Dissecting The Effect Of Microtubule Acetylation On Tau Toxicity

Microtubule-associated protein tau is hyperphosphorylated in Alzheimer’s disease(AD)and other related neurodegenerative diseases.These diseases are collectively known as tauopathies.Neuronal microtubule network in AD patients brains has been destroyed in early stages of disease,considered as an important cause for neuronal dysfunctions in pathophysiology.Some research works illustrated that treatment with microtubule stabilizing drug can effectively rescue the pathological features of transport and cognitive defects in transgenic mouse models of tauopathy.Previous studies showed that histone deacetylase 6(HDAC6)mutations could increase the acetylated microtubule and rescue the abnormal developmental phenotypes of NMJ(Neuromuscular junction)and the microtubule defects in muscle cells caused by tau over-expression in Drosophila(Xiong et al.,2013).However,HDAC6 could acetylate multiple substrates and also took part in the regulation of autophagy(Iwata et al.,2005;Lee et al.,2010;Pandey et al.,2007).Therefore,the relationship between the acetylated microtubules and the causal pathogenesis of neurodegenerative diseases is still unclear.In this study,we intend to use the CRISPR/Cas9 system to simulate acetylated microtubules and non-acetylated microtubules,which may further reveal the role of acetylated microtubules in the pathogenesis of tauopathy.Using the CRISPR/Cas9 technique,we have obtained the site-directed a-tubule K40Q mutant fly.Next we will check that whether the the a-tubule K40Q mutant can rescue the destructive MT,caused by the ectopic expression of human tau in NMJ or muscle cells.In addition,we test the potential effect of two selective HDAC6 inhibitors,tubastatin A and ACY-1215,on rescuing tau-induced MT defects in muscle cells in Drosophila.Previous studies showed that tubacin,another inhibitor of the tubulin-specific deacetylase activity of HDAC6,could rescue the tau-induced MT defects(Xiong et al.,2013).However,the drug treatment were from the early embryonic stages.Now we want to know whether tubastatin A and ACY-1215 could rescue the distructive phenotype when the drug treatment is postponed until the Drosophila larvae grows to 2nd instar.Preliminary results showed that tubastatin A and ACY-1215 could significantly rescue tau-induced MT defects.This suggested that the functional inhibition of HDAC6 by ACY or Tubastatin A could recover the defected MTs by inhibiting the tau4R overexpression toxicity in neuronal system.These results may provide the mechanism of tauopathology related to destruction of microtubules.