title: An siRNA screen for NFAT activation identifies septins as coordinators of store-operated Ca2+ entry.
abstract: The STIM1-ORAI1 pathway of store-operated Ca(2+) entry is an essential component of cellular Ca(2+) signalling. STIM1 senses depletion of intracellular Ca(2+) stores in response to physiological stimuli, and relocalizes within the endoplasmic reticulum to plasma-membrane-apposed junctions, where it recruits and gates open plasma membrane ORAI1 Ca(2+) channels. Here we use a genome-wide RNA interference screen in HeLa cells to identify filamentous septin proteins as crucial regulators of store-operated Ca(2+) entry. Septin filaments and phosphatidylinositol-4,5-bisphosphate (also known as PtdIns(4,5)P2) rearrange locally at endoplasmic reticulum-plasma membrane junctions before and during formation of STIM1-ORAI1 clusters, facilitating STIM1 targeting to these junctions and promoting the stable recruitment of ORAI1. Septin rearrangement at junctions is required for PtdIns(4,5)P2 reorganization and efficient STIM1-ORAI1 communication. Septins are known to demarcate specialized membrane regions such as dendritic spines, the yeast bud and the primary cilium, and to serve as membrane diffusion barriers and/or signalling hubs in cellular processes such as vesicle trafficking, cell polarity and cytokinesis. Our data show that septins also organize the highly localized plasma membrane domains that are important in STIM1-ORAI1 signalling, and indicate that septins may organize membrane microdomains relevant to other signalling processes.
authors.affiliation: La Jolla Institute for Allergy and Immunology, La Jolla, California 92037, USA.
authors.forename: Sonia
authors.initials: S
authors.lastname: Sharma
authors.forename: Ariel
authors.initials: A
authors.lastname: Quintana
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Findlay
authors.forename: Marcel
authors.initials: M
authors.lastname: Mettlen
authors.forename: Beate
authors.initials: B
authors.lastname: Baust
authors.forename: Mohit
authors.initials: M
authors.lastname: Jain
authors.forename: Roland
authors.initials: R
authors.lastname: Nilsson
authors.forename: Anjana
authors.initials: A
authors.lastname: Rao
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Hogan
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015894:Genome, Human; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism; D000071740:ORAI1 Protein; D021381:Protein Transport; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics*; D058112:Septins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000071737:Stromal Interaction Molecule 1
chemical_list: D015220:Calcium Channels; D008565:Membrane Proteins; D050778:NFATC Transcription Factors; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D034741:RNA, Small Interfering; C103530:STIM1 protein, human; D000071737:Stromal Interaction Molecule 1; C492027:SEPTIN4 protein, human; D058112:Septins; D002118:Calcium