CAST and Alzheimer disease: In a mouse model of PD overexpressing CAST the observed decreased calpain activity was found to be accompanied by a concomitant reduction of the cleaved synaptic protein α‐synuclein ameliorating the observed neurodegeneration.77 In support, using calpain inhibitor A‐705053 treatment in 3xTg‐AD mice model significantly increased the levels of synapsin‐1 and PSD95 to nontransgenic animal level thereby ameliorating the synaptic loss observed in these AD mice model.78