Functional expression of calcium homeostasis modulator 2 (CALHM2) regulates the bioenergetic transition of BV2 microglial cells.

Microglia play pivotal roles in neuroinflammation and central nervous system disorders. The Calcium Homeostasis Modulator (CALHM) family forms large-pore ion channels implicated in ATP release and mitochondrial function. Here, we identified the functional expression of CALHM in BV2 microglial cells. Whole-cell patch-clamp recordings revealed a thermosensitive, voltage-gated slow outward current, consistent with the cloned CALHM channel current (ICALHM). RT-PCR confirmed that CALHM2 is the predominantly expressed isoform in BV2. CRISPR/Cas9-mediated knockout of Calhm2 (CALHM2-/-) abolished the ICALHM in BV2. While ATP release and Ca2+ influx rate was not affected, Seahorse XF analysis revealed an impaired metabolic flexibility in CALHM2-/-. Specifically, the LPS-induced increase in the oxygen consumption rate (OCR) was abolished, and the extracellular acidification rate (ECAR) was reduced in the LPS-treated CALHM2-/- cells. These results demonstrate that CALHM2 ​in microglia might be essential for the metabolic shift required during inflammatory activation.