Multi-modal mechanisms of the metastasis suppressor, NDRG1: Inhibition of WNT/β-catenin signaling by stabilization of protein kinase Cα

J Biol Chem. 2024 Jul;300(7):107417. doi: 10.1016/j.jbc.2024.107417. Epub 2024 May 28.

Abstract

The metastasis suppressor, N-myc downstream regulated gene-1 (NDRG1), inhibits pro-oncogenic signaling in pancreatic cancer (PC). This investigation dissected a novel mechanism induced by NDRG1 on WNT/β-catenin signaling in multiple PC cell types. NDRG1 overexpression decreased β-catenin and downregulated glycogen synthase kinase-3β (GSK-3β) protein levels and its activation. However, β-catenin phosphorylation at Ser33, Ser37, and Thr41 are classically induced by GSK-3β was significantly increased after NDRG1 overexpression, suggesting a GSK-3β-independent mechanism. Intriguingly, NDRG1 overexpression upregulated protein kinase Cα (PKCα), with PKCα silencing preventing β-catenin phosphorylation at Ser33, Ser37, and Thr41, and decreasing β-catenin expression. Further, NDRG1 and PKCα were demonstrated to associate, with PKCα stabilization occurring after NDRG1 overexpression. PKCα half-life increased from 1.5 ± 0.8 h (3) in control cells to 11.0 ± 2.5 h (3) after NDRG1 overexpression. Thus, NDRG1 overexpression leads to the association of NDRG1 with PKCα and PKCα stabilization, resulting in β-catenin phosphorylation at Ser33, Ser37, and Thr41. The association between PKCα, NDRG1, and β-catenin was identified, with the formation of a potential metabolon that promotes the latter β-catenin phosphorylation. This anti-oncogenic activity of NDRG1 was multi-modal, with the above mechanism accompanied by the downregulation of the nucleo-cytoplasmic shuttling protein, p21-activated kinase 4 (PAK4), which is involved in β-catenin nuclear translocation, inhibition of AKT phosphorylation (Ser473), and decreased β-catenin phosphorylation at Ser552 that suppresses its transcriptional activity. These mechanisms of NDRG1 activity are important to dissect to understand the marked anti-cancer efficacy of NDRG1-inducing thiosemicarbazones that upregulate PKCα and inhibit WNT signaling.

Keywords: N-myc downstream regulated gene-1; metastasis; pancreatic cancer; protein kinase Cα; signaling; β-catenin.

MeSH terms

  • Cell Cycle Proteins* / genetics
  • Cell Cycle Proteins* / metabolism
  • Cell Line, Tumor
  • Gene Expression Regulation, Neoplastic
  • Glycogen Synthase Kinase 3 beta / genetics
  • Glycogen Synthase Kinase 3 beta / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins* / genetics
  • Intracellular Signaling Peptides and Proteins* / metabolism
  • Pancreatic Neoplasms / genetics
  • Pancreatic Neoplasms / metabolism
  • Pancreatic Neoplasms / pathology
  • Phosphorylation
  • Protein Kinase C-alpha* / genetics
  • Protein Kinase C-alpha* / metabolism
  • Protein Stability
  • Wnt Signaling Pathway*
  • beta Catenin* / genetics
  • beta Catenin* / metabolism

Substances

  • beta Catenin
  • Cell Cycle Proteins
  • Glycogen Synthase Kinase 3 beta
  • Intracellular Signaling Peptides and Proteins
  • N-myc downstream-regulated gene 1 protein
  • PRKCA protein, human
  • Protein Kinase C-alpha