Synaptotagmin-7 Is an Asynchronous Calcium Sensor for Synaptic Transmission in Neurons Expressing SNAP-23

Synchronization of neurotransmitter release with the presynaptic action potential is essential for maintaining fidelity of information transfer in the central nervous system. However, synchronous release is frequently accompanied by an asynchronous release component that builds up during repetitive stimulation, and can even play a dominant role in some synapses. Here, we show that substitution of SNAP-23 for SNAP-25 in mouse autaptic glutamatergic hippocampal neurons results in asynchronous release and a higher frequency of spontaneous release events (mEPSCs). Use of neurons from double-knock-out (SNAP-25, synaptotagmin-7) mice in combination with viral transduction showed that SNAP-23-driven release is triggered by endogenous synaptotagmin-7. In the absence of synaptotagmin-7 release became even more asynchronous, and the spontaneous release rate increased even more, indicating that synaptotagmin-7 acts to synchronize release and suppress spontaneous release. However, compared to synaptotagmin-1, synaptotagmin-7 is a both leaky and asynchronous calcium sensor. In the presence of SNAP-25, consequences of the elimination of synaptotagmin-7 were small or absent, indicating that the protein pairs SNAP-25/synaptotagmin-1 and SNAP-23/synaptotagmin-7 might act as mutually exclusive calcium sensors. Expression of fusion proteins between pHluorin (pH-sensitive GFP) and synaptotagmin-1 or -7 showed that vesicles that fuse using the SNAP-23/synaptotagmin-7 combination contained synaptotagmin-1, while synaptotagmin-7 barely displayed activity-dependent trafficking between vesicle and plasma membrane, implying that it acts as a plasma membrane calcium sensor. Overall, these findings support the idea of alternative syt∶SNARE combinations driving release with different kinetics and fidelity

Penggambaran superhero pada tokoh Deadpool dalam film Deadpool

Deadpool merupakan film superhero yang diproduksi oleh Marvel Studio pada tahun 2016. Film ini menceritakan sosok superhero yang memiliki sisi lain dari superhero pada umumnya. Penelitian ini bertujuan untuk melihat bagaimana tanda-tanda penggambaran superhero pada tokoh Deadpool dalam film Deadpool. Superhero merupakan sosok yang memiliki kekuatan diluar nalar manusia dan mereka selalu menutupi identitasnya. Metode analisis semiotika Charles Sanders Pierce digunakan untuk meneliti tanda penggambaran pada tokoh Deadpool dalam film Deadpool. Melalui tanda-tanda yang muncul dalam film Deadpool, peneliti menemukan bahwa menjadi superhero tidak harus menjadi sosok yang sempurna baik fisik maupun sifatnya. Selain itu film ini mempertegas bahwa menjadi superhero hanya membutuhkan kemauan yang kuat, jiwa kepahlawanan yang besar dan usaha yang maksimal

Mechanismen und Regulation von Synaptogeneseprozessen in kultivierten neocortikalen Neuronen

Chemische Synapsen sind essentiell für die Informationsverarbeitung im Nervensystem. Die Mechanismen der Entstehung von Synapsen in neocortikalen Neuronen wurden exemplarisch untersucht: Durch eine elektrophysiologische Analyse der Lokalisation von N-methyl-D-aspartat (NMDA)-Rezeptoren in kultivierten Neuronen einer genetisch veränderten Maus (NR2BdeltaC) konnte gezeigt werden, daß die Akkumulation dieser Rezeptoren in der postsynaptischen Dichte glutamaterger Synapsen von der Anwesenheit der c-terminalen, intrazellulären Domäne der Untereinheit NR2B abhängt. Diese Domäne scheint auch die Offenwahrscheinlichkeit des Rezeptors zu regulieren. Weiterhin wurde die Reifung des präsynaptischen Vesikelpools funktionell mittels FM1-43-Färbungen und elektrophysiologischen Methoden analysiert. Dabei konnte für glutamaterge Synapsen im Gegensatz zu GABAergen Synapsen eine spezifische langfristige Verbesserung der Freisetzungsfähigkeit aufgrund einer Vergrößerung des Reservepools festgestellt werden

MODELLING THE TMF-LIFE OF A SALT BATH EXPERIMENT WITH VISCOPLASTIC CONSTITUTIVE EQUATIONS

ABSTRACT The salt bath experiment was chosen because of the load characteristics. It is simple enough to allow treatment at moderate cost while containing a geometrical concentration of stress subject to cyclic loading under displacement control (equivalent to thermal control) and leading to a typical situation of creep and localized plasticity with realistic levels of stress and temperature

Fast Vesicle Fusion in Living Cells Requires at Least Three SNARE Complexes

Exocytosis requires formation of SNARE [soluble N-ethylmaleimide - sensitive factor attachment protein (SNAP) receptor] complexes between vesicle and target membranes. Recent assessments in reduced model systems have produced divergent estimates of the number of SNARE complexes needed for fusion. Here, we used a titration approach to answer this question in intact, cultured chromaffin cells. Simultaneous expression of wild-type SNAP-25 and a mutant unable to support exocytosis progressively altered fusion kinetics and fusion-pore opening, indicating that both proteins assemble into heteromeric fusion complexes. Expressing different wild-type:mutant ratios revealed a third-power relation for fast (synchronous) fusion and a near-linear relation for overall release. Thus, fast fusion typically observed in synapses and neurosecretory cells requires at least three functional SNARE complexes, whereas slower release might occur with fewer complexes. Heterogeneity in SNARE-complex number may explain heterogeneity in vesicular release probability