GPR146 Deficiency Enhances Microglial Phagocytosis and Blood-Brain Barrier-Associated Markers in an Acute Amyloid-β Model.

Dysregulation of brain cholesterol homeostasis is increasingly recognized as a critical driver of Alzheimer's disease (AD) pathogenesis. G protein-coupled receptor 146 (GPR146) has emerged as a pivotal regulator of systemic cholesterol metabolism; however, its role in the central nervous system and AD remains elusive. Here, we report that GPR146 deficiency in mice modulates ERK/PKA signaling without affecting baseline physiology or general behavior. Following intracerebroventricular (i.c.v.) injection of amyloid-β (Aβ)42 oligomers, GPR146 was associated with altered Aβ42-evoked ERK/PKA/Akt signaling both in vivo and in vitro. Mechanistically, Gpr146 ablation potentiated microglial Aβ phagocytosis, which correlated with the transcriptional upregulation of phagocytic receptors, including TREM2, GPR34, P2Y6, and CR3, alongside increased expression of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6). Moreover, GPR146 deficiency was linked to elevated levels of blood-brain barrier (BBB)-associated markers Cldn-5 and Glut-1 protein levels, while attenuating Aβ‑induced inflammatory responses in brain endothelial cells. At the metabolic level, GPR146 knockout modulated the expression of key enzymes governing glucose (GLUT1, GLUT3, G6PD, PFK, HK) and lipid (HMGCS1, ACACA, FASN, SCD1) metabolism and markedly reduced Aβ‑elicited lipid droplet accumulation in the cortex and hippocampus. Collectively, our findings establish GPR146 as a novel neurometabolic regulator whose deficiency correlates with enhanced Aβ phagocytosis, maintenance of BBB-associated proteins, and altered cerebral metabolism, thereby presenting a potential therapeutic axis for early AD intervention.