Limits...
The role of caveolae and caveolin 1 in calcium handling in pacing and contraction of mouse intestine.

Daniel EE, Eteraf T, Sommer B, Cho WJ, Elyazbi A - J. Cell. Mol. Med. (2008)

Bottom Line: We found that a number of calcium handling/dependent molecules are associated with caveolae, including L-type Ca(2+) channels, Na(+)-Ca(2+) exchanger type 1 (NCX1), plasma membrane Ca(2+) pumps and neural nitric oxide synthase (nNOS), and that caveolae are close to the peripheral endo-sarcoplasmic reticulum (ER-SR).We found evidence that these channels were associated with Cav-1.These changes were all consistent with the hypothesis that a reduction of the extracellular calcium associated with caveolae in ICC of the myenteric plexus, the state of L-type Ca(2+) channels or an increase in the distance between caveolae and SR affected calcium handling.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Alberta, Edmonton, AB, Canada. edaniel@ualberta.ca

ABSTRACT
In mouse intestine, caveolae and caveolin-1 (Cav-1) are present in smooth muscle (responsible for executing contractions) and in interstitial cells of Cajal (ICC; responsible for pacing contractions). We found that a number of calcium handling/dependent molecules are associated with caveolae, including L-type Ca(2+) channels, Na(+)-Ca(2+) exchanger type 1 (NCX1), plasma membrane Ca(2+) pumps and neural nitric oxide synthase (nNOS), and that caveolae are close to the peripheral endo-sarcoplasmic reticulum (ER-SR). Also we found that this assemblage may account for recycling of calcium from caveolar domains to SR through L-type Ca (+) channels to sustain pacing and contractions. Here we test this hypothesis further comparing pacing and contractions under various conditions in longitudinal muscle of Cav-1 knockout mice (lacking caveolae) and in their genetic controls. We used a procedure in which pacing frequencies (indicative of functioning of ICC) and contraction amplitudes (indicative of functioning of smooth muscle) were studied in calcium-free media with 100 mM ethylene glycol tetra-acetic acid (EGTA). The absence of caveolae in ICC inhibited the ability of ICC to maintain frequencies of contraction in the calcium-free medium by reducing recycling of calcium from caveolar plasma membrane to SR when the calcium stores were initially full. This recycling to ICC involved primarily L-type Ca(2+) channels; i.e. pacing frequencies were enhanced by opening and inhibited by closing these channels. However, when these stores were depleted by block of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) pump or calcium release was activated by carbachol, the absence of Cav-1 or caveolae had little or no effect. The absence of caveolae had little impact on contraction amplitudes, indicative of recycling of calcium to SR in smooth muscle. However, the absence of caveolae slowed the rate of loss of calcium from SR under some conditions in both ICC and smooth muscle, which may reflect the loss of proximity to store operated Ca channels. We found evidence that these channels were associated with Cav-1. These changes were all consistent with the hypothesis that a reduction of the extracellular calcium associated with caveolae in ICC of the myenteric plexus, the state of L-type Ca(2+) channels or an increase in the distance between caveolae and SR affected calcium handling.

Show MeSH

Related in: MedlinePlus

(A) Effects on contraction frequencies of LM segments from two successive exposures of control (Cav+/+) and Cav-1 knockout (Cav−/−) to Ca2+ Krebs solution with 0.1 mM EGTA. Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments the bars for the Cav+/+ tissues are red. (B) Effect on contraction amplitudes in the experiments shown in Fig. 1A, with data from the final responses to 10−5 M CCH. . Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments in spontaneous contraction amplitudes the bars for the Cav+/+ tissues are red but difference in amplitudes of contractions to CCH are in red for Cav−/− tissues. Responses to CCH after exposure to 0.1 mM EGTA are shown by perpendicular hatching and responses after exposure to 1 mM EGTA are shown with diagonal hatching.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3823361&req=5

fig01: (A) Effects on contraction frequencies of LM segments from two successive exposures of control (Cav+/+) and Cav-1 knockout (Cav−/−) to Ca2+ Krebs solution with 0.1 mM EGTA. Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments the bars for the Cav+/+ tissues are red. (B) Effect on contraction amplitudes in the experiments shown in Fig. 1A, with data from the final responses to 10−5 M CCH. . Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments in spontaneous contraction amplitudes the bars for the Cav+/+ tissues are red but difference in amplitudes of contractions to CCH are in red for Cav−/− tissues. Responses to CCH after exposure to 0.1 mM EGTA are shown by perpendicular hatching and responses after exposure to 1 mM EGTA are shown with diagonal hatching.

Mentions: Five minutes after two washes in nominally Ca2+-free KR solution with 0.1 or 1 mM EGTA (Fig. 1A), Cav+/+ segments of LM maintained frequencies significantly (P< 0.05) better than did Cav−/− segments, in both concentrations of EGTA. These higher frequencies persisted after an additional two washes for a total of 10 min. in Cav+/+ compared to Cav−/− segments in 0.1 mM EGTA. Contractions were abolished in both strains after 10 min. at 1 mM EGTA. These results imply that the absence of caveolae diminishes the supply of calcium or the ability of this extracellular calcium source to recycle calcium to ICC SR. This source survives in 0.1 mM EGTA for 10 min., but not in 1.0 mM EGTA.


The role of caveolae and caveolin 1 in calcium handling in pacing and contraction of mouse intestine.

Daniel EE, Eteraf T, Sommer B, Cho WJ, Elyazbi A - J. Cell. Mol. Med. (2008)

(A) Effects on contraction frequencies of LM segments from two successive exposures of control (Cav+/+) and Cav-1 knockout (Cav−/−) to Ca2+ Krebs solution with 0.1 mM EGTA. Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments the bars for the Cav+/+ tissues are red. (B) Effect on contraction amplitudes in the experiments shown in Fig. 1A, with data from the final responses to 10−5 M CCH. . Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments in spontaneous contraction amplitudes the bars for the Cav+/+ tissues are red but difference in amplitudes of contractions to CCH are in red for Cav−/− tissues. Responses to CCH after exposure to 0.1 mM EGTA are shown by perpendicular hatching and responses after exposure to 1 mM EGTA are shown with diagonal hatching.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3823361&req=5

fig01: (A) Effects on contraction frequencies of LM segments from two successive exposures of control (Cav+/+) and Cav-1 knockout (Cav−/−) to Ca2+ Krebs solution with 0.1 mM EGTA. Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments the bars for the Cav+/+ tissues are red. (B) Effect on contraction amplitudes in the experiments shown in Fig. 1A, with data from the final responses to 10−5 M CCH. . Significant differences between the first and second exposures and initial values are indicated by #, the number symbol, and between comparable tissues by asterisks. When there were significant differences between Cav+/+ and Cav−/− segments in spontaneous contraction amplitudes the bars for the Cav+/+ tissues are red but difference in amplitudes of contractions to CCH are in red for Cav−/− tissues. Responses to CCH after exposure to 0.1 mM EGTA are shown by perpendicular hatching and responses after exposure to 1 mM EGTA are shown with diagonal hatching.
Mentions: Five minutes after two washes in nominally Ca2+-free KR solution with 0.1 or 1 mM EGTA (Fig. 1A), Cav+/+ segments of LM maintained frequencies significantly (P< 0.05) better than did Cav−/− segments, in both concentrations of EGTA. These higher frequencies persisted after an additional two washes for a total of 10 min. in Cav+/+ compared to Cav−/− segments in 0.1 mM EGTA. Contractions were abolished in both strains after 10 min. at 1 mM EGTA. These results imply that the absence of caveolae diminishes the supply of calcium or the ability of this extracellular calcium source to recycle calcium to ICC SR. This source survives in 0.1 mM EGTA for 10 min., but not in 1.0 mM EGTA.

Bottom Line: We found that a number of calcium handling/dependent molecules are associated with caveolae, including L-type Ca(2+) channels, Na(+)-Ca(2+) exchanger type 1 (NCX1), plasma membrane Ca(2+) pumps and neural nitric oxide synthase (nNOS), and that caveolae are close to the peripheral endo-sarcoplasmic reticulum (ER-SR).We found evidence that these channels were associated with Cav-1.These changes were all consistent with the hypothesis that a reduction of the extracellular calcium associated with caveolae in ICC of the myenteric plexus, the state of L-type Ca(2+) channels or an increase in the distance between caveolae and SR affected calcium handling.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacology, University of Alberta, Edmonton, AB, Canada. edaniel@ualberta.ca

ABSTRACT
In mouse intestine, caveolae and caveolin-1 (Cav-1) are present in smooth muscle (responsible for executing contractions) and in interstitial cells of Cajal (ICC; responsible for pacing contractions). We found that a number of calcium handling/dependent molecules are associated with caveolae, including L-type Ca(2+) channels, Na(+)-Ca(2+) exchanger type 1 (NCX1), plasma membrane Ca(2+) pumps and neural nitric oxide synthase (nNOS), and that caveolae are close to the peripheral endo-sarcoplasmic reticulum (ER-SR). Also we found that this assemblage may account for recycling of calcium from caveolar domains to SR through L-type Ca (+) channels to sustain pacing and contractions. Here we test this hypothesis further comparing pacing and contractions under various conditions in longitudinal muscle of Cav-1 knockout mice (lacking caveolae) and in their genetic controls. We used a procedure in which pacing frequencies (indicative of functioning of ICC) and contraction amplitudes (indicative of functioning of smooth muscle) were studied in calcium-free media with 100 mM ethylene glycol tetra-acetic acid (EGTA). The absence of caveolae in ICC inhibited the ability of ICC to maintain frequencies of contraction in the calcium-free medium by reducing recycling of calcium from caveolar plasma membrane to SR when the calcium stores were initially full. This recycling to ICC involved primarily L-type Ca(2+) channels; i.e. pacing frequencies were enhanced by opening and inhibited by closing these channels. However, when these stores were depleted by block of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) pump or calcium release was activated by carbachol, the absence of Cav-1 or caveolae had little or no effect. The absence of caveolae had little impact on contraction amplitudes, indicative of recycling of calcium to SR in smooth muscle. However, the absence of caveolae slowed the rate of loss of calcium from SR under some conditions in both ICC and smooth muscle, which may reflect the loss of proximity to store operated Ca channels. We found evidence that these channels were associated with Cav-1. These changes were all consistent with the hypothesis that a reduction of the extracellular calcium associated with caveolae in ICC of the myenteric plexus, the state of L-type Ca(2+) channels or an increase in the distance between caveolae and SR affected calcium handling.

Show MeSH
Related in: MedlinePlus