The functional relevance of the GRP75–APOE interaction has not been further examined, but the interaction was observed only in APOE4 astrocytes (not in APOE3 and APOE2) and was different in the human hippocampus depending on the AD or non-AD status and APOE isoforms, with the lowest interaction observed in non-AD APOEε3 carriers, followed by APOEε3 AD, and the highest in APOEε4 AD [86]. The gene discussed is HSPA9; the disease is Alzheimer disease.