GSKIP-Mediated Anchoring Increases Phosphorylation of Tau by PKA but Not by GSK3beta via cAMP/PKA/GSKIP/GSK3/Tau Axis Signaling in Cerebrospinal Fluid and iPS Cells in Alzheimer Disease

Abstract

Based on the protein kinase A (PKA)/GSK3β interaction protein (GSKIP)/glycogen synthase kinase 3β (GSK3β) axis, we hypothesized that these might play a role in Tau phosphorylation. Here, we report that the phosphorylation of Tau Ser409 in SHSY5Y cells was increased by overexpression of GSKIP WT more than by PKA- and GSK3β-binding defective mutants (V41/L45 and L130, respectively). We conducted in vitro assays of various kinase combinations to show that a combination of GSK3β with PKA but not Ca2+/calmodulin-dependent protein kinase II (CaMK II) might provide a conformational shelter to harbor Tau Ser409. Cerebrospinal fluid (CSF) was evaluated to extend the clinical significance of Tau phosphorylation status in Alzheimer’s disease (AD), neurological disorders (NAD), and mild cognitive impairment (MCI). We found higher levels of different PKA–Tau phosphorylation sites (Ser214, Ser262, and Ser409) in AD than in NAD, MCI, and normal groups. Moreover, we used the CRISPR/Cas9 system to produce amyloid precursor protein (APPWT/D678H) isogenic mutants. These results demonstrated an enhanced level of phosphorylation by PKA but not by the control. This study is the first to demonstrate a transient increase in phosphor-Tau caused by PKA, but not GSK3β, in the CSF and induced pluripotent stem cells (iPSCs) of AD, implying that both GSKIP and GSK3β function as anchoring proteins to strengthen the cAMP/PKA/Tau axis signaling during AD pathogenesis.

Compartmentalized Signaling in Aging and Neurodegeneration

“…This process appears connected to GSKIP (GSK3β-Interacting Protein), a small cytosolic AKAP [ 275 ] that directly interacts with both GSK3β and PKA, coordinating their actions. The involvement of a cAMP/GSKIP/GSK3β/PKA/Tau axis in Tau phosphorylation was recently studied in SHSY5Y cells and confirmed in cerebrospinal fluid and pluripotent stem cells of AD patients [ 276 ]. The authors demonstrated the existence of a molecular complex consisting of GSKIP, RII-based PKA, GSK3β and Tau (tethered to GSK3β) that enhances the cAMP/PKA signalling, resulting in increased Tau phosphorylation at distinct PKA-dependent phosphorylation sites (Ser214, Ser262, and Ser409) during AD pathogenesis [ 276 ].…”

“…The involvement of a cAMP/GSKIP/GSK3β/PKA/Tau axis in Tau phosphorylation was recently studied in SHSY5Y cells and confirmed in cerebrospinal fluid and pluripotent stem cells of AD patients [ 276 ]. The authors demonstrated the existence of a molecular complex consisting of GSKIP, RII-based PKA, GSK3β and Tau (tethered to GSK3β) that enhances the cAMP/PKA signalling, resulting in increased Tau phosphorylation at distinct PKA-dependent phosphorylation sites (Ser214, Ser262, and Ser409) during AD pathogenesis [ 276 ]. Among several Tau phosphorylation sites associated with neurodegeneration [ 277 , 278 ], Ser262 hyperphosphorylation significantly reduces the affinity of Tau for microtubules [ 279 ] and is associated with the initial steps of AD [ 280 ].…”

Deciphering the evolution of composite-type GSKIP in mitochondria and Wnt signaling pathways

“…CLU1 and ARMC4 contain DUF727; however, CLU1 contains other parts of CLU-N, CLU, CLU central, winged helix-like DNA-binding domains, and tetratricopeptide-like helical domains, but ARMC4 only contains 13X Armadillo repeats [43,44]. DUF refers to a "domain of unknown function" [19][20][21][22][23]45]. A short domain in the clustered mitochondria protein is involved in its mitochondrial cytoplasmic distribution [46,47].…”

“…ARMC4 may function as a competitor to APC and β-catenin. In addition, the pangolin protein (TCF/LEF) is involved in the Wnt signaling pathway in pangolins, an intermediate host species for SARS (modified from [19,51]). https://doi.org/10.1371/journal.pone.0262138.g006…”

Induced Pluripotent Stem Cell (iPSC)-Based Neurodegenerative Disease Models for Phenotype Recapitulation and Drug Screening

“…Furthermore, iPSC-derived forebrain neurons from APP and PSEN1 mutated AD patients were evaluated in phenotype studies and revealed a higher Aβ42/40 ratio and Aβ oligomer accumulations [62][63][64][65][66][67][68][69]. Increased Tau and hyper-phosphorylated Tau protein levels, early endosome accumulation, GSK3β overactivation, and increased reactive oxygen species (ROS) production were also observed in amyloid precursor protein (APP)-mutated forebrain neurons [62,63,65,66,70]. AD-associated astrocytes were themselves neurotoxic and capable of damaging healthy neurons by reducing lactate secretion, increasing Aβ release and cytokine production, and inducing abnormal calcium flux [63,71,72].…”