Expression of interleukin-6 receptor α in normal and injured rat sciatic nerve

Interleukin-6 (IL-6) is a pleiotropic cytokine synthesized by many different cells after appropriate stimulation. IL-6 binds first to the interleukin-6 receptor alpha (IL6-Rα) and then this complex binds to the signal-transducing gp130 receptor, forming a functional hexameric receptor complex. We observed by Western blot analysis with anti-IL6-Rα two bands of ∼80 kDa and ∼110 kDa in the rat sciatic nerve, cerebral cortex, spleen, pancreas and liver, corresponding to the mature glycosylated form and possibly to the dimer of the non-glycosylated precursor protein. By immunohistochemistry, high levels of IL6-Rα expression are observed in non-myelinating Schwann cells. In myelinating Schwann cells IL6-Rα is present as discrete dots in the perinuclear region, in distinct membrane domains of the Schwann cell sheath and at the nodes of Ranvier, suggesting that IL6-Rα is clustered both on the axonal side of the node and within the Schwann cells. After sciatic nerve crush injury IL6-Rα is upregulated in denervated Schwann cells between the myelin ovoids during the period of Schwann cell proliferation. The expression of IL6-Rα continues during the period of remyelination, suggesting that IL6-Rα might be involved in both Schwann cell proliferation and remyelination of the rat sciatic nerve.