Hippocampal clock regulates memory retrieval via Dopamine and PKA-induced GluA1 phosphorylation

Area of Science:

• Neuroscience
• Chronobiology
• Molecular Biology

Background:

• Cognitive performance, particularly memory retrieval, exhibits daily fluctuations.
• The precise role of local brain circadian clocks in modulating memory performance is not fully understood.

Purpose of the Study:

• To investigate the function of the hippocampal circadian clock, controlled by BMAL1, in regulating time-of-day memory retrieval.
• To elucidate the molecular mechanisms linking the hippocampal clock to memory retrieval deficits.

Main Methods:

• Utilized inducible transgenic dominant negative BMAL1 (dnBMAL1) mice to disrupt hippocampal clock function.
• Assessed memory retrieval at specific Zeitgeber times.
• Analyzed hippocampal Dopamine-cAMP signaling, including Dopamine Receptor (D1-R and D5-R) expression and PKA-mediated GluA1 phosphorylation.
• Employed pharmacological interventions and knock-in mouse models (GluA1 S845A) for mechanistic validation.

Main Results:

• Disruption of hippocampal BMAL1 function in dnBMAL1 mice led to impaired memory retrieval during specific times of day (Zeitgeber Time 8-12).
• This impairment was linked to reduced hippocampal Dopamine-cAMP signaling, specifically decreased D1/5R expression and PKA-mediated GluA1-S845 phosphorylation.
• Pharmacological activation of cAMP signaling or D1/5Rs restored memory retrieval in dnBMAL1 mice.
• GluA1 S845A knock-in mice exhibited similar retrieval deficits, highlighting the critical role of this phosphorylation site.

Conclusions:

• The hippocampal circadian clock, orchestrated by BMAL1, is essential for regulating daily memory retrieval patterns.
• Memory retrieval is modulated by the D1/5R-cAMP-PKA signaling pathway, which is influenced by the hippocampal clock.
• This study reveals a molecular mechanism connecting circadian regulation to memory recall via specific signaling cascades.