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KMID : 0578320100290040387
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Molecules and Cells
2010 Volume.29 No. 4 p.387 ~ p.395
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IP3-Induced Cytosolic and Nuclear Ca2+ Signals in HL-1 Atrial Myocytes: Possible Role of IP3 Receptor Subtypes
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Kim Joon-Chul
Son Min-Jeong
Krishna P. Subedi
Kim Do-Han
Woo Sun-Hee
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Abstract
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HL-1 cells are the adult cardiac cell lines available that continuously divide while maintaining an atrial pheno-type. Here we examined the expression and localization of inositol 1,4,5-trisphosphate receptor (IP3R) subtypes, and investigated how pattern of IP3-induced subcellular local Ca2+ signaling is encoded by multiple IP3R subtypes in HL-1 cells. The type 1 IP3R (IP3R1) was expressed in the peri-nucleus with a diffuse pattern and the type 2 IP3R (IP3R2) was expressed in the cytosol with a punctate distribution. Extracellular ATP (1 mM) elicited transient intracellular Ca2+ releases accompanied by a Ca2+ oscillation, which was eliminated by the blocker of IP3Rs, 2-APB, and attenuated by ryanodine. Direct introduction of IP3 into the permeabilized cells induced Ca2+ transients with Ca2+ oscillations at ≥20 μM of IP3, which was removed by the inhibition of IP3Rs using 2-APB and heparin. IP3-induced local Ca2+ transients contained two distinct time courses: a rapid oscillation and a monophasic Ca2+ transient. The magnitude of Ca2+ oscillation was significantly larger in the cytosol than in the nucleus, while the monophasic Ca2+ transient was more pronounced in the nucleus. These results provide evidence for the molecular and functional expression of IP3R1 and IP3R2 in HL-1 cells, and suggest that such distinct local Ca2+ signaling may be correlated with the punctate distribution of IP3R2s in the cytosol and the diffuse localization of IP3R1 in the peri-nucleus.
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KEYWORD
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Ca2+ oscillation, confocal imaging, HL-1 cell, local Ca2+ signal, localization, IP3R subtypes
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