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Protein synthesis in plasma cells is regulated by crosstalk between endoplasmic reticulum stress and mTOR signaling.

Authors
  • Goldfinger, Meidan1
  • Shmuel, Miri
  • Benhamron, Sandrine
  • Tirosh, Boaz
  • 1 Institute for Drug Research, The School of Pharmacy, The Hebrew University, Jerusalem, Israel. , (Israel)
Type
Published Article
Journal
European Journal of Immunology
Publisher
Wiley (John Wiley & Sons)
Publication Date
Feb 01, 2011
Volume
41
Issue
2
Pages
491–502
Identifiers
DOI: 10.1002/eji.201040677
PMID: 21268018
Source
Medline
License
Unknown

Abstract

Plasma cells (PCs) secrete copious levels of immunoglobulins. To achieve this, their endoplasmic reticulum (ER) undergoes expansion in a process that requires continuous ER stress and activation of the unfolded protein response. It is important that protein synthesis, the driver of ER stress, is regulated in a manner that does not induce apoptosis. We followed protein synthesis in murine splenic B cells activated in vitro with LPS. Total protein synthesis levels increased and then steeply decreased when the cells acquired a secretory phenotype. We explored the involvement of two mechanisms in controlling protein synthesis levels, namely ER stress-mediated phosphorylation of eukaryote initiation factor 2α (eIF2α) and the mammalian target of rapamycin (mTOR) pathway, which attenuate or activate mRNA translation, respectively. We show that induction of ER stress in activated B cells counter-intuitively led to dephosphorylation of eIF2α. Despite the reduction in phosphorylated eIF2α, expression of activating transcription factor 4, an effector of hyper eIF2α phosphorylation, was induced. In addition, ER stress attenuated the mTOR pathway, which ultimately reduced protein synthesis. Finally, B cells engineered to overactivate the mTOR pathway exhibited higher apoptosis in the course of LPS stimulation. We conclude that protein synthesis in PCs is controlled by an ER stress-mediated mTOR regulation, which is needed for optimal cell viability.

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