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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.

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(A) This cartoon represents a possible distribution if Ca2+ handling proteins related to caveolae and Cav-1 based on our findings. The peripheral ER/SR is shown near a caveola, with a restricted space in between them, containing a higher Ca2+ concentration than in the general cytosol. Sequestered Ca2+ is also shown associated with the caveolar extracellular membrane and adjacent raft tissue. This is the Ca2+ which is protected from the Ca2+-free medium we used and provides ions for recycling to the restricted space and the ER/SR (and in Cav-1 knockout tissue provides some Ca2+ for recycling). Owing to space limitations this recycling Ca2+ is depicted adjacent to the restricted space. Proteins apparently co-localized with Cav-1 including VDCC, PMCA4, myogenic nNOS, and store operated Ca2+ Channels are shown associated with the caveola membrane. Under the control conditions in Ca2+-free medium, the VDCC were the main entry route for Ca2+ to be recycled, but store operated channels contribute when the VDCC are blocked. The SERCA pump and Leak or Release Sites in SR are also depicted. The Ca2+ stored in the ER/SR is the other main source of Ca2+ to maintain recycling and when it is emptied, recycling stops quickly. (B) This cartoon depicts the proposed changes in the Cav-1 knockout tissues. The restricted space is lost as well as the higher local Ca2+ concentration which promotes its recycling to the ER/SR. VDCC, PMCA and store operated Ca2+ Channels persist, but the myogenic nNOS is missing. The proximity of the remaining Ca2+ molecules to the ER/SR is lost. There is also less sequestered Ca2+ available for recycling. The result is more rapid loss of pacing in Ca2+-free medium. There is also less rapid clearing of Ca2+ released or leaked from ER/SR by the PMCA and other clearance mechanisms. The main route for Ca2+ entry remains the VDCC with a possible contribution from the store operated channel.
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fig07: (A) This cartoon represents a possible distribution if Ca2+ handling proteins related to caveolae and Cav-1 based on our findings. The peripheral ER/SR is shown near a caveola, with a restricted space in between them, containing a higher Ca2+ concentration than in the general cytosol. Sequestered Ca2+ is also shown associated with the caveolar extracellular membrane and adjacent raft tissue. This is the Ca2+ which is protected from the Ca2+-free medium we used and provides ions for recycling to the restricted space and the ER/SR (and in Cav-1 knockout tissue provides some Ca2+ for recycling). Owing to space limitations this recycling Ca2+ is depicted adjacent to the restricted space. Proteins apparently co-localized with Cav-1 including VDCC, PMCA4, myogenic nNOS, and store operated Ca2+ Channels are shown associated with the caveola membrane. Under the control conditions in Ca2+-free medium, the VDCC were the main entry route for Ca2+ to be recycled, but store operated channels contribute when the VDCC are blocked. The SERCA pump and Leak or Release Sites in SR are also depicted. The Ca2+ stored in the ER/SR is the other main source of Ca2+ to maintain recycling and when it is emptied, recycling stops quickly. (B) This cartoon depicts the proposed changes in the Cav-1 knockout tissues. The restricted space is lost as well as the higher local Ca2+ concentration which promotes its recycling to the ER/SR. VDCC, PMCA and store operated Ca2+ Channels persist, but the myogenic nNOS is missing. The proximity of the remaining Ca2+ molecules to the ER/SR is lost. There is also less sequestered Ca2+ available for recycling. The result is more rapid loss of pacing in Ca2+-free medium. There is also less rapid clearing of Ca2+ released or leaked from ER/SR by the PMCA and other clearance mechanisms. The main route for Ca2+ entry remains the VDCC with a possible contribution from the store operated channel.

Mentions: Figure 7A and B summarize the current status of this hypothesis [3] and propose the differences between cell functions with and without caveolae.


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) This cartoon represents a possible distribution if Ca2+ handling proteins related to caveolae and Cav-1 based on our findings. The peripheral ER/SR is shown near a caveola, with a restricted space in between them, containing a higher Ca2+ concentration than in the general cytosol. Sequestered Ca2+ is also shown associated with the caveolar extracellular membrane and adjacent raft tissue. This is the Ca2+ which is protected from the Ca2+-free medium we used and provides ions for recycling to the restricted space and the ER/SR (and in Cav-1 knockout tissue provides some Ca2+ for recycling). Owing to space limitations this recycling Ca2+ is depicted adjacent to the restricted space. Proteins apparently co-localized with Cav-1 including VDCC, PMCA4, myogenic nNOS, and store operated Ca2+ Channels are shown associated with the caveola membrane. Under the control conditions in Ca2+-free medium, the VDCC were the main entry route for Ca2+ to be recycled, but store operated channels contribute when the VDCC are blocked. The SERCA pump and Leak or Release Sites in SR are also depicted. The Ca2+ stored in the ER/SR is the other main source of Ca2+ to maintain recycling and when it is emptied, recycling stops quickly. (B) This cartoon depicts the proposed changes in the Cav-1 knockout tissues. The restricted space is lost as well as the higher local Ca2+ concentration which promotes its recycling to the ER/SR. VDCC, PMCA and store operated Ca2+ Channels persist, but the myogenic nNOS is missing. The proximity of the remaining Ca2+ molecules to the ER/SR is lost. There is also less sequestered Ca2+ available for recycling. The result is more rapid loss of pacing in Ca2+-free medium. There is also less rapid clearing of Ca2+ released or leaked from ER/SR by the PMCA and other clearance mechanisms. The main route for Ca2+ entry remains the VDCC with a possible contribution from the store operated channel.
© Copyright Policy
Related In: Results  -  Collection

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

fig07: (A) This cartoon represents a possible distribution if Ca2+ handling proteins related to caveolae and Cav-1 based on our findings. The peripheral ER/SR is shown near a caveola, with a restricted space in between them, containing a higher Ca2+ concentration than in the general cytosol. Sequestered Ca2+ is also shown associated with the caveolar extracellular membrane and adjacent raft tissue. This is the Ca2+ which is protected from the Ca2+-free medium we used and provides ions for recycling to the restricted space and the ER/SR (and in Cav-1 knockout tissue provides some Ca2+ for recycling). Owing to space limitations this recycling Ca2+ is depicted adjacent to the restricted space. Proteins apparently co-localized with Cav-1 including VDCC, PMCA4, myogenic nNOS, and store operated Ca2+ Channels are shown associated with the caveola membrane. Under the control conditions in Ca2+-free medium, the VDCC were the main entry route for Ca2+ to be recycled, but store operated channels contribute when the VDCC are blocked. The SERCA pump and Leak or Release Sites in SR are also depicted. The Ca2+ stored in the ER/SR is the other main source of Ca2+ to maintain recycling and when it is emptied, recycling stops quickly. (B) This cartoon depicts the proposed changes in the Cav-1 knockout tissues. The restricted space is lost as well as the higher local Ca2+ concentration which promotes its recycling to the ER/SR. VDCC, PMCA and store operated Ca2+ Channels persist, but the myogenic nNOS is missing. The proximity of the remaining Ca2+ molecules to the ER/SR is lost. There is also less sequestered Ca2+ available for recycling. The result is more rapid loss of pacing in Ca2+-free medium. There is also less rapid clearing of Ca2+ released or leaked from ER/SR by the PMCA and other clearance mechanisms. The main route for Ca2+ entry remains the VDCC with a possible contribution from the store operated channel.
Mentions: Figure 7A and B summarize the current status of this hypothesis [3] and propose the differences between cell functions with and without caveolae.

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