Strauch A R, Min B, Reeser J C, Yan H, Foster D N, Berman M D
Department of Cell Biology, Neurobiology, and Anatomy, College of Medicine, Ohio State University, Columbus 43210.
J Cell Biochem. 1992 Nov;50(3):266-78. doi: 10.1002/jcb.240500307.
The expression of vascular smooth muscle (VSM) alpha-actin mRNA during BC3H1 myogenic cell differentiation is specifically stimulated by conditions of high cell density. Non-proteolytic dissociation of cell-cell and cell-matrix contacts in post-confluent cultures of BC3H1 myocytes using EDTA promotes loss of the differentiated morphological phenotype. EDTA-dispersed myocytes exhibit an undifferentiated fibroblastoid appearance and contained reduced levels of both VSM and skeletal alpha-actin mRNA. Muscle alpha-actin mRNA levels in EDTA-dispersed myocytes were not restored to that observed in confluent myocyte preparations by experimental manipulation of cell density conditions. Pulse-labeling techniques using L-[35S]cysteine to identify muscle actin biosynthetic intermediates revealed that EDTA-dispersed myocytes expressed nascent forms of both the VSM and skeletal muscle alpha-actin polypeptide chains. However EDTA-dispersed myocytes were less efficient in the post-translational processing of immature VSM alpha-actin compared to non-dispersed myocytes. Simple cell-to-cell contact may mediate VSM alpha-actin processing efficiency since high-density preparations of EDTA-dispersed myocytes processed more VSM alpha-actin intermediate than myocytes plated at low density. The actin isoform selectivity of the response to modulation of intercellular contacts suggests that actin biosynthesis in BC3H1 myogenic cells involves mechanisms capable of discriminating between different isoform classes of nascent actin polypeptide chains.
在BC3H1成肌细胞分化过程中，血管平滑肌（VSM）α-肌动蛋白mRNA的表达受到高细胞密度条件的特异性刺激。使用EDTA在BC3H1肌细胞汇合后培养物中进行细胞间和细胞与基质接触的非蛋白水解解离，会导致分化的形态表型丧失。经EDTA分散的肌细胞呈现未分化的成纤维样外观，且VSM和骨骼肌α-肌动蛋白mRNA水平均降低。通过实验操纵细胞密度条件，经EDTA分散的肌细胞中的肌肉α-肌动蛋白mRNA水平未恢复到汇合肌细胞制剂中观察到的水平。使用L-[35S]半胱氨酸的脉冲标记技术来鉴定肌肉肌动蛋白生物合成中间体，结果显示经EDTA分散的肌细胞表达VSM和骨骼肌α-肌动蛋白多肽链的新生形式。然而，与未分散的肌细胞相比，经EDTA分散的肌细胞在未成熟VSMα-肌动蛋白的翻译后加工方面效率较低。简单的细胞间接触可能介导VSMα-肌动蛋白的加工效率，因为高密度的经EDTA分散的肌细胞制剂比低密度接种的肌细胞加工更多的VSMα-肌动蛋白中间体。对细胞间接触调节反应的肌动蛋白同工型选择性表明，BC3H1成肌细胞中的肌动蛋白生物合成涉及能够区分新生肌动蛋白多肽链不同同工型类别的机制。
