Caveolae and calcium handling, a review and a hypothesis.

FULL TEXT Abstract: Caveolae are associated with molecules crucial for calcium handling
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Caveolae and Calcium Handling, a Review and a Hypothesis.

Caveolae are associated with molecules crucial for calcium handling. This review considers the roles of caveolae in calcium handling for smooth muscle and interstitial cells of Cajal (ICC). Structural studies showed that the plasma membrane calcium pump (PMCA), a sodium-calcium exchanger (NCX1), and a myogenic nNOS appear to be colocalized with caveolin I, the main constituent of these caveolae. Voltage dependent calcium channels (VDCC) are associated but not co-localized with caveolin 1, as are proteins of the peripheral sarcoplasmic reticulum (SR) such as calreticulin. Only the nNOS is absent from caveolin 1 knockout animals. Functional studies in calcium free media sugest that a source of calcium in tonic smooth muscles exists, partly sequestered from extracellular EGTA. This source supported sustained contractions to carbachol using VDCC and dependent on activity of the SERCA pump. This source is postulated to be caveolae, near peripheral SR. New evidence, presented here, suggests that a similar source exists in phasic smooth muscle of the intestine and its ICC. These results suggest that caveolae and peripheral SR are a functional unit recycling calcium through VDCC and controlling its local concentration. Calcium handling molecules associated with caveolae in smooth muscle and ICC were identified and their possible functions also reviewed.

02/01/2018 · Caveolae are associated with molecules crucial for calcium handling
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Caveolae and calcium handling, a review and a hypothesis , J

When extracellular calcium levels are restricted by removing calcium from the medium and adding 0.1 mM EGTA, a source of calcium resistant to removal and available for recycling to SR stores in ICC-MP and longitudinal smooth muscle is revealed. Availability of this source for recycling depends in part on the presence of Cav-1 and caveolae. The main route for recycling is through L-type Ca2+ channels. It is still present, but operates less effectively, in the absence of caveolae. When caveolae are present and L-type Ca2+ channels are blocked, an additional route for recycling of calcium to SR is revealed, possibly a store operated channel. The differences which depend on the presence of caveolae are more prominent in the functioning of ICC-MP than in functioning of longitudinal smooth muscle, possibly because pacing by these ICC requires calcium recycling continuously.

Caveolae and calcium handling, a review and a hypothesis
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Thus, our aim was to determine the consequences of the absence of caveolae and Cav-1 on calcium handling. We postulated that the loss of close association between caveolae and SR would reduce recycling of calcium in both directions.

calcium handling: a review and a hypothesis.
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