We identify IRAK1, a serine/threonine kinase, to be hyperactivated in PBMCs from treatment naïve Multiple Sclerosis patients compared to control PBMCs. This could be explained by our finding that SHP1, a protein tyrosine phosphatase which binds to the ITIM motif in IRAK1 blocking its kinase activity, is low in cells from MS patients. In MS interferonb has been used as a first line treatment regimen for the past 15 years, reducing relapse rates and disability in patients. However ~30% of MS patients show no therapeutic benefit to interferonb. Previous work has shown that interferonb treatment of PBMCS from MS patients show increased IL-27 cytokine production in the clinically defined responding group, no such increase is seen in the non-responding group. We have found a novel role for IRAK1 as a regulator of the IFNAR pathway, and using an IRAK1/4 inhibitor show increased IL-27 production with inteferonb treatment. We found no increase in IL-27 cytokine production following interferonb treatment of PBMCs in 25% (4 of 16) of MS patients compared to 9% (1 of 11) control subjects. Pre-treating PBMCs with IRAK1/4 inhibitor in the MS ‘non-responder’ group reversed this interferonb nonresponsiveness in 100% of cases. We have identified SHP2 as a novel substrate of TBK1 through in vitro kinase assays and we will be determining if SHP2 is also a substrate of IKKe. SHP2 is an SH2 domain containing protein tyrosine phosphatase, which is involved in the negative regulation of the TLR3, 4 and -9-NFkB pathway and TRIF-interferon response. In this proposal we aim to determine the significance of this finding to the TLR-and IFNAR-signalling pathways in immune cells. We will also examine pIKKe/pTBK1 by Western blot analysis following TLR3 stimulation to determine if their activity is deregulated in immune cells from MS patients.
