MAPT and Alzheimer disease: In the context of AD, the expression of MMP3 was also upregulated by the PI3K/Akt pathway in microglia in response to Aβ1–42 (Ito et al., 2007), while MMP3 was shown to correlate with total and phospho-Tau levels in the CSF of AD patients (Stomrud et al., 2010).