LRRC8/VRAC channels at the biophysical interface between cell-volume regulation and context-dependent cell-state transitions.

Cell volume is a dynamic physical state variable that changes membrane geometry, intracellular ionic strength, macromolecular concentration, molecular surface density, and reaction kinetics. Leucine-rich repeat-containing 8/volume-regulated anion channels (LRRC8/VRACs) provide a molecularly tractable system for testing how these biophysical changes influence cellular behavior. This review critically evaluates evidence linking LRRC8 channel composition, gating, inorganic-anion and organic-solute transport, regulatory volume decrease, and context-dependent cell-state transitions. We distinguish five mechanistic levels: canonical osmotic volume recovery; biophysical signal transduction through volume-dependent preservation of signaling-molecule density or membrane-potential change; transport of signaling metabolites, nucleotides, neurotransmitters, and drugs; channel-associated protein interactions; and tissue-level phenotypes in which the proximal mechanism remains unresolved. Activated mouse T-cells provide a clear mechanistic example: LRRC8A supports blast formation under weak stimulation, with signaling-density preservation tested using acute hypotonic swelling. In other settings, LRRC8 subunit composition modifies cyclic GMP-AMP, ATP, glutamate, taurine, glutathione, and platinum-drug transport, producing lineage-, stimulus-, and cargo-specific outcomes. Studies in nervous, immune, metabolic, vascular, epithelial, reproductive, and malignant tissues reveal substantial biological breadth but also expose recurring interpretive limitations, including incomplete definition of native channel stoichiometry, reliance on nonspecific inhibitors, inadequate separation of conductance from scaffolding, and failure to measure volume, substrate flux, signaling, and phenotype within the same causal sequence. We synthesize conflicting findings, identify model-dependent explanations, and propose experimental standards based on subunit-resolved rescue, pore-mutants, orthogonal-mechanical and osmotic perturbations, compartment-specific flux measurements, and time-resolved single-cell analysis. Current evidence supports LRRC8/VRAC as a family of context-dependent biophysical and metabolic gates rather than a universal cell-fate switch.