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Implication of three isoforms of PLA(2) in human T-cell proliferation
Christian Tessier1, Aziz Hichami, Naim Akhtar Khan
1UPRES Lipides and Nutrition, Université de Bourgogne, Faculté des Sciences de la Vie, 6 Boulevard Gabriel, 21000 Dijon, France.
Abstract:
We observed that human (Jurkat) T-cells constitutively expressed the mRNA, encoding for the four isoforms of phospholipase A(2) (PLA(2)), i.e. two secretory (type IB and type V), and two cytosolic (type IV, Ca(2+)-dependent and type VI, Ca(2+)-independent). In order to assess whether these PLA(2) isoforms are active, we labeled Jurkat T-cells with [(3)H]arachidonic acid ([(3)H]AA) and determined its release into the extracellular medium in the presence of phorbol 12-myristate 13-acetate (PMA) and ionomycin. The three PLA(2) isoforms seem functional as aristolochic acid and bromoenol lactone (BEL), the respective inhibitors of type IB/type V and type VI PLA(2)s, significantly inhibited the release of free [(3)H]AA. On the other hand, arachidonyl trifluoromethyl ketone (AACOCF(3)), an inhibitor of type IV PLA(2), failed to curtail significantly the release of free [(3)H]AA into the extracellular medium. We assessed the implication of these PLA(2) isoforms in transcription of the interleukin-2 (IL-2) gene, involved in T-cell proliferation. Hence, aristolochic acid and BEL, but not AACOCF(3), significantly inhibited the PMA and ionomycin-induced induction of mRNA of IL-2. Similarly, aristolochic acid and BEL, but not AACOCF(3), significantly inhibited the PMA and ionomycin-induced secretion of IL-2 in the culture supernatants. Together these results suggest that human Jurkat T-cells possess two secretory and two cytosolic PLA(2) isoforms and only three of them (type IB, type V and type VI) are implicated in T-cell proliferation.
Insights
Human Jurkat T-cells express four phospholipase A(2) (PLA(2)) isoforms. Three PLA(2) isoforms (types IB, V, and VI) are functional and involved in T-cell proliferation and interleukin-2 (IL-2) gene expression.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Phospholipase A(2) (PLA(2)) enzymes play critical roles in cellular signaling pathways.
- Understanding PLA(2) isoform function in T-cells is crucial for elucidating immune responses.
- Interleukin-2 (IL-2) is a key cytokine regulating T-cell proliferation.
Purpose of the Study:
- To investigate the expression and functional activity of PLA(2) isoforms in human Jurkat T-cells.
- To determine the role of specific PLA(2) isoforms in T-cell activation and IL-2 production.
Main Methods:
- Human Jurkat T-cells were analyzed for the expression of four PLA(2) mRNA isoforms.
- Cells were labeled with [(3)H]arachidonic acid and treated with phorbol 12-myristate 13-acetate (PMA) and ionomycin.
- The release of free [(3)H]arachidonic acid and IL-2 mRNA/protein levels were measured in the presence of specific PLA(2) inhibitors.
Main Results:
- Human Jurkat T-cells constitutively express mRNA for secretory (type IB, V) and cytosolic (type IV, VI) PLA(2) isoforms.
- Inhibitors of type IB/V and type VI PLA(2)s significantly reduced [(3)H]arachidonic acid release, indicating their functionality.
- Type IB, V, and VI PLA(2)s, but not type IV, were implicated in the PMA/ionomycin-induced IL-2 gene transcription and secretion.
Conclusions:
- Human Jurkat T-cells express functional secretory and cytosolic PLA(2) isoforms.
- PLA(2) types IB, V, and VI are critically involved in T-cell activation pathways regulating IL-2 production and proliferation.
- These findings highlight specific PLA(2) isoforms as potential targets for modulating T-cell responses.