ATP6V1E1 and Alzheimer disease: V‐type proton ATPase subunit E 1 (ATP6V1E1), a subunit of the V1 complex of vacuolar (H+)‐ATPase (V‐ATPase), was involved in the maintenance of lysosomal acidic environment, which may participate in the AD development by affecting the degradation of Aβ.16