ABIN-2 forms a ternary complex with TPL-2 and NF-kappa B1 p105 and is essential for TPL-2 protein stability.
NF-kappa B1 p105 forms a high-affinity, stoichiometric interaction with TPL-2, a MEK kinase essential for TLR4 activation of the ERK mitogen-activated protein kinase cascade in lipopolysaccharide (LPS)-stimulated macrophages. Interaction with p105 is required to maintain TPL-2 metabolic stability and also negatively regulates TPL-2 MEK kinase activity. Here, affinity purification identified ... A20-binding inhibitor of NF-kappa B 2 (ABIN-2) as a novel p105-associated protein. Cotransfection experiments demonstrated that ABIN-2 could interact with TPL-2 in addition to p105 but preferentially formed a ternary complex with both proteins. Consistently, in unstimulated bone marrow-derived macrophages (BMDMs), a substantial fraction of endogenous ABIN-2 was associated with both p105 and TPL-2. Although the majority of TPL-2 in these cells was complexed with ABIN-2, the pool of TPL-2 which could activate MEK after LPS stimulation was not, and LPS activation of TPL-2 was found to correlate with its release from ABIN-2. Depletion of ABIN-2 by RNA interference dramatically reduced steady-state levels of TPL-2 protein without affecting levels of TPL-2 mRNA or p105 protein. In addition, ABIN-2 increased the half-life of cotransfected TPL-2. Thus, optimal TPL-2 stability in vivo requires interaction with ABIN-2 as well as p105. Together, these data raise the possibility that ABIN-2 functions in the TLR4 signaling pathway which regulates TPL-2 activation.
Mesh Terms:
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Animals, Base Sequence, Carrier Proteins, Cell Line, DNA, Complementary, Enzyme Activation, HeLa Cells, Humans, MAP Kinase Kinase Kinases, Macromolecular Substances, Macrophages, Membrane Glycoproteins, Mice, Mice, Inbred BALB C, Mice, Knockout, Molecular Sequence Data, NF-kappa B p50 Subunit, Proto-Oncogene Proteins, RNA, Small Interfering, Receptors, Cell Surface, Recombinant Proteins, Signal Transduction, Solubility, Toll-Like Receptor 4, Toll-Like Receptors, Transcription Factors, Transfection
Adaptor Proteins, Signal Transducing, Amino Acid Sequence, Animals, Base Sequence, Carrier Proteins, Cell Line, DNA, Complementary, Enzyme Activation, HeLa Cells, Humans, MAP Kinase Kinase Kinases, Macromolecular Substances, Macrophages, Membrane Glycoproteins, Mice, Mice, Inbred BALB C, Mice, Knockout, Molecular Sequence Data, NF-kappa B p50 Subunit, Proto-Oncogene Proteins, RNA, Small Interfering, Receptors, Cell Surface, Recombinant Proteins, Signal Transduction, Solubility, Toll-Like Receptor 4, Toll-Like Receptors, Transcription Factors, Transfection
Mol. Cell. Biol.
Date: Jun. 01, 2004
PubMed ID: 15169888
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