These studies are directed toward the regulatory protein (Gs) of adenylate cyclase. Adenylate cyclase is composed of at least three protein components: 1) hormone receptors, 2) a catalytic moiety, and 3) a regulatory protein (Gs) that binds guanine nucleotides. Gs functions to modulate agonist-occupied receptor affinity, and to couple hormone-receptor complexes to the catalytic unit. Gs thus regulates the hormonal activation of adenylate cyclase. Strong evidence supports a defect in adenylate cyclase as the cause of hormone resistance in pseudohypoparathyroidism (PHP), a metabolic disorder characterized by resistance of the target organs bone and kidney to the actions of parathyroid hormone. Recently, a deficiency in Gs activity has been described in cell membranes from many subjects with PHP. Unlike tissue-specific hormone receptors, Gs is similar in all cells, and deficient Gs activity is implicated as the cause of decreased synthesis of cAMP and hormone resistance in diverse tissues in many patients with PHP. For these reasons it is both interesting and important to study further the structure and mechanism(s) of action of Gs. These studies propose 1) to purify Gs from human erythrocyte membranes by a novel approach: cholera toxin catalyzes the covalent ADP-ribosylation of a 42,000-dalton subunit of Gs; T4 RNA ligase can attach polyadenylate specifically to the ADP-ribosylated Gs peptide and oligo- d(T) affinity chromatography will be used to resolve the modified Gs from other membrane proteins. 2) to use the purified (modified) Gs peptide in the production of reagent antibodies to Gs; 3) to use these antibodies in the development and application of methods for assessing the immunologic and biologic properties of Gs from erythrocyte membranes of subjects with PHP; 4) to determine the applicability of the oligo d(T) chromatography methods to the resolution of other proteins (e.g., transducin, and the inhibitory guanine nucleotide binding protein) that are specific ADP-ribose substrates. These studies may help to elucidate molecular lesions(s) in Gs which impair adenylate cyclase hormone responsiveness, and may provide further insight into hormone resistance in PHP. Ultimately, it is hoped that an immunologic approach to the study of the mechanism(s) of action of Gs will help identify the domain or subunits of Gs that regulate the complex interactions of the regulatory protein with hormone receptors and the catalytic unit.
| Sanchez, Janine; Perera, Erasmo; Jan de Beur, Suzanne et al. (2011) Madelung-like deformity in pseudohypoparathyroidism type 1b. J Clin Endocrinol Metab 96:E1507-11 |
| Lietman, Steven A; Germain-Lee, Emily L; Levine, Michael A (2010) Hypercalcemia in children and adolescents. Curr Opin Pediatr 22:508-15 |
| Lietman, Steven A; Yin, Lihong; Levine, Michael A (2010) SH3BP2 mutations potentiate osteoclastogenesis via PLC?. J Orthop Res 28:1425-30 |
| Lietman, Steven A; Yin, Lihong; Levine, Michael A (2008) SH3BP2 is an activator of NFAT activity and osteoclastogenesis. Biochem Biophys Res Commun 371:644-8 |
| Lietman, Steven A; Goldfarb, James; Desai, Nina et al. (2008) Preimplantation genetic diagnosis for severe albright hereditary osteodystrophy. J Clin Endocrinol Metab 93:901-4 |
| Germain-Lee, Emily L (2006) Short stature, obesity, and growth hormone deficiency in pseudohypoparathyroidism type 1a. Pediatr Endocrinol Rev 3 Suppl 2:318-27 |
| Lietman, Steven A; Ding, Changlin; Levine, Michael A (2005) A highly sensitive polymerase chain reaction method detects activating mutations of the GNAS gene in peripheral blood cells in McCune-Albright syndrome or isolated fibrous dysplasia. J Bone Joint Surg Am 87:2489-94 |
| Germain-Lee, Emily L; Schwindinger, William; Crane, Janet L et al. (2005) A mouse model of albright hereditary osteodystrophy generated by targeted disruption of exon 1 of the Gnas gene. Endocrinology 146:4697-709 |
| Lietman, Steven A; Ding, Changlin; Cooke, David W et al. (2005) Reduction in Gsalpha induces osteogenic differentiation in human mesenchymal stem cells. Clin Orthop Relat Res :231-8 |
| Jan de Beur, Suzanne; Ding, Changlin; Germain-Lee, Emily et al. (2003) Discordance between genetic and epigenetic defects in pseudohypoparathyroidism type 1b revealed by inconsistent loss of maternal imprinting at GNAS1. Am J Hum Genet 73:314-22 |
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