Liprin-α is involved in exocytosis and cell spreading in mast cells

The active zone is a specialized region of the presynaptic plasma membrane where the neurotransmitter release occurs by exocytosis. Mast cells also release inflammatory mediators by exocytosis resulting in induction of allergic responses. In our previous reports, we found that active zone proteins, Munc13-1 and ELKS regulates exocytosis of mast cell positively. In this study, we investigated the involvement of liprin-alpha, another active zone protein, in exocytosis in mast cells. We found that three isoforms of liprin-alpha, liprin-alpha 1, -alpha 2 and -alpha 3 were expressed. Immunocytochemical experiments revealed that liprin-alpha 1 resided both in the cytoplasm and on the plasma membrane. Upon stimulation with antigen, the area of a cell increased remarkably due to cell spreading and the distribution of liprin-alpha 1 became punctuated. Interestingly, knockdown of liprin-alpha 1 caused decrease in exocytotic release and cell spreading. These results suggest that liprin-alpha 1 facilitates exocytosis and cell spreading, and these events might have correlated each other in mast cells. (C) 2011 Elsevier B.V. All rights reserved.