Interleukin-6 receptor subunit alpha (sIL-6R) (sIL-6R)

The soluble Interleukin-6 receptor (sIL-6R) is a circulating form of the IL-6 receptor alpha subunit, generated through the proteolytic shedding of the membrane-bound receptor by ADAM17 or via alternative mRNA splicing [1, 2]. Unlike most soluble receptors that function as antagonists, sIL-6R acts as an agonist by forming a complex with IL-6 that can activate gp130-expressing cells that do not naturally express the IL-6 receptor, a process known as trans-signaling [2, 3]. This mechanism is a major driver of systemic inflammation and is implicated in the pathogenesis of autoimmune diseases such as rheumatoid arthritis, as well as cytokine release syndrome and certain malignancies [3, 4]. Therapeutic monoclonal antibodies like tocilizumab and sarilumab bind to both soluble and membrane-bound forms of the receptor to inhibit IL-6 signaling [5, 6]. Newer therapeutic approaches, such as the fusion protein olamkicept, specifically target the sIL-6R/IL-6 complex to selectively block pro-inflammatory trans-signaling while sparing the regenerative classic signaling pathway [7]. Monitoring biomarkers like C-reactive protein is standard practice to evaluate the clinical efficacy of drugs targeting this receptor [5, 8]. Safety concerns associated with inhibiting this pathway include an increased risk of serious infections and potential gastrointestinal perforations [5, 6]. Overall, sIL-6R represents a critical node in the IL-6 signaling network, distinguishing between homeostatic and pathological immune responses [3, 8].

Other names

CD126IL-6R-alphagp80Soluble IL-6 receptor alphaSoluble CD126

Competitive inhibition of IL-6 binding to the alpha subunit of the receptor, thereby preventing the formation of the signaling complex with gp130; selective neutralization of the IL-6/sIL-6R complex to inhibit trans-signaling [5, 7].