Protein kinase C-delta mediates down-regulation of heterogeneous nuclear ribonucleoprotein K protein: involvement in apoptosis induction.
We reported previously that NSC606985, a camptothecin analogue, induces apoptosis of acute myeloid leukemia (AML) cells through proteolytic activation of protein kinase C delta (DeltaPKC-delta). By subcellular proteome analysis, heterogeneous nuclear ribonucleoprotein K (hnRNP K) was identified as being significantly down-regulated in NSC606985-treated leukemic NB4 cells. HnRNP K, a docking protein for DNA, RNA, and transcriptional or translational molecules, is implicated in a host of processes involving the regulation of gene expression. However, the molecular mechanisms of hnRNP K reduction and its roles during apoptosis are still not understood. In the present study, we found that, following the appearance of the DeltaPKC-delta, hnRNP K protein was significantly down-regulated in NSC606985, doxorubicin, arsenic trioxide and ultraviolet-induced apoptosis. We further provided evidence that DeltaPKC-delta mediated the down-regulation of hnRNP K protein during apoptosis: PKC-delta inhibitor could rescue the reduction of hnRNP K; hnRNP K failed to be decreased in PKC-delta-deficient apoptotic KG1a cells; conditional induction of DeltaPKC-delta in U937T cells directly down-regulated hnRNP K protein. Moreover, the proteasome inhibitor also inhibited the down-regulation of hnRNP K protein by apoptosis inducer and the conditional expression of DeltaPKC-delta. More intriguingly, the suppression of hnRNP K with siRNA transfection significantly induced apoptosis. To our knowledge, this is the first demonstration that proteolytically activated PKC-delta down-regulates hnRNP K protein in a proteasome-dependent manner, which plays an important role in apoptosis induction.
Gao
Feng-Hou
FH
No.3 People's Hospital affiliated to Shanghai Jiao-Tong University School of Medicine (SJTU-SM), Shanghai, China.
Wu
Ying-Li
YL
Zhao
Meng
M
Liu
Chuan-Xu
CX
Wang
Li-Shun
LS
Chen
Guo-Qiang
GQ
D017209:Apoptosis; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000235:genetics; D034641:Heterogeneous-Nuclear Ribonucleoprotein K / Q000235:genetics*; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000378:metabolism* / Q000473:pathology; D046988:Proteasome Endopeptidase Complex; D051745:Protein Kinase C-delta / Q000502:physiology*
D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D051745:Protein Kinase C-delta; D046988:Proteasome Endopeptidase Complex