The emerging tools for precisely manipulating microtubules

Cells generate a highly diverse microtubule network to carry out different activities. This network is comprised of distinct tubulin isotypes, tubulins with different post-translational modifications, and many microtubule-based structures. Defects in this complex system cause numerous human disorders. However, how different microtubule subtypes in this network regulate cellular architectures and activities remains largely unexplored. Emerging tools such as photosensitive pharmaceuticals, chemogenetics, and optogenetics enable the spatiotemporal manipulation of structures, dynamics, post-translational modifications, and cross-linking with actin filaments in target microtubule subtypes. This review summarizes the design rationale and applications of these new approaches and aims to provide a roadmap for researchers navigating the intricacies of microtubule dynamics and their post-translational modifications in cellular contexts, thereby opening new avenues for therapeutic interventions.

Opto-vTrap, an optogenetic trap for reversible inhibition of vesicular release, synaptic transmission, and behavior

Spatiotemporal control of brain activity by optogenetics has emerged as an essential tool to study brain function. For silencing brain activity, optogenetic probes, such as halorhodopsin and archaerhodopsin, inhibit transmitter release indirectly by hyperpolarizing membrane potentials. However, these probes cause an undesirable ionic imbalance and rebound spikes. Moreover, they are not applicable to use in non-excitable glial cells. Here we engineered Opto-vTrap, a light-inducible and reversible inhibition system to temporarily trap the transmitter-containing vesicles from exocytotic release. Light activation of Opto-vTrap caused full vesicle clusterization and complete inhibition of exocytosis within 1 min, which recovered within 30 min after light off. We found a significant reduction in synaptic and gliotransmission upon activation of Opto-vTrap in acute brain slices. Opto-vTrap significantly inhibited hippocampus-dependent memory retrieval with full recovery within an hour. We propose Opto-vTrap as a next-generation optogenetic silencer to control brain activity and behavior with minimal confounding effects.

Quantitative real-time kinetics of optogenetic proteins CRY2 and CIB1/N using single-molecule tools

In this work we evaluate the interaction of two optogenetic protein variants (CIB1, CIBN) with their complementary protein CRY2 by single-molecule tools in cell-free extracts. After validating the blue light induced co-localization of CRY2 and CIB1/N by Förster resonance energy transfer (FRET) in live cells, a fluorescence correlation spectroscopy (FCS) based method was developed to quantitatively determine the in vitro association of the extracted proteins. Our experiments suggest that CIB1, in comparison with CIBN, possesses a better coupling efficiency with CRY2 due to its intact protein structure and lower diffusion rate within 300s detection window.