CLU alleviates Alzheimer's disease-relevant processes by modulating astrocyte reactivity and microglia-dependent synaptic density [RNA-Seq]

Genetic studies implicate Clusterin (CLU) in the pathogenesis of Alzheimer's disease (AD), yet its precise molecular impact remains unclear. Through unbiased proteomic profiling and functional validation in CLU-deficient astrocytes, we identify increased NfkB-dependent signaling and complement C3 secretion. Reduction of astrocyte CLU induced microglia dependent modulation of extracellular APOE and phosphorylated tau, as well as increased microglial phagocytosis and reduced synapse numbers. By integrating mouse and human cellular models with comprehensive analyses of human plasma and brain tissue, we demonstrate that CLU AD risk alleles are associated with reduced CLU protein and heightened inflammatory profiles. These findings establish a mechanistic link between AD genetic risk factors, astrocyte reactivity, and microglia-mediated effects on synaptic integrity. Collectively, these results support a model in which CLU upregulation in response to neuropathology is associated with maintenance of cognitive function, while diminished astrocyte CLU levels heighten disease susceptibility. Overall design: Mice of all control and experimental genotypes (5xFAD and 5xFAD/CLU-2kb-KI) and both sexes (n=4-5 per sex) were used for bulk RNA sequencing. Mice were anesthetized at 4 months of age using CO2 inhalation. Following transcardial perfusion with 1X phosphate-buffered saline (PBS), brains were extracted, and hemispheres were separated along the midline. The left hippocampus was dissected and flash-frozen on dry ice. Samples were pulverized using a Bessman Tissue Pulverizer. Half of pulverized hippocampus was used for bulk RNA sequencing.