Based on limited published evidence, CALHM4 is a calcium homeostasis modulator that assembles into gap junction channel-like structures for intercellular communication. Cryo-EM structures reveal decameric and undecameric assemblies with large cylindrical pores where membrane lipids occupy a bilayer-like arrangement 1. Channel gating and ion conductance are regulated by membrane lipids rather than voltage or extracellular calcium [UniProt]. CALHM4 forms heteromeric channels with CALHM2 in placental tissue, with subunits segregating into preferred conformations 2. The protein exhibits monoatomic cation channel activity localized to the plasma membrane.