Analysis of the Role of TRPC3 in Ca2+ Signaling of RBL-2H3 Mast Cells

Abstract

Direct or indirect involvement of TRPC channels in store-operated Ca2+ entry (SOCE) has repeatedly been proposed. In this study, we explored the role of TRPC3 in SOCE-associated Ca2+ signaling of RBL-2H3 mast cells by employing both genetic and pharmacological strategies. Mast cells overexpressing a fluorescence-tagged, functional TRPC3 fusion protein displayed enhanced Ca2+ entry in a classical thapsigargin-induced store depletion/calcium re-entry protocol. A well-characterized dominant-negative, n-terminal fragment of TRPC3 (aa 1-302) reduced SOCE significantly down to basal entry. A similar extent of inhibition was observed with a dominant negative mutant of Orai1 (E106Q). Two pore mutants of TRPC3 (E616K and E630Q), which represent a non-functional, dominant negative protein and a protein with distinctly altered cation permeability, respectively, failed to affect SOCE in RBL-2H3 cells. The pyrazol compound Pyr3 (ethyl-1-(4-(2,3,3-trichloroacrylamide)phenyl)-5-(trifluoromethyl)-1H-pyrazole-4-carboxylate), which was recently proposed as a selective inhibitor of TRPC3 channels, effectively suppressed SOCE in wild-type controls as well as TRPC3 over-expressing cells. Our results argue against a role of TRPC3 as part of the store-operated Ca2+ permeation pathway in RBL-2H3 cells and point towards an indirect link between TRPC3 and SOCE.Supported by the FWF project P18475 and P19820