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Cell volume controlled by LRRC8A-formed volume-regulated anion channels fine-tunes T cell activation and function

ABSTRACT: To become fully functional effector T cells, naïve T cells undergo a drastic metabolic status shift from quiescence to substantial biosynthesis. The synthesis of biomass initiated by T cell receptor (TCR) signals drives the cell volume increase during T cell activation (T lymphoblast), which resembles the slowest extreme of hypotonic cell swelling. However, the fundamental role of cell volume regulation in TCR signaling during T lymphoblast and its underlying mechanisms remain a long-standing enigma. Here we show that optimal T cell activation and function require appropriate cell volume regulation by regulated volume decrease (RVD) mediated via volume-regulated anion channels (VRACs) during T cell blast. Pharmacological blockade of VRACs and genetic deletion of LRRC8A in T cells, the essential component of VRACs, impair T cell activation and function, particularly under weak TCR stimulation, such as low-affinity TCR-pMHC engagement and unsaturated anti-CD3e crosslinking. Additionally, LRRC8A has distinct influences on mRNA transcriptional profiles driven by various TCR signal strengths, revealing the prominent effects of cell volume regulation for T cell functions. More importantly, LRRC8A-deficient mice have defective antiviral immunity and obstacles in effector-memory transition of CD8+ T cells. Furthermore, LRRC8A escorts the thymic selection of T cells and shapes the T cell repertoire in the thymus. Mechanistically, LRRC8A governs stringent cell volume increase via RVD during T cell blast induced by activation-driven intracellular osmolytes accumulation to keep the proximal TCR signaling molecules at adequate density. T cell blast driven by TCR signal feedbacks to control T cell activation. Together, our results reveal a previously unappreciated layer of T cell activation regulation that LRRC8A acts as a cell volume controlling "valve" to facilitate T cell activation and function

ORGANISM(S): Mus musculus

PROVIDER: GSE243574 | GEO | 2023/09/23

REPOSITORIES: GEO

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Project description:MLC1 is membrane protein highly expressed by brain perivascular astrocytes. Mutations in MLC1 account for megalencephalic leukoencephalopathy with subcortical cysts (MLC), an incurable leu-kodystrophy characterized by macrocephaly, brain edema and cysts, myelin vacuolation and as-trocyte swelling, that cause cognitive and motor dysfunctions. MLC pathological models demon-strated that in astrocytes MLC1 mutations affect the swelling-activated Cl- currents (ICl,swell) medi-ated by volume-regulated anion channel (VRAC) and the consequent regulatory volume decrease (RVD), and also induce the abnormal activation of intracellular signaling pathways linked to in-flammation/osmotic stress. Despite this knowledge, MLC1 function and MLC molecular pathogen-esis are still elusive. Following the observations that calcium regulates all the MLC1-modulated processes and that intracellular Ca2+ homeostasis is altered in MLC1-defective cells, we applied biochemistry, molecular biology, video imaging, electrophysiology and proteomic techniques on cultured human and mouse astrocytes to study MLC1/calcium signaling relationships. We revealed that MLC1 binds the Ca2+ effector proteins calmodulin (CaM) and Ca2+/CaM-dependent protein ki-nase II (CaMKII) and, as result, changes its assembly, localization and functional properties in re-sponse to Ca2+ influx or release. Noteworthy, CaM binding to the COOH terminal promotes MLC1 trafficking to the plasma membrane, while CaMKII phosphorylation of the NH2 end potentiates MLC1 activation of ICl,swell, that are critically important for RVD. Overall, our results show that MLC1 is a Ca2+-regulated protein linking VRAC function and volume regulation to Ca2+ signaling in astro-cytes, opening new avenues to clarify the defective molecular pathways of MLC and other diseas-es where astrocyte swelling and brain edema underlie the pathological process. In this contest we submit here the MS data showing MLC phosphorylation on Threonine 17.

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Cell volume controlled by LRRC8A-formed volume-regulated anion channels fine-tunes T cell activation and function

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