Mechanism Of Action Of ATF6 And Its Downstream Genes In Alzheimer's Disease

BackgroundAt present,the etiology and pathogenesis of Alzheimer’s disease(AD)have not been elucidated.Its pathological characteristics are extracellular senile plaques formed by β-amyloid(Aβ)deposition and neurofibrillary tangles formed by tau protein hyperphosphorylation,as well as neuron loss and glial cell proliferation.Autophagy plays an important role in the production and metabolism of Aβ and the assembly of tau protein.Its dysfunction may lead to the development of AD.Endoplasmic reticulum stress can affect amyloid cascade reaction,tau protein phosphorylation and synaptic function through different mechanisms.Endoplasmic reticulum stress triggers unfolded protein response(UPR).UPR disorder in AD may not depend on A β and tau cytotoxicity to affect neuron function.Three endoplasmic reticulum stress proteins,PERK,IRE and ATF6,all promote autophagy.The gaseous mediator H2S can play a neuroprotective role by anti-oxidation,anti-apoptosis,anti-inflammatory and promoting autophagy,and alleviate a variety of pathogenic factors of AD.Autophagy,ER stress and H2S play an important role in protecting neurons and glial cells in AD.In this study,we explore the relationship between endoplasmic reticulum stress protein ATF6,H2S and autophagy,which provides theoretical basis for exploring the pathogenesis and potential therapeutic targets of AD.MethodsWestern Blot and Real-time PCR were used to detect the expression of ATF6 and H2S producing enzyme CTH and CBS in the brain of APP/PS1 transgenic mice;after overexpression or knockdown of ATF6 in LN229 and U87MG cells,the expression of CTH and CBS was detected;the relationship between ATF6 and H2S producing enzymes,CTH and CBS,was further verified in ATF6-/-mice and ATF6-/-APP/PS1 transgenic mice;the regulation of ATF6 and other transcription factors on the promoter of CTH were explored by dual-luciferase reporter gene assay;the effect of ATF6 and CTH on H2S production was detected by methylene blue method;the effect of ATF6 on the secretion of Aβ 42 was detected by ELISA;the ratio of LC3 Ⅱ/Ⅰ and the expression of p62 protein were detected after overexpression of CTH and ATF6 in LN229 and U87MG cells;the effect of CTH on aSNAP sulfhydration was tested by biotin switch assay;the primary astrocytes of wild mice and ATF6-/-mice were isolated to verify the effect of ATF6 mediated autophagy on Aβ production.ResultsAPP/PS1 transgenic mice showed a significant decrease ATF6 and CTH expression in cortex and hippocampus,but no change in CBS expression.Cell and animal experiments showed that ATF6 regulated CTH mRNA transcription and protein expression;ATF6 mediated transcription activation through direct binding with the CTH promoter sequence.ATF6 inhibited the expression of APP and the secretion of Aβ42 by promoting the production of H2S;ATF6 promotes autophagy through the S-Sulfhydration of aSNAP by H2S.Astrocytes maight participate in the level regulation of APP protein and the clearance of Aβ through ATF6 mediated autophagy,ATF6 could be a potential therapeutic target for AD.ConclusionsThe study of ATF6-/-mouse and ATF6-/-APP/PS1 mouse model shows that ATF6 mediates autophagy by transcriptionally activating the H2S producing enzyme,CTH,to alleviate the symptoms of Alzheimer’s disease.