Analysis of stimulation-G protein subunit coupling by using active insulin-like growth factor II receptor peptide.

Abstract

The peptide Arg2"'0-Lys2423 (peptide 14) of the human insulin-like growth factor il/mannose 6-phosphate receptor directly activates G12, a GTP-bnding protein (G protein), and is responsible for G1.2 activating function of the receptor. To characterize the basic mechanism of couplings between receptor stimulation and subunits of G proteins, we constructed a system consisting of peptide 14 and a and Ay subunits of G1.2 in aqueous solution. Peptide 14 significantly increased the rate of guanosine 5'-[y-thio]triphosphate binding to isolated G-2,, from 0.50 ± 0.03 (mean ± SE; n = 3) to 0.75 ± 0.02 mol per mol of G1.2.. per 3 min (n = 3) at 100 FzM. In this system, Gpy dose dependently potentiated the peptide 14 action on Gi12; and Gp.-induced potentiation reached saturation at a concentration comparable to that ofG. u. An antibody specific for the C-terminal decapeptide of G. u reduced peptide 14-stimulated GDP release from Gi-2 to the basal level. This simplified system indicates that (i) the receptor sequence directly interacts with isolated Gi1u at its C-terminal region and (is) Gpy potentiates the stimulation-Ga coupling in a stoichiometrical manner for Ga.Guanine nucleotide-binding proteins (G proteins) are functional dimers consisting of a (Ga) and fBy (Gpy) subunits, which carry receptor-generated signals to membrane effectors (1). Whereas in an unstimulated state, G proteins are afry forms bound to GDP, upon receptor stimulation they dissociate to GTP-bound Ga and nucleotide-free Go,, leading to the activation of effectors. Studies elucidating the effects of pertussis toxin on transducin and G, proteins (2) and studies using S49 cell unc mutant of Gsa (3, 4) and chimeric G5-Gj proteins (5, 6) have indicated that the extreme C-terminal

Leu27IGF2 plays an opposite role to IGF1 to induce H9c2 cardiomyoblast cell apoptosis via Gαq signaling

“…Several investigations have shown that IGF2R interacts with the Ga protein to affect cell behaviors by activating specific intracellular signaling cascades (Okamoto & Nishimoto 1991, McKinnon et al 2001, Hawkes et al 2006. Conversely, in mouse L-cell membranes and phospholipid vesicles, IGF2R is not able to interact with a small G-protein (Korner et al 1995).…”

“…Conversely, IGF2 to IGF1R or InR triggers a series of mitotic signaling cascades that function in cell development, growth, survival, and metabolic effect regulation ( Jones & Clemmons 1995, Diaz et al 2007, Blum & Baumrucker 2008. Recent evidence has shown that in spite of degrading IGF2 in the lysosome, IGF2R may spark intracellular signaling cascades in cell behavior regulation (Okamoto & Nishimoto 1991, McKinnon et al 2001, Hawkes et al 2006, but the function of IGF2R in signaling transduction in the heart remains unclear.…”

Single Transmembrane Spanning Heterotrimeric G Protein-Coupled Receptors and Their Signaling Cascades

“…Thus, in Balb/c3T3 or Chinese hamster ovary cells, IGF-II by stimulating its receptor has been shown to increase calcium influx via activation of Gi (Nishimoto et al, 1987a;Matsunaga et al, 1988;Okamoto et al, 1991a). The coupling of the IGF-II receptor to Gi was also demonstrated in reconstituted phospholipid vesicles (Nishimoto et al, 1989;Murayama et al, 1990;Okamoto et al, 1990a) and a region comprising 14 amino acids within the IGF-II receptor was identified as the G protein-activating sequence (Okamoto et al, 1990a;Okamoto and Nishimoto, 1991). Indeed, substitution of amino acids within this region changes the specificity of the coupling between IGF-II receptor and G proteins .…”

IGF-II/mannose-6-phosphate receptor signaling induced cell hypertrophy and atrial natriuretic peptide/BNP expression via Gαq interaction and protein kinase C-α/CaMKII activation in H9c2 cardiomyoblast cells

“…Moreover, the existence of a putative G-protein-binding site within the cytoplasmic domain of the IGF2R suggests that IGF-II may regulate small G proteins that activate signaling pathways through IGF2R (Nishimoto et al 1989, Murayama et al 1990, Okamoto & Nishimoto 1991, Ikezu et al 1995. Based on these findings, we propose that the binding of IGF-II to IGF2R may trigger an intracellular signaling cascade response to cardiac hypertrophy and that the role of this signaling is completely different from that of IGF1R-derived physiological hypertrophy.…”