Limits...
Morphological control of inositol-1,4,5-trisphosphate-dependent signals.

Fink CC, Slepchenko B, Moraru II, Schaff J, Watras J, Loew LM - J. Cell Biol. (1999)

Bottom Line: We conclude that the characteristic calcium dynamics requires rapid, high-amplitude production of [InsP(3)](cyt) in the neurite.This requisite InsP(3) spatiotemporal profile is provided, in turn, as an intrinsic consequence of the cell's morphology, demonstrating how geometry can locally and dramatically intensify cytosolic signals that originate at the plasma membrane.In addition, the model predicts, and experiments confirm, that stimulation of just the neurite, but not the soma or growth cone, is sufficient to generate a calcium response throughout the cell.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.

ABSTRACT
Inositol-1,4,5-trisphosphate (InsP(3))-mediated calcium signals represent an important mechanism for transmitting external stimuli to the cell. However, information about intracellular spatial patterns of InsP(3) itself is not generally available. In particular, it has not been determined how the interplay of InsP(3) generation, diffusion, and degradation within complex cellular geometries can control the patterns of InsP(3) signaling. Here, we explore the spatial and temporal characteristics of [InsP(3)](cyt) during a bradykinin-induced calcium wave in a neuroblastoma cell. This is achieved by using a unique image-based computer modeling system, Virtual Cell, to integrate experimental data on the rates and spatial distributions of the key molecular components of the process. We conclude that the characteristic calcium dynamics requires rapid, high-amplitude production of [InsP(3)](cyt) in the neurite. This requisite InsP(3) spatiotemporal profile is provided, in turn, as an intrinsic consequence of the cell's morphology, demonstrating how geometry can locally and dramatically intensify cytosolic signals that originate at the plasma membrane. In addition, the model predicts, and experiments confirm, that stimulation of just the neurite, but not the soma or growth cone, is sufficient to generate a calcium response throughout the cell.

Show MeSH

Related in: MedlinePlus

a, BK-induced calcium wave in an N1E-115 neuroblastoma. At time = 0, 500 nM BK was externally applied to the bathing medium of a cell stained with fura-2. Fluorescence from the 380-nm excitation was collected with a cooled CCD camera, converted to a relative [Ca2+] change, and displayed in pseudocolored form. For regions of interest in the soma and neurite (indicated by the colored rectangles), the relative change in [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm. b, Calcium dynamics after global InsP3 uncaging in an N1E-115 neuroblastoma. Cells were microinjected with CG-1 and NPE-InsP3, and CG-1 fluorescence was measured on a Zeiss LSM410 confocal microscope. At time = 4 s, the cell was uniformly exposed to UV light for 500 ms using a raster scanned UV argon ion laser (364 nm). For regions of interest in the soma and neurite (indicated by the colored arrows), [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2169350&req=5

Figure 1: a, BK-induced calcium wave in an N1E-115 neuroblastoma. At time = 0, 500 nM BK was externally applied to the bathing medium of a cell stained with fura-2. Fluorescence from the 380-nm excitation was collected with a cooled CCD camera, converted to a relative [Ca2+] change, and displayed in pseudocolored form. For regions of interest in the soma and neurite (indicated by the colored rectangles), the relative change in [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm. b, Calcium dynamics after global InsP3 uncaging in an N1E-115 neuroblastoma. Cells were microinjected with CG-1 and NPE-InsP3, and CG-1 fluorescence was measured on a Zeiss LSM410 confocal microscope. At time = 4 s, the cell was uniformly exposed to UV light for 500 ms using a raster scanned UV argon ion laser (364 nm). For regions of interest in the soma and neurite (indicated by the colored arrows), [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm.

Mentions: When stimulated with a saturating concentration of BK, a nonapeptide neuromodulator, N1E-115 neuroblastomas show a highly reproducible calcium response (Fig. 1 a). After a brief latency (mean ± SEM; 2.97 ± 0.23 s; n = 16), a calcium increase started in the neurite and propagated bidirectionally as a wave towards the soma and growth cone. The wave typically traversed the soma with an average velocity of 39.2 ± 3.7 μm/s (n = 16), and peak calcium concentrations approximating 1 μM (1190 ± 46 nM; n = 21). The calcium wave propagated more quickly through the neurite (147.8 ± 31.3 μm/s; n = 9; P = 0.0001, compared with wave velocity in the soma) although the amplitude of the calcium response was not significantly different than observed in the soma (1106 ± 29 nM; n = 17; P > 0.05). [Ca2+]cyt relaxation to basal levels occurred within 30 s of stimulation. Subsequent stimulations with BK did not evoke new calcium signals even after BK washout. This calcium response is known to be mediated by InsP3 generation (Iredale et al. 1992; Coggan and Thompson 1995) and subsequent release of calcium from ER stores. The amplitude of the calcium response is not dependent upon extracellular calcium, indicating that the elevation of [Ca2+]cyt comes strictly from intracellular stores. In addition, all calcium efflux from the ER is through InsP3-sensitive channels, since this cell type lacks ryanodine receptors (calcium-induced calcium release; Coggan and Thompson 1995).


Morphological control of inositol-1,4,5-trisphosphate-dependent signals.

Fink CC, Slepchenko B, Moraru II, Schaff J, Watras J, Loew LM - J. Cell Biol. (1999)

a, BK-induced calcium wave in an N1E-115 neuroblastoma. At time = 0, 500 nM BK was externally applied to the bathing medium of a cell stained with fura-2. Fluorescence from the 380-nm excitation was collected with a cooled CCD camera, converted to a relative [Ca2+] change, and displayed in pseudocolored form. For regions of interest in the soma and neurite (indicated by the colored rectangles), the relative change in [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm. b, Calcium dynamics after global InsP3 uncaging in an N1E-115 neuroblastoma. Cells were microinjected with CG-1 and NPE-InsP3, and CG-1 fluorescence was measured on a Zeiss LSM410 confocal microscope. At time = 4 s, the cell was uniformly exposed to UV light for 500 ms using a raster scanned UV argon ion laser (364 nm). For regions of interest in the soma and neurite (indicated by the colored arrows), [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169350&req=5

Figure 1: a, BK-induced calcium wave in an N1E-115 neuroblastoma. At time = 0, 500 nM BK was externally applied to the bathing medium of a cell stained with fura-2. Fluorescence from the 380-nm excitation was collected with a cooled CCD camera, converted to a relative [Ca2+] change, and displayed in pseudocolored form. For regions of interest in the soma and neurite (indicated by the colored rectangles), the relative change in [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm. b, Calcium dynamics after global InsP3 uncaging in an N1E-115 neuroblastoma. Cells were microinjected with CG-1 and NPE-InsP3, and CG-1 fluorescence was measured on a Zeiss LSM410 confocal microscope. At time = 4 s, the cell was uniformly exposed to UV light for 500 ms using a raster scanned UV argon ion laser (364 nm). For regions of interest in the soma and neurite (indicated by the colored arrows), [Ca2+] versus time was plotted in the lower right corner. Bar, 25 μm.
Mentions: When stimulated with a saturating concentration of BK, a nonapeptide neuromodulator, N1E-115 neuroblastomas show a highly reproducible calcium response (Fig. 1 a). After a brief latency (mean ± SEM; 2.97 ± 0.23 s; n = 16), a calcium increase started in the neurite and propagated bidirectionally as a wave towards the soma and growth cone. The wave typically traversed the soma with an average velocity of 39.2 ± 3.7 μm/s (n = 16), and peak calcium concentrations approximating 1 μM (1190 ± 46 nM; n = 21). The calcium wave propagated more quickly through the neurite (147.8 ± 31.3 μm/s; n = 9; P = 0.0001, compared with wave velocity in the soma) although the amplitude of the calcium response was not significantly different than observed in the soma (1106 ± 29 nM; n = 17; P > 0.05). [Ca2+]cyt relaxation to basal levels occurred within 30 s of stimulation. Subsequent stimulations with BK did not evoke new calcium signals even after BK washout. This calcium response is known to be mediated by InsP3 generation (Iredale et al. 1992; Coggan and Thompson 1995) and subsequent release of calcium from ER stores. The amplitude of the calcium response is not dependent upon extracellular calcium, indicating that the elevation of [Ca2+]cyt comes strictly from intracellular stores. In addition, all calcium efflux from the ER is through InsP3-sensitive channels, since this cell type lacks ryanodine receptors (calcium-induced calcium release; Coggan and Thompson 1995).

Bottom Line: We conclude that the characteristic calcium dynamics requires rapid, high-amplitude production of [InsP(3)](cyt) in the neurite.This requisite InsP(3) spatiotemporal profile is provided, in turn, as an intrinsic consequence of the cell's morphology, demonstrating how geometry can locally and dramatically intensify cytosolic signals that originate at the plasma membrane.In addition, the model predicts, and experiments confirm, that stimulation of just the neurite, but not the soma or growth cone, is sufficient to generate a calcium response throughout the cell.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.

ABSTRACT
Inositol-1,4,5-trisphosphate (InsP(3))-mediated calcium signals represent an important mechanism for transmitting external stimuli to the cell. However, information about intracellular spatial patterns of InsP(3) itself is not generally available. In particular, it has not been determined how the interplay of InsP(3) generation, diffusion, and degradation within complex cellular geometries can control the patterns of InsP(3) signaling. Here, we explore the spatial and temporal characteristics of [InsP(3)](cyt) during a bradykinin-induced calcium wave in a neuroblastoma cell. This is achieved by using a unique image-based computer modeling system, Virtual Cell, to integrate experimental data on the rates and spatial distributions of the key molecular components of the process. We conclude that the characteristic calcium dynamics requires rapid, high-amplitude production of [InsP(3)](cyt) in the neurite. This requisite InsP(3) spatiotemporal profile is provided, in turn, as an intrinsic consequence of the cell's morphology, demonstrating how geometry can locally and dramatically intensify cytosolic signals that originate at the plasma membrane. In addition, the model predicts, and experiments confirm, that stimulation of just the neurite, but not the soma or growth cone, is sufficient to generate a calcium response throughout the cell.

Show MeSH
Related in: MedlinePlus