Lateral diffusion of TGF-β type I receptor studied by single-molecule imaging

In this report, we investigated the lateral diffusion of transforming growth factor β (TGF-β) type I receptor (TβRI) in living cells by imaging and tracking individual green fluorescent protein tagged TβRI on the cell membrane. We found that when co-expressed with TGF-β type II receptor (TβRII), the mobility of TβRI decreased significantly after TGF-β1 stimulation. However, in the cells that had been depleted of cholesterol with Nystatin or methyl-β-cyclodextrin, the diffusion rate of TβRI was not changed by TGF-β1 treatment. Our observations suggest that membrane lipid-rafts provide an environment that facilitates the association of TβRI and TβRII for cell signaling.