CAMKK2 and Alzheimer disease: The consistent reduction of P-TF (pH~3-4 fraction) in the serum of CaMKK2 KO mice, 3xTg-AD mice, and in the CSF and serum from EOAD and LOAD postmortem human patients indicate that P-TF (pH~3-4 fraction) profile is a promising novel biomarker for AD.