PPIA and Alzheimer disease: Just over half of the proteins showing increased secretion in response to media containing Aβ oligomers (APOE, COL1A1, COL1A2, PCOLCE, PDIA3, PEBP1, PPIA, PPIB, PREP, PREDX1, PTGDS, and SOD3) were identified as altered in AD CSF.