Calcineurin ? protects brain after injury by activating the unfolded protein response.

ABSTRACT: The Ca(2+)-dependent phosphatase, calcineurin (CN) is thought to play a detrimental role in damaged neurons; however, its role in astrocytes is unclear. In cultured astrocytes, CN? expression increased after treatment with a sarco/endoplasmic reticulum Ca(2+)-ATPase inhibitor, thapsigargin, and with oxygen and glucose deprivation, an in vitro model of ischemia. Similarly, CN? was induced in astrocytes in vivo in two different mouse models of brain injury - photothrombotic stroke and traumatic brain injury (TBI). Immunoprecipitation and chemical activation dimerization methods pointed to physical interaction of CN? with the unfolded protein response (UPR) sensor, protein kinase RNA-like endoplasmic reticulum kinase (PERK). In accordance, induction of CN? resulted in oligomerization and activation of PERK. Strikingly, the presence of a phosphatase inhibitor did not interfere with CN?-mediated activation of PERK, suggesting a hitherto undiscovered non-enzymatic role for CN?. Importantly, the cytoprotective function of CN? was PERK-dependent both in vitro and in vivo. Loss of CN? in vivo resulted in a significant increase in cerebral damage, and correlated with a decrease in astrocyte size, PERK activity and glial fibrillary acidic protein (GFAP) expression. Taken together, these data reveal a critical role for the CN?-PERK axis in not only prolonging astrocyte cell survival but also in modulating astrogliosis after brain injury.

SUBMITTER: Chen Y 

PROVIDER: S-EPMC4983525 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature