Imaging calcium and redox signals using genetically encoded fluorescent indicators.

Area of Science:

• Cellular biology
• Biochemistry
• Molecular signaling

Background:

• Calcium (Ca2+) and reactive oxygen/nitrogen species (ROS/RNS) are crucial cellular signals, but their localized roles remain poorly understood.
• Cellular functions are increasingly recognized to be regulated by transient micro-domains or compartmentalized signaling, rather than global ion/species concentrations.
• High spatial and temporal resolution is essential for studying these localized signals within single cells.

Purpose of the Study:

• To review and compare popular genetically encoded fluorescent indicators (GEFIs) for Ca2+ and redox signaling.
• To provide a guide for selecting appropriate GEFIs based on their properties and applications.
• To highlight the importance of GEFIs for investigating localized cellular signaling.

Main Methods:

• Description of commonly used genetically encoded fluorescent indicators for Ca2+ and redox signals.
• Discussion of the advantages and disadvantages of various GEFIs based on practical experience.
• Presentation of example applications demonstrating the utility of GEFIs.

Main Results:

• GEFIs offer superior spatial and temporal resolution for detecting intracellular Ca2+ and redox signals.
• A greater variety of GEFIs are available for Ca2+ detection compared to redox signaling.
• GEFIs can be engineered for specific cellular compartments and possess distinct spectral properties.

Conclusions:

• GEFIs are indispensable tools for dissecting localized Ca2+ and redox signaling pathways.
• Careful selection of GEFIs is critical for addressing specific research questions in cellular signaling.
• Further development of redox-sensitive GEFIs is needed to match the availability of Ca2+ sensors.