title: IP3-induced cytosolic and nuclear Ca2+ signals in HL-1 atrial myocytes: possible role of IP3 receptor subtypes.
abstract: HL-1 cells are the adult cardiac cell lines available that continuously divide while maintaining an atrial phenotype. Here we examined the expression and localization of inositol 1,4,5-trisphosphate receptor (IP(3)R) subtypes, and investigated how pattern of IP(3)-induced subcellular local Ca(2+) signaling is encoded by multiple IP(3)R subtypes in HL-1 cells. The type 1 IP(3)R (IP(3)R1) was expressed in the perinucleus with a diffuse pattern and the type 2 IP(3)R (IP(3)R2) was expressed in the cytosol with a punctate distribution. Extracellular ATP (1 mM) elicited transient intracellular Ca(2+) releases accompanied by a Ca(2+) oscillation, which was eliminated by the blocker of IP(3)Rs, 2-APB, and attenuated by ryanodine. Direct introduction of IP(3) into the permeabilized cells induced Ca(2+) transients with Ca(2+) oscillations at [Symbol: see text] 20 muM of IP(3), which was removed by the inhibition of IP(3)Rs using 2-APB and heparin. IP(3)-induced local Ca(2+) transients contained two distinct time courses: a rapid oscillation and a monophasic Ca(2+) transient. The magnitude of Ca(2+) oscillation was significantly larger in the cytosol than in the nucleus, while the monophasic Ca(2+) transient was more pronounced in the nucleus. These results provide evidence for the molecular and functional expression of IP(3)R1 and IP(3)R2 in HL-1 cells, and suggest that such distinct local Ca(2+) signaling may be correlated with the punctate distribution of IP(3)R2s in the cytosol and the diffuse localization of IP(3)R1 in the peri-nucleus.
authors.affiliation: College of Pharmacy, IDRD, Chungnam National University, Daejeon, 305-764, Korea.
authors.forename: Joon-Chul
authors.initials: JC
authors.lastname: Kim
authors.forename: Min-Jeong
authors.initials: MJ
authors.lastname: Son
authors.forename: Krishna P
authors.initials: KP
authors.lastname: Subedi
authors.forename: Do Han
authors.initials: DH
authors.lastname: Kim
authors.forename: Sun-Hee
authors.initials: SH
authors.lastname: Woo
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006325:Heart Atria / Q000166:cytology; D007150:Immunohistochemistry; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology*; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008297:Male; D051379:Mice; D018613:Microscopy, Confocal; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
chemical_list: D053496:Inositol 1,4,5-Trisphosphate Receptors; D020033:Protein Isoforms; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D002118:Calcium