Inactivation of NSF ATPase Leads to Cathepsin B Release After Transient Cerebral Ischemia.

Abstract

Neurons have extraordinary large cell membrane surface area, thus requiring extremely high levels of intracellular membrane-trafficking activities. Consequently, defects in the membrane-trafficking activities preferentially affect neurons. A critical molecule for controlling the membrane-trafficking activities is the N-ethylmaleimide-sensitive factor (NSF) ATPase. This study is to investigate the cascade of events of NSF ATPase inactivation, resulting in a massive buildup of late endosomes (LEs) and fatal release of cathepsin B (CTSB) after transient cerebral ischemia using the 2-vessel occlusion with hypotension (2VO+Hypotension) global brain ischemia model. Rats were subjected to 20min of transient cerebral ischemia followed by 0.5, 4, 24, and 72h of reperfusion. Neuronal histopathology and ultrastructure were examined by the light and electron microscopy, respectively. Western blotting and confocal microscopy were utilized for analyzing the levels, redistribution, and co-localization of Golgi apparatus and endosome or lysosome markers. Transient cerebral ischemia leads to delayed neuronal death that occurs at 48-72h of reperfusion mainly in hippocampal CA1 and neocortical (Cx) layers 3 and 5 pyramidal neurons. During the delayed period, NSF ATPase is irreversibly trapped into inactive protein aggregates selectivelyin post-ischemic neurons destined to die. NSF inactivation leads to a massive buildup of Golgi fragments, transport vesicles (TVs) and late endosomes (LEs), and release of the 33kDa LE type of CTSB, which is followed by delayed neuronal death after transient cerebral ischemia. The results support a novel hypothesis that transient cerebral ischemia leads to NSF inactivation, resulting in acascade of events offatal release of CTSB and delayed neuronal death after transient cerebral ischemia.