PKA restricts ERK signaling in learning and memory Kenyon cell neurons

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Signaling

Background:

• Protein Kinase A (PKA) and Extracellular Signal-Regulated Kinase (ERK) are crucial for learning and memory.
• Understanding kinase interactions in neural circuits is key to deciphering memory formation.

Purpose of the Study:

• To investigate the signaling interactions between PKA and ERK in Drosophila Kenyon cells.
• To elucidate the role of PKA in regulating ERK activity within the learning and memory circuit.

Main Methods:

• Utilized separation of phases-based activity reporter of kinase (SPARK) biosensors for in vivo imaging.
• Employed genetic manipulations to activate or inhibit PKA and ERK signaling pathways.
• Stimulated circuit activity using NaChBac ion channels, TRPA1 channels, and a seizure model.

Main Results:

• Constitutively active RAF (RAF^gof) enhanced ERK signaling in low PKA domains; PKA inhibition elevated ERK signaling.
• ERK loss did not affect PKA, but RAF^gof expanded PKA signaling, indicating a unidirectional interaction.
• Potentiating circuit activity increased PKA and ERK signaling, with PKA inhibition synergistically boosting ERK.
• PKA was found to limit both baseline and activity-dependent ERK signaling.

Conclusions:

• PKA negatively regulates ERK signaling within Drosophila Kenyon cells.
• PKA acts as a brake on activity-dependent ERK signaling, influencing learning and memory processes.
• This study reveals a critical inhibitory crosstalk between PKA and ERK in a key neural circuit.