The role of phosphatidylinositol 4-kinase type IIalpha in degranulation of RBL-2H3 cells.

OBJECTIVE AND DESIGN

We have studied the role of phosphatidylinositol 4-kinase IIalpha (PI4KIIalpha) in activation of rat basophilic leukemia (RBL-2H3) cells.

MATERIALS AND METHODS

Antigen-mediated intracellular Ca(2+) concentration (Ca(2+)) increase and beta-hexosaminidase secretion were measured using RBL-2H3 cells stably expressing PI4KIIalpha-yellow fluorescent protein (YFP) or its kinase-deficient mutant PI4KIIalpha (K151A)-YFP.

RESULTS

Neither PI4KIIalpha-YFP nor PI4KIIalpha (K151A)-YFP were distributed on the plasma membranes but on the exocytotic vesicles. The RBL-2H3 cells stably expressing PI4KIIalpha-YFP showed significantly enhanced beta-hexosaminidase secretion but not an increase in Ca(2+) after antigen stimulation. The cells with PI4KIIalpha (K151A)-YFP showed no change in the Ca(2+) increase nor degranulation. The promotion of secretion by PI4KIIalpha-YFP was not observed using co-stimulation with Ca(2+) ionophore and the protein kinase C activator, phorbol myristate acetate.

CONCLUSIONS

These results suggest that PI4KIIalpha plays a role in the exocytotic process downstream of Ca(2+) signaling in antigen-mediated mast cell activation.