Differential activation of a calcium-dependent endonuclease in human B lymphocytes. Role in ionomycin-induced apoptosis.
Differential activation of a calcium-dependent endonuclease in human B lymphocytes. Role in ionomycin-induced apoptosis.
复制标题
人 B 淋巴细胞中钙依赖性核酸内切酶的差异激活。
作者：
K. Aagaard;D. Jelinek
B细胞成熟的状态深刻地影响结果，即，激活，生长停滞，或程序性细胞死亡，各种刺激，包括钙离子载体，离子霉素。最初的研究证实了这样的观察，即代表未成熟B细胞的细胞系，即，伯基特淋巴瘤细胞系，诱导进行细胞凋亡，响应于离子霉素，而更成熟的B细胞系没有，而是经历细胞周期停滞在G1期间隔。为了理解这种不同的结果，我们集中于比较由离子霉素诱导的经历程序性细胞死亡的细胞（拉莫斯）与对离子霉素诱导的程序性细胞死亡具有抗性的细胞（Ly 1）中核酸内切酶的表达和活化。我们的结果表明，低分子量。加入离子霉素后，内源性Ca 2 +/Mg（2+）依赖性核酸内切酶的一部分在拉莫斯细胞中被激活，但在激活的Ly 1细胞中没有。然而，令人感兴趣的是，低分子量。当分离的Ly 1细胞核用外源钙处理时，内源性核酸内切酶活性被诱导。使用场反转凝胶电泳进一步表明，DNA裂解成大分子量。在拉莫斯细胞或离子霉素抗性的Ly 1细胞中，DNA片段（> 50 kbp）不先于离子霉素诱导的核小体间切割。总之，这些数据支持离子霉素诱导的细胞凋亡涉及潜在的低m.w.，钙响应性核酸内切酶，并建议控制核酸内切酶抑制可能有助于细胞特异性调节钙离子载体诱导的细胞凋亡。
The state of B cell maturation profoundly influences the outcome, i.e., activation, growth arrest, or programmed cell death, of a variety of stimuli, including the calcium ionophore, ionomycin. Initial studies confirmed the observation that cell lines representative of immature B cells, i.e., Burkitt lymphoma cell lines, were induced to undergo apoptosis in response to ionomycin, whereas more mature B cell lines did not, and instead underwent cell cycle arrest in the G1 interval. To understand this differential outcome, we have focused on comparing the expression and activation of an endonuclease(s) in cells induced by ionomycin to undergo programmed cell death (Ramos) with cells resistant to ionomycin-induced programmed cell death (Ly1). Our results demonstrated that a low m.w. fraction of an endogenous Ca2+/Mg(2+)-dependent endonuclease was activated in Ramos cells, but not in activated Ly1 cells, following the addition of ionomycin. Of interest, however, low m.w. endogenous endonuclease(s) activity was induced when isolated Ly1 cell nuclei were treated with exogenous calcium instead. Use of field inversion gel electrophoresis further indicated that cleavage of DNA into large m.w. (> 50 kbp) DNA fragments does not precede ionomycin-induced internucleosomal cleavage in Ramos cells or in ionomycin-resistant Ly1 cells. In summary, these data support the conclusion that ionomycin-induced apoptosis involves the activation of a latent, low m.w., calcium-responsive endonuclease and suggest that control of endonuclease depression may contribute to cell-specific regulation of calcium ionophore-induced apoptosis.