Biology subjects

Tang, A.-H.

Publications and source records attributed to Tang, A.-H..

5 recordsLinked to original sources

bioRxiv2024

Highly Dynamic and Sensitive NEMOer Calcium Indicators for Imaging ER Calcium Signals in Excitable Cells

Endoplasmic/sarcoplasmic reticulum (ER/SR) sits at the heart of the calcium (Ca2+) signaling machinery, yet current genetically encoded Ca2+ indicators (GECIs) lack the ability to detect elementary Ca2+ release events from ER/SR, particularly in muscle cells. Here we report a set of organellar GECIs, termed NEMOer, to efficiently capture ER Ca2+ dynamics with increased sensitivity and responsiveness. Compared to G-CEPIA1er, NEMOer indicators exhibit dynamic ranges that are an order of magnitude larger, which enables up to 5-fold more sensitive detection of Ca2+ oscillation in both non-excitable and excitable cells. The ratiometric version further allows super-resolution monitoring of local ER Ca2+ homeostasis and dynamics. Notably, the NEMOer-f variant enabled the inaugural detection of Ca2+ blinks, elementary Ca2+ releasing signals from the SR of cardiomyocytes, as well as in vivo spontaneous SR Ca2+ releases in zebrafish. In summary, the highly dynamic NEMOer sensors expand the repertoire of organellar Ca2+ sensors that allow real-time monitoring of intricate Ca2+ dynamics and homeostasis in live cells with high spatiotemporal resolution.

synthetic biology↗

bioRxiv2022

Engineering of NEMO as calcium indicators with ultra-high dynamics and sensitivity

Genetically-encoded calcium indicators (GECI) are indispensable tools for real-time monitoring of intracellular calcium signals and cellular activities in living organisms. Current GECIs face the challenge of sub-optimal peak signal-to-baseline-ratio (SBR) with limited resolution for reporting subtle calcium transients. We report herein the development of a suite of calcium sensors, designated NEMO, with fast kinetics and wide dynamic ranges (>100-fold). NEMO indicators report Ca2+ transients with peak SBRs ~20-fold larger than the top-of-the-range GCaMP series. NEMO sensors further enable the quantification of absolution calcium concentration with ratiometric or photochromic imaging. Compared to GCaMPs, NEMOs could detect single action potentials in neurons with a peak SBR two times higher and a median peak SBR four times larger in vivo, thereby outperforming most existing state-of-the-art GECIs. Given their high sensitivity and resolution to report intracellular Ca2+ signals, NEMO sensors may find broad applications in monitoring neuronal activities and other Ca2+-modulated physiological processes in both mammals and plants.

synthetic biology↗

bioRxiv2021

Subsynaptic positioning of AMPARs by LRRTM2 controls synaptic strength

Recent evidence suggests that nanoorganization of proteins within synapses may control the strength of communication between neurons in the brain. The unique subsynaptic distribution of glutamate receptors, which cluster in nanoalignment with presynaptic sites of glutamate release, supports this idea. However, testing it has been difficult because mechanisms controlling subsynaptic organization remain unknown. Reasoning that transcellular interactions could position AMPA receptors, we targeted a key transsynaptic adhesion molecule implicated in controlling AMPAR number, LRRTM2, using engineered, rapid proteolysis. Severing the LRRTM2 extracellular domain led quickly to nanoscale de-clustering of AMPARs away from release sites, not prompting their escape from synapses until much later. This rapid remodeling of AMPAR position produced significant deficits in evoked, but not spontaneous, postsynaptic receptor activation. These results dissociate receptor numbers from their nanopositioning in determination of synaptic function, and support the novel concept that adhesion molecules acutely position AMPA receptors to dynamically control synaptic strength.

neuroscience↗

bioRxiv2020

Expansion Revealing: Decrowding Proteins to Unmask Invisible Brain Nanostructures

Cells and tissues are made out of nanoscale building blocks, such as proteins, organized in crowded nanostructures. We show that many biomolecules, and the nanostructures in which they are embedded, may be invisible to prior imaging techniques, due to the inaccessibility of labels (e.g., antibodies) to biomolecules embedded within such crowded structures. We developed a technology, expansion revealing (ExR), which isotropically decrowds proteins from each other, to enable their labeling. We use ExR to discover the alignment of presynaptic calcium channels with postsynaptic machinery in intact brain circuits, as well as the existence of periodic amyloid nanoclusters containing ion channel proteins in Alzheimers model mice. Thus, ExR reveals nanostructures within complex biological specimens that were not previously visualizable, and may find broad use in biology. One Sentence SummaryDe-crowding biomolecules with Expansion Revealing unmasks fundamentally new nanostructures in intact brain tissue, which remained invisible otherwise.

bioengineering↗

bioRxiv2019

Quantitative Analysis of Trans-synaptic Protein Alignment

Nanoscale distribution of proteins and their relative positioning within a defined subcellular region are key to their physiological functions. Thanks to the super-resolution imaging methods, especially the single-molecule localization microscopy (SMLM), mapping the three-dimensional distribution of multiple proteins has been easier and more efficient than ever. In spite of the many tools available for efficient localization detection and image rendering, it has been a challenge to quantitatively analyze the 3D distribution and relative positioning of proteins in these SMLM data. Here, using the heterogeneously distributed synaptic proteins as examples, we describe in detail a series of analytical methods including detection of nanoscale density clusters, quantification of the trans-synaptic alignment between these protein densities, and automatic enface projection and averaging. These analyses were performed within customized Matlab routines and we make the full scripts available. The concepts behind these analytical methods and the scripts can be adapted for quantitative analysis of spatial organization of other macromolecular complexes.\n\nHighlightsO_LILocalization microscopy provides sufficient data for precise quantitative analysis.\nC_LIO_LIAn algorithm to identify local density peaks within a 3D localization cluster.\nC_LIO_LINew methods for quantitative analysis of trans-synaptic proteins alignment and enrichment.\nC_LIO_LIThese algorithms can be easily adapted to analysis of other subcellular organizations.\nC_LI

neuroscience↗