Detection of Acute Hypoxia in Cardiac Myocytes using Calcium Channel Activity and O2-Sensitive Coverslips

Abstract

Familial Alzheimer's disease (FAD) is caused by mutations in presenilin-1 (PS1) gene in approximately 50% of cases. It was found that FAD PS1 mutants disrupt calcium homeostasis in hippocampal neurons disrupting Ca 2þ storage in the lumen of endoplasmic reticulum (ER). Recently calcium sensors of ER STIM1 were found to negatively regulate the activity of L-type voltagegated calcium channels. Therefore it was suggested that FAD PS1 mutants could affect the activity of L-type channels in neurons. To study the activity of voltage-gated calcium channels experiments with a patch-clamp technique in whole-cell mode were performed with human neuroblastoma SK-N-SH cell line transfected with PS1 M146V mutant or PS1 WT. Currents were induced by 10 mV voltage steps per 200 ms from À80 to þ40 mV. PS1 M146V mutant expression enchased the amplitude of integral current at positive potentials comparing to cells with expression of PS1 WT and untransfected control cells. Currents were found to be blocked by application 10 uM of nifedipine. Knock-down of STIM1 with shRNA abolished the difference between cells with mutant and PS1 WT expressions but in the same time mock shRNA left the difference unchanged. Knock-down of STIM1 was controlled by western-blot of cell lysates. Expression PS1 M146V enhanced the amplitude of calcium entry in mouse hippocampal neurons induced by depolarization with 140 KCl in calcium imaging experiments with Fura2-AM comparing to PS1 WT expressing cells. It was concluded that PS1 M146V mutant connected with FAD affect activity of L-type calcium channels through the STIM1 calcium sensors.