Abstract
A common mutation in the gene encoding the cytoplasmic sensor Nod2, involving a frameshift insertion at nucleotide 3020 (3020insC), is strongly associated with Crohn's disease. How 3020insC contributes to this disease is a controversial issue. Clinical studies have identified defective production of interleukin 10 (IL-10) in patients with Crohn's disease who bear the 3020insC mutation, which suggests that 3020insC may be a loss-of-function mutation. However, here we found that 3020insC Nod2 mutant protein actively inhibited IL10 transcription. The 3020insC Nod2 mutant suppressed IL10 transcription by blocking phosphorylation of the nuclear ribonucleoprotein hnRNP-A1 via the mitogen-activated protein kinase p38. We confirmed impairment in phosphorylation of hnRNP-A1 and binding of hnRNP-A1 to the IL10 locus in peripheral blood mononuclear cells from patients with Crohn's disease who bear the 3020insC mutation and have lower production of IL-10.