An essential host dietary fatty acid stimulates TcpH inhibition of TcpP proteolysis enabling virulence gene expression in Vibrio cholerae

Vibrio cholerae is a Gram-negative gastrointestinal pathogen responsible for the diarrheal disease cholera. Expression of key virulence factors, cholera toxin and toxin-coregulated pilus, is regulated indirectly by two single-pass membrane-localized transcription regulators (MLTR), ToxR and TcpP, that promote expression of the transcription activator toxT . TcpP abundance and activity are controlled by TcpH, a single-pass transmembrane protein, which protects TcpP from a two-step proteolytic process known as regulated intramembrane proteolysis (RIP). The mechanism of TcpH mediated protection of TcpP represents a major gap in our understanding of V. cholerae pathogenesis. Absence of tcpH leads to unimpeded degradation of TcpP in vitro and a colonization defect in a neonate mouse model of V. cholerae colonization. Here, we show that TcpH protects TcpP from RIP via direct interaction. We also demonstrate that a dietary fatty acid, α-linolenic acid, promotes TcpH-dependent inhibition of RIP via co-association of TcpP and TcpH molecules within detergent-resistant membranes (DRMs; also known as lipid rafts) in a mechanism requiring the TcpH transmembrane domain. Taken together our data support a model where V. cholerae cells use exogenous α-linolenic acid to remodel the phospholipid bilayer in vivo , leading to co-association of TcpP and TcpH within DRMs where RIP of TcpP is inhibited by TcpH, thereby promoting V. cholerae pathogenicity. Significance Statement V. cholerae continues to pose a significant global burden on health infection millions of people every year resulting in ∼100,000 deaths annually. The importance of toxT gene expression in V. cholerae pathogenesis has been well established. Our results show that TcpP, one of the major regulators of toxT gene expression, is protected from proteolysis by TcpH, via direct interaction, in the presence of α-linolenic acid, an essential dietary fatty acid. Here we identify a physiological relevant host factor that stimulates V. cholerae pathogenicity via TcpH-dependent antagonism of TcpP proteolysis.