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A longer isoform of Stim1 is a negative SOCE regulator but increases cAMP modulated NFAT signaling

ABSTRACT: Alternative splicing is a potent modifier of protein function. Stromal interaction molecule 1 (Stim1) is the essential activator of store-operated Ca2+ entry (SOCE) triggering activation of transcription factors. Here, we characterize Stim1A, a splice variant with an additional 31 amino acid domain inserted in frame within its cytosolic domain. Prominent expression of exon A is found in astrocytes, heart, kidney and testes. Full length Stim1A functions as a dominant-negative regulator of SOCE and ICRAC, facilitating sequence specific fast calcium dependent inactivation and destabilizing gating or Orai1. Downregulation or absence of native Stim1A results in increased SOCE. Despite reducing SOCE, Stim1A leads to increased NFAT translocation. Differential proteomics revealed interference of Stim1A with the cAMP-SOCE crosstalk by altered modulation of phosphodiesterase (PDE8B), resulting in reduced cAMP degradation and increased PIP5K activity, facilitating an increased NFAT activation. Our study uncovers a hitherto unknown mechanism regulating NFAT activation and indicates that cell type specific splicing of Stim1 is a potent means to regulate the NFAT signalosome and cAMP-SOCE crosstalk.

INSTRUMENT(S): TripleTOF 5600

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: David Zimmer

LAB HEAD: Barbara Niemeyer

PROVIDER: PXD028974 | Pride | 2021-11-11

REPOSITORIES: Pride

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Project description:The nephrotoxic ifosfamide-metabolite chloroacetaldehyde (CAA) induces changes in intracellular Ca2+-concentration of human RPTEC. This effect is due to a PKA-dependent inhibition of Na+/Ca2+ exchange (Benesic, A., Schwerdt, G. at. al. (2005) Kidney Int 68, 2029-2041). Thus, possible effects of CAA-exposure on cAMP and Ca2+ regulated genes as well the Ca2+/NFAT pathway were investigated by cDNA-microarray analysis. Both microarrays (cAMP/Ca2+ and Ca2+(NFAT) were performed twice. After 24 h CAA exposure a marked downregulation of c-fos and junB was observed in all arrays performed. In the cAMP/Ca2+-arrays downregulation of FOS, ADRB1, INHBA, CDK5, IL2, PLN, SRF, GCG, SGK, JUNB, BDNF, S100A6, CCNA1, MIF, HK2, SST and EGR2 by CAA was observed in two independent experiments. From the AP-1 family expression of junD and fosB were not altered. Overexpression by CAA of CREB and DDIT3 were only observed in one of two experiments. JUND, FOSB, FOSL1, CREM and CREBBP expression was not influenced in reproducible manner, as well as all members of the NFAT-family. In the Ca2+/NFAT-Arrays, PPP3CB, VAV3, NFATC1, IL8, IL6, FASLG, IL3, IFNB1, FOS, BCL2, EGR3, CD3G, HRAS, EP300, IL4, CALM3, RELA, EGR2, NPPB, IFNG, NFATC4, KPNA5, CAMK2BNFKB2 , VEGF, IL8RA, IL2,GATA4, MEF2A, PTPRC, ICOS, NFKBIE, CDKN1A, CSNK2B, ACTB, MEF2B and JUNB mRNA´s were repeatedly reduced by CAA exposure. The only gene with upregulation in both experiments was found to be IFN-alpha. Thus CAA exposure for 24 h leads to a downregulation of of the AP-1 members JUNB and FOS, whereas there is small positive effect on CREB mRNA. CAA reproducibly lowers the expression of IL-2, 3, 4, 6 and 8, whereas the levels of TNFalpha and TGFbeta1 and 3 mRNA were not altered. IFN-alpha mRNA levels were reproducibly increased (>2-fold). In conclusion, CAA seems to interact with Ca2+ and cAMP signalling pathways, with a strong impact on AP-1 proteins and inflammatory signalling. Keywords: stress response to toxic agent

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A longer isoform of Stim1 is a negative SOCE regulator but increases cAMP modulated NFAT signaling

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