Figure 5.

Functional correlate of the association between GABA_B heterodimers (a) top: Scheme representing the various combinations of subunits co-expressed: ST-GABA_B1(blue) with flag-GAB A_B2KKXX (red, the KKXX motif being the intracellular retention sequence added after the coiled coil domain), with (right) or without (left) the HA-GB1-HD, corresponding to the GB1 subunit deleted of both its extracellular and intracellular domains. Bottom: TR-FRET intensities measured between two ST-GABA_B1 labeled with BG-K and BG-d2 (left (1)), between ST-GABA_B1 labeled with BG-K and HA-GB1-HD labeled with d2-conjugated anti-HA antibodies (middle (2)), and between ST-GABA_B1 labeled with BG-K and flag-GAB A_B2KKXX labeled with d2-conjugated anti-flag antibodies (right (3)), in the absence (white columns) and in the presence (grey columns) of HA-GB1-HD. b) Ca²⁺ signals generated in cells expressing ST-GABA_B1 and flag-GABA_B2KKXX together (filled squares), or in the presence of over-expressed HA-GB1-HD (open squares), or in the presence of over-expressed CD4 (filled circles). Data are means ± sem of triplicate determinations from a typical experiment.