Abstract：
OBJECTIVE: βII spectrin is a cytoskeletal protein known to be tightly linked to heart development and cardiovascular electrophysiology. However, the roles of βII spectrin in cardiac contractile function and pathological post-myocardial infarction remodeling remain unclear. Here, we investigated whether and how βII spectrin, the most common isoform of non-erythrocytic spectrin in cardiomyocytes, is involved in cardiac contractile function and ischemia/reperfusion (I/R) injury.
RESULTS: We observed that the levels of serum βII spectrin breakdown products (βII SBDPs) were significantly increased in patients with acute myocardial infarction (AMI). Concordantly, βII spectrin was degraded into βII SBDPs by calpain in mouse hearts after I/R injury. Using tamoxifen-inducible cardiac-specific βII spectrin knockout mice, we found that deletion of βII spectrin in the adult heart resulted in spontaneous development of cardiac contractile dysfunction, cardiac hypertrophy and fibrosis at 5 weeks after tamoxifen treatment. Moreover, at 1 week after tamoxifen treatment, although spontaneous cardiac dysfunction in cardiac-specific βII spectrin knockout mice had not developed, deletion of βII spectrin in the heart exacerbated I/R-induced cardiomyocyte death and heart failure. Furthermore, restoration of βII spectrin expression via adenoviral small activating RNA (saRNA) delivery into the heart reduced I/R injury. Immunoprecipitation coupled with mass spectrometry (IP-LC-MS/MS) analyses and functional studies revealed that βII spectrin is indispensable for mitochondrial complex I activity and respiratory function. Mechanistically, βII spectrin promotes translocation of NADH:ubiquinone oxidoreductase 75 kDa Fe-S protein 1 (NDUFS1) from the cytosol to mitochondria by crosslinking with actin filaments (F-actin) to maintain F-actin stability.
CONCLUSIONS: βII spectrin is an essential cytoskeletal element for preserving mitochondrial homeostasis and cardiac function. Defects in βII spectrin exacerbate cardiac I/R injury.
RESULTS: We observed that the levels of serum βII spectrin breakdown products (βII SBDPs) were significantly increased in patients with acute myocardial infarction (AMI). Concordantly, βII spectrin was degraded into βII SBDPs by calpain in mouse hearts after I/R injury. Using tamoxifen-inducible cardiac-specific βII spectrin knockout mice, we found that deletion of βII spectrin in the adult heart resulted in spontaneous development of cardiac contractile dysfunction, cardiac hypertrophy and fibrosis at 5 weeks after tamoxifen treatment. Moreover, at 1 week after tamoxifen treatment, although spontaneous cardiac dysfunction in cardiac-specific βII spectrin knockout mice had not developed, deletion of βII spectrin in the heart exacerbated I/R-induced cardiomyocyte death and heart failure. Furthermore, restoration of βII spectrin expression via adenoviral small activating RNA (saRNA) delivery into the heart reduced I/R injury. Immunoprecipitation coupled with mass spectrometry (IP-LC-MS/MS) analyses and functional studies revealed that βII spectrin is indispensable for mitochondrial complex I activity and respiratory function. Mechanistically, βII spectrin promotes translocation of NADH:ubiquinone oxidoreductase 75 kDa Fe-S protein 1 (NDUFS1) from the cytosol to mitochondria by crosslinking with actin filaments (F-actin) to maintain F-actin stability.
CONCLUSIONS: βII spectrin is an essential cytoskeletal element for preserving mitochondrial homeostasis and cardiac function. Defects in βII spectrin exacerbate cardiac I/R injury.
摘要：
目的：βII血影蛋白是一种细胞骨架蛋白，已知与心脏发育和心血管电生理密切相关。然而,βII血影蛋白在心脏收缩功能和病理性心肌梗死后重塑中的作用尚不清楚.这里,我们调查了βII是否以及如何，心肌细胞中最常见的非红细胞血影蛋白同种型，参与心脏收缩功能和缺血/再灌注(I/R)损伤。
结果：我们观察到急性心肌梗死（AMI）患者的血清βII血谱分解产物（βIISBDP）水平显着升高。和谐地，I/R损伤后，小鼠心脏中的βII血影蛋白被钙蛋白酶降解为βIISBDP。使用他莫昔芬诱导的心脏特异性βII血影蛋白敲除小鼠，我们发现成人心脏中βII血影蛋白的缺失导致心脏收缩功能障碍的自发发展，他莫昔芬治疗后5周的心肌肥厚和纤维化。此外，在他莫昔芬治疗后1周，尽管心脏特异性βII血影蛋白基因敲除小鼠的自发性心功能不全尚未发展，心脏中βII血影蛋白的缺失加剧了I/R诱导的心肌细胞死亡和心力衰竭。此外，通过将腺病毒小激活RNA（saRNA）递送到心脏中，恢复βII血影蛋白的表达减少了I/R损伤。免疫沉淀与质谱（IP-LC-MS/MS）分析和功能研究表明，βII血影蛋白对于线粒体复合物I的活性和呼吸功能是必不可少的。机械上,βII血影蛋白通过与肌动蛋白丝（F-肌动蛋白）交联以维持F-肌动蛋白的稳定性，促进NADH：泛醌氧化还原酶75kDaFe-S蛋白1（NDUFS1）从胞质溶胶到线粒体的易位。
结论：βII血影蛋白是维持线粒体稳态和心脏功能的必需细胞骨架元件。βII血影蛋白的缺陷会加剧心脏I/R损伤。
结果：我们观察到急性心肌梗死（AMI）患者的血清βII血谱分解产物（βIISBDP）水平显着升高。和谐地，I/R损伤后，小鼠心脏中的βII血影蛋白被钙蛋白酶降解为βIISBDP。使用他莫昔芬诱导的心脏特异性βII血影蛋白敲除小鼠，我们发现成人心脏中βII血影蛋白的缺失导致心脏收缩功能障碍的自发发展，他莫昔芬治疗后5周的心肌肥厚和纤维化。此外，在他莫昔芬治疗后1周，尽管心脏特异性βII血影蛋白基因敲除小鼠的自发性心功能不全尚未发展，心脏中βII血影蛋白的缺失加剧了I/R诱导的心肌细胞死亡和心力衰竭。此外，通过将腺病毒小激活RNA（saRNA）递送到心脏中，恢复βII血影蛋白的表达减少了I/R损伤。免疫沉淀与质谱（IP-LC-MS/MS）分析和功能研究表明，βII血影蛋白对于线粒体复合物I的活性和呼吸功能是必不可少的。机械上,βII血影蛋白通过与肌动蛋白丝（F-肌动蛋白）交联以维持F-肌动蛋白的稳定性，促进NADH：泛醌氧化还原酶75kDaFe-S蛋白1（NDUFS1）从胞质溶胶到线粒体的易位。
结论：βII血影蛋白是维持线粒体稳态和心脏功能的必需细胞骨架元件。βII血影蛋白的缺陷会加剧心脏I/R损伤。
