title: Calcineurin β 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, CNβ 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, CNβ 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 CNβ with the unfolded protein response (UPR) sensor, protein kinase RNA-like endoplasmic reticulum kinase (PERK). In accordance, induction of CNβ resulted in oligomerization and activation of PERK. Strikingly, the presence of a phosphatase inhibitor did not interfere with CNβ-mediated activation of PERK, suggesting a hitherto undiscovered non-enzymatic role for CNβ. Importantly, the cytoprotective function of CNβ was PERK-dependent both in vitro and in vivo. Loss of CNβ 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 CNβ-PERK axis in not only prolonging astrocyte cell survival but also in modulating astrogliosis after brain injury.
authors.affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, TX, USA.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, TX, USA.
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Holstein
authors.affiliation: Instituto de Investigación Médica M y M Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina.
authors.forename: Sofia
authors.initials: S
authors.lastname: Aime
authors.affiliation: Instituto de Investigación Médica M y M Ferreyra, INIMEC-CONICET, Universidad Nacional de Córdoba, Córdoba, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Bollo
authors.affiliation: Department of Cellular and Structural Biology, University of Texas Health Science Center at San Antonio, TX, USA; Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, TX, USA. Electronic address: lechleiter@uthscsa.edu.
authors.forename: James D
authors.initials: JD
authors.lastname: Lechleiter
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D001930:Brain Injuries / Q000378:metabolism*; D019703:Calcineurin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009474:Neurons / Q000378:metabolism; D056811:Unfolded Protein Response / Q000502:physiology; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D019892:eIF-2 Kinase; D019703:Calcineurin; D002118:Calcium
keywords: Calcium; Endoplasmic reticulum; Ischemia; Stress; Traumatic brain injury