Research ArticleNeurodegeneration

Pin1 mediates Aβ42-induced dendritic spine loss

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Sci. Signal.  20 Mar 2018:
Vol. 11, Issue 522, eaap8734
DOI: 10.1126/scisignal.aap8734

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Pinpointing amyloid’s toxicity

An increase in the amount of amyloid-β (Aβ) in neurons alters calcium signaling and causes synaptic dysfunction and dendritic spine loss, which is believed to cause neurodegeneration and cognitive deficits in Alzheimer’s disease (AD). The decreased activity of Pin1, a protein that structurally alters the function of serine- and threonine-phosphorylated proteins (including amyloid precursor protein and tau in the postsynaptic space of neurons), is also associated with AD. Using mouse models of AD, Stallings et al. found that Pin1 was dephosphorylated and inactivated by the calcium-dependent phosphatase calcineurin, whose activity in postsynaptic neurons was induced by Aβ. Aβ-induced spine loss was prevented by treating mice with the calcineurin inhibitor FK506 (also known as tacrolimus), an immunosuppressant used to reduce the rejection of organ transplants, suggesting that this drug might be repurposed to treat patients with AD.

Abstract

Early-stage Alzheimer’s disease is characterized by the loss of dendritic spines in the neocortex of the brain. This phenomenon precedes tau pathology, plaque formation, and neurodegeneration and likely contributes to synaptic loss, memory impairment, and behavioral changes in patients. Studies suggest that dendritic spine loss is induced by soluble, multimeric amyloid-β (Aβ42), which, through postsynaptic signaling, activates the protein phosphatase calcineurin. We investigated how calcineurin caused spine pathology and found that the cis-trans prolyl isomerase Pin1 was a critical downstream target of Aβ42-calcineurin signaling. In dendritic spines, Pin1 interacted with and was dephosphorylated by calcineurin, which rapidly suppressed its isomerase activity. Knockout of Pin1 or exposure to Aβ42 induced the loss of mature dendritic spines, which was prevented by exogenous Pin1. The calcineurin inhibitor FK506 blocked dendritic spine loss in Aβ42-treated wild-type cells but had no effect on Pin1-null neurons. These data implicate Pin1 in dendritic spine maintenance and synaptic loss in early Alzheimer’s disease.

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