Pistritto G, Jost M, Srinivasula S M, Baffa R, Poyet J-L, Kari C, Lazebnik Y, Rodeck U, Alnemri E S
Center for Apoptosis Research, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Cell Death Differ. 2002 Sep;9(9):995-1006. doi: 10.1038/sj.cdd.4401061.
Caspase-14 is a recent addition to the caspase family of aspartate proteases involved in apoptotic processes. Human caspase-14 appears to be only weakly processed during apoptosis, and it does not cleave classical caspase substrates. Post partum, caspase-14 is prominently expressed by human keratinocytes and reportedly participates in terminal differentiation of complex epithelia. Here we provide evidence challenging the view that caspase-14 expression or processing is linked exclusively to terminal keratinocyte differentiation. We demonstrate that caspase-14 expression extended to multiple cell lines derived from simple epithelia of the breast, prostate, and stomach. In keratinocytes and breast epithelial cells, caspase-14 expression was upregulated in high-density cultures and during forced suspension culture. These effects were primarily due to transcriptional activation as indicated by reporter gene assays using a 2 kb caspase-14 promoter fragment. Importantly, caspase-14 was not cleaved during forced suspension culture of either cell type although this treatment induced caspase-dependent apoptosis (anoikis). Forced expression of caspase-14 in immortalized human keratinocytes had no effect on cell death in forced suspension nor was the transfected caspase-14 processed in this setting. In contrast to postconfluent and forced suspension culture, terminal differentiation of keratinocytes induced in vitro by Ca2+ treatment was not associated with increased caspase-14 expression or promoter activity. Our results indicate that (1) caspase-14 is expressed not only in complex but also simple epithelia; (2) cells derived from complex and simple epithelia upregulate caspase-14 expression in conditions of high cell density or lack of matrix interaction and; (3) in both cell types this phenomenon is due to transcriptional regulation.
半胱天冬酶 -14是最近才加入参与凋亡过程的天冬氨酸蛋白酶半胱天冬酶家族的成员。人类半胱天冬酶 -14在凋亡过程中似乎只有微弱的加工过程，并且它不会切割经典的半胱天冬酶底物。产后，人类角质形成细胞显著表达半胱天冬酶 -14，据报道它参与复层上皮的终末分化。在这里，我们提供的证据对以下观点提出了挑战，即半胱天冬酶 -14的表达或加工仅与角质形成细胞的终末分化有关。我们证明，半胱天冬酶 -14的表达扩展到源自乳腺、前列腺和胃的单层上皮的多种细胞系。在角质形成细胞和乳腺上皮细胞中，高密度培养和强制悬浮培养期间半胱天冬酶 -14的表达上调。这些效应主要是由于转录激活，使用2 kb半胱天冬酶 -14启动子片段的报告基因分析表明了这一点。重要的是，在两种细胞类型的强制悬浮培养过程中，半胱天冬酶 -14都没有被切割，尽管这种处理诱导了半胱天冬酶依赖性凋亡（失巢凋亡）。在永生化的人类角质形成细胞中强制表达半胱天冬酶 -14对强制悬浮培养中的细胞死亡没有影响，在这种情况下转染的半胱天冬酶 -14也没有被加工。与汇合后和强制悬浮培养相反，通过Ca2+处理在体外诱导的角质形成细胞的终末分化与半胱天冬酶 -14表达或启动子活性的增加无关。我们的结果表明：（1）半胱天冬酶 -14不仅在复层上皮中表达，也在单层上皮中表达；（2）源自复层上皮和单层上皮的细胞在高细胞密度或缺乏基质相互作用的条件下上调半胱天冬酶 -14的表达；（3）在这两种细胞类型中，这种现象都是由于转录调控。
