title: Calcineurin proteolysis in astrocytes: Implications for impaired synaptic function.
abstract: Mounting evidence suggests that astrocyte activation, found in most forms of neural injury and disease, is linked to the hyperactivation of the protein phosphatase calcineurin. In many tissues and cell types, calcineurin hyperactivity is the direct result of limited proteolysis. However, little is known about the proteolytic status of calcineurin in activated astrocytes. Here, we developed a polyclonal antibody to a high activity calcineurin proteolytic fragment in the 45-48kDa range (ΔCN) for use in immunohistochemical applications. When applied to postmortem human brain sections, the ΔCN antibody intensely labeled cell clusters in close juxtaposition to amyloid deposits and microinfarcts. Many of these cells exhibited clear activated astrocyte morphology. The expression of ΔCN in astrocytes near areas of pathology was further confirmed using confocal microscopy. Multiple NeuN-positive cells, particularly those within microinfarct core regions, also labeled positively for ΔCN. This observation suggests that calcineurin proteolysis can also occur within damaged or dying neurons, as reported in other studies. When a similar ΔCN fragment was selectively expressed in hippocampal astrocytes of intact rats (using adeno-associated virus), we observed a significant reduction in the strength of CA3-CA1 excitatory synapses, indicating that the hyperactivation of astrocytic calcineurin is sufficient for disrupting synaptic function. Together, these results suggest that proteolytic activation of calcineurin in activated astrocytes may be a central mechanism for driving and/or exacerbating neural dysfunction during neurodegenerative disease and injury.
authors.affiliation: Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: melanie.pleiss@uky.edu.
authors.forename: Melanie M
authors.initials: MM
authors.lastname: Pleiss
authors.affiliation: Sanders Brown Center on Aging, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: pradoldej.sompol@uky.edu.
authors.forename: Pradoldej
authors.initials: P
authors.lastname: Sompol
authors.affiliation: Sanders Brown Center on Aging, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: susan.kraner@uky.edu.
authors.forename: Susan D
authors.initials: SD
authors.lastname: Kraner
authors.affiliation: Sanders Brown Center on Aging, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: hafiz_biochem75@yahoo.com.
authors.forename: Hafiz Mohmmad
authors.initials: HM
authors.lastname: Abdul
authors.affiliation: Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: jennifer.furman@utsouthwestern.edu.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Furman
authors.affiliation: Department of Psychology, University of West Florida, Pensacola, FL, USA. Electronic address: rguttmann@uwf.edu.
authors.forename: Rodney P
authors.initials: RP
authors.lastname: Guttmann
authors.affiliation: Sanders Brown Center on Aging, University of Kentucky College of Medicine, Lexington, KY, USA; Department of Physiology, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: donna.wilcock@uky.edu.
authors.forename: Donna M
authors.initials: DM
authors.lastname: Wilcock
authors.affiliation: Sanders Brown Center on Aging, University of Kentucky College of Medicine, Lexington, KY, USA; Department of Pathology and Laboratory Medicine, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: pnels2@uky.edu.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Nelson
authors.affiliation: Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, KY, USA; Sanders Brown Center on Aging, University of Kentucky College of Medicine, Lexington, KY, USA. Electronic address: cnorr2@uky.edu.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Norris
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism / Q000473:pathology; D000818:Animals; D000918:Antibody Specificity; D001253:Astrocytes / Q000378:metabolism* / Q000473:pathology; D001921:Brain / Q000378:metabolism / Q000473:pathology; D019703:Calcineurin / Q000276:immunology / Q000378:metabolism*; D002478:Cells, Cultured; D002544:Cerebral Infarction / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D010446:Peptide Fragments / Q000276:immunology / Q000378:metabolism; D059748:Proteolysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000378:metabolism*
chemical_list: D010446:Peptide Fragments; D019703:Calcineurin
keywords: Alzheimer's disease; Astrocytes; Calcineurin; Microinfarct; Proteolysis