Project description: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.
Project description:Aberrant splice variants are involved in the initiation and/or progression of glial brain tumors. We therefore set out to identify splice variants that are differentially expressed between histological subgroups of gliomas. Splice variants were identified using a novel platform that profiles the expression of virtually all known and predicted exons present in the human genome. Exon-level expression profiling was performed on 26 glioblastomas, 22 oligodendrogliomas and 6 control brain samples. Our results demonstrate that Human Exon arrays can identify subgroups of gliomas based on their histological appearance and genetic aberrations. We next used our expression data to identify differentially expressed splice variants. In two independent approaches, we identified 49 and up to 459 exons that are differentially spliced between glioblastomas and oligodendrogliomas a subset of which (47% and 33%) were confirmed by RT-PCR. In addition, exon-level expression profiling also identified >700 novel exons. Expression of ~67% of these candidate novel exons was confirmed by RT-PCR. Our results indicate that exon-level expression profiling can be used to molecularly classify brain tumor subgroups, can identify differentially regulated splice variants and can identify novel exons. The splice variants identified by exon-level expression profiling may help to detect the genetic changes that cause or maintain gliomas and may serve as novel treatment targets. Keywords: cell type comparison 6 adult non diseased brain, 26 glioblastomas, 21 oligodendrogliomas
Project description:STIM1 is a Ca2+ sensor of intracellular Ca2+ stores and essentially activates the Ca2+ entry channels of the plasma membrane. STIM1 is predicted to activate transient receptor potential canonical (TRPC) channels and Orai channels, and has a critical role in promoting the development of cardiac hypertrophy. Gene array experiments were performed to analyze the effects of STIM1 deficiency using total RNA from the left ventricles of WT sham, WT TAC, STIM1KO sham and STIM1KO TAC 4 weeks after the operation.
Project description:DNA damage represents a challenge for cells as this damage must be eliminated to preserve cell viability and the transmission of genetic information. To reduce or eliminate unscheduled chemical modifications in genomic DNA, an extensive signaling network, known as the DNA damage response (DDR) pathway, ensures this repair. In this work, and by means of a proteomic analysis aimed at the study of the STIM1 protein interactome, we have found that STIM1 is closely related to the protection from endogenous DNA damage, replicative stress, as well as in the response to interstrand crosslinks (ICLs). Here we show that STIM1 has a nuclear localization signal (NLS) that mediates its translocation to the nucleus, and that this translocation and the association of STIM1 to chromatin is enhanced in response to mitomycin C (MMC), an ICL-inducing agent. Consequently, STIM1-deficient cell lines show a higher level of basal DNA damage, replicative stress, and a higher sensitivity to MMC. We show that STIM1 normalizes FANCD2 protein levels in the nucleus, explaining the increased sensitivity to MMC in STIM1-KO cells. Our results show for the first time a nuclear function for the endoplasmic reticulum protein STIM1 and increase the number of genes involved in DNA repair.
Project description:Influence of STIM1 on the transcriptome of CD4+ T cell subsets STIM1 is critical for the regulation of the intracellular Ca2+ homeostasis in CD4+ T cell. Loss of function mutations in STIM1 in patients result in severe immuno deficiency and recurrent infections. Using conditional knock out mice for STIM1, we investigated the role of STIM1 in T cells during chronic infections by in-vivo and in-vitro experiments. We found that STIM1 is required for T cell-mediated immunity to chronic infection with Mycobacterium tuberculosis (Mtb) as STIM1-deficient mice succumb to infection faster than littermate controls, have increased mycobacterial burdens and severe pulmonary infiltration with myeloid and lymphoid cells .Using the Affymetrix Mouse Exon 1.0 platform, we analyzed the influence of STIM1 expression on the transcriptom of CD4+T cells in-vitro. We found that STIM1 is required for the regulation of apoptosis related genes after TCR stimulation as well as for the induction of a transcriptonal program that polarizes naive CD4+ T cells into inducible CD4+ T regulatory cells (iTreg). Together with our in-vivo findings, these experiments reveal that STIM1 is essential for immune regulation to prevent an injurious inflammatory response during chronic infection.
Project description:STIM1 is an ER transmembrane protein that serve as the main intracellular calcium (iCa2+) sensors in several mammalian cells. Humans with mutated STIM1 present with severely defective enamel which suggests a critical role of STIM1 protein in enamel formation. We established an ameloblast specific (Amelx-iCre) Stim1 conditional deletion mouse model (Stim1 cKO). RNAseq on micro-dissected ameloblasts from 4 weeks old mice to evaluate changes in the gene expression levels of several key ameloblast genes.
Project description:Aberrant splice variants are involved in the initiation and/or progression of glial brain tumors. We therefore set out to identify splice variants that are differentially expressed between histological subgroups of gliomas. Splice variants were identified using a novel platform that profiles the expression of virtually all known and predicted exons present in the human genome. Exon-level expression profiling was performed on 26 glioblastomas, 22 oligodendrogliomas and 6 control brain samples. Our results demonstrate that Human Exon arrays can identify subgroups of gliomas based on their histological appearance and genetic aberrations. We next used our expression data to identify differentially expressed splice variants. In two independent approaches, we identified 49 and up to 459 exons that are differentially spliced between glioblastomas and oligodendrogliomas a subset of which (47% and 33%) were confirmed by RT-PCR. In addition, exon-level expression profiling also identified >700 novel exons. Expression of ~67% of these candidate novel exons was confirmed by RT-PCR. Our results indicate that exon-level expression profiling can be used to molecularly classify brain tumor subgroups, can identify differentially regulated splice variants and can identify novel exons. The splice variants identified by exon-level expression profiling may help to detect the genetic changes that cause or maintain gliomas and may serve as novel treatment targets. Keywords: cell type comparison