SSTR2/SSTR3 exhibit heterodimerization at cell surface A (i). Membrane extracts prepared from cotransfected cells were immunoprecipitated with HA antibody (SSTR3) and probed for SSTR2 as described in Materials and methods. The receptor-specific band for the heteromeric complex of SSTR2/SSTR3 was detected at the expected size of ~117 kDa. A (ii-iii). The membranes were reprobed to detect SSTR3 and SSTR2 monomers, respectively. A (iv-vi). The specificity of the heterodimer was confirmed in HEK-293 cells and monotransfectants expressing SSTR2 and SSTR3 B. Cotransfected cells were treated with SST (1, 50 nM and 1 μM), L-779976 (10 and 100 nM) and L-796778 (25 and 50 nM) or in combination for 10 min at 37°C and subjected to microscopic Pb-FRET analysis. Histogram represents relative FRET efficiency of 14.9% in control suggesting the presence of SSTR2/SSTR3 heterodimers. However, the heterodimer is stable upon treatment with SST and receptor-specific agonists, albeit with decreased relative FRET efficiency. Results are expressed as mean ± S.D of three independent experiments.