title: Stimulus-dependent regulation of nuclear Ca2+ signaling in cardiomyocytes: a role of neuronal calcium sensor-1.
abstract: In cardiomyocytes, intracellular calcium (Ca2+) transients are elicited by electrical and receptor stimulations, leading to muscle contraction and gene expression, respectively. Although such elevations of Ca2+levels ([Ca2+]) also occur in the nucleus, the precise mechanism of nuclear [Ca2+] regulation during different kinds of stimuli, and its relationship with cytoplasmic [Ca2+] regulation are not fully understood. To address these issues, we used a new region-specific fluorescent protein-based Ca2+ indicator, GECO, together with the conventional probe Fluo-4 AM. We confirmed that nuclear Ca2+ transients were elicited by both electrical and receptor stimulations in neonatal mouse ventricular myocytes. Kinetic analysis revealed that electrical stimulation-elicited nuclear Ca2+ transients are slower than cytoplasmic Ca2+ transients, and chelating cytoplasmic Ca2+ abolished nuclear Ca2+ transients, suggesting that nuclear Ca2+ are mainly derived from the cytoplasm during electrical stimulation. On the other hand, receptor stimulation such as with insulin-like growth factor-1 (IGF-1) preferentially increased nuclear [Ca2+] compared to cytoplasmic [Ca2+]. Experiments using inhibitors revealed that electrical and receptor stimulation-elicited Ca2+ transients were mainly mediated by ryanodine receptors and inositol 1,4,5-trisphosphate receptors (IP3Rs), respectively, suggesting different mechanisms for the two signals. Furthermore, IGF-1-elicited nuclear Ca2+ transient amplitude was significantly lower in myocytes lacking neuronal Ca2+ sensor-1 (NCS-1), a Ca2+ binding protein implicated in IP3R-mediated pathway in the heart. Moreover, IGF-1 strengthened the interaction between NCS-1 and IP3R. These results suggest a novel mechanism for receptor stimulation-induced nuclear [Ca2+] regulation mediated by IP3R and NCS-1 that may further fine-tune cardiac Ca2+ signal regulation.
authors.affiliation: Department of Molecular Physiology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan.
authors.forename: Shu
authors.initials: S
authors.lastname: Nakao
authors.affiliation: Department of Molecular Physiology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan; Department of Cardiac Physiology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Wakabayashi
authors.affiliation: Department of Molecular Physiology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan.
authors.forename: Tomoe Y
authors.initials: TY
authors.lastname: Nakamura
mesh_terms: D000814:Aniline Compounds; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D004558:Electric Stimulation; D005456:Fluorescent Dyes; D005786:Gene Expression Regulation; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000235:genetics* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D017136:Ion Transport; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051580:Neuronal Calcium-Sensor Proteins / Q000172:deficiency / Q000235:genetics*; D009479:Neuropeptides / Q000172:deficiency / Q000235:genetics*; D061251:Primary Cell Culture; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics / Q000378:metabolism; D014966:Xanthenes
chemical_list: D000814:Aniline Compounds; C409648:Fluo 4; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; D019837:Ryanodine Receptor Calcium Release Channel; D014966:Xanthenes; C101464:frequenin calcium sensor proteins; C519530:insulin-like growth factor-1, mouse; D007334:Insulin-Like Growth Factor I; D002118:Calcium