Peutz-Jeghers LKB1 Mutants Fail to Activate GSK-3beta, Preventing It From Inhibiting Wnt Signaling

Mol Genet Genomics. 2005 Apr;273(2):184-96. doi: 10.1007/s00438-005-1124-y. Epub 2005 Feb 25.

Abstract

Peutz-Jeghers syndrome (PJS) is caused by germline mutations in the LKB1 gene, which encodes a serine-threonine kinase that regulates cell proliferation and polarity. This autosomal dominant disorder is characterized by mucocutaneous melanin pigmentation, multiple gastrointestinal hamartomatous polyposis and an increased risk of developing various neoplasms. To understand the molecular pathogenesis of PJS phenotypes, we used microarrays to analyze gene expression profiles in proliferating HeLa cells transduced with lentiviral vectors expressing wild type or mutant LKB1 proteins. We show that gene expression is differentially affected by mutations that impair the kinase activity (K78I) or alter the cellular localization of the LKB1 protein. However, both mutations abrogate the ability of LKB1 to up-regulate the transcription of several genes involved in Wnt signaling, including DKK3, WNT5B and FZD2. In addition-and in contrast to the wild type protein-these LKB1 mutants fail to activate the GSK-3beta kinase, which otherwise phosphorylates beta-catenin. The increase in beta-catenin phosphorylation that occurs upon expression of wild-type LKB1 results in transcriptional inhibition of a canonical Wnt reporter gene. This suggests that pathogenic LKB1 mutations that lead to activation of the Wnt/beta-catenin pathway could contribute to the cancer predisposition of PJS patients.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cytoskeletal Proteins / metabolism
  • Flow Cytometry
  • Gene Expression Regulation*
  • Genetic Vectors
  • Glycogen Synthase Kinase 3 / metabolism*
  • Glycogen Synthase Kinase 3 beta
  • HeLa Cells
  • Humans
  • Immunoblotting
  • Intercellular Signaling Peptides and Proteins / metabolism*
  • Lentivirus
  • Luciferases / metabolism
  • Mutation / genetics
  • Oligonucleotide Array Sequence Analysis
  • Peutz-Jeghers Syndrome / genetics*
  • Peutz-Jeghers Syndrome / metabolism
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / physiology*
  • Trans-Activators / metabolism
  • Transfection
  • Wnt Proteins
  • beta Catenin

Substances

  • CTNNB1 protein, human
  • Cytoskeletal Proteins
  • Intercellular Signaling Peptides and Proteins
  • Trans-Activators
  • Wnt Proteins
  • beta Catenin
  • Luciferases
  • STK11 protein, human
  • GSK3B protein, human
  • Glycogen Synthase Kinase 3 beta
  • Protein-Serine-Threonine Kinases
  • Glycogen Synthase Kinase 3