IRAK2 directs stimulus-dependent nuclear export of inflammatory mRNAs

Area of Science:

• Immunology
• Molecular Biology
• Post-transcriptional Regulation

Background:

• Post-transcriptional regulation, including mRNA metabolism, controls inflammatory gene expression.
• The precise mechanisms of stimulus- and transcript-dependent nuclear export in inflammation are not fully understood.

Purpose of the Study:

• To elucidate a novel pathway involving IRAK2 in the nuclear export of inflammatory mRNAs.
• To investigate the role of IRAK2 kinase activity and its interaction with other proteins in regulating mRNA export.

Main Methods:

• Murine macrophages were treated with LPS to activate the TLR4 pathway.
• Nuclear localization and translocation of IRAK2 were assessed.
• IRAK2 sumoylation and its dependence on kinase activity were analyzed.
• RNA immunoprecipitation (RIP) and array analysis were used to identify IRAK2-dependent mRNAs and binding motifs.
• Phosphorylation of SRSF1 by nuclear IRAK2 and its effect on RNA binding adaptors were investigated.

Main Results:

• LPS/TLR4 engagement induces nuclear localization of IRAK2 in macrophages.
• IRAK2 kinase activity is essential for its sumoylation by RanBP2 and subsequent nuclear translocation.
• mRNAs containing SRSF1-binding motifs are preferentially exported via an IRAK2-dependent pathway.
• Nuclear IRAK2 phosphorylates SRSF1, reducing its mRNA binding and facilitating ALYREF and Nxf1 loading for export.
• This pathway selectively exports specific inflammation-related mRNAs for cytoplasmic translation.

Conclusions:

• LPS activates a nuclear function of IRAK2 that is critical for inflammatory gene expression.
• IRAK2 acts as a key regulator of mRNA nuclear export by modulating the RNA-binding protein complex.
• This pathway provides new insights into the post-transcriptional control of inflammation.