Chitin‐binding protein GbpA of Vibrio cholerae induces interleukin‐8 gene expression in intestinal cells through a TLR2/TLR1/CD14 complex

Abstract

Vibrio cholerae N‐acetylglucosamine binding protein (GbpA) is a secretory protein which is essential for bacterial survival in environment as well as in human gut. Here we show that GbpA binds to toll‐like receptor 2 (TLR2) and initiates downstream cellular inflammatory signaling pathway by IL8 secretion. GbpA triggered formation of lipid raft microdomain on intestinal cell surface by interacting with TLR2 with a Kd of 76 nM. The microdomain contains TLR1, CD14 and flotilin in addition to TLR2. As a downstream effect, the lipid raft complex triggered IL8 secretion and the effect was specific in HT29 intestinal cells. The critical involvement of the GbpA‐induced lipid raft microdomain complex in IL8 secretion was indicated by the decrease in secretion caused by disruption of the raft by extraction of cholesterol by methyl‐β‐D‐cyclodextrin and by its restoration by extraneous addition of cholesterol. The GbpA‐mediated elevation in IL8 secretion involved activation of NFκB and formation of AP1 complex which eventually increased IL8 promoter activity. Taken together, the results suggest that GbpA is a key player in pathogenesis of cholera by triggering pro‐inflammatory response in infection by inducing downstream activation through clustering of GbpA‐TLR1/2‐CD14 complex in lipid raft microdomain. [Supported in part by grant from CSIR, Govt. of India No. 37(1410)/10/EMR‐II]