Human‐Xenopus chimeras of G<sub>s</sub>α reveal a new region important for its activation of adenylyl cyclase

Antonelli, Marcelo; Birnbaumer, Lutz; Allende, Jorge E.; Olate, Juan

doi:10.1016/0014-5793(94)80148-7

Cited by 32 publications

(35 citation statements)

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“…␤␥-subunits versus ␣-subunit), or effector enzymes themselves in the two cell systems (31). In support of the former, studies have shown that the G s -␣ subunit in Xenopus differs substantially from mammalian G s -␣ subunits, suggesting that primary sequence differences between these and other ␣-subunits could underlie the signaling differences we observed (32).…”

Section: Table II Single-alanine Mutations In the C0 Segment Of The Imentioning

confidence: 52%

The N-terminal Region of the Third Intracellular Loop of the Parathyroid Hormone (PTH)/PTH-related Peptide Receptor Is Critical for Coupling to cAMP and Inositol Phosphate/Ca2+ Signal Transduction Pathways

Huang

Chen²,

Pratt

et al. 1996

Journal of Biological Chemistry

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Structural determinants within the parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor that mediate G-protein activation of adenylate cyclase and phospholipase C are unknown. We investigated the role of the N-terminal region of the third intracellular loop of the opossum PTH/PTHrP receptor in coupling to two signal transduction pathways. We mutated residues in this region by tandem-alanine scanning and expressed these mutant receptors in COS-7 cells and/ The parathyroid hormone (PTH) 1 /PTH-related peptide (PTHrP) receptor is a G-protein-coupled receptor (GPCR) that initiates biological responses to PTH, the major endocrine regulator of calcium and skeletal homeostasis, as well as PTHrP, a cytokine essential for normal endochondral bone formation (1-3). The PTH/PTHrP receptor, by primary sequence alignment, belongs to a distinct subfamily of GPCRs, the PTH/ secretin receptor subfamily, which includes receptors for calcitonin, secretin, vasoactive intestinal polypeptide, gastric inhibitory peptide, glucagon, glucagon-like peptide-1 (GLP-1), corticotrophin-releasing factor, pituitary adenylate cyclase-activating polypeptide (PACAP), and the insect diuretic hormone (4). The PTH/PTHrP receptor mediates its actions by coupling to second messenger generation (cAMP, inositol trisphosphate (IP 3 ), and intracellular Ca 2ϩ ), presumably through activation of G s and G q /G q -like proteins (5, 6). The ability to generate second messengers through two signaling pathways is a distinct functional property shared among many members of the PTH/secretin receptor subfamily. Thus far, the structural features responsible for coupling to dual signaling pathways are unknown for any receptor in this subfamily.Structure-function studies of signal transduction properties of GPCRs have been best described for members of the rhodopsin/adrenergic receptor subfamily. Overall, these studies have showed that all intracellular regions of the receptors contribute to the domains which couple to signaling pathways (7,8). Four intracellular regions (the N-and C-terminal portions of the third intracellular (IC-3) loop, the C-terminal portion of the IC-2 loop, and N-terminal portion of the cytoplasmic tail) have all been shown to play a critical role in G-protein coupling (7,8). Direct sequence comparisons of these intracellular regions between members of the PTH/secretin and the rhodopsin/adrenergic receptor subfamilies, however, have revealed no sequence homologies in these regions. This, therefore, excludes the possibility of identifying shared sequence motifs required for G-protein coupling among these receptors.Studies of signal transduction mediated by the PTH/secretin receptor subfamily have, thus far, provided limited information. Studies comparing different splice variants of members of this subfamily suggested that inserted sequences in the Nterminal region of the IC-1 loop and the C-terminal region of the IC-3 loop could play a role in modulating receptor-G-protein coupling. Insertions in the IC-1 domain of receptors for both...

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Section: Table II Single-alanine Mutations In the C0 Segment Of The Imentioning

confidence: 52%

The N-terminal Region of the Third Intracellular Loop of the Parathyroid Hormone (PTH)/PTH-related Peptide Receptor Is Critical for Coupling to cAMP and Inositol Phosphate/Ca2+ Signal Transduction Pathways

Huang

Chen²,

Pratt

et al. 1996

Journal of Biological Chemistry

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“…It is a regulator and activator of the Gsa-subunit function although it is not directly involved with the nucleotide-binding site or the interdomain interface (20). The part within the helical domain that extends from residue 70 to 140 is functionally important for adenylyl cyclase activation, allthough the exact steric sequence is unclear (21). Our patient's mutation in residue Ile-106 is located within this important part of the helical domain.…”

Section: Discussionmentioning

confidence: 80%

Early manifestation of calcinosis cutis in pseudohypoparathyroidism type Ia associated with a novel mutation in the GNAS gene

et al. 2005

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Objective: To clarify the molecular defect for the clinical finding of congenital hypothyroidism combined with the manifestation of calcinosis cutis in infancy. Case report: The male patient presented with moderately elevated blood thyrotropin levels at neonatal screening combined with slightly decreased plasma thyroxine and tri-iodothyronine concentrations, necessitating thyroid hormone substitution 2 weeks after birth. At the age of 7 months calcinosis cutis was seen and the patient underwent further investigation. Typical features of Albright's hereditary osteodystrophy (AHO), including round face, obesity and delayed psychomotor development, were found. Methods and results: Laboratory investigation revealed a resistance to parathyroid hormone (PTH) with highly elevated PTH levels and a reduction in adenylyl cyclase-stimulating protein (Gsa) activity leading to the diagnosis of pseudohypoparathyroidism type Ia (PHP Ia). A novel heterozygous mutation (c364T . G in exon 5, leading to the amino acid substitution Ile-106 ! Ser) was detected in the GNAS gene of the patient. This mutation was not found in the patient's parents, both of whom showed normal Gsa protein activity in erythrocytes and no features of AHO. A de novo mutation is therefore likely. Conclusions: Subcutaneous calcifications in infancy should prompt the clinician to a thorough search for an underlying disease. The possibility of AHO and PHP Ia should be considered in children with hypothyroidism and calcinosis cutis. Systematic reviews regarding the frequency of calcinosis in AHO are warranted.

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“…1) have led to the proposal that it may serve as an effector-recognition domain (8). Various other possible functions for the HD have been postulated, including increasing the affinity of GTP binding (9), acting as a tethered intrinsic GTPase activating protein (10,11), participating in effector recognition (5,12,13), participating in the inactive-active conformational transitions of G␣ (14), and regulating G␣ oligomerization (15,16).…”

mentioning

confidence: 99%

The helical domain of a G protein α subunit is a regulator of its effector

Liu

Northup

1998

Proc. Natl. Acad. Sci. U.S.A.

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The ␣ subunit (G␣) of heterotrimeric G proteins is a major determinant of signaling selectivity. The G␣ structure essentially comprises a GTPase ''Ras-like'' domain (RasD) and a unique ␣-helical domain (HD). We used the vertebrate phototransduction model to test for potential functions of HD and found that the HD of the retinal transducin G␣ (G␣ t ) and the closely related gustducin (G␣ g ), but not G␣ i1 , G␣ s , or G␣ q synergistically enhance guanosine 5-␥[-thio]triphosphate bound G␣ t (G␣ t GTP␥S) activation of bovine rod cGMP phosphodiesterase (PDE). In addition, both HD t and HD g , but not HD i1 , HD s , or HD q attenuate the trypsin-activated PDE. G␣ t GDP and HD t attenuation of trypsin-activated PDE saturate with similar affinities and to an identical 38% of initial activity. These data suggest that interaction of intact G␣ t with the PDE catalytic core may be caused by the HD moiety, and they indicate an independent site(s) for the HD moiety of G␣ t within the PDE catalytic core in addition to the sites for the inhibitory P␥ subunits. The HD moiety of G␣ t GDP is an attenuator of the activated catalytic core, whereas in the presence of activated G␣ t GTP␥S the independently expressed HD t is a potent synergist. Rhodopsin catalysis of G␣ t activation enhances the PDE activation produced by subsaturating levels of G␣ t , suggesting a HDmoiety synergism from a transient conformation of G␣ t . These results establish HD-selective regulations of vertebrate retinal PDE, and they provide evidence demonstrating that the HD is a modulatory domain. We suggest that the HD works in concert with the RasD, enhancing the efficiency of G protein signaling.Heterotrimeric G proteins play a central role in many cellsignaling processes (1). These signaling proteins are members of an extensive superfamily of GTP-binding regulatory proteins characterized by a conserved GTP-binding motif (2). The G proteins differ from the monomeric members of this family in a distinct heterotrimeric quaternary structure, including a ␤␥ subunit dimer complexed with the GTP-binding ␣ subunit (1, 3). The ␣ subunit (G␣) is also distinct from other GTPbinding proteins in the presence of a unique folding motif, the ␣-helical domain (HD), which is characteristic of G proteins (4, 5). Although the ␣ subunit has received the most attention because most of the known structural determinants of receptor-G protein or effector-G protein interactions reside in G␣ proteins (1,3,6), the G␤␥ also is involved in receptor recognition and effector modulation (7). Solutions for the crystal structures of the ␣ subunits of transducin (G t ) and G i revealed that these proteins fold into two essentially separate domains, the conserved GTPase or ''Ras-like'' domain (RasD) and the unique ␣-helical domain (HD) (4, 5). To date, all sites for G␣ subunit interactions with receptors and effectors have been mapped to the RasD and the ␣ amino-terminal sequence (1, 3, 4). Little is known about the corresponding function(s) of the HD. The HD is unique to the heterotr...

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Human‐Xenopus chimeras of G_sα reveal a new region important for its activation of adenylyl cyclase

Cited by 32 publications

References 35 publications

The N-terminal Region of the Third Intracellular Loop of the Parathyroid Hormone (PTH)/PTH-related Peptide Receptor Is Critical for Coupling to cAMP and Inositol Phosphate/Ca2+ Signal Transduction Pathways

The N-terminal Region of the Third Intracellular Loop of the Parathyroid Hormone (PTH)/PTH-related Peptide Receptor Is Critical for Coupling to cAMP and Inositol Phosphate/Ca2+ Signal Transduction Pathways

Early manifestation of calcinosis cutis in pseudohypoparathyroidism type Ia associated with a novel mutation in the GNAS gene

The helical domain of a G protein α subunit is a regulator of its effector

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Human‐Xenopus chimeras of Gsα reveal a new region important for its activation of adenylyl cyclase

Cited by 32 publications

References 35 publications

The N-terminal Region of the Third Intracellular Loop of the Parathyroid Hormone (PTH)/PTH-related Peptide Receptor Is Critical for Coupling to cAMP and Inositol Phosphate/Ca2+ Signal Transduction Pathways

The N-terminal Region of the Third Intracellular Loop of the Parathyroid Hormone (PTH)/PTH-related Peptide Receptor Is Critical for Coupling to cAMP and Inositol Phosphate/Ca2+ Signal Transduction Pathways

Early manifestation of calcinosis cutis in pseudohypoparathyroidism type Ia associated with a novel mutation in the GNAS gene

The helical domain of a G protein α subunit is a regulator of its effector

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Human‐Xenopus chimeras of G_sα reveal a new region important for its activation of adenylyl cyclase