Expression of interleukin-6 receptor alpha 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-Ralpha) 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-Ralpha two bands of approximately 80 kDa and approximately 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-Ralpha expression are observed in non-myelinating Schwann cells. In myelinating Schwann cells IL6-Ralpha 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-Ralpha is clustered both on the axonal side of the node and within the Schwann cells. After sciatic nerve crush injury IL6-Ralpha is upregulated in denervated Schwann cells between the myelin ovoids during the period of Schwann cell proliferation. The expression of IL6-Ralpha continues during the period of remyelination, suggesting that IL6-Ralpha might be involved in both Schwann cell proliferation and remyelination of the rat sciatic nerve.