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- Title
Turnover of bis-diphosphoinositol tetrakisphosphate in a smooth muscle cell line is regulated by ß<sub>2</sub>-adrenergic receptors through a cAMP-mediated, A-kinase-independent mechanism.
- Authors
Safrany, Stephen T.; Shears, Stephen B.
- Abstract
Bisdiphosphoinositol tetrakisphosphate ([PP]2-InsP4 or ‘InsP8’) is a ‘high-energy’ inositol phosphate; we report that its metabolism is receptor-regulated in DDT1 MF-2 smooth muscle cells. This conclusion arose by pursuing the mechanism by which F decreased cellular levels of [PP]2-InsP4 up to 70%. A similar effect was induced by elevating cyclic nucleotide levels, either with IBMX or by application of either Bt2cAMP (EC50 = 14.7 μM), Bt2cGMP (EC50 = 7.9 μM) or isoproterenol (EC50 = 0.4 nM). Isoproterenol (1 μM) decreased [PP]2-InsP4 levels 25% by 5 min, and 71% by 60 min. This novel, agonist-mediated regulation of [PP]2-InsP4 turnover was very specific; isoproterenol did not decrease the cellular levels of either inositol pentakisphosphate, inositol hexakisphosphate or other diphosphorylated inositol polyphosphates. Bradykinin, which activated phospholipase C, did not affect [PP]2-InsP4 levels. Regulation of [PP]2-InsP4 turnover by both isoproterenol and cell-permeant cyclic nucleotides was unaffected by inhibitors of protein kinases A and G. The effectiveness of the kinase inhibitors was confirmed by their ability to block phosphorylation of the cAMP response element-binding protein. Our results indicate a new signaling action of cAMP, and furnish an important focus for future research into the roles of diphosphorylated inositol phosphates in signal transduction.
- Subjects
INOSITOL phosphates; METABOLISM; SMOOTH muscle; CYCLIC nucleotides; ISOPROTERENOL; PHOSPHOLIPASE C; PHOSPHORYLATION; CELLULAR signal transduction
- Publication
EMBO Journal, 1998, Vol 17, Issue 6, p1710
- ISSN
0261-4189
- Publication type
Article
- DOI
10.1093/emboj/17.6.1710