MAPT and Alzheimer disease: SUMO-1 has been found to co-localize with aggregated phosphorylated tau in the brains of AD patients and mouse models, and the level of SUMO-1 is also increased in the plasma of AD patients [385–387].In vitro studies demonstrate that tau protein at Lys340 can undergo SUMOylation, and SUMOylation of tau at Lys340 reciprocally promotes its phosphorylation at multiple AD-associated sites.