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

• Main Authors: Huey-Jiun Ko, Shean-Jaw Chiou, Yu-Hui Wong, Yin-Hsuan Wang, Yun-Ling Lai, Chia-Hua Chou, Chihuei Wang, Joon-Khim Loh, Ann-Shung Lieu, Jiin-Tsuey Cheng, Yu-Te Lin, Pei-Jung Lu, Ming-Ji Fann, Chi-Ying Huang, Yi-Ren Hong
• Format: Article
• Language: English
• Published: MDPI AG 2019-10-01
• Series: Journal of Clinical Medicine
• Subjects: pka/gskip/gsk3β/tau axis; sh-sy5y; ips cells; cerebrospinal fluid; alzheimer’s disease
• Online Access: https://www.mdpi.com/2077-0383/8/10/1751

Based on the protein kinase A (PKA)/GSK3&#946; interaction protein (GSKIP)/glycogen synthase kinase 3&#946; (GSK3&#946;) 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 GSK3&#946;-binding defective mutants (V41/L45 and L130, respectively). We conducted in vitro assays of various kinase combinations to show that a combination of GSK3&#946; 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&#8217;s disease (AD), neurological disorders (NAD), and mild cognitive impairment (MCI). We found higher levels of different PKA&#8722;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 (<i>APP</i>^WT/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 GSK3&#946;, in the CSF and induced pluripotent stem cells (iPSCs) of AD, implying that both GSKIP and GSK3&#946; function as anchoring proteins to strengthen the cAMP/PKA/Tau axis signaling during AD pathogenesis.