Screening tyrosine kinases for their involvement in synaptotoxicity induced by tau microtubule‐binding region fibrils

Abstract

AbstractBackgroundSynapse loss is an early event in Alzheimer’s disease (AD); yet, mechanisms of synaptotoxicity induced by amyloid‐β and tau –hallmarks of AD pathology– remain unclear. We have recently developed a lab‐on‐a‐chip device that fluidically isolates synapses of primary neurons from their cell bodies, thereby enabling us to exclusively access synaptic, as well as pre‐ and postsynaptic compartments. Our aim is to identify molecular mechanisms of synaptotoxicity related to AD.MethodUsing the said in vitro model, we assessed the impact of exogenously applied monomeric and fibrillar forms of tau microtubule‐binding region (tau‐MTBR), as well as of full‐length tau isoforms, on synaptic connectivity, quantified through distance‐based assignment of postsynaptic puncta to presynaptic puncta. After confirming that the fibrillar form of tau‐MTBR induces a detrimental effect on mature synapses, we conducted a medium‐throughput compound screening, in which we tested small molecule inhibitors of 25 tyrosine kinases for their capacity to block tau‐MTBR‐induced synaptotoxicity.ResultFive compounds that protected synapses from the detrimental effect of tau‐MTBR were considered potentially protective. Dose‐response analysis conducted on these five compounds highlighted FIIN‐2, a highly specific inhibitor of FGF receptor (FGFR) family. We are currently validating this finding with an alternative compound against FGFR and assessing whether tau interacts with cell surface FGFR. In parallel, we are functionally validating the observed toxic and protective effects using electrophysiological recordings in microfluidic devices integrated with microelectrode arrays.ConclusionDeciphering downstream signaling mechanisms in tau‐induced synaptotoxicity will improve our understanding of AD pathophysiology and allow us to identify potential therapeutic targets.