WORTMANNIN INHIBITS TRANSCYTOSIS OF DIMERIC IEA BY THE POLYMERIC IMMUNOGLOBULIN RECEPTOR

Phosphatidyl inositol 3-kinase (PI3K) plays an essential role in numer ous signaling events, and increasingly has been implicated in regulati on of certain membrane traffic events, The polymeric immunoglobulin re ceptor (pIgR) transcytoses dimeric IgA (dlgA) across epithelial cells and into external secretions, where the dIgA forms the first specific immunological defense against infection, We show here that wortmannin, a highly specific inhibitor of PI3K, inhibits transcytosis of dIgA by the pIgR. Instead, the dIgA is recycled back to the basolateral surfa ce of the epithelial cell, PI3K therefore plays an essential role in r egulating the transcytosis of dIgA, a key step in the mucosal immune r esponse.