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Publication Abstract from PubMed

Macrophage inflammatory protein-1 (MIP-1), MIP-1alpha (CCL3) and MIP-1beta (CCL4) are chemokines crucial for immune responses towards infection and inflammation. Both MIP-1alpha and MIP-1beta form high-molecular-weight aggregates. Our crystal structures reveal that MIP-1 aggregation is a polymerization process and human MIP-1alpha and MIP-1beta form rod-shaped, double-helical polymers. Biophysical analyses and mathematical modelling show that MIP-1 reversibly forms a polydisperse distribution of rod-shaped polymers in solution. Polymerization buries receptor-binding sites of MIP-1alpha, thus depolymerization mutations enhance MIP-1alpha to arrest monocytes onto activated human endothelium. However, same depolymerization mutations render MIP-1alpha ineffective in mouse peritoneal cell recruitment. Mathematical modelling reveals that, for a long-range chemotaxis of MIP-1, polymerization could protect MIP-1 from proteases that selectively degrade monomeric MIP-1. Insulin-degrading enzyme (IDE) is identified as such a protease and decreased expression of IDE leads to elevated MIP-1 levels in microglial cells. Our structural and proteomic studies offer a molecular basis for selective degradation of MIP-1. The regulated MIP-1 polymerization and selective inactivation of MIP-1 monomers by IDE could aid in controlling the MIP-1 chemotactic gradient for immune surveillance.

Polymerization of MIP-1 chemokine (CCL3 and CCL4) and clearance of MIP-1 by insulin-degrading enzyme.,Ren M, Guo Q, Guo L, Lenz M, Qian F, Koenen RR, Xu H, Schilling AB, Weber C, Ye RD, Dinner AR, Tang WJ EMBO J. 2010 Oct 19. PMID:20959807^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.