Deciphering the secretion mechanism and novel protein-protein interactions of TecA, a Burkholderia cenocepacia toxin

Burkholderia cenocepacia (Bc) is an environmental opportunistic pathogen that causes persistent, often severe, lung infections in individuals with cystic fibrosis and other underlying diseases. Rho GTPases are central molecular switches that regulate cytoskeletal dynamics, trafficking, immune responses and cell proliferation in eukaryotic cells. Many microbes produce proteins that target Rho GTPase signalling. Bc employs a type VI secretion system (T6SS) to survive in macrophages by disarming Rho GTPases and causing actin cytoskeletal defects. Bc protein TecA is a non-VgrG T6SS effector that is responsible for actin disruption. TecA and other bacterial homologs bear a cysteine protease-like catalytic triad, which inactivates Rho GTPases by deamidating a conserved asparagine in the GTPase switch-I region. RhoA deamidation induces Pyrin inflammasome activation1. Our goal is to determine the detailed TecA secretion mechanism and the interacting partners inside the bacterial cytoplasm and inside the macrophages. In this study, we found by Co-IP/MS analysis that TecA interacts with the T6SS tube protein HcP, the membrane anchored TssM and with the elongation factor Tu. We also found that TecA is secreted in the absence of HcP and the secretion mechanism is discussed. 1. Aubert, D.F., X. Hao, J. Yang, X. Shi, W. Gao, L. Li, F. Bisaro, S. Chen, M.A. Valvano, and F. Shao. 2016. A Burkholderia Type VI Effector Deamidates Rho GTPases to Activate the Pyrin Inflammasome. Cell Host and Microbe 19 : 664–674.