Proteolysis of calcineurin is increased in human hippocampus during mild cognitive impairment and is stimulated by oligomeric Abeta in primary cell culture.
Recent reports demonstrate that the activation and interaction of the protease calpain (CP) and the protein phosphatase calcineurin (CN) are elevated in the late stages of Alzheimer's disease (AD). However, the extent to which CPs and CN interact during earlier stages of disease progression remains unknown. Here, we investigated CP and CN protein levels in cytosolic, nuclear, and membrane fractions prepared from human postmortem hippocampal tissue from aged non-demented subjects, and subjects diagnosed with mild cognitive impairment (MCI). The results revealed a parallel increase in CP I and the 48 kDa CN-Aα (ΔCN-Aα48) proteolytic fragment in cytosolic fractions during MCI. In primary rat hippocampal cultures, CP-dependent proteolysis and activation of CN was stimulated by application of oligomeric Aβ((1-42)) peptides. Deleterious effects of Aβ on neuronal morphology were reduced by blockade of either CP or CN. NMDA-type glutamate receptors, which help regulate cognition and neuronal viability, and are modulated by CPs and CN, were also investigated in human hippocampus. Relative to controls, MCI subjects showed significantly greater proteolytic levels of the NR2B subunit. Within subjects, the extent of NR2B proteolysis was strongly correlated with the generation of ΔCN-Aα48 in the cytosol. A similar proteolytic pattern for NR2B was also observed in primary rat hippocampal cultures treated with oligomeric Aβ and prevented by inhibition of CP or CN. Together, the results demonstrate that the activation and interaction of CPs and CN are increased early in cognitive decline associated with AD and may help drive other pathologic processes during disease progression.
Mohmmad Abdul
Hafiz
H
The Sanders-Brown Center on Aging , University of Kentucky, Lexington, KY 40536, USA.
Baig
Irfan
I
Levine
Harry
H
Guttmann
Rodney P
RP
Norris
Christopher M
CM
D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics / Q000378:metabolism; D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D019703:Calcineurin / Q000378:metabolism; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism; D016022:Case-Control Studies; D018929:Cell Culture Techniques; D002458:Cell Fractionation; D003072:Cognition Disorders / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology*; D018450:Disease Progression; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism / Q000503:physiopathology*; D006801:Humans; D008297:Male; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology*; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D012189:Retrospective Studies; D015398:Signal Transduction
D016229:Amyloid beta-Peptides; D065095:Calcineurin Inhibitors; D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D016194:Receptors, N-Methyl-D-Aspartate; C075222:amyloid beta-protein (1-42); D018698:Glutamic Acid; D019703:Calcineurin; D002154:Calpain; D002118:Calcium