PSEN1 and Alzheimer disease: One of the first pieces of evidence showing that MERCS can be altered in AD was based on the fact that SH-SY5Y cells overexpressing PS2 with the FAD T122R mutation showed increased Ca2+ transfer from the ER to mitochondria and closer juxtaposition between the ER and mitochondria compared to the cells overexpressing WT PS2 [195].