Background/Purpose: Background/Purpose:Anti-TNF agents have revolutionized the clinical outcomes of patients with  rheumatoid and psoriatic diseases. However, up to 40% of patients do not respond or partially respond, or lose efficacy of therapeutic response over time. There are no clinical tests available to predict responsiveness to anti-TNF therapy ahead of time. Small studies have supported that patients carrying TNFR2-M196R, (approx. 20% prevalence in general population) demonstrate a higher risk of being an inadequate responders to anti-TNF drugs, however, the underlying mechanisms are unclear. We have shown previously that non-muscle myosin (myosin) functions as a negative regulator of TNFR2 activation. Here, we test the hypothesis that a defect in myosin binding to TNFR2-M196R causes a TNF-independent proinflammatory activity and that  leads to reduced responsiveness to anti-TNF agents.

Methods: Methods:We expressed equal levels of recombinant TNFR2-M196R or TNFR2 in primary endothelial cells and Jurkat T cells using lentiviral approach. To test whether myosin binds with TNFR2-M196R, we immunoprecipitated the recombinant TNFR2-M196R from the cells and probed for myosin by immunoblot. Proinflammatory gene induction in response to TNF in cells expressing TNFR2-M196R was measured at mRNA and Protein level by Q-PCR and ELISA, respectively. ROCK1 activity, which cause the release of  myosin from TNFR2 were measured using  Immunoprecipitated ROCK1 followed by MYPT1 phosphorylation.

Results: Results:Our co-immunoprecipitation studies demonstrate that TNFR2-M196R variant does not  bind to myosin as opposed to TNFR2.  We also found TNFR2-M196R expressing cells show TNF-independent, ROCK1 activity and proinflammatory gene induction (e.g. ICAM1, CXCL10) in endothelial cells and Jurkat T- cells. Importantly, a TNF-neutralizing antibody failed to inhibit this constitutive gene induction in TNFR2-M196R expressing cells. ROCK1 inhibition blocks this TNF-independent activity.  Furthermore, elevated proinflammatory gene induction upon TNF is sustained for longer time period in TNFR2-M196R expressing cells is (8 -10 hour) compared to TNFR2 expressing cells (4-6 hour). Mechanistically, TNFR2-M196R drives cells to a constitutive proinflammatory statepotentially due to a defect in myosin binding. Since this constitutive activity is TNF-independent, and given that ~20% of the general population carry TNFR2-M196R polymorphic variant, our findings may potentially explain in part, why a significant percentage of patients do not adequately respond to anti-TNF therapy.

Conclusion: Conclusions: Our mechanism-based approach implicating TNFR2-M196R could be tested in patients that are candidates for anti TNF therapy. Our approach not only may help to predict anti-TNF responsiveness but may also reveal novel pathways that can be targeted to treat inadequate responders of anti-TNF therapy in a subset of patients with rheumatoid and psoriatic diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/myosin-regulation-of-tnf-receptor-2-signaling-may-contribute-to-anti-tnf-therapy-response/