How does Tau protein causes Progressive supernuclear palsy?

I am a Masters student in Microbiology and I was given an presentation on how tau protein causes Progressive supernuclear palsy( psp). Could you guys who knows about this topic could just give me some resources/ explain so that I could read on the topic and do my presentation.I have tried numerous sites but it failed me to make me understand how does Tau protein causes this disease and for the relevant papers I have to subscribe but I am in no situation to spend money on these subscriptions.