PACAP-PAC1 Signaling Regulates Serotonin 2A Receptor Internalization

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• Mice lacking pituitary adenylate cyclase-activating polypeptide (PACAP) exhibit psychomotor abnormalities.
• These abnormalities are often improved by atypical antipsychotics targeting serotonin 5-HT_2A receptors.
• PACAP may influence 5-HT_2A signaling, but the mechanism is unknown.

Purpose of the Study:

• To investigate if PACAP modulates 5-HT_2A signaling through cellular protein localization.
• To elucidate the neurobiological mechanisms underlying the interaction between PACAP and 5-HT_2A receptors.

Main Methods:

• HEK293T cells were used to assess receptor internalization upon PACAP stimulation.
• Primary cultured cortical neurons and mouse frontal cortex membranes were analyzed for receptor levels.
• In vivo studies involved intracerebroventricular PACAP administration in mice.

Main Results:

• PACAP stimulation increased 5-HT_2A receptor internalization in HEK293T cells, an effect dependent on PAC1 receptor and protein kinase C.
• PACAP reduced cell surface 5-HT_2A levels in primary neurons and increased them in frontal cortex of PACAP-deficient mice.
• PACAP administration suppressed 5-HT_2A agonist-induced behavioral responses in mice.

Conclusions:

• PACAP-PAC1 signaling promotes 5-HT_2A receptor internalization, attenuating 5-HT_2A-mediated signaling.
• This mechanism may contribute to the behavioral phenotypes observed in PACAP-deficient mice.
• Further research is needed to fully understand the link between PACAP, 5-HT_2A internalization, and behavioral abnormalities.