Optogenetic toolkit for precise control of calcium signaling

Abstract

Calcium acts as a second messenger to regulate a myriad of cell functions, ranging from short-term muscle contraction and cell motility to long-term changes in gene expression and metabolism. To study the impact of Ca2+-modulated ‘ON’ and ‘OFF’ reactions in mammalian cells, pharmacological tools and ‘caged’ compounds are commonly used under various experimental conditions. The use of these reagents for precise control of Ca2+ signals, nonetheless, is impeded by lack of reversibility and specificity. The recently developed optogenetic tools, particularly those built upon engineered Ca2+ release-activated Ca2+ (CRAC) channels, provide exciting opportunities to remotely and non-invasively modulate Ca2+ signaling due to their superior spatiotemporal resolution and rapid reversibility. In this review, we briefly summarize the latest advances in the development of optogenetic tools (collectively termed as ‘genetically encoded Ca2+ actuators’, or GECAs) that are tailored for the interrogation of Ca2+ signaling, as well as their applications in remote neuromodulation and optogenetic immunomodulation. Our goal is to provide a general guide to choosing appropriate GECAs for optical control of Ca2+ signaling in cellulo, and in parallel, to stimulate further thoughts on evolving non-opsin-based optogenetics into a fully fledged technology for the study of Ca2+-dependent activities in vivo.

Molecular Determinants for STIM1 Activation During Store- Operated Ca2+ Entry

“…Furthermore, SOAR/CAD domain, once exposed following the store depletion, can mediate further oligomerization of STIM1 to drive the full activation of STIM1. These findings not only afford novel insights into the SOCE activation mechanism, but also provide guidance for future optimization of STIM1-based optogenetic tools to control Ca 2+ signaling [51-54]. Two outstanding questions remain to be addressed in the future: what is the exact STIM1:ORAI1 stoichiometry at ER-PM junctional sites?…”

Optogenetic engineering to probe the molecular choreography of STIM1-mediated cell signaling

“…The prototypical CRAC channel made of ORAI1 and STIM1 serves as a major route for Ca 2+ entry in many cell types. Various optogenetic modules have been engineered into STIM1 to confer light-sensitivity to CRAC channel over the past five years 5,6,[41][42][43][44][45][46][47] . We call these tools as genetically encoded Ca 2+ actuators (GECAs) 6 , as opposed to genetically encoded Ca 2+ indicators (GECIs) that are widely used for monitoring Ca 2+ signals 48 .…”

“…Compared with conventional biophysical and biochemical methods, the optogenetic approach rivals by non-invasiveness, reversibility, and high spatiotemporal precision 4 . Over the past decade, we have witnessed an explosion of optogenetic applications in multiple fields, including neuroscience, immunology, cell biology, and developmental biology [3][4][5][6] . While most studies are centered on applying optogenetics to control biological systems at the cellular and system levels, the potential of optogenetics to aid the mechanistic dissection of protein behaviors per se remains disproportionately underexplored.…”

Light‐Controlled Mammalian Cells and Their Therapeutic Applications in Synthetic Biology

“…[104,105] PACR was developed by Fukuda et al by inserting a LOV2 domain into the calmodulin-M13 fusion protein. [106] This complex is destroyed upon illumination, which induces conformational changes in the LOV2 domain, resulting in Ca 2+ release from the calmodulin moiety and causing a transient increase of Ca 2+ concentration.…”