Exploring cells with targeted biosensors

Abstract

Cellular signaling networks are composed of multiple pathways, often interconnected, that form complex networks with great potential for cross-talk. Signal decoding depends on the nature of the message as well as its amplitude, temporal pattern, and spatial distribution. In addition, the existence of membrane-bound organelles, which are both targets and generators of messages, add further complexity to the system. The availability of sensors that can localize to specific compartments in live cells and monitor their targets with high spatial and temporal resolution is thus crucial for a better understanding of cell pathophysiology. For this reason, over the last four decades, a variety of strategies have been developed, not only to generate novel and more sensitive probes for ions, metabolites, and enzymatic activity, but also to selectively deliver these sensors to specific intracellular compartments. In this review, we summarize the principles that have been used to target organic or protein sensors to different cellular compartments and their application to cellular signaling.

Interrogating cyclic AMP signaling using optical approaches

“…Since these early efforts, there has been a continuous evolution of genetically encoded biosensors for cyclic nucleotides (Figure 1), including new designs that have moved beyond the classical FRET paradigm for reporting cAMP levels [22–24]. In this review article we will provide a concise summary of some of the newer optical approaches for interrogating cAMP, and discuss how sensor design might be predicted to advance in the future to yield better, brighter, and more useable reporters for this ubiquitous signaling molecule.…”

“…A significant number of targeted constructs have been generated to monitor cAMP in subcellular compartments and organelles, for example in mitochondria, which are impermeant to cAMP generated in the cytosol, and host an independent cAMP signaling circuit contained within the matrix [24, 69, 70]. Another potential cAMP microdomain of interest is the primary cilium, which contains specific adenylyl cyclases and cell surface receptors coupled to cAMP production [71] [62].…”

The in vivo detection and measurement of the unfolded protein response in recombinant cellulase producing Saccharomyces cerevisiae strains

“…ER stress sensors and UPR detection methods that have been developed and applied in the past were based on the Ire1p‐mediated unconventional splicing of HAC1 mRNA introns and makes use of Northern analysis or reverse transcriptase quantitative PCR (RT‐qPCR) . These methods can prove to be cumbersome and expensive, and thus more recently fluorescence reporter constructs and enzyme‐based reporter systems have been reported . These methods are more sensitive than RT‐qPCR and allows for continuous and live detections of the UPR.…”

Wheat Germ Agglutinin Conjugated Fluorescent pH Sensors for Visualizing Proton Fluxes

“…Approaches that specifically target fluorescent biosensors to cellular domains are of great interest because they are valuable tools to investigate physiological activity in cells, tissues, and living organisms. Indeed, a review of biosensors that primarily targeted intracellular compartments was published in the JGP in 2017 (Pendin et al, 2017). In contrast, there is a paucity of approaches that target fluorescent biosensors to detect ions and metabolites on the extracellular side of the plasma membrane (Marvin et al, 2013;Patriarchi et al, 2018;Lobas et al, 2019;Sun et al, 2018).…”