Caveolae modulate excitation–contraction coupling and β2-adrenergic signalling in adult rat ventricular myocytes

Calaghan, Sarah; White, Ed

doi:10.1016/j.cardiores.2005.10.006

Cited by 83 publications

(99 citation statements)

References 52 publications

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“…This is not surprising as b 2 -adrenoreceptors colocalize with Cav-3 in ventricular and sinoatrial myocytes, and chemical disruption of caveolae affects the excitation-contraction coupling and b-adrenergic responsiveness of adult cardiac myocytes. [37][38][39] In this study, we did not detect any signs of arrhythmia in our patient or in her heterozygous daughter.…”

Section: Discussioncontrasting

confidence: 57%

Caveolin-3 T78M and T78K missense mutations lead to different phenotypes in vivo and in vitro

Traverso

Gazzerro

Assereto

et al. 2008

Laboratory Investigation

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Caveolins are the principal protein components of caveolae, invaginations of the plasma membrane involved in cell signaling and trafficking. Caveolin-3 (Cav-3) is the muscle-specific isoform of the caveolin family and mutations in the CAV3 gene lead to a large group of neuromuscular disorders. In unrelated patients, we identified two distinct CAV3 mutations involving the same codon 78. Patient 1, affected by dilated cardiomyopathy and limb girdle muscular dystrophy (LGMD)-1C, shows an autosomal recessive mutation converting threonine to methionine (T78M). Patient 2, affected by isolated familiar hyperCKemia, shows an autosomal dominant mutation converting threonine to lysine (T78K). Cav-3 wild type (WT) and Cav-3 mutations were transiently transfected into Cos-7 cells. Cav-3 WT and Cav-3 T78M mutant localized at the plasma membrane, whereas Cav-3 T78K was retained in a perinuclear compartment. Cav-3 T78K expression was decreased by 87% when compared with Cav-3 WT, whereas Cav-3 T78M protein levels were unchanged. To evaluate whether Cav-3 T78K and Cav-3 T78M mutants behaved with a dominant negative pattern, Cos-7 cells were cotransfected with green fluorescent protein (GFP)-Cav-3 WT in combination with either mutant or WT Cav-3. When cotransfected with Cav-3 WT or Cav-3 T78M, GFP-Cav-3 WT was localized at the plasma membrane, as expected. However, when cotransfected with Cav-3 T78K, GFP-Cav-3 WT was retained in a perinuclear compartment, and its protein levels were reduced by 60%, suggesting a dominant negative action. Accordingly, Cav-3 protein levels in muscles from a biopsy of patient 2 (T78K mutation) were reduced by 80%. In conclusion, CAV3 T78M and T78K mutations lead to distinct disorders showing different clinical features and inheritance, and displaying distinct phenotypes in vitro.

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Section: Discussioncontrasting

confidence: 57%

Caveolin-3 T78M and T78K missense mutations lead to different phenotypes in vivo and in vitro

Traverso

Gazzerro

Assereto

et al. 2008

Laboratory Investigation

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“…Interestingly a recent study using the cholesterol-depleting agent methyl-β-cyclodextrin showed no change in membrane capacitance or t-tubule structure in rat ventricular myocytes (Calaghan & White, 2006), although previous work has shown that methyl-β-cyclodextrin disrupts the t-tubules in myotubes (Pouvreau et al, 2004), so that the structure of skeletal and cardiac t-tubules may rely to different extents on cholesterol. It might be expected, however, that insertion of cholesterol in the membrane would increase membrane thickness, and thus decrease capacitance.…”

Section: Effect Of Cholesterol On Membrane Capacitancementioning

confidence: 95%

“…However since membrane composition can alter protein function it is also possible that a high cholesterol concentration in the t-tubule membrane may itself alter the function of proteins located in the t-tubule membrane, although a recent study has shown that the cholesterol-depleting agent methyl-β-cyclodextrin has no significant effect on I Ca in rat ventricular myocytes (Calaghan & White, 2006).…”

Section: Consequences Of Incomplete Detubulation and Reduced Specificmentioning

confidence: 99%

Quantification of t-tubule area and protein distribution in rat cardiac ventricular myocytes

Pásek

Brette

Nelson

et al. 2008

Progress in Biophysics and Molecular Biology

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The transverse (t-) tubules of cardiac ventricular myocytes are invaginations of the surface membrane that form a complex network within the cell. Many of the key proteins involved in excitation-contraction coupling appear to be located predominantly at the t-tubule membrane.Despite their importance, the fraction of cell membrane within the t-tubules remains unclear: measurement of cell capacitance following detubulation suggests ~32%, whereas optical measurements suggest up to ~65%. We have therefore investigated the factors that may account for this discrepancy. Calculation of the combinations of t-tubule radius, length and density that produce t-tubular membrane fractions of 32% or 56% suggest that the true fraction is at the upper end of this range. Assessment of detubulation using confocal and electron microscopy suggests that incomplete detubulation can account for some, but not all of the difference. High cholesterol, and a consequent decrease in specific capacitance, in the t-tubule membrane, may also cause the ttubule fraction calculated from the loss of capacitance following detubulation to be underestimated. Correcting for both of these factors results in an estimate that is still lower than that obtained from optical measurements suggesting either that optical methods overestimate the fraction of membrane in the t-tubules, or that other, unknown, factors, reduce the apparent fraction obtained by detubulation. A biophysically realistic computer model of a rat ventricular myocyte, incorporating a t-tubule network, is used to assess the effect of the altered estimates of t-tubular membrane fraction on the calculated distribution of ion flux pathways.

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“…Rafts and/or caveolae have been postulated to play an important role in ECC; in the adult rat ventricular myocyte, removing cholesterol and disrupting the caveolae and/or rafts using methyl--cyclodextrin (MBC) reduced both the amplitude of the [Ca 2+ ] i transient and the contraction (Calaghan and White, 2006). The use of MBC in rat arterial smooth muscle and neonatal cardiomyocytes, which lack a defined TATS, much like atrial myocytes, resulted in a reduction in the frequency, width and amplitude of Ca 2+ sparks, without modulation of the current through the Ca v 1.2 channels (Lohn et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

Couplons in rat atria form distinct subgroups defined by their molecular partners

Schulson

Scriven

Fletcher

et al. 2011

Journal of Cell Science

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Standard local control theory, which describes Ca2+ release during excitation–contraction coupling (ECC), assumes that all ryanodine receptor 2 (RyR2) complexes are equivalent. Findings from our laboratory have called this assumption into question. Specifically, we have shown that the RyR2 complexes in ventricular myocytes are different, depending on their location within the cell. This has led us to hypothesize that similar differences occur within the rat atrial cell. To test this hypothesis, we have triple-labelled enzymatically isolated fixed myocytes to examine the distribution and colocalization of RyR2, calsequestrin (Casq), voltage-gated Ca2+ channels (Cav1.2), the sodium–calcium exchanger (Ncx) and caveolin-3 (Cav3). A number of different surface RyR2 populations were identified, and one of these groups, in which RyR2, Cav1.2 and Ncx colocalized, might provide the structural basis for ‘eager’ sites of Ca2+ release in atria. A small percentage of the dyads containing RyR2 and Cav1.2 were colocalized with Cav3, and therefore could be influenced by the signalling molecules it anchors. The majority of the RyR2 clusters were tightly linked to Cav1.2, and, whereas some were coupled to both Ca 1.2 and Ncx, none were with Ncx alone. This suggests that Cav1.2-mediated Ca2+ -induced Ca2+ release is the primary method of ECC. The two molecules studied that were found in the interior of atrial cells, RyR2 and Casq, showed significantly less colocalization and a reduced nearest-neighbour distance in the interior, compared with the surface of the cell. These differences might result in a higher excitability for RyR2 in the interior of the cells, facilitating the spread of excitation from the periphery to the centre. We also present morphometric data for all of the molecules studied, as well as for those colocalizations found to be significant.

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Caveolae modulate excitation–contraction coupling and β2-adrenergic signalling in adult rat ventricular myocytes

Cited by 83 publications

References 52 publications

Caveolin-3 T78M and T78K missense mutations lead to different phenotypes in vivo and in vitro

Caveolin-3 T78M and T78K missense mutations lead to different phenotypes in vivo and in vitro

Quantification of t-tubule area and protein distribution in rat cardiac ventricular myocytes

Couplons in rat atria form distinct subgroups defined by their molecular partners

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