It has become increasingly apparent that the stimulated labeling of phosphatidate (PA) and phosphatidylinositol (PI), upon addition of muscarinic ligands to various tissues, is a reflection of lipid turnover in which the receptor-ligand interaction initiates the breakdown of inositide, especially of phosphatidylinositol 4,5 bisphosphate (PIP2). Inositol trisphosphate (IP3), the product of PIP2 cleavage, has been implicated as a second messenger. Our laboratory is particularly interested in the CNS muscarinic receptor in nerve endings (synaptosomes). We have chosen as auxiliary models the murine neuroblastoma cell (clone N1E-115) and the avian salt gland (duck), since like the nerve ending preparation, the cells do not engage in exocytotic secretion. In addition to the advantages of studying intact cells which seemingly share a common mechanism, there is the useful technical property that in these cells lipid changes associated with the receptor-ligand response will easily be distinguished from the more gross effects seen in lipid metabolism following exocytotic secretion seen in most other models. Parameters of interest associated with the intracellular response include changes in cyclin GMP and Ca2+. In addition, we hope to reconstruct a broken cell preparation in which the receptor-ligand interaction will directly affect the action of a phospholipase C-type phosphodiesterase which breaks down PIP2 to IP3 and diacylglycerol. A prior suggestion that PIP2 cleavage yields a 1,2-cyclic IP3 derivative (cIP3) will be reinvestigated in view of its possible messenger function. These experiments have relevance, not only in that they may constitute a novel second messenger system, but also that they may explain the therapeutic role of Li+ in affective disorders, since low concentrations of Li+ are known to affect the breakdown of intracellular inositol monophosphate produced from the degradation of the inositol lipids.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS015413-10
Application #
3396221
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1979-07-01
Project End
1990-06-30
Budget Start
1988-07-01
Budget End
1989-06-30
Support Year
10
Fiscal Year
1988
Total Cost
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Type
Schools of Medicine
DUNS #
791277940
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Heacock, A M; Seguin, E B; Agranoff, B W (1993) Measurement of receptor-activated phosphoinositide turnover in rat brain: nonequivalence of inositol phosphate and CDP-diacylglycerol formation. J Neurochem 60:1087-92
Stubbs Jr, E B; Walker, B A; Owens, C A et al. (1992) Formyl peptide stimulates and ATP gamma S potentiates [3H]cytidine 5'-diphosphate diglyceride accumulation in human neutrophils. J Immunol 148:2242-7
Heacock, A M; Seguin, E B; Agranoff, B W (1990) Developmental and regional studies of the metabolism of inositol 1,4,5-trisphosphate in rat brain. J Neurochem 54:1405-11
Fisher, S K; Heacock, A M; Seguin, E B et al. (1990) Polyphosphoinositides are the major source of inositol phosphates in carbamoylcholine-stimulated SK-N-SH neuroblastoma cells. Mol Pharmacol 38:54-63
Chiba, T; Fisher, S K; Agranoff, B W et al. (1989) Autoregulation of muscarinic and gastrin receptors on gastric parietal cells. Am J Physiol 256:G356-63
Chiba, T; Fisher, S K; Park, J et al. (1988) Carbamoylcholine and gastrin induce inositol lipid turnover in canine gastric parietal cells. Am J Physiol 255:G99-105
Agranoff, B W; Fisher, S K; Heacock, A M et al. (1988) The phosphoinositide-linked CNS muscarinic receptor. Adv Exp Med Biol 236:195-215
Heacock, A M; Fisher, S K; Agranoff, B W (1987) Enhanced coupling of neonatal muscarinic receptors in rat brain to phosphoinositide turnover. J Neurochem 48:1904-11
Fisher, S K; Agranoff, B W (1987) Receptor activation and inositol lipid hydrolysis in neural tissues. J Neurochem 48:999-1017
Fisher, S K; Snider, R M (1987) Differential receptor occupancy requirements for muscarinic cholinergic stimulation of inositol lipid hydrolysis in brain and in neuroblastomas. Mol Pharmacol 32:81-90

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