Differential accumulation of splice variants and transcripts as a result of PI3K inhibition in T lymphocytes and the potential role of their gene products in T cell silencing

Using measles virus induced T cell suppression as a model, we established that T cell inhibitory protein isoforms can be produced from alternatively spliced pre-mRNAs as a result of virus-mediated ablation of T cell receptor dependent activation of the phosphatidylinositol-3-kinase (PI3K). To asses production of alternative splice variants in response to PI3K abrogation in T cells at a whole cell level, we performed a Human Exon 1.0 ST Array on RNAs isolated from T cells stimulated only or stimulated after PI3K inhibition. We developed a simple algorithm based on a splicing index to detect genes that undergo alternative splicing (AS) or are differentially regulated (RG) on T cell suppression. Applying our algorithm on this model 9% of the genes were assigned as AS, while only 3% were attributed to RG. Though there are overlaps, AS and RG genes differed with regard to functional regulated at the level of AS or RG were found enriched in different functional groups with AS targeting e. g. extra cellular matrix (ECM)-receptor interaction and focal adhesion, while cytokine-receptor interaction, Jak-STAT and p53 pathways were mainly RG. When combined, AS/RG dependent alterations targeted pathways essential for T cell receptor signaling, cytoskeletal dynamics and cell cycle entry strongly supporting the notion that PI3K abrogations interferes with key T cell activation processes at both levels, and that candidates represented within both categories bear the potential to actively contribute to T cell suppression

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Riedel A, Mofolo B, Avota E, Schneider-Schaulies S, Meintjes A, Mulder N, Kneitz S