Heterotrimeric G proteins containing Gβ1γ2 subunits exhibit subtype-specific mobility differences in live cells

Heterotrimeric G proteins are key signal transducers in all eukaryotic cells. Anchored to the inner leaflet of the plasma membrane, they transmit and amplify extracellular chemical and physical signals downstream of G protein-coupled receptors. Despite numerous available studies, many biophysical aspects that regulate G protein signaling, including membrane mobility, remain poorly understood. Here, using single-molecule imaging, we show that different subtypes of heterotrimeric G proteins containing Gβ ₁ γ ₂ subunits exhibit high diversity in their membrane mobility. We demonstrate that the nature of the Gα subunit plays a major role in defining the mobility of such heterotrimers. Our results indicate that heterotrimers containing Gα ₁₂ and Gα ₁₃ subunits exhibit markedly reduced mobility compared to those containing Gα _i/o and Gα _s subunits. These findings identify subtype-specific lateral membrane mobility of G proteins as a factor that can affect their signaling dynamics in living cells.