CHOLESTEROL REMODELING IMPAIRS NEURONAL MECHANOTRANSDUCTION AND SYNAPTIC INTEGRITY IN AGING BRAIN

Aging is accompanied by dysregulation of sterol metabolism in the brain. Cholesterol, together with sphingolipids, maintains membrane integrity and regulates the function of ion channels, cytoskeletal and adhesion complexes, synaptic integrity, and multiple signaling pathways essential for neuronal activity. We hypothesized that age related cholesterol remodeling disrupts membrane–cytoskeleton coupling, lowering the activation threshold of mechanosensitive ion channels such as Piezo1, while simultaneously impairing the biophysical conditions required for presynaptic vesicle docking and fusion, thereby weakening synaptic function. Studies show that cholesterol synthesis and catabolism are altered in the aging brain. To experimentally model cholesterol remodeling, neuronal membrane cholesterol was acutely depleted using MβCD or chronically reduced through overexpression of the cholesterol catabolizing enzyme CYP46A1. Conversely, cholesterol accumulation was induced by shRNA-mediated knockdown of CYP46A1, providing a complementary approach. Cholesterol depletion significantly disturbed synapse integrity, as indicated by altered expression of the pre and postsynaptic markers synaptophysin and Shank2. Moreover, cholesterol integrity was required for effective Piezo1 mediated signaling to CREB transcription regulation. Both cholesterol depletion and pharmacological inhibition of Piezo1 with GsMTx-4 significantly reduced CREB phosphorylation, indicative of impaired mechanosensitive Ca²⁺ influx and activity dependent transcription. Activation of Piezo1 with Yoda1 enhanced pCREB transcription in neurons, but in MβCD treated cells this effect was abolished, demonstrating that cholesterol loss overrides channel activation. Together, these findings indicate that neuronal cholesterol remodeling compromises synaptic structure, disrupts mechanosensitive Ca²⁺ signaling, and attenuates CREB-mediated transcription, providing a mechanistic link between altered lipid homeostasis, impaired mechanosignaling, and synaptic dysfunction during brain aging.