Astrocyte-derived miR-124 impairs glioma cell volume regulation and migration by reducing Ca²⁺-dependent IK channel...

Astrocytes play a key role in regulating glioma cell volume, a major determinant of tumor invasiveness. We previously reported that astrocyte-derived extracellular vesicles (ADEVs) transfer microRNA miR-124 to murine glioma cells, impairing cell volume regulation and reducing the functional expression of volume-regulated anion channel (VRAC). Here, we identify the intermediate-conductance Ca²⁺-activated K⁺ (IK) channel, the only volume-regulated K⁺ channel acting in concert with VRAC in GL261 glioma cells, as an additional indirect target of miR-124. Mechanistically, ADEV-derived miR-124 decreases the expression of ryanodine receptor type-1 (RyR1) and inositol 1,4,5-trisphosphate receptor type-3 (IP₃R3), the principal endoplasmic reticulum (ER) Ca²⁺ release channels in these cells. This reduction in ER-mediated Ca²⁺ signaling markedly decreases ERK1/2 phosphorylation and IK channel gene transcription. Consistent with these molecular effects, fetal bovine serum-induced IK channel activation, driven by ER Ca²⁺ release, was strongly reduced by ADEVs and miR-124, and three-dimensional migration was impaired. Notably, combined pharmacological inhibition of IK and VRAC recapitulated the deficits in volume regulation induced by ADEVs and miR-124. Collectively, these findings show that ADEVs restrict glioma cell migration through a miR-124-dependent pathway that suppresses ER Ca²⁺ release, reduces ERK1/2 activation, and diminishes IK channel expression and function. Together with our previous in vivo evidence for ADEVs- and miR-124 -mediated targeting of VRAC, these results identify coordinated regulation of K⁺ and Cl⁻ channels as a mechanism by which astrocytes constrain glioma progression.