Shotgun Brain Proteomics Reveals Early Molecular Signature in Presymptomatic Mouse Model of Alzheimer's Disease

Abstract

AβpE3-42 (N-terminal truncated amyloid-β peptide starting with pyroglutamate at the third position) is abundant in Alzheimer's disease (AD) brain and has high aggregation propensity and cellular toxicity. Transgenic TBA42 mice expressing AβpE3-42 exhibit a neurological phenotype evident at the age of 12 months. As AD has a long presymptomatic period, early detection of imminent neurodegeneration is highly desirable. In the present work we used four-month-old presymptomatic TBA42 mice and performed a whole-brain proteome analysis in order to elucidate early AD-related pathological changes and the molecular networks involved. At least three proteins were found to be moderately (by 17% to 28%) but statistically significantly upregulated, including: nectin-like molecule 1 involved in cell-cell adhesion; Homer proteins involved in scaffolding, organizing proteins at synapse and regulating intracellular calcium within neurons; and inositol-trisphosphate 3-kinase A, which is important for InsP3 induced calcium signaling in the brain. Analysis of key nodes (regulatory molecules found on pathway intersections) identified Rho-kinase (ROCK), a serine/threonine kinase and one of the major downstream effectors of the small GTPase Rho, as well as three key nodes of the mTOR/p70S6K signaling pathway previously implicated in multiple fundamental biological processes including synaptic plasticity, and upregulated in AD. These data confirm that AD-typical molecular pathways can be detected by whole-brain shotgun proteomics in young presymptomatic mice long before the onset of behavioral changes.

Pyk2 Signaling through Graf1 and RhoA GTPase Is Required for Amyloid-β Oligomer-Triggered Synapse Loss

“…Neuronal stimulation has been shown to increase active RhoA association with class I mGluRs (Schubert et al, 2006), which are upstream of Fyn/Pyk2 in the A␤o/PrP C signaling cascade (Um et al, 2013;. Others have observed RhoA activation in AD or AD model systems (Petratos et al, 2008;Huesa et al, 2010;Chacon et al, 2011;Herskowitz et al, 2013;Pozueta et al, 2013;Yang et al, 2013;Bolognin et al, 2014;Chang et al, 2015;Henderson et al, 2016), consistent with this mechanism.…”

“…richment, we hypothesized that Pyk2 in turn regulates the RhoGAP activity of Graf1c to alter spine morphology. RhoA signaling is a well known modulator of F-actin and dendritic spine dynamics (Tashiro et al, 2000;Petratos et al, 2008;Huesa et al, 2010;Bolognin et al, 2014;Newell-Litwa et al, 2015) and has been implicated in AD (Petratos et al, 2008;Herskowitz et al, 2013;Yang et al, 2013;Chang et al, 2015;Henderson et al, 2016). Thus, A␤o signaling might enhance Pyk2-Graf1c interaction at the synapse, and this interaction might then impair the physiological Graf1c-RhoA regulation leading to a net local decrease in Graf1c-mediated inhibition of RhoA in the spine head, and driving net dendritic spine retraction.…”

Structure of the heterophilic interaction between the nectin-like 4 and nectin-like 1 molecules

“…Heterophilic interactions among Necl proteins contribute to multiple developmental processes, including synapse formation (30,31), axon guidance (13), myelination (14,32), and pathological diseases, such as Alzheimer's disease (33), autism spectrum disorder (ASD) (34)(35)(36), attention-deficit hyperactivity disorder (ADHD) (37,38), and cancer (39)(40)(41). Among the heterophilic interactions among Necl family members, the trans interaction between Necl-4 and Necl-1 is critical for their functions (14,15).…”

ROCK1 Is Associated with Alzheimer’s Disease-Specific Plaques, as well as Enhances Autophagosome Formation But not Autophagic Aβ Clearance

“…They are involved in several aspects of cell behavior, such as cell motility, cell proliferation and apoptosis (Chang et al, 2006; Yang et al, 2013; Loirand, 2015; Swanger et al, 2015). Research indicates that ROCKs are potential therapeutic targets for Aβ metabolism modulation (Weggen et al, 2001; Jacobs et al, 2006; Salminen et al, 2008).…”