Imaging the cAMP Signaling Microdomain of the Primary Cilium Using Targeted FRET-Based Biosensors

Area of Science:

• Cell Biology
• Molecular Biology
• Biophysics

Background:

• Primary cilia are small, non-dividing cellular appendages crucial for various signaling pathways.
• The primary cilium acts as an independent signaling organelle, sequestering specific cyclic adenosine monophosphate (cAMP)-linked G protein-coupled receptors (GPCRs) and signaling machinery.
• Assessing cAMP signaling within the confined volume of primary cilia presents significant experimental challenges.

Purpose of the Study:

• To provide a practical guide for assessing ciliary cAMP signals in live cells.
• To detail methods for overcoming challenges in measuring cAMP in primary cilia, such as low signal and movement artifacts.
• To enable time-resolved visualization of cAMP dynamics within the primary cilium.

Main Methods:

• Utilized targeted genetically encoded Förster Resonance Energy Transfer (FRET) biosensors for cAMP detection.
• Employed ratio imaging techniques for time-resolved visualization of ciliary cAMP.
• Developed strategies to address signal limitations and movement artifacts in small, dynamic organelles.

Main Results:

• Successfully demonstrated the feasibility of measuring ciliary cAMP signals in live cells.
• Provided a robust methodology for distinguishing ciliary cAMP signals from cell body signals.
• Established protocols adaptable to various cell types and microscopy platforms.

Conclusions:

• Genetically encoded FRET biosensors offer a powerful tool for studying primary ciliary signaling.
• The described ratio imaging methods facilitate accurate, time-resolved assessment of cAMP dynamics within primary cilia.
• This approach enhances our understanding of primary cilia's role in cellular communication and organelle-specific signaling.