Abstract 1939: Association between LRRK2 and 4E-BP1 protein levels in normal and malignant cells

Abstract

Translational control is a crucial component of cancer development and progression. Eukaryotic initiation factor 4E (eIF4E) 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. The search for new kinases that could be implicated in 4E-BP1 phosphorylation, and determination of the mechanisms that affect 4E-BP1 stability are important to understand the role of eIF4E in cell transformation. In this study, we investigate 48 kinases that may be implicated 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 (MDA-MB 231 cells). With the use of this method, several kinases that affect 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 novel findings provide evidence that 4E-BP1 can be regulated and stabilized by multiple kinases implicated in several cell signaling pathways. We also found that LRRK2 downregulation affects 4E-BP1 stability and causes degradation of this factor in various cell types. Interestingly, inhibition of proteasome activity by MG132 restored total 4E-BP1 protein levels in cells where LRRK2 was downregulated. In addition, these stabilization events appear to be functionally important for cell growth control in normal cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1939. doi:10.1158/1538-7445.AM2011-1939

Autophagy and mTOR pathways in mouse embryonic stem cell, lung cancer and somatic fibroblast cell lines

“…The eIF4E‐binding protein 4E‐BP1 regulates this translation initiation by phosphorylating several regions. PRKCA is one of the kinases that directly or indirectly phosphorylate 4E‐BP1 . 4E‐BP1 hypo‐phosphorylation downregulates translation.…”

“…PRKCA is one of the kinases that directly or indirectly phosphorylate 4E-BP1. 53 4E-BP1 hypo-phosphorylation downregulates translation. However, hyperphosphorylation of 4E-BP1 via mTOR stimulated by stimuli such as hormones, cytokines or growth factors, allows the initiation of translation by stopping the activity of this kinase.…”

Integration of proteomics into systems biology of cancer

“…An increase in the hyperphosphorylated form of the eIF4E‐BP1 protein in the metastatic cell line was found that may have contributed to increased activation of cap‐dependent translation of certain mRNAs. A multitude of kinases have been investigated specifically for their role in 4E‐BP1 phosphorylation and stability in cancer, leading to the identification of several kinases that may be involved in cancer development 18. EIF4B, another translation initiation factor, has been found to regulate translation of proliferative and prosurvival mRNAs.…”