Nanoscale Distribution of Transforming Growth Factor Receptor on Post-Golgi Vesicle Revealed by Super-resolution Microscopy.

Transforming growth factor-β (TGF-β) type II receptor (TβRII) plays a critical role in the initiation of TGF-β signaling pathway; therefore, the study of its synthesis and transport processes is of great important. In this work, we achieved super-resolution imaging of a new type of TβRII-containing post-Golgi vesicle by our home-built stimulated emission depletion (STED) microscope. We visualized the ring-shaped structure of these vesicles containing newly synthesized TβRII in the cytoplasm and characterized their size distribution from 300 to 1000 nm. These vesicles could be swollen by chloroquine treatment. Further investigation revealed that TβRII formed clusters on the outer ring of the post-Golgi vesicles. This study offers new information on the intracellular transportation of TGF-β receptors for better understanding its signaling process.