From the Department of Medicine (J.Z., A.K.P., M.K., H.C., S.M.H., J.K.T., D.F., Y.G., N.D.D., Y.C., J.K.T., D.F., Y.G., N.D.D., Y.C., R.L., K.L.P., J.C., A.D.M., R.S.R.), University of California San Diego, La Jolla, CA.
Department of Bioengineering (K.P.V., A.D.M.), University of California San Diego, La Jolla, CA.
Circ Res. 2020 Jul 3;127(2):284-297. doi: 10.1161/CIRCRESAHA.119.315539. Epub 2020 Apr 29.
ZO-1 (Zonula occludens-1), a plasma membrane-associated scaffolding protein regulates signal transduction, transcription, and cellular communication. Global deletion of ZO-1 in the mouse is lethal by embryonic day 11.5. The function of ZO-1 in cardiac myocytes (CM) is largely unknown.
To determine the function of CM ZO-1 in the intact heart, given its binding to other CM proteins that have been shown instrumental in normal cardiac conduction and function.
We generated ZO-1 CM-specific knockout (KO) mice using α-Myosin Heavy Chain-nuclear Cre (ZO-1cKO) and investigated physiological and electrophysiological function by echocardiography, surface ECG and conscious telemetry, intracardiac electrograms and pacing, and optical mapping studies. ZO-1cKO mice were viable, had normal Mendelian ratios, and had a normal lifespan. Ventricular morphometry and function were not significantly different between the ZO-1cKO versus control (CTL) mice, basally in young or aged mice, or even when hearts were subjected to hemodynamic loading. Atrial mass was increased in ZO-1cKO. Electrophysiological and optical mapping studies indicated high-grade atrioventricular (A-V) block in ZO-1cKO comparing to CTL hearts. While ZO-1-associated proteins such as vinculin, connexin 43, N-cadherin, and α-catenin showed no significant change with the loss of ZO-1, Connexin-45 and Coxsackie-adenovirus (CAR) proteins were reduced in atria of ZO-1cKO. Further, with loss of ZO-1, ZO-2 protein was increased significantly in ventricular CM in a presumed compensatory manner but was still not detected in the AV nodal myocytes. Importantly, the expression of the sodium channel protein NaV1.5 was altered in AV nodal cells of the ZO-1cKO versus CTL.
ZO-1 protein has a unique physiological role in cardiac nodal tissue. This is in alignment with its known interaction with CAR and Cx45, and a new function in regulating the expression of NaV1.5 in AV node. Uniquely, ZO-1 is dispensable for function of the working myocardium.
ZO-1（封闭带蛋白-1）是一种与细胞质膜相关的支架蛋白，调节信号转导、转录和细胞通讯。在小鼠中，ZO-1 的全局缺失会导致胚胎 11.5 天死亡。ZO-1 在心肌细胞（CM）中的功能在很大程度上尚不清楚。
鉴于 ZO-1 与已证明对正常心脏传导和功能至关重要的其他 CM 蛋白结合，确定 CM ZO-1 在完整心脏中的功能。
我们使用α-肌球蛋白重链-核 Cre（ZO-1cKO）生成了 ZO-1 CM 特异性敲除（KO）小鼠，并通过超声心动图、体表心电图和清醒遥测、心内电图和起搏以及光学映射研究来研究生理和电生理功能。ZO-1cKO 小鼠存活，孟德尔比率正常，寿命正常。在年轻或年老的小鼠中，ZO-1cKO 与对照（CTL）小鼠的心室形态和功能没有显著差异，即使在心脏受到血流动力学负荷时也是如此。ZO-1cKO 的心房质量增加。与 CTL 心脏相比，电生理和光学映射研究表明 ZO-1cKO 存在高级房室（A-V）阻滞。虽然 ZO-1 相关蛋白，如粘着斑蛋白、连接蛋白 43、N-钙粘蛋白和α-连环蛋白，在 ZO-1 缺失时没有明显变化，但连接蛋白 45 和柯萨奇病毒-腺病毒（CAR）蛋白在 ZO-1cKO 的心房中减少。此外，随着 ZO-1 的缺失，ZO-2 蛋白在心室 CM 中显著增加，这可能是一种代偿性的方式，但在 AV 结心肌细胞中仍未检测到。重要的是，与 CTL 相比，AV 结细胞中钠通道蛋白 NaV1.5 的表达在 ZO-1cKO 中发生改变。
ZO-1 蛋白在心脏结组织中具有独特的生理作用。这与其与 CAR 和 Cx45 的已知相互作用以及在调节 AV 结中 NaV1.5 表达方面的新功能一致。独特的是，ZO-1 对于工作心肌的功能是可有可无的。
