P38 MAPK-dependent AlphaB-crystallin Phosphorylation in Alzheimer's Disease-like Pathology in OXYS Rats

Alzheimer's disease (AD) is an age-related neurodegenerative disorder. Development of AD is closely related to alterations of proteostasis including the deposition of amyloid beta (Aβ) and hyperphosphorylated tau in the brain. Molecular chaperones such as αB-crystallin (CryaB) can prevent aggregation of proteins and enable their correct refolding. The p38 mitogen-activated protein kinase signaling (MAPK) pathway regulates CryaB activity through phosphorylation of CryaB. Here, we examined CryaB and phospho-(p-)Ser59-CryaB protein amounts in the prefrontal cortex of the senescence-accelerated OXYS rats at different stages of the development of AD-like pathology and in Wistar rats (control). We compared this result with the changes in the expression of genes involved in the p38 MAPK signaling pathway in the prefrontal cortex of both rat strains. Manifestation and progression of AD-like pathology in OXYS rats were accompanied by an increased level of detergent-insoluble p-Ser59-CryaB in the brain cortex, while the CryaB amount did not change. p-Ser59-CryaB was absent in the detergent-soluble protein fraction of the cortex in both rat strains. Immunostaining of brain slices revealed notable colocalization of p-Ser59-CryaB with Aβ in 18-month-old OXYS rats. According to RNA sequencing data, the development of AD-like pathology in OXYS rats is accompanied in the cortex by up- and downregulation of genes involved in p38 MAPK signaling. In general, we demonstrated that the manifestation AD-like pathology in OXYS rats occurs against the background of activation of p38 MAPK-dependent CryaB phosphorylation and alterations of the p38 MAPK signaling pathway. The increased p-Ser59-CryaB amount and its colocalization with Aβ can be considered a response to the accumulation of protein aggregates and may be an important part of an endogenous mechanism of AD development.