Binding to type I collagen is essential for the infectivity of Vibrio parahaemolyticus to host cells

Vibrio parahaemolyticus is a globally present marine bacterium that often leads to acute gastroenteritis. Two type III secretion systems (T3SSs), T3SS1 and T3SS2, are important for host infection. Type I collagen is a component of the extracellular matrix and is abundant in the small intestine. However, whether type I collagen serves as the cellular receptor for V. parahaemolyticus infection of host cells remains enigmatic. In this study, we discovered that type I collagen is not only important for the attachment of V. parahaemolyticus to host cells but is also involved in T3SS1-dependent cytotoxicity. In addition, 2 virulence factors, MAM7 and VpadF enable V. parahaemolyticus to interact with type I collagen and mediate T3SS2-dependent host cell invasion. Type I collagen, the collagen receptor α1 integrin, and its downstream factor phosphatidylinositol 3-kinase (PI3K) are responsible for V. parahaemolyticus invasion of host cells. Further biochemical studies revealed that VpadF mainly relies on the C-terminal region for type I collagen binding and MAM7 relies on mce domains to bind to type I collagen. As MAM7 and/or VpadF homologues are widely distributed in the genus Vibrio, we propose that Vibrios have evolved a unique strategy to infect host cells by binding to type I collagen.