Association between LRRK2 and 4E-BP1 protein levels in normal and malignant cells

Oncol Rep. 2012 Jan;27(1):225-31. doi: 10.3892/or.2011.1462. Epub 2011 Sep 14.

Abstract

Translational control is a crucial component of cancer development and progression. Eukaryotic initiation factor (eIF) 4E mediates eIF4F association with the mRNA 5' cap structure to stimulate cap-dependent translation initiation. The eIF4E-binding protein, 4E-BP1, regulates cap-dependent translation through its phosphorylation at multiple sites. It has been described that some human carcinomas present a high level of p-4E-BP1, not always associated with high levels of p-mTOR. These previous observations suggest that other kinases could be involved in 4E-BP1 phosporylation. Investigation in new kinases that could be implicated in 4E-BP1 phosphorylation and mechanisms that affect 4E-BP1 stability is important to understand the role of eIF4E in cell transformation. In this study, we examined 48 kinases that could be involved in 4E-BP1 phosphorylation and stability. The screening study was based on analysis of 4E-BP1 status after inhibition of these kinases in a breast carcinoma cell line. Several kinases affecting 4E-BP1 stability (LRRK2, RAF-1, p38γ, GSK3β, AMPKα, PRKACA and PRKACB) and 4E-BP1 phosphorylation (CDK1, PDK1, SRC, PRKCB1, PAK2, p38β, PRKCA and CaMKKB) were identified. These findings provide evidence that 4E-BP1 can be regulated and stabilized by multiple kinases implicated in several cell signaling pathways. We focus on the finding that LRRK2 down-regulation was associated with a clearly decreased 4E-BP1 protein (and not with mRNA down-regulation). Importantly, knockdown of LRRK2 associated with high proliferative rate in normal cells and treatment with rapamycin and/or proteosome inhibition suppressed 4E-BP1 protein degradation. These results offer new insights into the regulation of total and phosphorylated 4E-BP1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism*
  • Blotting, Western
  • Cell Cycle Proteins
  • Cell Transformation, Neoplastic / metabolism*
  • Female
  • Gene Expression Regulation, Neoplastic
  • Gene Knockdown Techniques
  • Humans
  • Leucine-Rich Repeat Serine-Threonine Protein Kinase-2
  • Neoplasms / metabolism*
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • Protein Serine-Threonine Kinases / metabolism*
  • Protein Stability
  • RNA, Small Interfering
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction

Substances

  • Adaptor Proteins, Signal Transducing
  • Cell Cycle Proteins
  • EIF4EBP1 protein, human
  • Phosphoproteins
  • RNA, Small Interfering
  • LRRK2 protein, human
  • Leucine-Rich Repeat Serine-Threonine Protein Kinase-2
  • Protein Serine-Threonine Kinases