Watson P A, Hannan R, Carl L L, Giger K E
Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2615, USA.
Am J Physiol. 1996 Aug;271(2 Pt 1):C684-9. doi: 10.1152/ajpcell.1996.271.2.C684.
Accumulation of tubulin protein and an increased array of microtubules have been associated with contractile dysfunction in cardiac myocytes after pressure overload in vivo. Experiments were performed to assess the ability of mechanical stimuli experienced by ventricular cardiac myocytes during the progression of hypertrophic and dilated pathology to increase beta-tubulin production in cultured neonatal rat cardiac myocytes. Results indicate that both contractile activity and load due to passive stretch increase beta-tubulin protein content in neonatal rat cardiac myocytes through accumulation of beta-tubulin mRNA, which occurs without increased beta-tubulin gene transcription. Western blot analysis demonstrated that contraction resulted in the accumulation of beta-tubulin in neonatal rat cardiac myocytes above increases observed in the content of total cellular protein. Northern blot analysis indicated that beta-tubulin mRNA content increased in response to both stretch and contraction. alpha-Adrenergic agonists that lead to pathophysiological growth in cardiac myocytes also stimulated an increase in beta-tubulin mRNA content. Treatment of contracting neonatal cardiac myocytes with angiotensin II (ANG II) further increased beta-tubulin mRNA content, whereas ANG II treatment in arrested neonatal cardiac myocytes failed to increase beta-tubulin mRNA. Nuclear run-on experiments indicate that contraction stimulates beta-tubulin mRNA accumulation without an increase in beta-tubulin gene transcription. These results imply that tubulin production in cultured cardiac myocytes can be regulated directly by mechanical forces. In mechanically challenged hearts, the accumulation of beta-tubulin and the development of contractile dysfunction may be directly related to the mechanical forces imposed on the myocardium during the onset and progression of cardiovascular disease.
在体内压力超负荷后，心肌细胞中微管蛋白的积累和微管阵列的增加与收缩功能障碍有关。进行实验以评估在肥厚性和扩张性病理过程中，心室心肌细胞所经历的机械刺激增加培养的新生大鼠心肌细胞中β-微管蛋白产生的能力。结果表明，收缩活动和被动拉伸引起的负荷均通过β-微管蛋白mRNA的积累增加新生大鼠心肌细胞中β-微管蛋白的含量，而β-微管蛋白基因转录并未增加。蛋白质免疫印迹分析表明，收缩导致新生大鼠心肌细胞中β-微管蛋白的积累，其增加幅度高于总细胞蛋白含量的增加。Northern印迹分析表明，β-微管蛋白mRNA含量在拉伸和收缩刺激下均增加。导致心肌细胞病理生理生长的α-肾上腺素能激动剂也刺激β-微管蛋白mRNA含量增加。用血管紧张素II（ANG II）处理收缩的新生心肌细胞可进一步增加β-微管蛋白mRNA含量，而用ANG II处理静止的新生心肌细胞则不能增加β-微管蛋白mRNA。细胞核连续转录实验表明，收缩刺激β-微管蛋白mRNA积累，但β-微管蛋白基因转录并未增加。这些结果表明，培养的心肌细胞中微管蛋白的产生可直接受机械力调节。在受到机械挑战的心脏中，β-微管蛋白的积累和收缩功能障碍的发展可能与心血管疾病发生和发展过程中心肌所承受的机械力直接相关。
