CONVERSION OF G-PROTEIN SPECIFICITY OF INSULIN-LIKE GROWTH FACTOR-II MANNOSE 6-PHOSPHATE RECEPTOR BY EXCHANGING OF A SHORT REGION WITH BETA-ADRENERGIC-RECEPTOR

The 14-residue peptide (peptide 14) corresponding to Arg2410-Lys2423 o f the insulin-like growth factor II receptor (IGF-IIR) can activate th e adenylate cyclase-inhibitor guanine nucleotide-binding protein G(i), and the 15-residue betaIII-2 peptide Arg259-Lys273 of the beta2-adren ergic receptor (beta2AR) can activate the stimulatory protein G(s). In phospholipid vesicles, IGF-IIR and beta2AR activate G(i) and G(s) in response to IGF-II and isoproterenol, respectively. We constructed a c himeric IGF-II receptor (betaIII-2/IGF-IIR) by converting its native p eptide 14 sequence to the betaIII-2 sequence. In cells expressing beta III-2/IGF-IIR, membrane adenylate cyclase activity markedly increased without IGF-II and was further promoted by IGF-II. This was verified b y measuring chloramphenicol acetyltransferase (CAT) activity in betaII I-2/IGF-IIR cells with cotransfection of a cAMP response element-CAT c onstruct. This study shows not only the conversion of G-protein specif icity of a receptor from G(i) to G(s) but also the simulation of G pro tein-coupled receptor signals by using a short receptor region and int act cells. These findings indicate that the G protein-activation signa ls are interchangeable, self-determined structural motifs that functio n in the setting of either a single-spanning or multiple-spanning rece ptor.