Transcriptional expression and enzymatic activity of Insulin-degrading enzyme is modulated by genetic and environmental factors.

SURACE EI; GHIGULLY M; LEAL MC; BULLOJ A; CASTAÑO EM; MORELLI L

Cancún, Mexico

Congreso; International Society for Neurochemistry; 2007

Insulin-degrading enzyme (IDE) is a ubiquitously expressed protease that is involved in the clearance of amyloid beta (Aâ). Accumulation of Aâ is invariably observed in the brains of Alzheimer’s disease (AD) patients. Decrease in the level or enzymatic activity of IDE may be a possible cause for the ineffective catabolism of Aâ in AD. In the present work, we sought to determine whether presenilin-1 (PS1) and hypoxia modulate expression and subsequent activity of IDE. First, rat primary astrocytic cultures were placed in hypoxia and IDE mRNA levels measured by reverse transcription-polymerase chain reaction. We observed a significant increase in IDE mRNA levels in astrocytes in hypoxia compared to normoxia. Next, we evaluated IDE mRNA levels on CHO cells stably expressing wild-type PS1 versus mock-transfected cells. A significant 23% increase in IDE expression was observed in cells overexpressing wild-type PS1 in normoxic conditions suggesting a direct involvement of PS1 in the modulation of IDE expression. When subjected to hypoxia, mock-transfected cells exhibited a 20% increase in IDE expression, in agreement with the observed effect in astrocytic cultures. Interestingly, cells overexpressing PS1 showed a 2-fold decrease in IDE expression suggesting the existence of a PS1-dependent IDE transcriptional inhibitor. Lastly, enzymatic activity was assessed in cytosol and membrane fractions from these cells. Only IDE activity from membrane fractions showed a significant increase in normoxia and decrease in hypoxia in PS1 compared to mock-transfected cells, in agreement with the results from the mRNA expression experiments. Overall, we show that PS1 is capable of modulating IDE expression and subsequent activity under normoxia and hypoxia, which may be relevant to AD pathogenesis.