Polymerization of MIP-1 chemokine (CCL3 and CCL4) and clearance of MIP-1 by insulin-degrading enzyme

Abstract

Macrophage inflammatory protein-1 (MIP-1), MIP-1α (CCL3) and MIP-1β (CCL4) are chemokines crucial for immune responses towards infection and inflammation. Both MIP-1α and MIP-1β form high-molecular-weight aggregates. Our crystal structures reveal that MIP-1 aggregation is a polymerization process and human MIP-1α and MIP-1β 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-1α, thus depolymerization mutations enhance MIP-1α to arrest monocytes onto activated human endothelium. However, same depolymerization mutations render MIP-1α 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.

Macrophage Inflammatory Protein Derivative ECI301 Enhances the Alarmin-Associated Abscopal Benefits of Tumor Radiotherapy

“…In fact, we found that MIP-1a could not reproduce the effect of ECI301 in the combination treatment with radiation (unpublished observation). It has been reported that the basic unit of one MIP-1a molecule is a dimer, whose primary contact is constituted by two antiparallel b strands formed by an N-terminal loop (38,39). In MIP-1a molecules, the hydrogen bonds between Asp27 and Arg46/ Arg48 residues, and between Asp6 and Ser33, and the hydrophobic interaction between Tyr28 and Phe24 residues are proposed to contribute to the interaction between the two dimers, and subsequent polymer formation.…”

“…In MIP-1a molecules, the hydrogen bonds between Asp27 and Arg46/ Arg48 residues, and between Asp6 and Ser33, and the hydrophobic interaction between Tyr28 and Phe24 residues are proposed to contribute to the interaction between the two dimers, and subsequent polymer formation. In ECI301, whose basic unit is also a dimer, Asp27 of MIP-1a is substituted with Ala. MIP-1a forms a double-helical polymer burring its receptor-binding sites, whereas substitution of Asp27 with Ala results in irregular polymers with possible dissociation (39). The ECI301 molecule used in the present investigation was found to be a mixture of tetramer (76%), dimer (20%), and polymers larger than tetramer (the remainder) at mg/mL concentration and no significant difference of this ratio was found at 10 mg/mL (unpublished results).…”

Arthrogenic Alphaviruses and Inflammatory Myopathies

“…In the macaque model of CHIKV infection, an up-regulation of IFN-/, IFN-, MCPs, IL-6 and TNF- was detected, all synonymous with a strong, macrophage-induced inflammatory response (Labadie et al, 2010). IL-1, RNI and TNF- are factors known to trigger apoptosis (Bhaumik & Khar, 1998;Griffin & Hardwick, 1997;Roulston et al, 1999) while MCP-1 and MIP-1 are involved in amplifying the inflammatory response (Carr et al, 1994;Lidbury et al, 2008;Ren et al, 2010;Wolpe et al, 1988). Macrophages have also been implicated as a cellular reservoir for alphavirus persistence and therefore a contributing factor in the development of chronic disease symptoms.…”

Conformational states and recognition of amyloidogenic peptides of human insulin-degrading enzyme

“…Our finding of the hyperactive mutation at the hinge loop also suggests a new way to boost IDE catalysis. Because IDE is a key protease in the destruction of amyloidogenic peptides (12) and novel biologically relevant substrates of IDE, such as MIP-1α and calcitonin generelated peptide, continue to be discovered (11,32), future studies will address how conformational dynamics are linked to the catalytic cycle of IDE and how to control such processes. Such information can also provide avenues to design IDE-based therapies for modulating proteostasis in humans.…”

“…S1) (3, 7). IDE uses the size, shape, and charge distribution of its chamber (∼13,000 Å 3 ) to selectively engulf structurally diverse peptides, such as insulin, Aβ, tumor growth factor-α, macrophage inflammatory protein-1α (MIP-1α), natriuretic peptides, and amylin (7)(8)(9)(10)(11). IDE substrates are presumably unraveled inside the catalytic chamber and then stochastically cleaved in regions that have a high propensity to convert into a β-strand for the formation of intermolecular cross-β sheets, the fundamental structural element of amyloid fibrils (7)(8)(9).…”