Remodeling of secretory lysosomes during education tunes functional potential in NK cells

Jodie P Goodridge,Lisa L Liu,Una Kjällquist,Kjetil Taskén,Susanne Lorenz,Aline Pfefferle,Andreas Brech,Quirin Hammer,Vincent Yi Sheng Oei,William E Louch,Johannes Landskron,Trevor Clancy,Harald Stenmark,Eivind Heggernes Ask,Dennis Clement,Sten Linnarsson,Bénédikt Jacobs ,Michelle Saetersmoen ,Leonardo A Meza‐Zepeda ,Christian Grimm,Ellen Skarpen,Merete Thune Wiiger,Sandip Patel,Karl Johan Malmberg

doi:10.1038/s41467-019-08384-x

Abstract

Inhibitory signaling during natural killer (NK) cell education translates into increased responsiveness to activation; however, the intracellular mechanism for functional tuning by inhibitory receptors remains unclear. Secretory lysosomes are part of the acidic lysosomal compartment that mediates intracellular signalling in several cell types. Here we show that educated NK cells expressing self-MHC specific inhibitory killer cell immunoglobulin-like receptors (KIR) accumulate granzyme B in dense-core secretory lysosomes that converge close to the centrosome. This discrete morphological phenotype is independent of transcriptional programs that regulate effector function, metabolism and lysosomal biogenesis. Meanwhile, interference of signaling from acidic Ca2+ stores in primary NK cells reduces target-specific Ca2+-flux, degranulation and cytokine production. Furthermore, inhibition of PI(3,5)P2 synthesis, or genetic silencing of the PI(3,5)P2-regulated lysosomal Ca2+-channel TRPML1, leads to increased granzyme B and enhanced functional potential, thereby mimicking the educated state. These results indicate an intrinsic role for lysosomal remodeling in NK cell education.

Highlights

Inhibitory signaling during natural killer (NK) cell education translates into increased responsiveness to activation; the intracellular mechanism for functional tuning by inhibitory receptors remains unclear
To address the mechanisms involved in the tuning of effector potential, the expression of granzyme B, a core effector molecule, was monitored by flow cytometry in mature NK cells stratified on the expression of self- versus non-self-specific killer cell immunoglobulin-like receptors (KIR)
In order to control for the stage of differentiation, which is known to influence the expression of effector molecules[17], these analyses were performed in NK cells that were NKG2A negative and CD57 negative (Supplementary Figure 1a)

Summary

Introduction

Inhibitory signaling during natural killer (NK) cell education translates into increased responsiveness to activation; the intracellular mechanism for functional tuning by inhibitory receptors remains unclear. We show that educated NK cells expressing self-MHC specific inhibitory killer cell immunoglobulin-like receptors (KIR) accumulate granzyme B in dense-core secretory lysosomes that converge close to the centrosome. This discrete morphological phenotype is independent of transcriptional programs that regulate effector function, metabolism and lysosomal biogenesis. 11 Department of Cell and Developmental Biology, University College London, Gower Street, Natural killer (NK) cells achieve specificity through unique combinations of germ-line encoded receptors These receptors are critical for the development of cell-intrinsic functional potential, enabling spontaneous activation upon recognition of target cells displaying reduced class I MHC expression[1]. These findings connect homeostatic receptor input to lysosomal homeostasis, which tune the functional potential in self-KIR+ NK cells

Methods

Results

Conclusion