Adenosine A1 receptor antagonist rolofylline reverses synaptopathy in a mouse model of Tau pathology
1 DZNE, Bonn
Aggregation of the neuronal protein Tau has been established as a hallmark of several neurodegenerative diseases; however, the precise mode of action of toxic Tau is poorly understood. Previous work in our lab, using a mouse model expressing a proaggregant mutant form of full-length human Tau (TauΔK280), had shown that the animals have reduced neuronal activity (paired-pulse ratio, basal synaptic transmission) and spatial memory deficits. However, treatment with the adenosine A1 receptor antagonist rolofylline (KW-3902) was able to reverse the synaptic deficits in the hippocampus and to restore spatial memory in these mice [Dennissen et al., PNAS 2016]. Here, we investigate the molecular mechanism by which rolofylline improves the neuronal functions in the TauΔK280 mice. Biochemical characterization of the presynaptic terminals in the hippocampal neurons revealed a reduction of the total pool of synaptic vesicles in TauΔK280 mice compared to its littermate controls. The cAMP-dependent activation of protein kinase A (PKA), a signaling pathway known to influence presynaptic vesicle release, was also reduced in TauΔK280 mice (reduced phosphorylated substrates of PKA and reduced CREB phosphorylation). Postsynaptic biochemical fractions from TauΔK280 mice showed a reduction of mature dendritic spine markers (PSD-95 and phospho-GluA1). Treatment with Rolofylline rescued the levels of the total pool of synaptic vesicles and PKA activity in the presynaptic compartment. In the postsynaptic biochemical fraction, rolofylline treatment also restored the levels of mature dendritic spine markers (PSD-95 and phospho-GLuA1) in TauΔK280 mice to littermate control levels. Thus, Rolofylline was able to reverse the suppression of neuronal activity inflicted by proaggregant Tau, by boosting the presynaptic vesicle release machinery, as well as increasing the components of postsynaptic glutamatergic synapses in the hippocampal neurons in this mouse model of neurodegeneration. The data are consistent with a scheme whereby proaggregant Tau causes an increase in extracellular adenosine, hence activation of adenosine A1 receptors and decrease of cellular metabolism via G-protein dependent signaling. Blocking A1 receptors liberates the brake and thus reverses the Tau-induced effects.