Coupling of GABAB receptor GABAB2 subunit to G proteins: evidence from Xenopus oocyte and baby hamster kidney cell expression system.

Coupling of functional GABAB receptors (GABABR) to G proteins was investigated with an expression system of baby hamster kidney (BHK) cells and Xenopus oocytes. Fluorescence resonance energy transfer (FRET) analysis of BHK cells coexpressing GABAB1a receptor (GB1aR) fused to Cerulean, a brighter variant of cyan fluorescent protein, and GABAB2 receptor (GB2R) fused to Venus, a brighter variant of yellow fluorescent protein, revealed that GB1aR-Cerulean and GB2R-Venus form a heterodimer. The GABABR agonists baclofen and 3-aminopropylphosphonic acid (3-APPA) elicited inward-rectifying K+ currents in a concentration-dependent manner in oocytes expressing GB1aR and GB2R, or GB1aR-Cerulean and GB2R-Venus, together with G protein-activated inward-rectifying K+ channels (GIRKs), but not in oocytes expressing GB1aR alone or GB2R alone together with GIRKs.

A novel long N-terminal isoform of human L-type Ca2+ channel is up-regulated by protein kinase C.

Human L-type voltage-dependent Ca(2+) channels (alpha(1C), or Ca(v)1.2) are up-regulated by protein kinase C (PKC) in native tissues, but in heterologous systems this modulation is absent. In rat and rabbit, alpha(1C) has two N-terminal (NT) isoforms, long and short, with variable initial segments of 46 and 16 amino acids, respectively.