PTEN-L dephosphorylates Parkin and Ub Ser65 to aggravate mitophagy dysfunction in prion disease cell models

PINK1-Parkin-dependent mitophagy dysfunction is a critical contributor to the accumulation of damaged mitochondria in prion disease, leading to impaired autophagy and neurons apoptosis. However, the specific molecular mechanisms underlying mitophagy dysfunction in prion disease remain unclear. Phosphorylation of Parkin at Ser65 (pSer65-Parkin) is a key determinant for the initiation of PINK1-Parkin-mediated mitophagy. In the prion disease cell model, we observed a significant reduction in pSer65-Parkin and pSer65-Ub expression. PTEN-L, an isoform of the PTEN family, has been implicated in the regulation of PINK1-Parkin-mediated mitophagy. Here, we demonstrate that PTEN-L acts as a phosphatase for Parkin and Ub, exerting a regulatory role in mitophagy in prion disease. We found that PTEN-L expression and mitochondrial translocation were elevated in PrP^106-126-treated SH-SY5Y cells. Increased PTEN-L dephosphorylates pSer65-Parkin pSer65-Ub, leading to reduced pSer65-Parkin and pSer65-Ub, then impaired mitophagy initiation. Overexpression of PTEN-L in SH-SY5Y cells mimicked the effects of PrP^106-126 treatment, reducing Parkin mitochondrial translocation and pSer65-Parkin levels. PTEN-L knockout alleviates these deficits, restoring Parkin and ubiquitin recruitment to mitochondria and increasing Ser65 phosphorylation in prion disease cell models. Furthermore, PTEN-L deficiency mitigated mitophagy dysfunction and apoptosis in neurons exposed by PrP^106-126. These findings suggest that PrP^106-126 upregulates PTEN-L, enhancing dephosphorylation of pSer65-Parkin and pSer65-Ub, thereby impairing mitophagy initiation. Targeting PTEN-L expression or activity may represent a novel therapeutic strategy for prion disease.