L'Ecuyer T J, Schulte D, Lin J J
Department of Pediatrics, University of Iowa, Iowa City 52242.
Pediatr Res. 1991 Sep;30(3):232-8. doi: 10.1203/00006450-199109000-00006.
Developmental differences in myocardial performance are known to exist. It is likely that the profile of protein isoforms present on the developing thin filament contributes to these observed differences. We have prepared thin filaments from developing and mature rat hearts by using an immunoprecipitation procedure developed in our laboratory. Analysis of these isolated thin filaments by Western immunoblots and two-dimensional gel electrophoresis demonstrates troponin I and troponin T isoform switching on the developing thin filament. Troponin I isoform switching begins by embryonic d 18 and is complete before the 3rd postnatal wk. Troponin T isoform switching begins between embryonic d 18 and birth and is complete between the 2nd and 3rd postnatal wk. The degree of phosphorylation of tropomyosin in thin filaments appears to be developmentally regulated, decreasing with advancing age. Nonmuscle isoforms of tropomyosin are also detectable in thin filaments from developing and mature rat hearts. These phenomena (troponin isoform switching, the degree of phosphorylation of tropomyosin, and the presence of nonmuscle isoforms of tropomyosin on cardiac thin filaments) likely play a role in the function of immature thin filaments and in the assembly of mature thin filaments.
已知心肌性能存在发育差异。发育中的细肌丝上存在的蛋白质异构体谱可能导致了这些观察到的差异。我们通过使用我们实验室开发的免疫沉淀程序，从发育中的和成熟的大鼠心脏中制备了细肌丝。通过蛋白质免疫印迹法和二维凝胶电泳对这些分离出的细肌丝进行分析，结果表明发育中的细肌丝上存在肌钙蛋白I和肌钙蛋白T异构体的转换。肌钙蛋白I异构体的转换在胚胎第18天开始，并在出生后第3周之前完成。肌钙蛋白T异构体的转换在胚胎第18天和出生之间开始，并在出生后第2周和第3周之间完成。细肌丝中肌动蛋白的磷酸化程度似乎受发育调控，随着年龄增长而降低。在发育中的和成熟的大鼠心脏的细肌丝中也可检测到非肌肉型肌动蛋白异构体。这些现象（肌钙蛋白异构体转换、肌动蛋白的磷酸化程度以及心脏细肌丝上非肌肉型肌动蛋白异构体的存在）可能在未成熟细肌丝的功能以及成熟细肌丝的组装中发挥作用。
