MONO ADP-RIBOSYLTRANSFERASES EXPRESSED ON THE SURFACE OF PULMONARY EPITHELIAL CELLS ARE REGULATED BY PATHOGEN-ASSOCIATED MOLECULAR PATTERNS

Mono ADP-ribosylation is a post-translational modification catalyzed by a family of enzymes, related to bacterial toxins, which possess adenosine diphosphate ribosyltransferase activity (ARTs). The expression of ART1, 3 and 4 at the apical surface of airway cells is consistent with the possibility that ARTs may have a role in inflammatory response. Since several studies have evidenced that Toll-like receptors (TLRs) are expressed in lung epithelial cells and given that there are a number of potential TLR agonists in the lung, we evaluated whether airway epithelial cells express transferase activity. We have assessed that A549 cells express ART1 on their surface and shown that lipotheicoic acid (LTA) and flagellin, but not lipopolysaccaride (LPS), peptidoglycan (PG) and poly (I:C), up-regulate ART1. This cell line was used to determine how bacterial components of Gram+ and Gram- bacteria affect ART activity and/or expression. The expression of ART1 relative to the actin obtained by qRT-PCR confirm the up-regulation exerted on ART1 gene by LTA but not by PAM and flagellin. LPS, LTA, PG, flagellin or poly(I:C) did not induce the expression of either ART3 or ART5 mRNA, while a strong stimulatory effect on ART4 mRNA expression was found after stimulation of cells with LPS, LTA and PG but not flagellin and poly(I:C). A pretreatment of cells with mAbs that antagonize TLR4 and TLR2, inhibited ART4 activation indicating TLR4 and TLR2 involved in the mediation of ART4 induction. The incubation with TLR2 antagonist specifically blocks the ART1 up-regulation by LTA indicating that the effect is mediated by this receptor.