A Small GTPase, RhoA, Inhibits Bacterial Infection Through Integrin Mediated Phagocytosis in Invertebrates

The Ras GTPase superfamily, including more than 100 members, plays a vital role in a number of cellular processes, such as cytoskeleton recombination, gene expression, and signaling pathway regulation. Some members of the superfamily participate in innate immunity in animals. However, there have been few studies of RhoA on this aspect. In the present study, we identified a RhoA GTPase in the shrimp and named it RhoA. Expression of was significantly upregulated in hemocytes and heart of shrimp challenged with . Overexpression of in shrimp caused the total bacterial number to decrease significantly and knockdown of increased the bacterial number obviously, with a consequent decline in shrimp survival. These results confirmed the antibacterial function of RhoA in shrimp. Further study showed that rate of phagocytosis of hemocytes was decreased in -knockdown shrimp. Interestingly, we observed that RhoA was translocated onto the hemocyte membrane at 1 h post . challenge. The expression levels of the β-integrin-mediated phagocytosis markers and declined significantly after knockdown of . These results suggested that the antibacterial function of RhoA was related to β-integrin-mediated phagocytosis in shrimp. Our previous study identified that a C-type lectin, hFcLec4, initiated β-integrin mediated phagocytosis after bacterial infection. Thus, knockdown of hFcLec4 and β-integrin was performed. The results showed that the translocation of RhoA from the cytoplasm to membrane was inhibited and the expression level of RhoA was decreased, suggesting that RhoA participated in hFcLec4-integrin mediated phagocytosis. Therefore, our study identified a new hFcLec4-integrin-RhoA dependent phagocytosis against bacterial infection in shrimp.