title: The polybasic lysine-rich domain of plasma membrane-resident STIM1 is essential for the modulation of store-operated divalent cation entry by extracellular calcium.
abstract: STIM1 acts as an endoplasmic reticulum Ca(2+) sensor that communicates the filling state of the intracellular stores to the store-operated channels. In addition, STIM1 is expressed in the plasma membrane, with the Ca(2+) binding EF-hand motif facing the extracellular medium; however, its role sensing extracellular Ca(2+) concentrations in store-operated Ca(2+) entry (SOCE), as well as the underlying mechanism remains unclear. Here we report that divalent cation entry stimulated by thapsigargin (TG) is attenuated by extracellular Ca(2+) in a concentration-dependent manner. Expression of the Ca(2+)-binding defective STIM1(D76A) mutant did not alter the surface expression of STIM1 but abolishes the regulation of divalent cation entry by extracellular Ca(2+). Orai1 and TRPC1 have been shown to play a major role in SOCE. Expression of the STIM1(D76A) mutant did not alter Orai1 phosphoserine content. TRPC1 silencing significantly attenuated TG-induced Mn(2+) entry. Expression of the STIM1(K684,685E) mutant impaired the association of plasma membrane STIM1 with TRPC1, as well as the regulation of TG-induced divalent cation entry by extracellular Ca(2+), which suggests that TRPC1 might be involved in the regulation of divalent cation entry by extracellular Ca(2+) mediated by plasma membrane-resident STIM1. Expression of the STIM1(D76A) or STIM1(K684,685E) mutants reduced store-operated divalent cation entry and resulted in loss of dependence on the extracellular Ca(2+) concentration, providing evidence for a functional role of plasma membrane-resident STIM1 in the regulation of store-operated divalent cation entry, which at least involves the EF-hand motif and the C-terminal polybasic lysine-rich domain.
authors: Institute of Biophysics, University of Linz, A-4040 Linz, Austria.
authors: Isaac
authors: I
authors: Jardin
authors: Natalia
authors: N
authors: Dionisio
authors: Irene
authors: I
authors: Frischauf
authors: Alejandro
authors: A
authors: Berna-Erro
authors: Geoffrey E
authors: GE
authors: Woodard
authors: José J
authors: JJ
authors: López
authors: Ginés M
authors: GM
authors: Salido
authors: Juan A
authors: JA
authors: Rosado
mesh_terms: D019943:Amino Acid Substitution; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism*; D002413:Cations, Divalent / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D000071740:ORAI1 Protein; D010766:Phosphorylation; D011107:Polylysine / Q000737:chemistry; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D002413:Cations, Divalent; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D034741:RNA, Small Interfering; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; D050052:TRPC Cation Channels; C096351:transient receptor potential cation channel, subfamily C, member 1; D011107:Polylysine; D019284:Thapsigargin; D002118:Calcium