Human genome-wide RNAi screen identifies an essential role for inositol pyrophosphates in Type-I interferon response.

Abstract

The pattern recognition receptor RIG-I is critical for Type-I interferon production. However, the global regulation of RIG-I signaling is only partially understood. Using a human genome-wide RNAi-screen, we identified 226 novel regulatory proteins of RIG-I mediated interferon-β production. Furthermore, the screen identified a metabolic pathway that synthesizes the inositol pyrophosphate 1-IP7 as a previously unrecognized positive regulator of interferon production. Detailed genetic and biochemical experiments demonstrated that the kinase activities of IPPK, PPIP5K1 and PPIP5K2 (which convert IP5 to1-IP7) were critical for both interferon induction, and the control of cellular infection by Sendai and influenza A viruses. Conversely, ectopically expressed inositol pyrophosphate-hydrolases DIPPs attenuated interferon transcription. Mechanistic experiments in intact cells revealed that the expression of IPPK, PPIP5K1 and PPIP5K2 was needed for the phosphorylation and activation of IRF3, a transcription factor for interferon. The addition of purified individual inositol pyrophosphates to a cell free reconstituted RIG-I signaling assay further identified 1-IP7 as an essential component required for IRF3 activation. The inositol pyrophosphate may act by β-phosphoryl transfer, since its action was not recapitulated by a synthetic phosphonoacetate analogue of 1-IP7. This study thus identified several novel regulators of RIG-I, and a new role for inositol pyrophosphates in augmenting innate immune responses to viral infection that may have therapeutic applications.

• Authors: Niyas Kudukkil Pulloor, Sajith Nair, Kathleen McCaffrey, Aleksandar D Kostic, Pradeep Bist, Jeremy D Weaver, Andrew M Riley, Richa Tyagi, Pradeep D Uchil, John D York, Solomon H Snyder, Adolfo García-Sastre, Barry V L Potter, Rongtuan Lin, Stephen B Shears, Ramnik J Xavier, Manoj N Krishnan
• Journal: PLoS pathogens (PLoS Pathog) Vol. 10 Issue 2 Pg. e1003981 (Feb 2014) ISSN: 1553-7374 [Electronic] United States
• PMID: 24586175 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, N.I.H., Intramural, Research Support, Non-U.S. Gov't)

Chemical References

• IRF3 protein, human
• Interferon Regulatory Factor-3
• Interferon Type I
• PLAAT4 protein, human
• RNA, Small Interfering
• Receptors, Retinoic Acid
• Phosphoric Monoester Hydrolases
• myo-inositol-1 (or 4)-monophosphatase

Topics

• Gene Expression Regulation (immunology)
• Humans
• Immunity, Innate (immunology)
• Interferon Regulatory Factor-3 (immunology)
• Interferon Type I (immunology)
• Phosphoric Monoester Hydrolases (immunology)
• RNA, Small Interfering
• Receptors, Retinoic Acid (immunology)
• Signal Transduction (immunology)