title: Effect of MANT-nucleotides on L-type calcium currents in murine cardiomyocytes.
abstract: Membranous adenylyl cyclases play a major role in G-protein-coupled receptor signalling and regulate various cellular responses, such as cardiac contraction. Cardiac apoptosis and development of cardiac dysfunction is prevented in mice lacking AC 5, a predominant isoform in the heart. In the search for a potent and selective AC 5 inhibitor, we recently identified 2'(3')-methylanthraniloyl-inosine-5'-triphosphate(MANT-ITP) as the most potent AC 5 inhibitor with a K ( i ) of 13 nM. Therefore, AC inhibition of MANT-ITP was assessed in ventricular cardiomyocytes and compared to three other MANT-nucleotides to evaluate its effect on cardiac signalling. Basal and isoproterenol-induced L-type calcium currents (I (Ca,L)) in murine ventricular cardiomyocytes were recorded by whole-cell patch-clamp technique, using four different MANT-nucleotides. The effects of the MANT-nucleotides on I (Ca,L) were unexpectedly complex. All MANT-nucleotides exhibited an inhibitory effect on basal I (Ca,L). Additionally, several MANT-nucleotides, i.e., MANT-ITPγS, MANT-ATP, and MANT-ITP, caused a strong initial increase in basal I (Ca,L) within the first 2.5 min that appeared to be unrelated to AC 5 inhibition. However, we detected a significant reduction on isoproterenol-induced I (Ca,L) with MANT-ITP, supporting the notion that AC 5 plays an important role in agonist-stimulated activation of I (Ca,L). Collectively, MANT-nucleotides are useful tools for the characterization of recombinant ACs, for fluorescence studies and crystallography, but in intact cardiomyocytes, caution must be exerted since MANT-nucleotides apparently possess additional effects than AC 5 inhibition, limiting their usefulness as tools for intact cell studies.
authors.affiliation: Department of Pharmacology and Toxicology, University of Regensburg, Regensburg, Germany.
authors.forename: Melanie
authors.initials: M
authors.lastname: Hübner
authors.forename: Sara
authors.initials: S
authors.lastname: Dizayee
authors.forename: Jan
authors.initials: J
authors.lastname: Matthes
authors.forename: Roland
authors.initials: R
authors.lastname: Seifert
authors.forename: Stefan
authors.initials: S
authors.lastname: Herzig
mesh_terms: D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D020746:Calcium Channels, L-Type / Q000187:drug effects* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007292:Inosine Nucleotides / Q000494:pharmacology*; D007293:Inosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism
chemical_list: D000067956:Adenylyl Cyclase Inhibitors; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D007292:Inosine Nucleotides; D043562:Receptors, G-Protein-Coupled; D007293:Inosine Triphosphate; D007545:Isoproterenol