The overall objective to this proposal is to characterize, in a differentiated mammalian cell type, a newly recognized biochemical pathway for regulation of intracellular Ca2+ and to establish the functional significance of this signalling system in endocrine secretory cells. In the sea urchin egg, it has been established that a novel metabolite of NAD+, called cyclic ADP-ribose (cADPR), releases intracellular Ca2+ from a non-Ins (1,4,5)P3-sensitive pool with a potency that is comparable to that of IP3. We have demonstrated that a cADPR-like molecule is synthesized by several rat tissues including the pituitary gland. We have also shown, for the first time, that authentic cADPR releases sequestered Ca2+ by a non IP3 dependent mechanism in permeabilized rat pituitary cells of the GH4C1 strain. Based on these findings, we propose to test the hypothesis that cADPR is a functional mediator of cytosolic Ca2+ regulation in mammalian pituitary cells. There are 4 Specific Aims. 1. To prove that authentic cADPR is synthesized by intact pituitary cells. 2. To investigate the control of cellular cADPR concentrations in response to secretagogue agonist hormones. 3. To establish the functional role of cADPR in regulation of [Ca2+}i and hormone secretion. And 4. To determine the biochemical mechanism of action of cADPR. The results of these experiments will contribute fundamental new knowledge on the complex regulation of intracellular Ca2+ in mammalian cells which is not fully explained by the inositol lipid pathway or by alterations in plasma membrane Ca2+ fluxes. Such understanding is important because [Ca2+]i plays such a pivotal role in cellular secretion, DNA synthesis, cell division, motility, expression of specific genes (e.g., prolactin), and regulation of a number of critical intracellular enzymes. Understanding further this new limb of intracellular Ca2+ regulation should prove insightful in designing new pharmacological approaches to modulation of specific cell functions.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK011011-27
Application #
2136665
Study Section
Biochemical Endocrinology Study Section (BCE)
Project Start
1975-09-01
Project End
1996-03-31
Budget Start
1994-04-01
Budget End
1995-03-31
Support Year
27
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Harvard University
Department
Pharmacology
Type
Schools of Public Health
DUNS #
082359691
City
Boston
State
MA
Country
United States
Zip Code
02115
Chen, F; Selinger, Z; Marks, P et al. (2001) Production and characterization of an antiserum which recognizes the native receptor for thyrotropin-releasing hormone. Biochem Biophys Res Commun 285:742-50
Chen, X; Tang, S; Tashjian Jr, A H (2000) Novel action of pituitary adenylate cyclase-activating polypeptide. Stimulation of extracellular acidification in rat pituitary GH4C1 cells. Cell Signal 12:255-63
Chen, L; Hoeger, C; Rivier, J et al. (1999) Structural basis for the binding specificity of a SSTR1-selective analog of somatostatin. Biochem Biophys Res Commun 258:689-94
Chen, L; Tashjian Jr, A H (1999) Identification of distinct signalling pathways for somatostatin receptors SSTR1 and SSTR2 as revealed by microphysiometry. Cell Signal 11:499-505
Petrou, C; Tashjian Jr, A H (1998) The thyrotropin-releasing hormone-receptor complex and G11alpha are both internalised into clathrin-coated vesicles. Cell Signal 10:553-9
Han, B; Tashjian Jr, A H (1998) User-friendly and versatile software for analysis of protein hydrophobicity. Biotechniques 25:256-9, 262-3
Chen, L; Fitzpatrick, V D; Vandlen, R L et al. (1997) Both overlapping and distinct signaling pathways for somatostatin receptor subtypes SSTR1 and SSTR2 in pituitary cells. J Biol Chem 272:18666-72
Petrou, C; Chen, L; Tashjian Jr, A H (1997) A receptor-G protein coupling-independent step in the internalization of the thyrotropin-releasing hormone receptor. J Biol Chem 272:2326-33
Xu, Y; Gilbert, B A; Rando, R R et al. (1996) Inhibition of capacitative Ca2+ entry into cells by farnesylcysteine analogs. Mol Pharmacol 50:1495-501
Han, B; Tashjian Jr, A H (1995) Identification of Asn289 as a ligand binding site in the rat thyrotropin-releasing hormone (THR) receptor as determined by complementary modifications in the ligand and receptor: a new model for THR binding. Biochemistry 34:13412-22

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