ncRNA | Free Full-Text | LINC00892 Is an lncRNA Induced by T Cell Activation and Expressed by Follicular Lymphoma-Resident T Helper Cells

As shown in Figure 2A, LINC00892 is strongly induced in Jurkat cells following treatment with a combination of PMA and ionomycin. The reason for the concomitant use of PMA and ionomycin to induce T cell activation is based on the need to activate multiple signal transduction pathways. PMA is a potent activator of the PKC pathway, while ionomycin, by increasing intracellular calcium levels, induces the activation of NFAT. Genes like IL2 typically require both drugs for full transcriptional activation, but for the activation of other genes, the presence of either PMA or ionomycin might be sufficient [38]. In order to characterize the details of LINC00892 expression following Jurkat cell activation, we performed several analyses. First, we analyzed the kinetics of LINC00892 expression following PMA/ionomycin treatment; second, we investigated whether transcriptional induction required the concomitant presence of PMA and ionomycin; third, we determined to what extent the intensity and duration of the stimulus influenced LINC00892 expression. As shown in Figure 6A, we found that, contrary to IL2 (Figure S5A), LINC00892 expression was late and persistent: following PMA and ionomycin treatment, its expression barely changed after 3 h, started to increase after 24 h and reached its maximum after 72 h. A second stimulation 4 days after stimulus withdrawal still increased LINC00892 expression but without reaching statistical significance. The expression behavior of LINC00892 in Jurkat cells is therefore strikingly similar to that observed in naïve and memory primary T cells (Figure 1C). We also found that most of the increase in LINC00892 expression after stimulation was due to the action of PMA only. The use of ionomycin alone did not vary LINC00892 expression, and the concomitant use of PMA and ionomycin resulted in a further but not significant increase relative to PMA alone (Figure 6B). Next, we tested several concentrations and stimuli durations and found that PMA at 1 ng/mL given for 5 min was already able to induce a strong increase in LINC00892 expression (Figure 6C). As shown in Figure S1, PMA and ionomycin treatment was accompanied by cell growth arrest with a strong induction of CDKN1A, the gene coding for the cell cycle inhibitor p21. As for LINC00892, CDKN1A induction was also dependent on PMA only (Figure S5B). Interestingly, PMA has already been shown to induce p21 expression and cell cycle arrest in other cell systems [39]. Given that LINC00892 expression in our experimental conditions was associated with p21 induction and growth arrest, we asked if other stimuli that induce cell cycle arrest and p21 induction would result in an increase in LINC00892 expression. As shown in Figure 6D, serum starvation of Jurkat cells for 48 h, although associated with a strong induction of CDKN1A, was not accompanied by an increase in LINC00892 expression.

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