Mono ADP-ribosylation, like phosporylation is a post-translational modification that alters key cellular events. This reaction is catalyzed by ADP-ribosyltransferases (ARTs), a class of functionally conserved enzymes present in prokaryotic and eukaryotic organisms. The family of known ARTs consists of seven members, except for ART1 and 5, which transfer ADP-ribose unit from NAD to arginine, the amino-acid acceptor of the other ARTs is still unknown. We have shown that apical surface of ciliated and intermediate epithelial cells purified from bronchoalveolar lavage express ART1, 3 and 4. This is consistent with the possibility that these ecto-enzymes may have a role in inflammatory responses in lung. Indeed, A549 cells, which retain features of type II alveolar epithelial cells, represent a good model to study ART functions in epithelia. Using an arginine-specific enzymatic assay, we have identified an ART activity, on the surface of A549 cells. Possible candidates for catalyzing the arginine-specific ADP-ribosylation are ART1 and ART5 that recognize arginine as ADP-ribose acceptor. By reverse transcription-PCR we detected only ART1 mRNA and western blot of A549 membrane proteins with α-ART1 polyclonal antibodies further showed the expression of ART1. Since airway epithelial cells can interact with respiratory pathogens or their toxins, we investigated whether ART1 activity and expression is induced by bacterial components of Gram+ and Gram- bacteria. While lipopolysaccharide, peptidoglycan and Poly-(I:C) had no effect on transferase activity, lipoteichoic acid or flagelllin exerted a 3.7- and a 2.7-fold increase respectively of the transferase activity over the basal levels after 24 h treatment. The same effectors up-regulated ART1 expression, as shown by western blot analysis of cell membrane proteins suggesting as the up-regulation of ART1 is not a general event simply associated with cell activation.
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|Titolo:||LIPOTEICHOIC ACID AND FLAGELLIN INDUCE UP-REGULATION OF ART1 INAIRWAY EPITHELIAL CELLS|
|Data di pubblicazione:||2005|
|Appare nelle tipologie:||Contributo in atto di convegno su volume|