Senescence marker protein-30 (SMP30) induces formation of microvilli and bile canaliculi in Hep G2 cells
Senescence marker protein-30 (SMP30) induces formation of microvilli and bile canaliculi in Hep G2 cells
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DOI：
10.1007/s00441-004-1073-5
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发表时间：
2005-05-01
影响因子：
3.6
通讯作者：
Maruyama, N
中科院分区：
文献类型：
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作者：
Ishigami, A;Fujita, T;Maruyama, N
衰老标志蛋白30 （SMP30）是一种雄激素非依赖性因子，随着年龄的增长而减少。为了阐明SMP30的生理功能，我们将人SMP30 cDNA转染人肝癌细胞系Hep G2。这些Hep G2/SMP30转染物稳定地表达大量SMP30，比模拟转染物（Hep G2/pcDNA3对照）增殖速度更慢，合成的DNA更少。因此，SMP30表达的增强延缓了Hep G2/SMP30细胞的生长。扫描电镜超微结构研究显示Hep G2/SMP30细胞表面有大量微绒毛覆盖，而对照细胞表面很少出现微绒毛。随后，透射电镜显示Hep G2/SMP30细胞组表现出胆管，并在质间膜上具有特殊的粘附接触，如紧密连接和桥粒。然而，在对照组中，只观察到两个细胞的单位，并且这些细胞缺乏专门的粘附连接。已知Moesin和ZO-1分别集中在微绒毛和紧密连接处。采用双免疫染色法检测Hep G2/SMP30细胞顶端带微绒毛的胆管中moesin和ZO-1是否表达。Hep G2/SMP30各组细胞接触区moesin和ZO-1染色强度明显高于对照细胞。此外，moesin染色更多的内部区域，与胆管微绒毛相对应。显然，Hep G2/SMP30细胞的顶端形成了带有微绒毛的胆管。这些结果表明SMP30作为细胞间相互作用的参与者具有重要的生理功能，并暗示SMP30在衰老过程中的下调有助于细胞相互作用的恶化。
Senescence marker protein-30 (SMP30) is an androgen-independent factor that decreases with aging. To elucidate the physiological functions of SMP30, we transfected human SMP30 cDNA into the human hepatoma cell line, Hep G2. These Hep G2/SMP30 transfectants, which stably expressed large amounts of SMP30, proliferated at a slower rate and synthesized less DNA than mock transfectants (Hep G2/pcDNA3 controls). Thus, enhanced expression of SMP30 retarded the growth of Hep G2/SMP30 cells. Ultrastructural studies by scanning electron microscopy revealed numerous microvilli covering the surfaces of Hep G2/SMP30 cells, whereas few microvilli appeared on control cells. Subsequently, transmission electron microscopy revealed that groups of Hep G2/SMP30 cells exhibited bile canaliculi and possessed specialized adhesion contacts, such as tight junctions and desmosomes, at interplasmic membranes. However, in controls, units of only two cells were seen, and these lacked specialized adhesion junctions. Moesin and ZO-1 are known to be concentrated in microvilli and at tight junctions, respectively. Double-immunostaining was performed to examine whether moesin and ZO-1 were expressed in bile canaliculi with microvilli at the apical regions of Hep G2/SMP30 cells. The intensity of moesin and ZO-1 staining in the contact regions of each cell was markedly higher in Hep G2/SMP30 than in control cells. Moreover, moesin stained more interior areas, which corresponded to the microvilli of bile canaliculi. Clearly, bile canaliculi with microvilli formed at the apical ends of Hep G2/SMP30 cells. These results indicate that SMP30 has an important physiological function as a participant in cell-to-cell interactions and imply that the down-regulation of SMP30 during the aging process contributes to the deterioration of cellular interactivity.