title: Influence of inositol 1,4,5-trisphosphate and guanine nucleotides on intracellular calcium release within the N1E-115 neuronal cell line.
abstract: The Ca2+ accumulating properties of a nonmitochondrial intracellular organelle within cultured N1E-115 neuroblastoma cells containing an (ATP + Mg2+)-dependent Ca2+ pump were recently described in detail (Gill, D. L., and Chueh, S. H. (1985) J. Biol. Chem. 260, 9289-9297). Using both saponin-permeabilized N1E-115 cells and microsomal membranes from cells, this report describes the effectiveness of both inositol 1,4,5-trisphosphate (IP3) and guanine nucleotides in mediating Ca2+ release from this internal organelle, believed to be endoplasmic reticulum. Using permeabilized N1E-115 cells, 2 microM IP3 effects rapid release (t1/2 less than 20 s) of approximately 40% of accumulated Ca2+ releasable with 5 microM A23187. Half-maximal Ca2+ release occurs with 0.5 microM IP3, and maximal release with 3 microM IP3. Using a frozen microsomal membrane fraction isolated from lysed cells, 2 microM IP3 rapidly releases (t1/2 less than 30 s) 10-20% of A23187-releasable Ca2+ accumulated within nonmitochondrial Ca2+-pumping vesicles, although only in the presence of 3% polyethylene glycol (PEG). 10 microM GTP, but not guanosine 5'-(beta, gamma-imido)triphosphate (GMPPNP), increases the extent of release in the presence of IP3. Importantly, however, GTP alone induces a substantial release of Ca2+ (up to 40% of releasable Ca2+) with a t1/2 value (60-90 s) slightly longer than that for IP3. The effects of IP3 and GTP are approximately additive, and both effects require 3% PEG. Half-maximal Ca2+ release occurs with 1 microM GTP, with maximal release at 3-5 microM GTP; 20 microM GMPPNP has no effect on release and only slightly inhibits 5 microM GTP; 20 microM GDP promotes full release, but only after a 90-s lag, and initially inhibits the action of 5 microM GTP. Using permeabilized N1E-115 cells, 5 microM GTP with 3% PEG releases greater than 50% of releasable Ca2+; without PEG, GTP still mediates approximately 30% release of Ca2+ from cells. Neither IP3, GTP, or both together (with or without PEG) effects release of Ca2+ accumulated within synaptic plasma membrane vesicles. The profound effectiveness of GTP on Ca2+ release has important implications for intracellular Ca2+ regulation and is probably related to Ca2+ release mediated by IP3.
authors.forename: T
authors.initials: T
authors.lastname: Ueda
authors.forename: S H
authors.initials: SH
authors.lastname: Chueh
authors.forename: M W
authors.initials: MW
authors.lastname: Noel
authors.forename: D L
authors.initials: DL
authors.lastname: Gill
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects; D006150:Guanine Nucleotides / Q000494:pharmacology*; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D051379:Mice; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009447:Neuroblastoma / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D012503:Saponins / Q000494:pharmacology; D013403:Sugar Phosphates / Q000494:pharmacology*
chemical_list: D006150:Guanine Nucleotides; D007295:Inositol Phosphates; D012503:Saponins; D013403:Sugar Phosphates; D006165:Guanylyl Imidodiphosphate; D000001:Calcimycin; D011092:Polyethylene Glycols; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D002118:Calcium