Specific induction of RGS16 (regulator of G-protein signalling 16) mRNA by protein kinase C in CEM leukaemia cells is mediated via tumour necrosis factor alpha in a calcium-sensitive manner.
The RGS (regulator of G-protein signalling) proteins are GTPase-activating proteins for activated Galpha subunits. We investigated the effects of protein kinase C (PKC) on RGS proteins in various T cell lines by treating them with PMA. mRNA levels of both RGS16 and tumour necrosis factor alpha (TNFalpha) were found to be up-regulated in CEM leukaemia cells in a PKC-dependent manner. Mezerein, a non-phorbol-ester activator of PKC, also elevated RGS16 and TNFalpha mRNA levels, while the specific PKC inhibitor Go6983 abrogated their expression. In view of the slower kinetics of PMA-induced RGS16 expression and the tight correlation between TNFalpha and RGS16 mRNA induction among the cell lines studied, we suggest that activation of PKC up-regulates RGS16 via TNFalpha. Indeed, addition of recombinant TNFalpha to CEM cells rapidly stimulated RGS16 mRNA expression independently of PKC. Furthermore, mobilization of calcium by A23187 and thapsigargin blocked the TNFalpha-mediated induction of RGS16, which was reversed by EGTA and by the immunosuppressants FK506 and cyclosporin A, suggesting that the calcineurin/NF-AT (nuclear factor of activated T cells) pathway may repress the up-regulation process. Our results demonstrate for the first time that activation of PKC induces RGS16 expression via TNFalpha in a calcium-sensitive manner, thereby implicating RGS16 in the regulation of T cell responses to inflammation.
Fong
C W
CW
Regulatory Biology Group, Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609.
Zhang
Y
Y
Neo
S Y
SY
Lin
S C
SC
D000730:Androstadienes / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D019703:Calcineurin / Q000378:metabolism; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D016572:Cyclosporine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011506:Proteins / Q000235:genetics*; D020710:RGS Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000235:genetics / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*; D000077191:Wortmannin
D000730:Androstadienes; D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D011506:Proteins; D020710:RGS Proteins; C107413:RGS16 protein; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000001:Calcimycin; D004533:Egtazic Acid; D003994:Bucladesine; D019284:Thapsigargin; D016572:Cyclosporine; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D019703:Calcineurin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium; D016559:Tacrolimus; D000077191:Wortmannin