Critical role of cyclin D1 nuclear import in cardiomyocyte proliferation
Critical role of cyclin D1 nuclear import in cardiomyocyte proliferation
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DOI：
10.1161/01.res.0000049105.15329.1c
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发表时间：
2003-01-10
影响因子：
20.1
通讯作者：
Ikeda, MA
中科院分区：
文献类型：
--
作者：
Tamamori-Adachi, M;Ito, H;Ikeda, MA
哺乳动物的心肌细胞在出生后不久就不可逆地失去了增殖能力，但其潜在的机制尚不清楚。细胞周期蛋白D1及其配偶体细胞周期蛋白依赖性激酶4（CDK 4）通过视网膜母细胞瘤（Rb）蛋白的磷酸化对促进G1期到S期的进展很重要。有丝分裂刺激诱导有丝分裂后心肌细胞肥大细胞生长并上调细胞周期蛋白D1的表达。在本研究中，我们发现，在新生大鼠心肌细胞中，D-型细胞周期蛋白和CDK 4主要是细胞质，而Rb仍然处于磷酸化不足的状态。异位表达的细胞周期蛋白D1定位于胎儿，但不是新生儿心肌细胞的核。为了将细胞周期蛋白D1有效地定位于细胞核，我们构建了一个与核定位信号（NLS）直接相关的细胞周期蛋白D1变体（D1 NLS）。共感染表达D1 NLS和CDK 4的重组腺病毒可诱导Rb磷酸化和CDK 2激酶活性。此外，D1 NLS/CDK 4足以促进重新进入细胞周期，导致细胞分裂。这些病毒共感染的心肌细胞的数量增加了3倍，感染后5天。最后，D1 NLS/CDK 4促进了注射这些病毒的成人心脏中心肌细胞的细胞周期重入，通过Ki-67的表达和BrdU掺入来评估，Ki-67在细胞周期的所有阶段中在增殖细胞中表达。因此，有丝分裂后的心肌细胞具有增殖的潜力，前提是细胞周期蛋白D1/CDK 4在细胞核中积累，并且防止其核输入作为防止心肌细胞增殖的物理屏障起着关键作用。我们的研究结果为开发诱导心肌细胞再生的治疗策略提供了新的见解。这篇文章的全文可以在http://www.circresaha.org上找到。
Mammalian cardiomyocytes irreversibly lose their capacity to proliferate soon after birth, yet the underlying mechanisms have been unclear. Cyclin D1 and its partner, cyclin-dependent kinase 4 (CDK4), are important for promoting the G1-to-S phase progression via phosphorylation of the retinobiastoma (Rb) protein. Mitogenic stimulation induces hypertrophic cell growth and upregulates expression of cyclin D1 in postmitotic cardiomyocytes. In the present study, we show that, in neonatal rat cardiomyocytes, D-type cyclins and CDK4 were predominantly cytoplasmic, whereas Rb remained in an underphosphorylated state. Ectopically expressed cyclin D1 localized in the nucleus of fetal but not neonatal cardiomyocytes. To target cyclin D1 to the nucleus efficiently, we constructed a variant of cyclin D1 (D1NLS), which directly linked to nuclear localization signals (NLSs). Coinfection of recombinant adenoviruses expressing D1NLS and CDK4 induced Rb phosphorylation and CDK2 kinase activity. Furthermore, D1NLS/CDK4 was sufficient to promote the reentry into the cell cycle, leading to cell division. The number of cardiomyocytes coinfected with these viruses increased 3-fold 5 days after infection. Finally, D1NLS/CDK4 promoted cell cycle reentry of cardiomyocytes in adult hearts injected with these viruses, evaluated by the expression of Ki-67, which is expressed in proliferating cells in all phases of the cell cycle, and BrdU incorporation. Thus, postmitotic cardiomyocytes have the potential to proliferate provided that cyclin D1/CDK4 accumulate in the nucleus, and the prevention of their nuclear import plays a critical role as a physical barrier to prevent cardiomyocyte proliferation. Our results provide new insights into the development of therapeutics strategies to induce regeneration of cardiomyocytes. The full text of this article is available at http://www.circresaha.org.