The Tyr216 phosphorylated form of GSK3β contributes to tau phosphorylation at PHF-1 epitope in response to Aβ in the nucleus of SH-SY5Y cells

Abstract

AimsGSK3β activation in Aβ conditions leading to tau phosphorylation at pathological sites is a well-known phenomenon. However, the serine/tyrosine phosphorylation processes implied in Aβ-induced GSK3β activation and responsible for tau phosphorylation, especially at the GSK3β specific Ser396/Ser404 (PHF-1) site, are still debated. Main methodsExperiments were performed on SH-SY5Y cells exposed to 20μM Aβ1–42 in a time ranging from 5min to 8h. The phophorylated forms (Ser9 and Tyr216) of GSK3β and pTau at PHF-1 epitope were measured by immunoblotting in nuclear extracts. Key findingsWe showed a superimposable time-dependent increase of nuclear pGSK3βTyr216 and nuclear pTau at PHF-1 site, both reaching their maximal level after 8h of Aβ1–42 exposure. In addition, nuclear accumulation of pTau is accompanied by its cytoplasmic decrease suggesting that pTau is translocated in response to Aβ treatment. Besides, our experiments showed that specific pGSK3βTyr216 inhibition is required to drop nuclear pTau, ensuring the involvement of Tyr216 phosphorylation in Aβ-mediated tau phosphorylation at PHF-1 epitope. SignificanceThese data suggested that in response to Aβ exposure in SH-SY5Y cells, GSK3β activation is performed through Tyr216 phosphorylation and resulted in tau phosphorylation at PHF-1 epitope and in its translocation.