Cross T, Griffiths G, Deacon E, Sallis R, Gough M, Watters D, Lord J M
MRC Centre for Immune Regulation, University of Birmingham, UK.
Oncogene. 2000 May 4;19(19):2331-7. doi: 10.1038/sj.onc.1203555.
Protein kinase C-delta is activated during apoptosis, following proteolytic cleavage by caspase 3. Furthermore, overexpression of the catalytic kinase fragment of PKC-delta induces the nuclear phenotype associated with apoptosis, though the molecular basis of this effect has not been determined. In these studies we have examined the role of PKC-delta in the disassembly of the nuclear lamina at apoptosis. The nuclear lamina is disassembled during mitosis and apoptosis and mitotic disassembly involves hyperphosphorylation of lamin proteins by mitotic lamin kinases. During apoptosis, lamin proteins are degraded by caspase 6 and the contribution made by phosphorylation has not been proven. We show here that protein kinase C-delta co-localized with lamin B during apoptosis and activation of PKC-delta by caspase 3 was concomitant with lamin B phosphorylation and proteolysis. Inhibition of PKC-delta delayed lamin proteolysis, even in the presence of active caspase 6, whilst inhibitors of mitotic lamin kinases were without effect. In addition recombinant human PKC-delta was able to phosphorylate lamin B in vitro suggesting that its actions are direct and not via an intermediary kinase. We propose that PKC-delta is an apoptotic lamin kinase and that efficient lamina disassembly at apoptosis requires both lamin hyperphosphorylation and caspase mediated proteolysis.
蛋白激酶C-δ在凋亡过程中被激活，这发生在被半胱天冬酶3进行蛋白水解切割之后。此外，蛋白激酶C-δ催化激酶片段的过表达会诱导与凋亡相关的核表型，尽管这种效应的分子基础尚未确定。在这些研究中，我们研究了蛋白激酶C-δ在凋亡时核纤层解体中的作用。核纤层在有丝分裂和凋亡过程中会解体，有丝分裂时的解体涉及核纤层蛋白被有丝分裂核纤层激酶过度磷酸化。在凋亡过程中，核纤层蛋白被半胱天冬酶6降解，磷酸化所起的作用尚未得到证实。我们在此表明，在凋亡过程中蛋白激酶C-δ与核纤层蛋白B共定位，半胱天冬酶3对蛋白激酶C-δ的激活与核纤层蛋白B的磷酸化和蛋白水解同时发生。对蛋白激酶C-δ的抑制会延迟核纤层蛋白的蛋白水解，即使在存在活性半胱天冬酶6的情况下也是如此，而有丝分裂核纤层激酶的抑制剂则没有效果。此外，重组人蛋白激酶C-δ能够在体外使核纤层蛋白B磷酸化，这表明其作用是直接的，而非通过中间激酶。我们提出，蛋白激酶C-δ是一种凋亡核纤层激酶，凋亡时核纤层的有效解体需要核纤层蛋白的过度磷酸化和半胱天冬酶介导的蛋白水解。
