphates (InsPs) and inositol pyrophosphates (PP-InsPs). Despite the essential cellular regulatory functions of InsPs and PP-InsPs (including telomere maintenance, phosphate sensing, cell migration, and insulin secretion), the majority of their protein targets remain unknown. Here, the development of InsP and PP-InsP affinity reagents is described to comprehensively annotate the interactome of these messenger molecules. By using the reagents as bait, >150 putative protein targets were discovered from a eukaryotic cell lysate (Saccharomyces cerevisiae). Gene Ontology analysis of the binding partners revealed a significant overrepresentation of proteins involved in nucleotide metabolism, glucose metabolism, ribosome biogenesis, and phosphorylation-based signal transduction pathways. Notably, we isolated and characterized additional substrates of protein pyrophosphorylation, a unique posttranslational modification mediated by the PP-InsPs. Our findings not only demonstrate that the PP-InsPs provide a central line of communication between signaling and metabolic networks, but also highlight the unusual ability of these molecules to access two distinct modes of action.

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Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP)
Campus Berlin-Buch
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13125 Berlin, Germany
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info(at)fmp-berlin.de

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