APC2 and supranuclear palsy, progressive, 1: There were only a total of five synaptic proteins upregulated in PSP SN; this includes one presynaptic protein (CHRM2) associated with trans-synaptic signaling, four postsynaptic proteins (APC2, MAP2, ALDOC and CHRM2) and ELAVL4, an RNA-binding protein involved in translation at the synapse.