In several cell types, proliferation initiated by growth factors is associated with a rapid increase in cytoplasmic pH (pH(i)). This cytoplasmic alkalinization is due to the activation of an amiloride-sensitive Na+/H+ antiport. It is unclear whether growth factor-induced activation of the antiport or the resultant increase in pH(i) is the trigger for proliferation, an obligatory requirement for proliferation, or simply an associated phenomenon. Interleukin 2 (IL 2) acts as a growth factor for mitogen or antigen-stimulated thymus-derived (T) lymphocytes. In this study, we established that IL 2 produces an increase in pH(i) and determined whether this increase in pH(i) plays a role in the proliferative response to IL 2. Monitoring pH(i) with an intracellularly trapped, pH-sensitive, fluorescent dye, 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein, we demonstrated that IL 2 rapidly (<90 s) initiates an increase in pH(i) in IL 2-sensitive human and murine T cells. Because intracellular alkalinization requires extracellular Na+ and is amiloride-sensitive, it likely occurs through activation of the Na+/H+ antiport. Using partitioning of a weak acid, 5,5-dimethyl-2,4-oxazolidinedione, we confirmed that the IL 2-dependent increase in pH(i) is sustained for several hours and returns to near base-line levels by 18 h. We also investigated the consequence of preventing Na+/H+ exchange on the proliferative response induced by IL 2. IL 2-driven proliferation occurred in nominally bicarbonate-free medium in the presence of concentrations of amiloride analogs sufficient to inhibit the Na+/H+ antiport and prevent intracellular alkalinization. These data suggest that although the antiport is activated by binding of IL 2 to its receptor, intracellular alkalinization is not essential for IL 2-dependent proliferation. It seems unlikely that either cytoplasmic alkalinization or activation of the Na+/H+ antiport are triggers for T cell proliferation.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - 1985|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology