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Comparative analysis of calcium spikes upon activation of serotonin(1A) and purinergic receptors.

Saxena R, Ganguly S, Chattopadhyay A - PLoS ONE (2012)

Bottom Line: Calcium signaling represents one of the most important signaling cascades in cells and regulates diverse processes such as exocytosis, muscle contraction and relaxation, gene expression and cell growth.In this work, we have described a set of parameters for the analysis of calcium transients that could provide novel insight into mechanisms responsible for maintaining signal specificity by shaping calcium transients.In summary, our analysis offers a novel approach to identify differences in calcium response patterns induced by various stimuli.

View Article: PubMed Central - PubMed

Affiliation: Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India.

ABSTRACT
Calcium signaling represents one of the most important signaling cascades in cells and regulates diverse processes such as exocytosis, muscle contraction and relaxation, gene expression and cell growth. G protein-coupled receptors (GPCRs) are the most important family of receptors that activate calcium signaling. Since calcium signaling regulates a large number of physiological responses, it is intriguing that how changes in cytosolic calcium levels by a wide range of stimuli lead to signal-specific physiological responses in the cellular interior. In order to address this issue, we have analyzed temporal calcium profiles induced by two GPCRs, the serotonin(1A) and purinergic receptors. In this work, we have described a set of parameters for the analysis of calcium transients that could provide novel insight into mechanisms responsible for maintaining signal specificity by shaping calcium transients. An interesting feature of calcium signaling that has emerged from our analysis is that the profile of individual transients in a calcium response could play an important role in maintaining downstream signal specificity. In summary, our analysis offers a novel approach to identify differences in calcium response patterns induced by various stimuli.

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Amplitude, full width at half maxima (FWHM) and area vary for individual spike in a multi-spike response.The amplitude of calcium spike represents the maximum fold change in cytosolic calcium level. The area of calcium spike corresponds to the amount of calcium released in the cytoplasm and FWHM denotes the life span of the calcium spike in the cytoplasm. Panels (A), (B) and (C) show amplitude, FWHM and area for serotonin-induced calcium spikes (blue triangle), and ATP-induced distinct (red triangle) and overlapping (•) calcium spikes, respectively. The temporal profile of calcium response was intensity-normalized such that the maximum and minimum (basal) intensities corresponded to values 2 and 1, respectively, before fitting it with a multi-gaussian function. In case of serotonin and ATP-stimulated calcium spikes, R2 values for fitting of calcium spikes with Gaussian function ranged from 0.92–0.98 and 0.94–0.99, respectively. Values represent means ± SEM of more than 50 cells from at least four independent experiments. See Materials and Methods for more details.
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pone-0051857-g006: Amplitude, full width at half maxima (FWHM) and area vary for individual spike in a multi-spike response.The amplitude of calcium spike represents the maximum fold change in cytosolic calcium level. The area of calcium spike corresponds to the amount of calcium released in the cytoplasm and FWHM denotes the life span of the calcium spike in the cytoplasm. Panels (A), (B) and (C) show amplitude, FWHM and area for serotonin-induced calcium spikes (blue triangle), and ATP-induced distinct (red triangle) and overlapping (•) calcium spikes, respectively. The temporal profile of calcium response was intensity-normalized such that the maximum and minimum (basal) intensities corresponded to values 2 and 1, respectively, before fitting it with a multi-gaussian function. In case of serotonin and ATP-stimulated calcium spikes, R2 values for fitting of calcium spikes with Gaussian function ranged from 0.92–0.98 and 0.94–0.99, respectively. Values represent means ± SEM of more than 50 cells from at least four independent experiments. See Materials and Methods for more details.

Mentions: We observed two different (distinct or overlapping) types of calcium response induced by serotonin or ATP. In the case of distinct spikes, each spike is clearly separated from its adjacent spikes. On the other hand, overlapping spikes are characterized by partial overlap of a spike with its adjacent spikes. In general, serotonin induced distinct calcium spikes. Calcium response induced by ATP, however, displayed both types of spikes (see Fig. 5). The probability of overlapping spikes increased with increase in ligand concentration. We monitored the dependence of amplitude, full width at half maxima (FWHM) and area of calcium spike on spike position. In case of serotonin stimulation, the amplitude (maximum fold change in cytosolic calcium) showed a reduction in case of second spike and remained similar for third spike. On the other hand, ATP-induced distinct and overlapping spikes displayed almost linear reduction in the amplitude of subsequent spikes (see Fig. 6A). FWHM signifies the lifespan of ligand-induced increase in cytosolic calcium concentration. FWHM is governed by all processes involved in rise and decay phases of calcium spikes. Fig. 6B shows the dependence of FWHM on spike position in ligand-induced calcium response. Both serotonin-induced spikes and ATP-mediated overlapping spikes showed an increase in FWHM for the second spike. On the other hand, FWHM of ATP-mediated distinct spikes was found to be more or less invariant with respect to spike position. The area under the spike represents the total amount of calcium released during the event of calcium spike. In addition, the area is dependent on both amplitude and FWHM of the spike. Fig. 6C shows the dependence of the area of calcium spike on its position in ligand-induced calcium response. The amount of calcium released was found to be similar for first two spikes and decreased for the third spike in case of serotonin-mediated response. In case of ATP-mediated overlapping spikes, the amount of calcium released was highest for the second spike. On the other hand, the area of ATP-mediated distinct spikes was found to be less sensitive to spike position.


Comparative analysis of calcium spikes upon activation of serotonin(1A) and purinergic receptors.

Saxena R, Ganguly S, Chattopadhyay A - PLoS ONE (2012)

Amplitude, full width at half maxima (FWHM) and area vary for individual spike in a multi-spike response.The amplitude of calcium spike represents the maximum fold change in cytosolic calcium level. The area of calcium spike corresponds to the amount of calcium released in the cytoplasm and FWHM denotes the life span of the calcium spike in the cytoplasm. Panels (A), (B) and (C) show amplitude, FWHM and area for serotonin-induced calcium spikes (blue triangle), and ATP-induced distinct (red triangle) and overlapping (•) calcium spikes, respectively. The temporal profile of calcium response was intensity-normalized such that the maximum and minimum (basal) intensities corresponded to values 2 and 1, respectively, before fitting it with a multi-gaussian function. In case of serotonin and ATP-stimulated calcium spikes, R2 values for fitting of calcium spikes with Gaussian function ranged from 0.92–0.98 and 0.94–0.99, respectively. Values represent means ± SEM of more than 50 cells from at least four independent experiments. See Materials and Methods for more details.
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pone-0051857-g006: Amplitude, full width at half maxima (FWHM) and area vary for individual spike in a multi-spike response.The amplitude of calcium spike represents the maximum fold change in cytosolic calcium level. The area of calcium spike corresponds to the amount of calcium released in the cytoplasm and FWHM denotes the life span of the calcium spike in the cytoplasm. Panels (A), (B) and (C) show amplitude, FWHM and area for serotonin-induced calcium spikes (blue triangle), and ATP-induced distinct (red triangle) and overlapping (•) calcium spikes, respectively. The temporal profile of calcium response was intensity-normalized such that the maximum and minimum (basal) intensities corresponded to values 2 and 1, respectively, before fitting it with a multi-gaussian function. In case of serotonin and ATP-stimulated calcium spikes, R2 values for fitting of calcium spikes with Gaussian function ranged from 0.92–0.98 and 0.94–0.99, respectively. Values represent means ± SEM of more than 50 cells from at least four independent experiments. See Materials and Methods for more details.
Mentions: We observed two different (distinct or overlapping) types of calcium response induced by serotonin or ATP. In the case of distinct spikes, each spike is clearly separated from its adjacent spikes. On the other hand, overlapping spikes are characterized by partial overlap of a spike with its adjacent spikes. In general, serotonin induced distinct calcium spikes. Calcium response induced by ATP, however, displayed both types of spikes (see Fig. 5). The probability of overlapping spikes increased with increase in ligand concentration. We monitored the dependence of amplitude, full width at half maxima (FWHM) and area of calcium spike on spike position. In case of serotonin stimulation, the amplitude (maximum fold change in cytosolic calcium) showed a reduction in case of second spike and remained similar for third spike. On the other hand, ATP-induced distinct and overlapping spikes displayed almost linear reduction in the amplitude of subsequent spikes (see Fig. 6A). FWHM signifies the lifespan of ligand-induced increase in cytosolic calcium concentration. FWHM is governed by all processes involved in rise and decay phases of calcium spikes. Fig. 6B shows the dependence of FWHM on spike position in ligand-induced calcium response. Both serotonin-induced spikes and ATP-mediated overlapping spikes showed an increase in FWHM for the second spike. On the other hand, FWHM of ATP-mediated distinct spikes was found to be more or less invariant with respect to spike position. The area under the spike represents the total amount of calcium released during the event of calcium spike. In addition, the area is dependent on both amplitude and FWHM of the spike. Fig. 6C shows the dependence of the area of calcium spike on its position in ligand-induced calcium response. The amount of calcium released was found to be similar for first two spikes and decreased for the third spike in case of serotonin-mediated response. In case of ATP-mediated overlapping spikes, the amount of calcium released was highest for the second spike. On the other hand, the area of ATP-mediated distinct spikes was found to be less sensitive to spike position.

Bottom Line: Calcium signaling represents one of the most important signaling cascades in cells and regulates diverse processes such as exocytosis, muscle contraction and relaxation, gene expression and cell growth.In this work, we have described a set of parameters for the analysis of calcium transients that could provide novel insight into mechanisms responsible for maintaining signal specificity by shaping calcium transients.In summary, our analysis offers a novel approach to identify differences in calcium response patterns induced by various stimuli.

View Article: PubMed Central - PubMed

Affiliation: Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Hyderabad, India.

ABSTRACT
Calcium signaling represents one of the most important signaling cascades in cells and regulates diverse processes such as exocytosis, muscle contraction and relaxation, gene expression and cell growth. G protein-coupled receptors (GPCRs) are the most important family of receptors that activate calcium signaling. Since calcium signaling regulates a large number of physiological responses, it is intriguing that how changes in cytosolic calcium levels by a wide range of stimuli lead to signal-specific physiological responses in the cellular interior. In order to address this issue, we have analyzed temporal calcium profiles induced by two GPCRs, the serotonin(1A) and purinergic receptors. In this work, we have described a set of parameters for the analysis of calcium transients that could provide novel insight into mechanisms responsible for maintaining signal specificity by shaping calcium transients. An interesting feature of calcium signaling that has emerged from our analysis is that the profile of individual transients in a calcium response could play an important role in maintaining downstream signal specificity. In summary, our analysis offers a novel approach to identify differences in calcium response patterns induced by various stimuli.

Show MeSH
Related in: MedlinePlus