Project Summary Bacteria coordinated autoprocessing secreted secreted central portion of often coordinate secreted virulence factors to fine-tune he host response during infection. These events can include toxins counteracting or amplifying effects of another toxin. Multifunctional- repeats-in toxin (MARTX) toxins are large, secreted proteins that are a unique hybrids of toxins and multi-effector delivery systems. Similar to many bacterial protein toxins, MARTX toxins are from the bacteria and then form a pore in the host cell plasma membrane. t After translocation of the the toxin, an autoprocessing cysteine protease domain is activated by binding inositol hexakisphosphate. CPD-mediated autoproteolysis of the large polypeptide results in release of the “MARTX effectors” to the cell cytosol, where they are free to move throughout the cell to access cellular targets and to exert their toxic effects. There are over 100 different bacterial taxa that carry a MARTX toxin. Across the different species, MARTX They together stoichiometric mechanism together repertoire MARTX could this virulence. Vibrio toxin this signal toxins carry up to 5 effector domains, selected from ten known effector domains. have thus been called “cluster bombs”. An important feature of these toxins is hat all the effectors l inked in a single polypeptide are delivered simultaneously to the same cell at the same time, at equal ratio. While previous studies have employed a reductionist approach to determine the of action of individual effector domains, little is known about how these ffector ctivities delivered may act in synergy to promote infection. Further, due to horizontal gene transfer, the toxin effector can change frequently resulting in novel toxinotypes. Thus, the same effector domain in a different toxins may have context-dependent differences in cell signaling and contribution to virulenc. This impac the pathogenic potential o different clinical isolates, even within the same bacterial species. In renewal study, we will focus on how different combinations of MARTX toxin effectors synergize to enhance The study will focus on how the actin crosslinking MARTX effector found i both Vibrio cholerae and vulnificus can reprogram host cell signaling. We wil further ask how effectors co-delivered on the same then complement or override this signaling program to optimally promote virulence. We will then expand study into other MARTX toxins to explore if other combinations also show context-dependent impact on coordination and pathogenesis. t , e a t f n l