科研之友
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摘要
We analyzed the distribution of ryanodine receptor (RyR) and Ca(v)1.2 clusters in adult rat ventricular myocytes using three-dimensional object-based colocalization metrics. We found that similar to 75% of the Ca(v)1.2 clusters and 65% of the RyR clusters were within couplons, and both were roughly two and a half times larger than their extradyadic counterparts. Within a couplon, Ca(v)1.2 was concentrated near the center of the underlying RyR cluster and accounted for similar to 67% of its size. These data, together with previous findings from binding studies, enable us to estimate that a couplon contains 74 RyR tetramers and 10 copies of the alpha-subunit of Ca(v)1.2. Extradyadic clusters of RyR contained similar to 30 tetramers, whereas the extradyadic Ca(v)1.2 clusters contained, on average, only four channels. Between 80% and 85% of both RyR and Ca(v)1.2 molecules are within couplons. RyR clusters were in the closest proximity, with a median nearest-neighbor distance of 552 nm; comparable values for Ca(v)1.2 clusters and couplons were 619 nm and 735 nm, respectively. Extradyadic RyR clusters were significantly closer together (624 nm) and closer to the couplons (674 nm) than the couplons were to each other. In contrast, the extradyadic clusters of Ca(v)1.2 showed no preferential localization and were broadly distributed. These results provide a wealth of morphometric data that are essential for understanding intracellular Ca2+ regulation and modeling Ca2+ dynamics.
- 出版日期2010-12-15
