Calpain-mediated Cleavage of Atg5 Determine Autophagy or Apoptosis of PMN, and C5a's Role / 生物化学与生物物理进展

ABSTRACT

Apoptosis of neutrophils controls the duration and the intensity of an inflammatory response and therefore the extent of neutrophil- mediated tissue damage, disturbance of neutrophil apoptosis has been associated with many diseases, underlying mechanism is not elucidated. C5a is a complement fragment that has multifunctional properties, which induces neutrophil chemoattraction, an oxidative burst, enhancement of phagocytosis, release of granule enzymes, and suppress neutrophil apoptosis. Several studies have reported calpain is involved in both neutrophil functions and apoptosis and it might play a more specific role in the regulation of neutrophil apoptosis. Diffenrent isoform of calpains is activted by diffenrent stimuli through different transduction pathway. It was reported previously that calpain is required for neutrophil migration and chemotaxis induced by C5a. In addition, autophagy is a ubiquitous physiological process that occurs in all eukaryotic cells and is considered to be a survival mechanism. Atg5 promotes autophagy and is indispensable to autophagosome formation. Upon calpain activation, Atg5 is cleaved and the resulting 24 ku Atg5 mediates apoptosis while losting the property of autophagy. Therefore, Atg5 represents a molecular switch between autophagy and apoptosis. The interaction among the C5a, calpain and Atg5 was introduced and new direction for further research was provided.