Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, USA.
Biophys J. 2011 Apr 6;100(7):1599-607. doi: 10.1016/j.bpj.2011.02.013.
Cardiomyocytes have a complex Ca(2+) behavior and changes in this behavior may underlie certain disease states. Intracellular Ca(2+) activity can be regulated by the phospholipase Cβ-Gα(q) pathway localized on the plasma membrane. The plasma membranes of cardiomycoytes are rich in caveolae domains organized by caveolin proteins. Caveolae may indirectly affect cell signals by entrapping and localizing specific proteins. Recently, we found that caveolin may specifically interact with activated Gα(q), which could affect Ca(2+) signals. Here, using fluorescence imaging and correlation techniques we show that Gα(q)-Gβγ subunits localize to caveolae in adult ventricular canine cardiomyoctyes. Carbachol stimulation releases Gβγ subunits from caveolae with a concurrent stabilization of activated Gα(q) by caveolin-3 (Cav3). These cells show oscillating Ca(2+) waves that are not seen in neonatal cells that do not contain Cav3. Microinjection of a peptide that disrupts Cav3-Gα(q) association, but not a control peptide, extinguishes the waves. Furthermore, these waves are unchanged with rynaodine treatment, but not seen with treatment of a phospholipase C inhibitor, implying that Cav3-Gα(q) is responsible for this Ca(2+) activity. Taken together, these studies show that caveolae play a direct and active role in regulating basal Ca(2+) activity in cardiomyocytes.
心肌细胞具有复杂的 Ca(2+)行为，这种行为的变化可能是某些疾病状态的基础。细胞内 Ca(2+)活性可以通过位于质膜上的磷脂酶 Cβ-Gα(q)途径来调节。心肌细胞的质膜富含由窖蛋白组成的小窝域。小窝可能通过捕获和定位特定的蛋白质来间接影响细胞信号。最近，我们发现窖蛋白可能特异性地与激活的 Gα(q)相互作用，从而影响 Ca(2+)信号。在这里，我们使用荧光成像和相关技术表明，Gα(q)-Gβγ亚基定位于成年心室犬心肌细胞的小窝中。乙酰胆碱刺激从小窝中释放 Gβγ亚基，同时窖蛋白-3（Cav3）稳定激活的 Gα(q)。这些细胞显示出振荡的 Ca(2+)波，而在不含有 Cav3 的新生细胞中则看不到。微注射一种破坏 Cav3-Gα(q)相互作用的肽，但不是对照肽，会使波消失。此外，这些波不受瑞诺定处理的影响，但在磷脂酶 C 抑制剂处理时则看不到，这表明 Cav3-Gα(q)负责这种 Ca(2+)活性。总之，这些研究表明，小窝在调节心肌细胞基础 Ca(2+)活性方面发挥着直接和积极的作用。
