The Ca(2+) sensor stromal interaction molecule 1 (STIM1) is necessary and sufficient for the store-operated Ca(2+) entry function of transient receptor potential canonical (TRPC) 1 and 4 channels in endothelial cells.
We addressed the requirement for stromal interaction molecule 1 (STIM1), the endoplasmic reticulum (ER) Ca(2+)-sensor, and Orai1, a Ca(2+) selective channel, in regulating Ca(2+) entry through the store-operated channels mouse transient receptor potential canonical (TRPC) 4 or human TRPC1. Studies were made using murine and human lung endothelial cells (ECs) challenged with thrombin known to induce Ca(2+) entry via TRPC1/4. Deletion or knockdown of TRPC4 abolished Ca(2+) entry secondary to depletion of ER Ca(2+) stores, preventing the disruption of the endothelial barrier. Knockdown of STIM1 (but not of Orai1or Orai3) or expression of the dominant-negative STIM1(K684E-K685E) mutant in ECs also suppressed Ca(2+) entry secondary to store depletion. Ectopic expression of WT-STIM1 or WT-Orai1 in TRPC4(-/-)-ECs failed to rescue Ca(2+) entry; however, WT-TRPC4 expression in TRPC4(-/-)-ECs restored Ca(2+) entry indicating the requirement for TRPC4 in mediating store-operated Ca(2+) entry. Moreover, expression of the dominant-negative Orai1(R91W) mutant or Orai3(E81W) mutant in WT-ECs failed to prevent thrombin-induced Ca(2+) entry. In contrast, expression of the dominant-negative TRPC4(EE647-648KK) mutant in WT-ECs markedly reduced thrombin-induced Ca(2+) entry. In ECs expressing YFP-STIM1, ER-store Ca(2+) depletion induced formation of fluorescent membrane puncta in WT but not in TRPC4(-/-) cells, indicating that mobilization of STIM1 and engagement of its Ca(2+) sensing function required TRPC4 expression. Coimmunoprecipitation studies showed coupling of TRPC1 and TRPC4 with STIM1 on depletion of ER Ca(2+) stores. Thus, TRPC1 and TRPC4 can interact with STIM1 to form functional store-operated Ca(2+)-entry channels, which are essential for mediating Ca(2+) entry-dependent disruption of the endothelial barrier.
Department of Pharmacology and Center for Lung and Vascular Biology, College of Medicine, University of Illinois, Chicago, Illinois 60612, USA.
Premanand C
PC
Sundivakkam
Marc
M
Freichel
Vandana
V
Singh
Joseph P
JP
Yuan
Stephen M
SM
Vogel
Veit
V
Flockerzi
Asrar B
AB
Malik
Chinnaswamy
C
Tiruppathi
D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D034741:RNA, Small Interfering; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels / Q000502:physiology*
D015220:Calcium Channels; D008562:Membrane Glycoproteins; D034741:RNA, Small Interfering; C100757:Stim1 protein, mouse; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; C096351:transient receptor potential cation channel, subfamily C, member 1; D002118:Calcium