Lysosomal adaptation to extracellular acidity compromises CD8+ T cell cytotoxicity

Extracellular acidosis is a hallmark of aggressive tumors and suppresses cytotoxic-T lymphocyte (CTL)-mediated killing, but how sustained acid exposure reshapes T cell cytotoxicity is poorly understood. Here we show that chronic acidosis drives lysosomal remodeling in human CD8 + T cells, converting the lysosome into a proton sink whose adaptation ultimately impairs killing by depleting the intracellular granzyme B reservoir through constitutive vesicle release. Quantitative proteomics of CD8 + T cells cultured at pH 6.5 identified lysosomes as the dominant target of acid-driven remodeling: CTLs upregulated the V1 sector of the vacuolar H + -ATPase and hyper-acidified the lysosomal lumen. The remodeled compartment accumulated lysosomal membrane proteins (LAMP1, LAMP2, CD63, CD68) post-transcriptionally, acquired higher cathepsin abundance and increased proteolytic activity. Chronic acidity also enlarged endoplasmic reticulum (ER) and lysosomal Ca 2+ stores without altering cytosolic Ca 2+ , and drives constitutive, Ca 2+ -dependent release of LAMP1 + lysosome-derived vesicles, which drains the intracellular reservoir of granzyme B, contributing to reduced CTL activity. These findings establish lysosomal adaptation as a cost of surviving extracellular acidosis and identify lysosomal hydrolase activity as a possible target for improving CTL function in the acidic tumor environment.

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Publication Details

Journal
bioRxiv (Cold Spring Harbor Laboratory)
Published
2026-10-27
DOI
https://doi.org/10.64898/2026.10.21.760659
Primary Topic
Autophagy in Disease and Therapy
Type
preprint

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preprint

Lysosomal adaptation to extracellular acidity compromises CD8+ T cell cytotoxicity

Benjamin Segain, Sofia Titah, Suman Mitra, Rahul Roychoudhuri et al.
2 links
bioRxiv (Cold Spring Harbor Laboratory)
Autophagy in Disease and Therapy
preprint

Lysosomal adaptation to extracellular acidity compromises CD8+ T cell cytotoxicity

Benjamin Segain, Sofia Titah, Suman Mitra, Rahul Roychoudhuri, Silvia Gaggero, Yasmine S. Touil, Christina M. Rollings, Angélina Kasprowicz, Bruno Quesnel, Adeline Cozzani, Linda V. Sinclair, Jonathan Martínez‐Fábregas, Elise Paulin, Robert Eil, Ignacio Moraga, Leila Mohammadnizad, Ryan Conesa
preprint en

Abstract

Extracellular acidosis is a hallmark of aggressive tumors and suppresses cytotoxic-T lymphocyte (CTL)-mediated killing, but how sustained acid exposure reshapes T cell cytotoxicity is poorly understood. Here we show that chronic acidosis drives lysosomal remodeling in human CD8 + T cells, converting the lysosome into a proton sink whose adaptation ultimately impairs killing by depleting the intracellular granzyme B reservoir through constitutive vesicle release. Quantitative proteomics of CD8 + T cells cultured at pH 6.5 identified lysosomes as the dominant target of acid-driven remodeling: CTLs upregulated the V1 sector of the vacuolar H + -ATPase and hyper-acidified the lysosomal lumen. The remodeled compartment accumulated lysosomal membrane proteins (LAMP1, LAMP2, CD63, CD68) post-transcriptionally, acquired higher cathepsin abundance and increased proteolytic activity. Chronic acidity also enlarged endoplasmic reticulum (ER) and lysosomal Ca 2+ stores without altering cytosolic Ca 2+ , and drives constitutive, Ca 2+ -dependent release of LAMP1 + lysosome-derived vesicles, which drains the intracellular reservoir of granzyme B, contributing to reduced CTL activity. These findings establish lysosomal adaptation as a cost of surviving extracellular acidosis and identify lysosomal hydrolase activity as a possible target for improving CTL function in the acidic tumor environment.

bioRxiv (Cold Spring Harbor Laboratory)
Centre National de la Recherche Scientifique (FR), Inserm (FR), Oregon Health & Science University (US), University of Dundee (GB), Université de Lille (FR), University of Cambridge (GB), Institut Pasteur de Lille (FR), Centro Andaluz de Biología Molecular y Medicina Regenerativa (ES), CANTHER - Hétérogénéité, Plasticité et Résistance aux Thérapies des Cancers (FR), Institut Curie (FR)
University of Dundee, Universidad de Sevilla, Ministerio de Ciencia, Innovación y Universidades, European Commission, Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación
Good health and well-being
Autophagy in Disease and Therapy
DOIOpen Access PDFOpenAlex
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