Abstract：
OBJECTIVE: Striatin (Strn) is a scaffold protein expressed in cardiomyocytes (CMs) and alteration of its expression are described in various cardiac diseases. However, the alteration underlying its pathogenicity have been poorly investigated.
METHODS: We studied the role(s) of cardiac Strn gene (STRN) by comparing the functional properties of CMs, generated from Strn-KO and isogenic WT mouse embryonic stem cell lines.
RESULTS: The spontaneous beating rate of Strn-KO CMs was faster than WT cells, and this correlated with a larger fast INa conductance and no changes in If. Paced (2-8 Hz) Strn-KO CMs showed prolonged action potential (AP) duration in comparison with WT CMs and this was not associated with changes in ICaL and IKr. Motion video tracking analysis highlighted an altered contraction in Strn-KO CMs; this was associated with a global increase in intracellular Ca2+, caused by an enhanced late Na+ current density (INaL) and a reduced Na+/Ca2+ exchanger (NCX) activity and expression. Immunofluorescence analysis confirmed the higher Na+ channel expression and a more dynamic microtubule network in Strn-KO CMs than in WT. Indeed, incubation of Strn-KO CMs with the microtubule stabilizer taxol, induced a rescue (downregulation) of INa conductance toward WT levels.
CONCLUSIONS: Loss of STRN alters CMs electrical and contractile profiles and affects cell functionality by a disarrangement of Strn-related multi-protein complexes. This leads to impaired microtubules dynamics and Na+ channels trafficking to the plasma membrane, causing a global Na+ and Ca2+ enhancement.
METHODS: We studied the role(s) of cardiac Strn gene (STRN) by comparing the functional properties of CMs, generated from Strn-KO and isogenic WT mouse embryonic stem cell lines.
RESULTS: The spontaneous beating rate of Strn-KO CMs was faster than WT cells, and this correlated with a larger fast INa conductance and no changes in If. Paced (2-8 Hz) Strn-KO CMs showed prolonged action potential (AP) duration in comparison with WT CMs and this was not associated with changes in ICaL and IKr. Motion video tracking analysis highlighted an altered contraction in Strn-KO CMs; this was associated with a global increase in intracellular Ca2+, caused by an enhanced late Na+ current density (INaL) and a reduced Na+/Ca2+ exchanger (NCX) activity and expression. Immunofluorescence analysis confirmed the higher Na+ channel expression and a more dynamic microtubule network in Strn-KO CMs than in WT. Indeed, incubation of Strn-KO CMs with the microtubule stabilizer taxol, induced a rescue (downregulation) of INa conductance toward WT levels.
CONCLUSIONS: Loss of STRN alters CMs electrical and contractile profiles and affects cell functionality by a disarrangement of Strn-related multi-protein complexes. This leads to impaired microtubules dynamics and Na+ channels trafficking to the plasma membrane, causing a global Na+ and Ca2+ enhancement.
摘要：
目的：纹状体蛋白（Strn）是在心肌细胞（CMs）中表达的支架蛋白，其表达在各种心脏疾病中都有描述。然而,对其致病性的改变研究甚少。
方法：我们通过比较CMs的功能特性研究了心脏Strn基因（STRN）的作用，从Strn-KO和等基因WT小鼠胚胎干细胞系产生。
结果：Strn-KOCMs的自发搏动速率快于WT细胞，这与更大的快速INa电导相关，而If没有变化。与WTCM相比，起搏（2-8Hz）Strn-KOCM显示出延长的动作电位（AP）持续时间，这与ICaL和IKr的变化无关。运动视频跟踪分析强调了Strn-KOCMs收缩的改变；这与细胞内Ca2+的全球增加有关，由晚期Na电流密度（INaL）增强和Na/Ca2交换剂（NCX）活性和表达降低引起。免疫荧光分析证实，与WT相比，Strn-KOCMs的Na通道表达更高，微管网络更动态。的确,用微管稳定剂紫杉醇孵育Strn-KOCMs，诱导INa电导向WT水平的拯救(下调)。
结论：STRN的丢失改变了CM的电和收缩谱，并通过与STRN相关的多蛋白复合物的排列来影响细胞功能。这导致受损的微管动力学和Na+通道运输到质膜，导致Na+和Ca2+整体增强。
方法：我们通过比较CMs的功能特性研究了心脏Strn基因（STRN）的作用，从Strn-KO和等基因WT小鼠胚胎干细胞系产生。
结果：Strn-KOCMs的自发搏动速率快于WT细胞，这与更大的快速INa电导相关，而If没有变化。与WTCM相比，起搏（2-8Hz）Strn-KOCM显示出延长的动作电位（AP）持续时间，这与ICaL和IKr的变化无关。运动视频跟踪分析强调了Strn-KOCMs收缩的改变；这与细胞内Ca2+的全球增加有关，由晚期Na电流密度（INaL）增强和Na/Ca2交换剂（NCX）活性和表达降低引起。免疫荧光分析证实，与WT相比，Strn-KOCMs的Na通道表达更高，微管网络更动态。的确,用微管稳定剂紫杉醇孵育Strn-KOCMs，诱导INa电导向WT水平的拯救(下调)。
结论：STRN的丢失改变了CM的电和收缩谱，并通过与STRN相关的多蛋白复合物的排列来影响细胞功能。这导致受损的微管动力学和Na+通道运输到质膜，导致Na+和Ca2+整体增强。
