<scp>PBX1</scp> Improves Cognition and Reduces Amyloid‐β Pathology in <scp>APP</scp> / <scp>PS1</scp> Mice by Transcriptionally Activating the <scp>CRTC2</scp> – <scp>CREB</scp> Pathway

Alzheimer's disease (AD) is characterized by progressive cognitive decline, amyloid β (Aβ) deposition, and synaptic dysfunction. However, the mechanisms underlying neurodegeneration remain poorly understood. In this study, we investigated the therapeutic potential of PBX1, a transcriptional regulator implicated in neurodevelopment and neuroprotection, against AD. PBX1 expression was significantly downregulated in postmortem hippocampal tissues from patients with AD and in the APP/PS1 mouse model. In vitro, PBX1a knockdown reduced neurite complexity and increased apoptosis. PBX1a overexpression reversed these effects and reduced soluble Aβ_1-40 and Aβ_1-42 levels. In vivo, hippocampal overexpression of PBX1a restored spatial learning and memory, reduced Aβ burden by 41%, and increased neurite length by 1.5-fold. These behavioral and structural improvements were accompanied by reduced levels of hyperphosphorylated Tau and toxic Aβ oligomers. Mechanistically, PBX1 directly activated the transcription of CRTC2-a coactivator of CREB, thereby increasing CRTC2 expression and its nuclear colocalization with phosphorylated CREB. Restoration of the PBX1-CRTC2-CREB axis enhanced neuronal survival and synaptic integrity. Notably, CRTC2 knockdown blocked PBX1-mediated reductions in Aβ deposition, apoptosis, and hyperphosphorylated Tau expression, confirming the role of the PBX1-CRTC2-CREB axis in conferring neuroprotection. Together, our findings indicate that PBX1 is a key modulator of neuronal resilience in AD and that it functions through transcriptional activation of the CRTC2/CREB pathway. By unraveling a mechanism that links transcriptional regulation to amyloid clearance and cognitive function, this study highlights PBX1 as a promising therapeutic target for AD.