Development of an IL-6 inhibitor based on the functional analysis of murine IL-6Ralpha(1).

Dysregulated cytokine production contributes to inflammatory and proliferative diseases. Therefore, inhibition of proinflammatory mediators such as TNF, IL-1, and IL-6 is of great clinical relevance. Actual strategies are aimed at preventing receptor activation through sequestration of the ligand. Here we describe the development of an inhibitor of murine IL-6 based on fused receptor fragments. Molecular modeling-guided analysis of the murine IL-6Ralpha revealed that mutations in the Ig-like domain D1 severely affect protein function, although D1 is not directly involved in the ligand-binding interface. The resulting single chain IL-6 inhibitor (mIL-6-RFP) consisting of domains D1-D3 of mgp130, a flexible linker, and domains D1-D3 of mIL-6Ralpha is a highly potent and specific IL-6 inhibitor. mIL-6-RFP will permit further characterization of the role of IL-6 in various disease models and could ultimately lead to anti-IL-6 therapy

A Role of Myosin Vb and Rab11-FIP2 in the Aquaporin-2 Shuttle

Arginine-vasopressin (AVP) regulates water reabsorption in renal collecting duct principal cells. Its binding to Gs-coupled vasopressin V2 receptors increases cyclic AMP (cAMP) and subsequently elicits the redistribution of the water channel aquaporin-2 (AQP2) from intracellular vesicles into the plasma membrane (AQP2 shuttle), thereby facilitating water reabsorption from primary urine. The AQP2 shuttle is a paradigm for cAMP-dependent exocytic processes. Using sections of rat kidney, the AQP2-expressing cell line CD8, and primary principal cells, we studied the role of the motor protein myosin Vb, its vesicular receptor Rab11, and the myosin Vb- and Rab11-binding protein Rab11-FIP2 in the AQP2 shuttle. Myosin Vb colocalized with AQP2 intracellularly in resting and at the plasma membrane in AVP-treated cells. Rab11 was found on AQP2-bearing vesicles. A dominant-negative myosin Vb tail construct and Rab11-FIP2 lacking the C2 domain (Rab11-FIP2-DeltaC2), which disrupt recycling, caused condensation of AQP2 in a Rab11-positive compartment and abolished the AQP2 shuttle. This effect was dependent on binding of myosin Vb tail and Rab11-FIP2-DeltaC2 to Rab11. In summary, we identified myosin Vb as a motor protein involved in AQP2 recycling and show that myosin Vb- and Rab11-FIP2-dependent recycling of AQP2 is an integral part of the AQP2 shuttle