Dynamic Synthetic Tissue: Controlling Junctional Assembly In Situ with Responsive Protein Switches

ABSTRACT:  Multicellular tissue – the hallmark of all animals – exhibits an exquisite array of morphological structures and material properties. The three-dimensional geometries and physical properties of living tissue are, however, far from static as they can adapt and evolve during developmental programs and when exposed to biological insults. When compared to common organic and inorganic inanimate structures, tissues possess surprising characteristics that offer unique and distinct advantages as materials, including high surface area morphologies, active elasticity, long-distance communication, vectorial transport, and self-repair, for a wide range of applications. By dynamically tuning tissue’s physical properties, synthetic tissue would be a promising new form of smart implants, adhesives, filters, and protective coatings. However, the lack of tools to control tissue properties dynamically with user-defined inputs remains a bottleneck. Here, my lab presents a strategy for controlling synthetic tissue properties by manipulating junctional assembly in situ with responsive protein switches. While individual cells are considered the fundamental unit of tissue, it is the junctions and their cytoskeleton that define macroscopic tissue properties. In this presentation, we describe the use of intramolecular association to engineer protein switches capable of controlling actin binding at cell junctions, which we term controllable actin-binding switch tools (CASTs). After introduction of a stimulus, such as a peptide, small molecule, or light, the conformation of the CAST changes to yield a functional binding partner for actin. With different stimuli, we present switching activity on single minutes, tens of minutes, and hours long timescales. We also describe installing CASTs into native proteins at cell junctions, which enables the dynamic modulation of tissue properties.