Engineered Networks of Synthetic and Natural Proteins To Control Cell Migration

Mammalian cells reprogrammed with engineered transgenes have the potential to be useful therapeutic platforms because they can support large genetic networks, can be taken from a host or patient, and perform useful functions such as migration and secretion. Successful engineering of mammalian cells will require the development of modules that can perform well-defined, reliable functions, such as directed cell migration toward a chemical or physical signal. One inherently modular cellular pathway is the Ca2+ signaling pathway: protein modules that mobilize and respond to Ca2+ are combined across cell types to create complexity. We have designed a chimera of Rac1, a GTPase that controls cell morphology and migration, and calmodulin (CaM), a Ca2+-responsive protein, to control cell migration. The Rac1-CaM chimera (named RACer) controlled lamellipodia growth in response to Ca2+. RACer was combined with LOVS1K (a previously engineered light-sensitive Ca2+-mobilizing module) and cytokine receptors to create protein networks where blue light and growth factors regulated cell morphology and, thereby, cell migration. To show the generalizability of our design, we created a Cdc42-CaM chimera that controls filopodia growth in response to Ca2+. The insights that have been gained into Ca2+ signaling and cell migration will allow future work to combine engineered protein systems to enable reprogrammed cell sensing of relevant therapeutic targets in vivo.