Selective agonist of TRPML2 reveals direct role in chemokine release from innate immune cells.

Eva Plesch,Hua Yinan,Franz Bracher,Anna Scotto Rosato,Dina Robaa,Angelika M Vollmar,Rosa Puertollano,Lesca M Holdt,Christian Grimm,Einar K Krogsaeter,Wolfgang Sippl,Cheng-Chang Chen,Martin Biel,Marco Keller,Daniel Teupser,Diego Medina,Christian Wahl-Schott,Karin Bartel,Elisabeth Butz

doi:10.7554/elife.39720

Abstract

Cytokines and chemokines are produced and secreted by a broad range of immune cells including macrophages. Remarkably, little is known about how these inflammatory mediators are released from the various immune cells. Here, the endolysosomal cation channel TRPML2 is shown to play a direct role in chemokine trafficking and secretion from murine macrophages. To demonstrate acute and direct involvement of TRPML2 in these processes, the first isoform-selective TRPML2 channel agonist was generated, ML2-SA1. ML2-SA1 was not only found to directly stimulate release of the chemokine CCL2 from macrophages but also to stimulate macrophage migration, thus mimicking CCL2 function. Endogenous TRPML2 is expressed in early/recycling endosomes as demonstrated by endolysosomal patch-clamp experimentation and ML2-SA1 promotes trafficking through early/recycling endosomes, suggesting CCL2 being transported and secreted via this pathway. These data provide a direct link between TRPML2 activation, CCL2 release and stimulation of macrophage migration in the innate immune response.

Highlights

Cytokines/chemokines are released from a wide range of immune cells such as macrophages, B- and T-lymphocytes, neutrophils, mast cells and dendritic cells
With the aim to further improve the characteristics of existing TRPML channel agonists, we generated more than 80 novel derivatives of recently reported lead activators of TRPML channels which had been originally identified by random screening of the MLSMR small molecule library (Scripps Research Institute Molecular Screening Center) (Grimm et al, 2010)
We describe here a novel, isoform-selective activator of the TRPML2 channel and describe how TRPML2 activation enhances endosomal trafficking to induce inflammatory mediator release in LPSstimulated macrophages

Summary

Introduction

Cytokines/chemokines are released from a wide range of immune cells such as macrophages, B- and T-lymphocytes, neutrophils, mast cells and dendritic cells. They are essential for intercellular communication in both innate and adaptive immunity. Our knowledge of the function of cytokines/chemokines in immunity is much more advanced than our knowledge about how they are packaged and secreted from immune cells. Understanding how innate immune cells release cytokines/chemokines is important, as these factors are indispensable for communication between immune and with non-immune cells to coordinate inflammatory responses (Lacy and Stow, 2011). Secretion pathways vary between different cell types.

Methods

Results

Conclusion