eIF4E-Binding Proteins 1 and 2 Limit Macrophage Anti-Inflammatory Responses through Translational Repression of IL-10 and Cyclooxygenase-2

Abstract

Macrophages represent one of the first lines of defense during infections and are essential for resolution of inflammation following pathogen clearance. Rapid activation or suppression of protein synthesis via changes in translational efficiency allows cells of the immune system, including macrophages, to quickly respond to external triggers or cues without de novo mRNA synthesis. The translational repressors eIF4E-binding proteins 4E-BP1 and 4E-BP2 (4E-BP1/2) are central regulators of proinflammatory cytokine synthesis during viral and parasitic infections. However, it remains to be established whether 4E-BP1/2 play a role in translational control of anti-inflammatory responses. By comparing translational efficiencies of immune-related transcripts in macrophages from wild-type and 4E-BP1/2 double-knockout mice, we found that translation of mRNAs encoding two major regulators of inflammation, IL-10 and PG-endoperoxide synthase 2/cyclooxygenase-2, is controlled by 4E-BP1/2. Genetic deletion of 4E-BP1/2 in macrophages increased endogenous IL-10 and PGE protein synthesis in response to TLR4 stimulation and reduced their bactericidal capacity. The molecular mechanism involves enhanced anti-inflammatory gene expression (s, ,, ) owing to upregulation of IL-10-STAT3 and PGE-C/EBPβ signaling. These data provide evidence that 4E-BP1/2 limit anti-inflammatory responses in macrophages and suggest that dysregulated activity of 4E-BP1/2 might be involved in reprogramming of the translational and downstream transcriptional landscape of macrophages during pathological conditions, such as infections and cancer.

Translational repression of Ccl5 and Cxcl10 by 4E‐BP1 and 4E‐BP2 restrains the ability of mouse macrophages to induce migration of activated T cells

“…Upon first consideration, these observations would seem inconsistent with our findings and those published in IFN‐γ‐stimulated 4E‐BP1 KO MEFs . However, these discrepancies could be attributed to specific translational programs triggered by different stimuli or stressors in immune versus nonimmune cells, as described by others and by us .…”

“…Bioinformatic analysis of transcripts regulated via 4E‐BP1/2 in MΦs indicated that Ccl5 and Cxcl10 fall into the category of those that harbor relatively short 5′ UTRs (57 and 75 nt, respectively) with a minimum free energy (MFE) of –17.8 and –16.2 kcal/mol, respectively (Supporting Information ). Interestingly, Ccl5 and Cxcl10 share these features with Il1 a, Il1b , Il10 , Il12b , Ccl12 , and Cd40 . These similarities suggest a common mechanism of 4E‐BP1/2‐dependent selective translational control of immune‐related mRNAs in MΦs.…”

“…Polysome‐profiling of WT and 4E‐BP1/2 DKO BMDM quantified by nCounter® assays (mouse immunology panel) (Fig. A) allowed us to identify several immune‐related mRNAs whose translational efficiency is under the control of 4E‐BP1/2 . Of note, the top two transcripts identified in our screening were those encoding CCL5 and CXCL10.…”

“…2). Interestingly, Ccl5 and Cxcl10 share these features with Il1a, Il1b, Il10, Il12b, Ccl12, and Cd40 [25]. These similarities suggest a common mechanism of 4E-BP1/2-dependent selective translational control of immune-related mRNAs in M s.…”

“…It is well documented that selective changes in mRNA translation via mTORC1 and MNK1/2 signaling contribute to shape pro-and anti-inflammatory responses in M s [22,23]. Notably, the translational repressors 4E-BP1/2 control M type I IFN-dependent antiparasitic activity and LPS-inducible antiinflammatory mediator production [24,25]. Herein, we report that 4E-BP1/2 limit translation efficiency of mRNAs encoding the potent pro-inflammatory chemokines CCL5 and CXCL10 in M s and thereby hinder their ability to induce the migration of activated T cells.…”