Single-molecule localization microscopy as a tool to quantify di/oligomerization of receptor tyrosine kinases and G protein-coupled receptors

Dimerization and oligomerization of membrane receptors, including G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) are fundamental for regulating cell signaling and diversifying downstream responses to mediate range of physiological processes. Receptor di/oligomers play roles in diverse facets of receptor function. Changes in receptor di/oligomers have been implicated in a range of diseases, therefore better understanding of the specific composition and interactions between receptors in complexes is essential, especially for the development of di/oligomer specific drugs. Previously, different optical microscopy approaches, and proximity based biophysical assays have been used to demonstrate di/oligomerization of membrane receptors. However, in recent years, single-molecule super-resolution microscopy techniques have allowed researchers to quantify and uncover the precise dynamics and stoichiometry of specific receptor complexes. This allows the organization of membrane protein receptors to be mapped across the plasma membrane, to explore effects of factors such as ligands, effectors, membrane environment and therapeutic agents. Quantification of receptor complexes is required to better understand the intricate balance of distinct receptor complexes in cells. In this brief review, we provide an overview of single-molecule approaches for quantification of receptor di/oligomerization. We will discuss the techniques commonly employed to study membrane receptor di/oligomerization and their relative advantages and limitations.