(276e) Mechanosensitive Regulation of Cell Volume and Its Implications in Cell Functions

Mammalian cells in physiological microenvironments are simultaneously exposed to an integration of solid stress, such as extracellular matrix stiffness, and fluidic cues, including osmotic and hydrostatic pressure. These stimuli can alter cell mechanics and drive water fluxes across the cell membrane, dramatically affecting cell size homeostasis. To adapt, cells rely on an active regulatory system that adjusts their volume and shape in response to these changes. A key open question is how actomyosin-mediated mechanical pressure, typically on the order of ~1 kPa (equivalent to ~0.5 mOsm),^[1] controls osmoregulatory processes that operate at a much larger scale at ~10-100 mOsm. ^[2,3]

Using a combination of microfluidics, quantitative microscopy, and DNA/RNA sequencing, we discovered a novel mechanism of mechanosensitive volume regulation. This response can be triggered by osmotic shock, mechanical stretch, or physiological hydrostatic pressure gradients. In this system, the cytoskeleton integrates signals from both fluid pressure and the extracellular matrix to regulate the activity of sodium-hydrogen exchanger 1 (NHE1), a key ion transporter involved in controlling intracellular volume and ion homeostasis.^[4] Through mathematical modeling and experimental validation, we demonstrate that this system is controlled by a biphasic interplay between cytoskeletal mechanics, PI3K/Akt-mediated biochemical signaling, and NHE1 activity.^[5]

In addition, we show that such mechanosensitive activity is capable of generating large-scale nuclear deformations and a cascade of epigenetic remodeling, leading to significant shifts in DNA methylation landscapes and gene expression profiles. Importantly, this regulatory mechanism is absent in many cancer cell lines. In normal cells, cytoskeletal activation of NHE1 under osmotic stress suppresses ERK-mediated proliferation. In contrast, cancer cells lacking this mechanism continue to proliferate despite environmental stressors.

Collectively, our study provides novel insights into the role of cytoskeletal mechanosensation in cell size regulation, with strong implications for understanding fluid-driven physiological and pathological processes.

Reference

[1] R. J. Petrie, H. Koo, K. M. Yamada, Science (1979) 2014, 345, 1062.

[2] Y. Li, K. Konstantopoulos, R. Zhao, Y. Mori, S. X. Sun, J Cell Sci 2020, 133, DOI 10.1242/jcs.240341.

[3] C. Cadart, L. Venkova, P. Recho, M. C. Lagomarsino, M. Piel, Nat Phys 2019, 15, 993.

[4] Q. Ni, Z. Ge, Y. Li, G. Shatkin, J. Fu, A. Sen, K. Bera, Y. Yang, Y. Wang, Y. Wu, A. C. Nogueira Vasconcelos, Y. Yan, D. Lin, A. P. Feinberg, K. Konstantopoulos, S. X. Sun, Cell Rep 2024, 43, 114992.

[5] Q. Ni, Z. Ge, A. Sen, Y. Wu, J. Fu, A. Amitrano, N. Srivastava, K. Konstantopoulos, S. Sun, bioRxiv 2025, DOI 10.1101/2025.04.02.646640.