Folkerts, S. | Search bioRxiv

bioRxiv2023

Optical Control of G-Actin with a Photoswitchable Latrunculin

Actin is one of the most abundant proteins in eukaryotic cells and a key component of the cytoskeleton. A range of small molecules have emerged that interfere with actin dynamics by either binding to polymeric F-actin or monomeric G-actin to stabilize or destabilize filaments or prevent their formation and growth, respectively. Amongst these, the latrunculins, which bind to G-actin and affect polymerization, are widely used as tools to investigate actin-dependent cellular processes. Here, we report a photoswitchable version of latrunculin, termed opto-latrunculin (OptoLat), which binds to G-actin in a light-dependent fashion and affords optical control over actin polymerization. OptoLat can be activated with 390 - 490 nm pulsed light and rapidly relaxes to the inactive form in the dark. Light activated OptoLat induced depolymerization of F-actin networks in oligodendrocytes and budding yeast, as shown by fluorescence microscopy. Subcellular control of actin dynamics in human cancer cell lines was demonstrated by live cell imaging. Light-activated OptoLat also reduced microglia surveillance in organotypic mouse brain slices while ramification was not affected. Incubation in the dark did not alter the structural and functional integrity of microglia. Together, our data demonstrate that OptoLat is a useful tool for the elucidation of G-actin dependent dynamic processes in cells and tissues.

pharmacology and toxicology↗

bioRxiv2017

Human Episodic Memory Retrieval Is Accompanied By A Neural Jump Back In Time

Cognitive psychologists have long hypothesized that experiences are encoded in a temporal context that changes gradually over time. When an episodic memory is retrieved, the state of context is recovered--a jump back in time. We recorded from single units in the MTL of epilepsy patients performing an item recognition task. The population vector changed gradually over minutes during presentation of the list. When a probe from the list was remembered with high confidence, the population vector reinstated the temporal context of the original presentation of that probe during study--a neural contiguity effect that provides a possible mechanism for behavioral contiguity effects. This pattern was only observed for well-remembered probes; old probes that were not well-remembered showed an anti-contiguity effect. These results constitute the first direct evidence that recovery of an episodic memory in humans is associated with retrieval of a gradually-changing state of temporal context--a neural \"jump-back-in-time\" that parallels the act of remembering.\n\nSignificance statementEpisodic memory is the ability to re-live a specific experience from ones life. For decades, researchers have hypothesized that, unlike other forms of memory that can be described as simple associations between stimuli, episodic memory depends on the recovery of a neural representation of spatiotemporal context. During study of a sequence of stimuli, the brain state of epilepsy patients changed slowly over at least a minute. When the participant remembered a particular event from the list, this gradually-changing state was recovered. This provides direct confirmation of the prediction from computational models of episodic memory. The resolution of this point means that the study of episodic memory can focus on the mechanisms by which this representation of spatiotemporal context is maintained and, sometimes recovered.

neuroscience↗