Abstract
Cell-surface receptors play a pivotal role as transducers of extracellular input. Although different cell types express the same receptor, the physiological roles of the receptor are highly dependent on cell type. To understand each role, tactics for cell-specific activation of the target receptor are in high demand. Herein, we developed an orthogonal activation method targeting metabotropic glutamate receptor 1 (mGlu1), a G-protein coupled receptor. In this method, direct activation via coordination-based chemogenetics (dA-CBC) was adopted, where activation of mGlu1 was artificially induced by a protein conformational change in response to the coordination of a metal ion or metal-ion complex. Our structure-based protein design and screening approach identified mGlu1 mutants that were directly activated by the coordination of Cu2+ or Zn2+, in addition to our previous Pd-complex-sensitive mGlu1 mutant. Notably, the activation of the mutants was mutually orthogonal, resulting in cell-type selective activation in a model system using HEK293 cells.
Highlights
The same receptor is found in different cells or tissues, yet the physiological roles of each different receptor are highly dependent on the cell or tissue type (Vassilatis et al, 2003)
We have developed a chemogenetic method termed “direct activation via coordination-based chemogenetics” targeting metabotropic glutamate receptor 1 by focusing on the structural changes upon glutamate binding (Kiyonaka et al, 2016; Kubota et al, 2019; Ojima et al, 2021). mGlu1, which belongs to class C G-protein coupled receptors (GPCRs), is composed of an extracellular ligand-binding domain called Venus Flytrap (VFT) domain, a cysteine rich domain (CRD), and a 7-transmembrane domain (7TMD) (Figure 1A)
We previously reported that the conformational change of the VFT domain from an open to closed conformation by Pd caused the selective activation of the mGlu1 (N264H) mutant
Summary
Several hundred types of receptors are expressed on the cell surfaces of mammals, each of which plays essential roles in transmitting extracellular information into cells. The same receptor is found in different cells or tissues, yet the physiological roles of each different receptor are highly dependent on the cell or tissue type (Vassilatis et al, 2003). Chemogenetics, a process in which proteins of interest (POIs) are genetically engineered to selectively interact with designed chemicals, is a potential approach for cell-specific activation of target receptors (Islam, 2015; Atasoy and Sternson, 2018; Tsai et al, 2021). Some representative examples of chemogenetics include the bump-and-hole approach (Bishop et al, 2000; Knight and Shokat, 2007), ligand-induced stabilization (i.e., chemical rescue) (Pratt et al, 2007), and chemically induced dimerization (Schreiber, 1998). Another well-known example of chemogenetic activation of Orthogonal Activation of mGlu
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