title: Dynamic assembly of a membrane signaling complex enables selective activation of NFAT by Orai1.
abstract: NFAT-dependent gene expression is essential for the development and function of the nervous, immune, and cardiovascular systems and kidney, bone, and skeletal muscle. Most NFAT protein resides in the cytoplasm because of extensive phosphorylation, which masks a nuclear localization sequence. Dephosphorylation by the Ca(2+)-calmodulin-activated protein phosphatase calcineurin triggers NFAT migration into the nucleus. In some cell types, NFAT can be activated by Ca(2+) nanodomains near open store-operated Orai1 and voltage-gated Ca(2+) channels in the plasma membrane. How local Ca(2+) near Orai1 is detected and whether other Orai channels utilize a similar mechanism remain unclear. Here, we report that the paralog Orai3 fails to activate NFAT. Orai1 is effective in activating gene expression via Ca(2+) nanodomains because it participates in a membrane-delimited signaling complex that forms after store depletion and brings calcineurin, via the scaffolding protein AKAP79, to calmodulin tethered to Orai1. By contrast, Orai3 interacts less well with AKAP79 after store depletion, rendering it ineffective in activating NFAT. A channel chimera of Orai3 with the N terminus of Orai1 was able to couple local Ca(2+) entry to NFAT activation, identifying the N-terminal domain of Orai1 as central to Ca(2+) nanodomain-transcription coupling. The formation of a store-dependent signaling complex at the plasma membrane provides for selective activation of a fundamental downstream response by Orai1.
authors.affiliation: Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK.
authors.forename: Pulak
authors.initials: P
authors.lastname: Kar
authors.affiliation: Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK.
authors.forename: Krishna
authors.initials: K
authors.lastname: Samanta
authors.affiliation: Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK.
authors.forename: Holger
authors.initials: H
authors.lastname: Kramer
authors.affiliation: Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK.
authors.forename: Otto
authors.initials: O
authors.lastname: Morris
authors.affiliation: Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Bakowski
authors.affiliation: Department of Physiology, Anatomy, and Genetics, Oxford University, Parks Road, Oxford OX1 3PT, UK. Electronic address: anant.parekh@dpag.ox.ac.uk.
authors.forename: Anant B
authors.initials: AB
authors.lastname: Parekh
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000235:genetics* / Q000378:metabolism; D020013:Calcium Signaling; D002460:Cell Line; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D050778:NFATC Transcription Factors / Q000235:genetics* / Q000378:metabolism; D000071740:ORAI1 Protein; D051381:Rats
chemical_list: D015220:Calcium Channels; D050778:NFATC Transcription Factors; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; C522867:Orai3 protein, human