Challenges in imaging cell surface receptor clusters

• Ring-like structure of BMP receptor subunit IB revealed by STED microscopy.
• BMP receptor subunits IB and II show different localization patterns.
• BMP receptor II joins BMP receptor IB clusters upon BMP-2 addition.

Super-resolution microscopy offers unique tools for visualizing and resolving cellular structures at the molecular level. STED microscopy is a purely optical method where neither complex sample preparation nor mathematical post-processing is required. Here we present the use of STED microscopy for imaging receptor cluster composition. We use two-color STED to further determine the distribution of two different receptor subunits of the family of receptor serine/threonine kinases in the presence or absence of their ligands. The implications of receptor clustering on the downstream signaling are discussed, and future challenges are also presented.