TPL-2 kinase regulates the proteolysis of the NF-κB-inhibitory protein NF-κB1 p105

The transcription factor NF-κB is composed of homodimeric andheterodimeric complexes of Rel/NF-κB-family polypeptides, which include Rel-A, c-Rel, Rel-B, NF-κB1/p50 and NF-κB2/p52 (ref. 1). The NF-κB1 gene encodes a larger precursor protein, p105, from which p50 is produced constitutively by proteasome-mediated removal of the p105 carboxy terminus. The p105 precursor also acts as an NFκB-inhibitory protein, retaining associated p50, c-Rel and Rel-A proteins in the cytoplasm through its carboxy terminus,. Following cell stimulation by agonists, p105 is proteolysed more rapidly and released Rel subunits translocate into the nucleus. Here we show that TPL-2 (ref. 11), which ishomologous to MAP-kinase-kinase kinases in its catalytic domain, forms a complex with the carboxy terminus of p105. TPL-2 was originally identified, in a carboxy-terminal-deleted form, as an oncoprotein in rats and is more than 90% identical to the human oncoprotein COT. Expression of TPL-2 results in phosphorylation and increased degradation of p105 while maintaining p50production. This releases associated Rel subunits or p50–Rel heterodimers to generate active nuclear NF-κB. Furthermore, kinase-inactive TPL-2 blocks the degradation of p105 induced by tumour-necrosis factor-α. TPL-2 is therefore a component of a new signalling pathway that controls proteolysis of NF-κB1 p105.

[1]  D. Pappin,et al.  Activation of MEK‐1 and SEK‐1 by Tpl‐2 proto‐oncoprotein, a novel MAP kinase kinase kinase. , 1996, The EMBO journal.

[2]  G. Nolan,et al.  Cloning of the p50 DNA binding subunit of NF-κB: Homology to rel and dorsal , 1990, Cell.

[3]  M J May,et al.  NF-kappa B and Rel proteins: evolutionarily conserved mediators of immune responses. , 1998, Annual review of immunology.

[4]  S. Ghosh,et al.  A glycine-rich region in NF-kappaB p105 functions as a processing signal for the generation of the p50 subunit , 1996, Molecular and cellular biology.

[5]  S. Goodbourn,et al.  Proteolytic degradation of MAD3 (IϰBα) and enhanced processing of the NF-ϰB precursor p105 are obligatory steps in the activation of NF-ϰB , 1993 .

[6]  Thomas Henkel,et al.  Intramolecular masking of the nuclear location signal and dimerization domain in the precursor for the p50 NF-κB subunit , 1992, Cell.

[7]  Tom Maniatis,et al.  The ubiquitinproteasome pathway is required for processing the NF-κB1 precursor protein and the activation of NF-κB , 1994, Cell.

[8]  E. Zandi,et al.  The IκB Kinase Complex (IKK) Contains Two Kinase Subunits, IKKα and IKKβ, Necessary for IκB Phosphorylation and NF-κB Activation , 1997, Cell.

[9]  M. Karin,et al.  p105 and p98 precursor proteins play an active role in NF-kappa B-mediated signal transduction. , 1993, Genes & development.

[10]  P. Tsichlis,et al.  Tumor progression locus 2 (Tpl-2) encodes a protein kinase involved in the progression of rodent T-cell lymphomas and in T-cell activation. , 1993, Proceedings of the National Academy of Sciences of the United States of America.

[11]  S. Ley,et al.  S‐acylation of LCK protein tyrosine kinase is essential for its signalling function in T lymphocytes , 1997, The EMBO journal.

[12]  T. Shinoda,et al.  Regulation of NFKB1 proteins by the candidate oncoprotein BCL‐3: generation of NF‐κB homodimers from the cytoplasmic pool of p50–p105 and nuclear translocation , 1997, The EMBO journal.

[13]  C. Marshall,et al.  Activation of MAP kinase kinase is necessary and sufficient for PC12 differentiation and for transformation of NIH 3T3 cells , 1994, Cell.

[14]  N. Copeland,et al.  Tpl-2 is an oncogenic kinase that is activated by carboxy-terminal truncation. , 1997, Genes & development.

[15]  A. Israël,et al.  The DNA binding subunit of NF-κB is identical to factor KBF1 and homologous to the rel oncogene product , 1990, Cell.

[16]  S. Ghosh,et al.  Signal transduction through NF-κB , 1998 .

[17]  A. Israël,et al.  Cytoplasmic retention, DNA binding and processing of the NF‐kappa B p50 precursor are controlled by a small region in its C‐terminus. , 1991, The EMBO journal.

[18]  D. Ballard,et al.  Proteolytic Processing of NF-B/IB in Human Monocytes , 1995, The Journal of Biological Chemistry.

[19]  A. Yaron,et al.  In vivo stimulation of I kappa B phosphorylation is not sufficient to activate NF-kappa B , 1995, Molecular and cellular biology.

[20]  W. Greene,et al.  Cotranslational Biogenesis of NF-κB p50 by the 26S Proteasome , 1998, Cell.

[21]  P. Legrain,et al.  Toward a functional analysis of the yeast genome through exhaustive two-hybrid screens , 1997, Nature Genetics.

[22]  T. Akiyama,et al.  The human cot proto-oncogene encodes two protein serine/threonine kinases with different transforming activities by alternative initiation of translation. , 1993, The Journal of biological chemistry.

[23]  T. Maniatis,et al.  Generation of p50 subunit of NF-kB by processing of p105 through an ATP-dependent pathway , 1991, Nature.

[24]  Matthias Mann,et al.  IKK-1 and IKK-2: Cytokine-Activated IκB Kinases Essential for NF-κB Activation , 1997 .

[25]  D. Baltimore,et al.  NF-κB: A pleiotropic mediator of inducible and tissue-specific gene control , 1989, Cell.

[26]  A. Weiss,et al.  ZAP-70 Protein Tyrosine Kinase Is Constitutively Targeted to the T Cell Cortex Independently of its SH2 Domains , 1997, The Journal of cell biology.

[27]  A. Israël,et al.  Phosphorylation of p105 PEST Sequences via a Redox-insensitive Pathway Up-regulates Processing to p50 NF-B (*) , 1996, The Journal of Biological Chemistry.

[28]  D. Wallach,et al.  MAP3K-related kinase involved in NF-KB induction by TNF, CD95 and IL-1 , 1997, Nature.

[29]  A. Israël,et al.  The precursor of NF-κB p50 has IκB-like functions , 1992, Cell.

[30]  Mike Rothe,et al.  IκB Kinase-β: NF-κB Activation and Complex Formation with IκB Kinase-α and NIK , 1997 .