The structure of calsequestrin in triads of vertebrate skeletal muscle: a deep-etch study.

Franzini-Armstrong, C; Kenney, Linda J.; Varriano-Marston, E.

doi:10.1083/jcb.105.1.49

Cited by 214 publications

(138 citation statements)

References 49 publications

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“…In addition, they have identical cluster diameters and similar intercluster distances (Table 6). In the ventricle, electron micrographs show that Casq is associated with the couplon (Franzini-Armstrong et al, 1987), so it is probable that there is significant overlap between the two groups, and that they form the triplet RyR-Ca v 1.2-Casq. If there is complete overlap between the two groups, and all of the RyR is in the triplet, summing the significant colocalizations indicates that over 20% of the RyR would not be accounted for.…”

Section: +mentioning

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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Section: +mentioning

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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“…The process of aggregation may imply a crosstalk between the lumen and the surrounding membrane, and this could contribute to the generation of specialized domains in the latter. In the SR, aggregates of CSQ are attached to the terminal cisternae junctional membrane by specific integral proteins (Franzini-Armstrong et al, 1987). In the case of calreticulin, the concentration at discrete sites might be mediated by the interaction with cyclophillin B (Arber et al, 1992).…”

Section: Specializations Of the Er Luminal Contentmentioning

confidence: 99%

Endoplasmic reticulum: a dynamic patchwork of specialized subregions.

Sitia

Meldolesi

1992

MBoC

150

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“…Proteins involved in calcium storage and release are also found in specialized regions of the ER. For example, the Ca++ binding protein, calsequestrin, is localized in smooth ER regions and concentrated in vesicles in Purkinje neurons (Villa et al, 1991;Takei et al, 1992), but is present only in the terminal cisternae of the sarcoplasmic reticulum in skeletal muscle (Franzini-Armstrong et al, 1987). In addition, the inositol 1,4,5-trisphosphate receptor, a…”

Section: Introductionmentioning

confidence: 99%

Different subcellular localization of Saccharomyces cerevisiae HMG-CoA reductase isozymes at elevated levels corresponds to distinct endoplasmic reticulum membrane proliferations.

Koning

Roberts

Wright

1996

MBoC

109

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In all eucaryotic cell types analyzed, proliferations of the endoplasmic reticulum (ER) can be induced by increasing the levels of certain integral ER proteins. One of the best characterized of these proteins is HMG-CoA reductase, which catalyzes the rate-limiting step in sterol biosynthesis. We have investigated the subcellular distributions of the two HMG-CoA reductase isozymes in Saccharomyces cerevisiae and the types of ER proliferations that arise in response to elevated levels of each isozyme. At endogenous expression levels, Hmglp and Hmg2p were both primarily localized in the nuclear envelope. However, at increased levels, the isozymes displayed distinct subcellular localization patterns in which each isozyme was predominantly localized in a different region of the ER. Specifically, increased levels of Hmglp were concentrated in the nuclear envelope, whereas increased levels of Hmg2p were concentrated in the peripheral ER. In addition, an Hmg2p chimeric protein containing a 77-amino acid lumenal segment from Hmglp was localized in a pattern that resembled that of Hmglp when expressed at increased levels. Reflecting their different subcellular distributions, elevated levels of Hmglp and Hmg2p induced sets of ER membrane proliferations with distinct morphologies. The ER membrane protein, Sec6lp, was localized in the membranes induced by both Hmglp and Hmg2p green fluorescent protein (GFP) fusions. In contrast, the lumenal ER protein, Kar2p, was present in Hmglp:GFP membranes, but only rarely in Hmg2p:GFP membranes. These results indicated that the membranes synthesized in response to Hmglp and Hmg2p were derived from the ER, but that the membranes were not identical in protein composition. We determined that the different types of ER proliferations were not simply due to quantitative differences in protein amounts or to the different half-lives of the two isozymes. It is possible that the specific distributions of the two yeast HMG-CoA reductase isozymes and their corresponding membrane proliferations may reveal regions of the ER that are specialized for certain branches of the sterol biosynthetic pathway.

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The structure of calsequestrin in triads of vertebrate skeletal muscle: a deep-etch study.

Cited by 214 publications

References 49 publications

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

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

Endoplasmic reticulum: a dynamic patchwork of specialized subregions.

Different subcellular localization of Saccharomyces cerevisiae HMG-CoA reductase isozymes at elevated levels corresponds to distinct endoplasmic reticulum membrane proliferations.

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