title: Differential roles for STIM1 and STIM2 in store-operated calcium entry in rat neurons.
abstract: The interaction between Ca(2+) sensors STIM1 and STIM2 and Ca(2+) channel-forming protein ORAI1 is a crucial element of store-operated calcium entry (SOCE) in non-excitable cells. However, the molecular mechanism of SOCE in neurons remains unclear. We addressed this issue by establishing the presence and function of STIM proteins. Real-time polymerase chain reaction from cortical neurons showed that these cells contain significant amounts of Stim1 and Stim2 mRNA. Thapsigargin (TG) treatment increased the amount of both endogenous STIM proteins in neuronal membrane fractions. The number of YFP-STIM1/ORAI1 and YFP-STIM2/ORAI1 complexes was also enhanced by such treatment. The differences observed in the number of STIM1 and STIM2 complexes under SOCE conditions and the differential sensitivity to SOCE inhibitors suggest their distinct roles. Endoplasmic reticulum (ER) store depletion by TG enhanced intracellular Ca(2+) levels in loaded with Fura-2 neurons transfected with YFP-STIM1 and ORAI1, but not with YFP-STIM2 and ORAI1, which correlated well with the number of complexes formed. Moreover, the SOCE inhibitors ML-9 and 2-APB reduced Ca(2+) influx in neurons expressing YFP-STIM1/ORAI1 but produced no effect in cells transfected with YFP-STIM2/ORAI1. Moreover, in neurons transfected with YFP-STIM2/ORAI1, the increase in constitutive calcium entry was greater than with YFP-STIM1/ORAI1. Our data indicate that both STIM proteins are involved in calcium homeostasis in neurons. STIM1 mainly activates SOCE, whereas STIM2 regulates resting Ca(2+) levels in the ER and Ca(2+) leakage with the additional involvement of STIM1.
authors.affiliation: Laboratory of Neurodegeneration, International Institute of Molecular and Cell Biology, Warsaw, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Gruszczynska-Biegala
authors.forename: Pawel
authors.initials: P
authors.lastname: Pomorski
authors.forename: Marta B
authors.initials: MB
authors.lastname: Wisniewska
authors.forename: Jacek
authors.initials: J
authors.lastname: Kuznicki
mesh_terms: D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001426:Bacterial Proteins / Q000378:metabolism; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology; D002614:Chelating Agents / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D008164:Luminescent Proteins / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000071740:ORAI1 Protein; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
chemical_list: C538758:2-aminoethyl diphenylborinate; D001381:Azepines; D001426:Bacterial Proteins; D001896:Boron Compounds; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D002614:Chelating Agents; D008164:Luminescent Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D000071740:ORAI1 Protein; C532493:Orai1 protein, rat; D012333:RNA, Messenger; C560435:STIM2 protein, rat; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; C054562:yellow fluorescent protein, Bacteria; C056218:ML 9; D019284:Thapsigargin; D002118:Calcium