Dysregulation of Inositol Polyphosphate 5-Phosphatase OCRL in Alzheimer's Disease: Implications for Autophagy Dysfunction.

Autophagy is impaired in Alzheimer's disease (AD), particularly at the stage of autophagosome-lysosome fusion. Recent studies suggest that the inositol polyphosphate 5-phosphatase OCRL (Lowe oculocerebrorenal syndrome protein) is involved in this fusion process; however, its role in AD pathophysiology remains largely unclear. In this study, we investigated the localization and expression of OCRL in post-mortem AD brains and in a 5XFAD transgenic mouse model. While RNA levels were not significantly altered, OCRL protein was markedly reduced in the RIPA-soluble fraction and positively correlated with the autophagy marker Beclin1. Immunohistochemical analysis revealed OCRL immunoreactivity in neuronal cytoplasm, granulovacuolar degeneration bodies, and plaque-associated dystrophic neurites in AD brains. Furthermore, OCRL overexpression in a FRET-based tau biosensor cell model significantly reduced the tau-seeding-induced FRET signal. These findings suggest that OCRL dysregulation may contribute to autophagic deficits and the progression of tau pathology in AD.