MAPT and Alzheimer disease: Not only will we see in this roundup of research what the effect of laser light is on ANT activity and how it reacts following drug photosensitization of isolated mitochondria, but also how the antiviral drug 3′-Azido-3′-deoxythymidine (AZT) affects it, and even how its impairment leads to mitochondrial energy deficit in Down syndrome (DS), as well as its involvement in Alzheimer disease (AD) progression, in which its function intertwines with those of the two AD proteins, i.e., β-amyloid and TAU, and so on.