β1-Integrin– and KV1.3 channel–dependent signaling stimulates glutamate release from Th17 cells
Katharina Birkner, … , Frauke Zipp, Stefan Bittner
Katharina Birkner, … , Frauke Zipp, Stefan Bittner
Published February 3, 2020; First published October 29, 2019
Citation Information: J Clin Invest. 2020;130(2):715-732. https://doi.org/10.1172/JCI126381.
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Research Article Autoimmunity Neuroscience

β1-Integrin– and KV1.3 channel–dependent signaling stimulates glutamate release from Th17 cells

Abstract

Although the impact of Th17 cells on autoimmunity is undisputable, their pathogenic effector mechanism is still enigmatic. We discovered soluble N-ethylmaleimide–sensitive factor attachment receptor (SNARE) complex proteins in Th17 cells that enable a vesicular glutamate release pathway that induces local intracytoplasmic calcium release and subsequent damage in neurons. This pathway is glutamine dependent and triggered by binding of β1-integrin to vascular cell adhesion molecule 1 (VCAM-1) on neurons in the inflammatory context. Glutamate secretion could be blocked by inhibiting either glutaminase or KV1.3 channels, which are known to be linked to integrin expression and highly expressed on stimulated T cells. Although KV1.3 is not expressed in CNS tissue, intrathecal administration of a KV1.3 channel blocker or a glutaminase inhibitor ameliorated disability in experimental neuroinflammation. In humans, T cells from patients with multiple sclerosis secreted higher levels of glutamate, and cerebrospinal fluid glutamine levels were increased. Altogether, our findings demonstrate that β1-integrin– and KV1.3 channel–dependent signaling stimulates glutamate release from Th17 cells upon direct cell-cell contact between Th17 cells and neurons.

Authors

Katharina Birkner, Beatrice Wasser, Tobias Ruck, Carine Thalman, Dirk Luchtman, Katrin Pape, Samantha Schmaul, Lynn Bitar, Eva-Maria Krämer-Albers, Albrecht Stroh, Sven G. Meuth, Frauke Zipp, Stefan Bittner

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Figure 1

Patients with MS have higher glutamine levels in the CSF and elevated glutamate secretion by T cells.

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Patients with MS have higher glutamine levels in the CSF and elevated gl...
(A) Glutamine levels were assessed in the CSF of patients with RRMS (n = 16) or noninflammatory neurological disease (NIND) (n = 14). (B) mRNA analysis of the enzyme glutaminase was performed in unstimulated and stimulated human Th1 and Th17 cells from 8 healthy donors (HDs) and 15 patients with MS after 24 hours (normalized to β-actin). (C) Human CD4+ cells were isolated from PBMCs of healthy donors (n = 17), and glutamate levels were measured after 24 hours. In another set of experiments, differentiated Th1 and Th17 cells from healthy donors (n = 6) and patients with MS (n = 7) were compared. (D) Post-embedment immunogold labeling of fixed l-glutamate was measured with an electron microscope. Unstimulated human Th17 cells showed only sporadic positive signals in the cytoplasm (left panels), whereas stimulated human Th17 cells showed clear positive signals in the cytoplasm and in vesicles (middle and right panels). Yellow circles highlight vesicular structures; black arrows indicate glutamate. Scale bars: 2 μm and 500 nm. (E) Quantification of glutamate-positive cells within unstained (n = 13), unstimulated (Th17 unstim) (n = 11), and stimulated (Th17 stim) (n = 17) human Th17 cells. Data indicate the mean ± SEM. *P < 0.05, by unpaired Student’s t test (A), 1-way ANOVA with Tukey’s post hoc test (B and C), or χ2 test (E).