In conclusion, the current results demonstrate higher levels of the mitochondrial serine protease OMI/HTRA2 in the AD brain and a coherent pattern of correlations between the activated form of OMI/HTRA2 and several key proteins and biomarkers involved in the AD pathology, warranting further studies to explore these observations in search for new therapeutic windows for treatment of this devastating disease. Here, HTRA2 is linked to Alzheimer disease.