AMP-activated protein kinase (AMPK) is a multifunctional kinase that regulates microtubule (MT) dynamic instability through CLIP-170 phosphorylation; however, its physiological relevance in vivo remains to be elucidated. In this study, we identified an active form of AMPK localized at the intercalated discs in the heart, a specific cell-cell junction present between cardiomyocytes. A contractile inhibitor, MYK-461, prevented the localization of AMPK at the intercalated discs, and the effect was reversed by the removal of MYK-461, suggesting that the localization of AMPK is regulated by mechanical stress. Time-lapse imaging analysis revealed that the inhibition of CLIP-170 Ser-311 phosphorylation by AMPK leads to the accumulation of MTs at the intercalated discs. Interestingly, MYK-461 increased the individual cell area of cardiomyocytes in CLIP-170 phosphorylation-dependent manner. Moreover, heart-specific CLIP-170 S311A transgenic mice demonstrated elongation of cardiomyocytes along with accumulated MTs, leading to progressive decline in cardiac contraction. In conclusion, these findings suggest that AMPK regulates the cell shape and aspect ratio of cardiomyocytes by modulating the turnover of MTs through homeostatic phosphorylation of CLIP-170 at the intercalated discs.

中文翻译：

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AMPK通过CLIP-170通过调节微管的周转来调节心肌细胞的细胞形状

AMP激活蛋白激酶（AMPK）是一种多功能激酶，可通过CLIP-170磷酸化调节微管（MT）的动态不稳定性；然而，其在体内的生理相关性尚待阐明。在这项研究中，我们确定了一种活性形式的AMPK定位在心脏的插层盘上，这是心肌细胞之间存在的一种特定的细胞-细胞连接。收缩抑制剂MYK-461阻止了AMPK在插层盘上的定位，并且通过去除MYK-461逆转了作用，这表明AMPK的定位受机械应力调节。延时成像分析表明，AMPK对CLIP-170 Ser-311磷酸化的抑制作用导致MTs在插层椎间盘上积聚。有趣的是 MYK-461以CLIP-170磷酸化依赖性方式增加了心肌细胞的单个细胞面积。此外，心脏特异性CLIP-170 S311A转基因小鼠表现出心肌细胞的伸长以及累积的MT，导致心脏收缩的进行性下降。总之，这些发现表明，AMPK通过在插入椎间盘上通过CLIP-170的稳态磷酸化来调节MT的代谢，从而调节心肌细胞的细胞形状和长宽比。