TBXT and Alzheimer disease: This CK1δ isoform phosphorylates τ at Ser-202, Thr-205, Ser-396 and Ser-404 residues and a combination of CK1δ and GSK-3 activities induce more than three-quarters of the Ser/Thr phosphorylations identified in τ-PHF, indicating that both protein kinases are involved in the pathogenesis of AD [61].