Glycogen Synthase Kinase 3β Is Positively Regulated by Protein Kinase Cζ-Mediated Phosphorylation Induced by Wnt Agonists

Abstract

The molecular events that drive Wnt-induced regulation of glycogen synthase kinase 3␤ (GSK-3␤) activity are poorly defined. In this study, we found that protein kinase C (PKC) and GSK-3␤ interact mainly in colon cancer cells. Wnt stimulation induced a rapid GSK-3␤ redistribution from the cytoplasm to the nuclei in malignant cells and a transient PKC-mediated phosphorylation of GSK-3␤ at a different site from serine 9. In addition, while Wnt treatment induced a decrease in PKC-mediated phosphorylation of GSK-3␤ in nonmalignant cells, in malignant cells, this phosphorylation was increased. Pharmacological inhibition and small interfering RNA (siRNA)-mediated silencing of PKC abolished all of these effects, but unexpectedly, it also abolished the constitutive basal activity of GSK-3␤. In vitro activity assays demonstrated that GSK-3␤ phosphorylation mediated by PKC enhanced GSK-3␤ activity. We mapped Ser147 of GSK-3␤ as the site phosphorylated by PKC, i.e., its mutation into alanine abolished GSK-3␤ activity, resulting in ␤-catenin stabilization and increased transcriptional activity, whereas phosphomimetic replacement of Ser147 by glutamic acid maintained GSK-3␤ basal activity. Thus, we found that PKC phosphorylates GSK-3␤ at Ser147 to maintain its constitutive activity in resting cells and that Wnt stimulation modifies the phosphorylation of Ser147 to regulate GSK-3␤ activity in opposite manners in normal and malignant colon cells.

GSK3: A Kinase Balancing Promotion and Resolution of Inflammation

“…In GSK3β, activating effects of Ser147 phosphorylation [83] and inhibitory effects of phosphorylated Thr43 (acting as a priming phosphorylation for Ser9-dependent inactivation [84]) as well as Ser389 and Thr390 have also been observed [39,79]. In mice, an additional dual-specificity tyrosine phosphorylation-regulated kinase 1A-mediated inhibitory phosphorylation at Thr356 has been described [85], which still has to be established in humans.…”

“…Interestingly, a Ser21/9 phosphorylation-independent mechanism of GSK3 inactivation in response to Wnt signaling has also been described [96], presumably involving GSK3 localization and restriction of substrate accessibility [7,97]. GSK3β-Ser147 phosphorylation is induced by Wnt signaling via PKCζ [83], Thr43 phosphorylation by growth factors via ERK [84], and Thr390 in response to cellular stress or Wnt proteins via p38 [98].…”

The role of lipid metabolism disorders, atypical isoforms of protein kinase C, and mutational status of cytosolic and mitochondrial forms of isocitrate dehydrogenase in carcinogenesis of glial tumors

“…В ряде исследований была показана роль ПКСζ в регуляции роста клеток первичной опухоли и реализации механизмов метастазирования при раке молочной железы, толстой кишки, гепатоцеллюлярной карциномы [67][68][69].…”

Concise Review: Lessons from Naïve Human Pluripotent Cells

“…PKCζ appears to be the primary isoform responsible for maintaining mESC pluripotency . Curiously, PKCζ inhibition can antagonize GSK3 activity in nonpluripotent cells , although the PKC inhibitor, Gö6983, used most often in conjunction with naïve hESC is not as potent against this isoform as against other PKC isoforms. PKC is effective in insulin stimulated glucose transport and many isoforms serve as MAPK agonists .…”