Using genetically engineered mice and cell lines derived from genetically engineered mice we show that depletion of ER delimited Ca2+ stores activates heteromeric Ca2+ entry (SOCE) channels formed obligatorily, but not exclusively by Orai1 molecules. Comparison of Orai-dependent Ca2+ entries revealed Orai1 to be dominant when compared to Orai2 and Orai3. Unexpectedly, we found that store-depletion-activated Ca2+ entry does not depend obligatorily on functionally intact TRPC molecules, as SOCE monitored with the Fura2 Ca2+ reporter dye is unaffected in cells in which all seven TRPC coding genes have been structurally and functionally inactivated. Unexpectedly as well, we found that TRPC-independent Gq-coupled receptor-operated Ca2+ entry (ROCE) also depends on Orai1. Biophysical measurements of Ca2+ release activated Ca2+ currents (Icrac) are likewise unaffected by ablation of all seven TRPC genes. We refer to mice and cells carrying the seven-fold disruption of TRPC genes as TRPC heptaKO mice and cells. TRPC heptaKO mice are fertile allowing the creation of a new homozygous inbred strain.
Keywords: Orai; ROCE; SOCE; TRPC.