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Abstract

Many bacteria employ a type III secretion system (T3SS) injectisome to
translocate proteins into eukaryotic host cells. Although the T3SS can
efficiently export heterologous cargo proteins, a lack of target cell
specificity currently limits its application in biotechnology and
healthcare. In this study, we exploit the dynamic nature of the T3SS to
govern its activity. Using optogenetic interaction switches to control
the availability of the dynamic cytosolic T3SS component SctQ,
T3SS-dependent effector secretion can be regulated by light. The
resulting system, LITESEC-T3SS (Light-induced translocation of effectors
through sequestration of endogenous components of the T3SS), allows
rapid, specific, and reversible activation or deactivation of the T3SS
upon illumination. We demonstrate the light-regulated translocation of
heterologous reporter proteins, and induction of apoptosis in cultured
eukaryotic cells. LITESEC-T3SS constitutes a new method to control
protein secretion and translocation into eukaryotic host cells with
unparalleled spatial and temporal resolution. The type III secretion
system (T3SS) of bacteria can be used to inject cargo into eukaryotic
cells but its lack of target specificity is a disadvantage. Here the
authors place the T3SS under the regulation of light by engineering
optogenetic switches into the dynamic cytosolic T3SS component SctQ.