Repression of transcription of presenilin-1 inhibits γ-secretase independent ER Ca2? leak that is impaired by FAD mutations.

摘要

Genetic deletion or mutations of presenilin genes (PS1/PS2) cause familial Alzheimer's disease and calcium (Ca2?) signaling abnormalities. PS1/PS2 act as endoplasmic reticulum (ER) Ca2? leak channels that facilitate passive Ca2? leak across ER membrane. Studies with PS1/PS2 double knockout (PS1/PS2-DKO) mouse embryonic fibroblasts showed that PS1/PS2 were responsible for 80% of passive Ca2? leak from the lumen of endoplasmic reticulum to cytosol. Transient transfection of the wild type PS1 expression construct increased cytoplasmic Ca2? as a result of Ca2? leak across ER membrane whereas the FADPS1 (PS1-M146V) mutation construct alone or in combination with the wild type PS1 expression construct abrogated Ca2? leak in SK-N-SH cells. Inhibition of basal c-jun-NH2-terminal kinase (JNK) activity by JNK inhibitor SP600125 repressed PS1 transcription and PS1 protein expression by augmenting p53 protein level in SK-N-SH cells (Lee and Das 2008). In this report we also showed that repression of PS1 transcription by JNK inhibitor SP600125 inhibited passive Ca2? leak across ER membrane which could be rescued by expressing PS1 wild type and not by expressing FADPS1 (PS1-M146V) under a SP600125 non-responsive promoter. Treatment of SK-N-SH cells with SP600125 also triggered InsP3R-mediated Ca2? release from the ER by addition of 500?nM bradykinin, an agonist of InsP3 receptor (InsP3R1) without changing the expression of InsP3R1. This data confirms that SP600125 increases the Ca2? store in the ER by inhibiting PS1-mediated Ca2? leak across ER membrane. p53, ZNF237 and Chromodomain helicase DNA-binding protein 3 which are repressors of PS1 transcription, also reduced Ca2? leak across ER membrane in SK-N-SH cells but γ-secretase inhibitor or dominant negative γ-secretase-specific PS1 mutant (PS1-D257A) had no significant effect. Therefore, p53, ZNF237, and Chromodomain helicase DNA-binding protein 3 inhibit the function ER Ca2? leak channels to regulate both ER and cytoplasmic Ca2? levels and may potentially control Ca2?-signaling function of PS1.