The Identification of Phosphatidylinositol 3,5-bisphosphate in T-lymphocytes and Its Regulation by Interleukin-2

• Published in: The Journal of biological chemistry 1999-06, Vol.274 (26), p.18407-18413
• Main Authors: Jones, D R, González-García, A, Díez, E, Martinez-A, C, Carrera, A C, Meŕida, I
• Format: Article
• Language: English
• Subjects: Animals; B-Lymphocytes - drug effects; B-Lymphocytes - metabolism; Cell Line; Chromatography, High Pressure Liquid; Humans; Interleukin-2 - pharmacology; Mice; Mitogens - pharmacology; Phosphatidylinositol Phosphates - metabolism; T-Lymphocytes - drug effects; T-Lymphocytes - metabolism; Ultraviolet Rays
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.26.18407

In recent times 3-phosphoinositides have emerged as important regulators of cell metabolism, survival, and proliferation. During the last year, the phospholipid phosphatidylinositol 3,5-bisphosphate (PtdIns3,5P 2 ) was identified in yeast, fibroblasts, SV40-transformed kidney (COS-7) cells, and platelets. The discovery of this novel phospholipid has increased the complexity of the metabolism relating to the generation of biologically active inositol-containing lipids. We describe here the identification of PtdIns3,5P 2 in the CTLL-2 mouse T-lymphocyte cell line using two in vivo radiolabeling protocols. Treatment of the cells with UV radiation led to an increase in the cellular content of PtdIns3,5P 2 . In contrast, preincubation of the cells with wortmannin or treatment with hypertonic medium (high concentration sorbitol) led to the opposite effect. Herein we demonstrate that interleukin-2 (IL-2), the growth factor required for CTLL-2 cell proliferation, was able to increase the level of PtdIns3,5P 2 with similar kinetics to that of the formation of phosphatidylinositol 3,4-bisphosphate (PtdIns3,4P 2 ). An increase in this novel 3-phosphorylated lipid in response to IL-2 seems to be a general property of this cytokine because a similar result was obtained when the pre-B cell line BaF/3 expressing the high affinity IL-2 receptor was used. Using a constitutively active regulatory subunit of type I phosphatidylinositol 3-kinase and cells expressing a deletion of the serine-rich domain of the IL-2 receptor β chain, which is required for IL-2-stimulated type I phosphatidylinositol 3-kinase activation, we demonstrate that IL-2-induced generation of PtdIns3,5P 2 is related to the activation of this enzyme. The results show for the first time the identification of PtdIns3,5P 2 in both T- and B-lymphocytes and indicate its positive regulation by the mitogen IL-2.