O-GlcNAc on PKCζ Inhibits the FGF4-PKCζ-MEK-ERK1/2 Pathway via Inhibition of PKCζ Phosphorylation in Mouse Embryonic Stem Cells

Summary Mouse embryonic stem cells (ESCs) differentiate into multiple cell types during organismal development. Fibroblast growth factor 4 (FGF4) signaling induces differentiation from ESCs via the phosphorylation of downstream molecules such as mitogen-activated protein kinase/extracellular signal-related kinase (MEK) and extracellular signal-related kinase 1/2 (ERK1/2). The FGF4-MEK-ERK1/2 pathway is inhibited to maintain ESCs in the undifferentiated state. However, the inhibitory mechanism of the FGF4-MEK-ERK1/2 pathway in ESCs is uncharacterized. O-linked β-N-acetylglucosaminylation (O-GlcNAcylation) is a post-translational modification characterized by the attachment of a single N-acetylglucosamine (GlcNAc) to the serine and threonine residues of nuclear or cytoplasmic proteins. Here, we showed that the O-GlcNAc on the phosphorylation site of PKCζ inhibits PKCζ phosphorylation (activation) and, consequently, the FGF4-PKCζ-MEK-ERK1/2 pathway in ESCs. Our results demonstrate the mechanism for the maintenance of the undifferentiated state of ESCs via the inhibition of the FGF4-PKCζ-MEK-ERK1/2 pathway by O-GlcNAcylation on PKCζ.
Graphical Abstract
Highlights • PKCζ activates the MEK-ERK1/2 pathway by FGF4 stimulation • O-GlcNAc on the phosphorylation site of PKCζ inhibits PKCζ activation in ESCs • FGF4-PKCζ-MEK-ERK1/2 pathway is inhibited by O-GlcNAc on PKCζ in ESCs
In this article, Nishihara and colleagues show that PKCζ is modified by O-GlcNAc and that O-GlcNAc on PKCζ inhibits PKCζ phosphorylation (activation) in mouse embryonic stem cells (ESCs). Phosphorylated PKCζ phosphorylates MEK-ERK1/2 via FGF4 stimulation, and phosphorylated ERK1/2 induces ESC differentiation. Inhibition of PKCζ phosphorylation by O-GlcNAc resulted in the inhibition of the FGF4 signal in ESCs.