Morrow T A, Muljo S A, Zhang J, Hardwick J M, Schlissel M S
Graduate Program in Immunology, The Johns Hopkins University School of Public Health, Baltimore, Maryland 21205, USA.
Mol Cell Biol. 1999 Aug;19(8):5608-18. doi: 10.1128/MCB.19.8.5608.
Using a subtractive cloning scheme on cDNA prepared from primary pro-B and pre-B cells, we identified several genes whose products regulate apoptosis. We further characterized one of these genes, encoding protein kinase Ceta (PKCeta). PKCeta transcripts were readily detected in pro-B cells but were absent in pre-B cells. Although both a full-length and a truncated form of PKCeta were detectable in bone marrow pro-B cells, transition to the pre-B-cell stage was associated with increased relative levels of truncated PKCeta. We found that PKCeta is proteolyzed in apoptotic lymphocytes, generating a kinase-active fragment identical to the truncated form which is capable of inducing apoptosis when expressed in a pro-B cell line. Caspase-3 can generate an identical PKCeta cleavage product in vitro, and caspase inhibitors prevent the generation of this product during apoptosis in transfected cell lines. Inducible overexpression of either the full-length or truncated form of PKCeta results in cell cycle arrest at the G(1)/S transition. These results suggest that the expression and proteolytic activation of PKCeta play an important role in the regulation of cell division and cell death during early B-cell development.
利用消减克隆技术，对从原B细胞和前B细胞制备的cDNA进行研究，我们鉴定出了几个其产物可调节细胞凋亡的基因。我们进一步对其中一个基因进行了表征，该基因编码蛋白激酶Ceta（PKCeta）。PKCeta转录本在原B细胞中易于检测到，但在前B细胞中不存在。虽然在骨髓原B细胞中可检测到全长和截短形式的PKCeta，但向前B细胞阶段的转变与截短形式的PKCeta相对水平增加有关。我们发现PKCeta在凋亡淋巴细胞中被蛋白酶解，产生一个与截短形式相同的激酶活性片段，当在原B细胞系中表达时能够诱导细胞凋亡。半胱天冬酶-3在体外可产生相同的PKCeta裂解产物，并且半胱天冬酶抑制剂可防止在转染细胞系凋亡过程中产生该产物。全长或截短形式的PKCeta的可诱导过表达导致细胞周期在G(1)/S期转换时停滞。这些结果表明，PKCeta的表达和蛋白水解激活在早期B细胞发育过程中的细胞分裂和细胞死亡调节中起重要作用。
