Question

You wish to experimentally demonstrate how the GABA B receptors are associated with the membrane. Describe three experimental conditions you might test and discuss what the expected results would indicate.

Answer 1

GABA B receptors are heterodimers composed of GABA B1 and GABA B2 linking their C-termini and facing N-termini towards the Extracellular matrix . It means N-terminal act as a receptor site , tranembrane domain is responsible for integration into membrane and heterodimerization and C-terminal is important for recruitment of adapter proteins and downstream signalling . So to demonstrate the association of GABAB receptors with the membrane we can perform flourescence microscopy using neuronal cultures .

Take 3 neuronal cell lines , one with mutated N-terminal fused to GFP , 2nd with mutated transmembrane domain fused with GFP and 3rd cell line with mutated C-terminal fused with GFP . Now analyze the cell lines under flourescence microscope .

Cell lines with mutated N-terminal will have GABA receptors in their membrane ( so N-terminal not associated with membrane ) .

Cell line with mutated or deleted transmembrane domain will have GABAB receptor in cytoplasm but not found in membrane so this domain is responsible for integration into membrane .

Cell line with muated C- terminal Domain will have GABA B receptors in the cell membrane so it can be deciphered that this domain is also not important for membrane integration.