title: Roles for TAB1 in regulating the IL-1-dependent phosphorylation of the TAB3 regulatory subunit and activity of the TAK1 complex.
abstract: The protein kinase TAK1 (transforming growth factor-beta-activated kinase 1), which has been implicated in the activation of MAPK (mitogen-activated protein kinase) cascades and the production of inflammatory mediators by LPS (lipopolysaccharide), IL-1 (interleukin 1) and TNF (tumour necrosis factor), comprises the catalytic subunit complexed to the regulatory subunits, termed TAB (TAK1-binding subunit) 1 and either TAB2 or TAB3. We have previously identified a feedback-control mechanism by which p38alpha MAPK down-regulates TAK1 and showed that p38alpha MAPK phosphorylates TAB1 at Ser(423) and Thr(431). In the present study, we identified two IL-1-stimulated phosphorylation sites on TAB2 (Ser(372) and Ser(524)) and three on TAB3 (Ser(60), Thr(404) and Ser(506)) in human IL-1R cells [HEK-293 (human embryonic kidney) cells that stably express the IL-1 receptor] and MEFs (mouse embryonic fibroblasts). Ser(372) and Ser(524) of TAB2 are not phosphorylated by pathways dependent on p38alpha/beta MAPKs, ERK1/2 (extracellular-signal-regulated kinase 1/2) and JNK1/2 (c-Jun N-terminal kinase 1/2). In contrast, Ser(60) and Thr(404) of TAB3 appear to be phosphorylated directly by p38alpha MAPK, whereas Ser(506) is phosphorylated by MAPKAP-K2/MAPKAP-K3 (MAPK-activated protein kinase 2 and 3), which are protein kinases activated by p38alpha MAPK. Studies using TAB1(-/-) MEFs indicate important roles for TAB1 in recruiting p38alpha MAPK to the TAK1 complex for the phosphorylation of TAB3 at Ser(60) and Thr(404) and in inhibiting the dephosphorylation of TAB3 at Ser(506). TAB1 is also required to induce TAK1 catalytic activity, since neither IL-1 nor TNFalpha was able to stimulate detectable TAK1 activity in TAB1(-/-) MEFs. Surprisingly, the IL-1 and TNFalpha-stimulated activation of MAPK cascades and IkappaB (inhibitor of nuclear factor kappaB) kinases were similar in TAB1(-/-), MEKK3(-/-) [MAPK/ERK (extracellular-signal-regulated kinase) kinase kinase 3] and wild-type MEFs, suggesting that another MAP3K (MAPK kinase kinase) may mediate the IL-1/TNFalpha-induced activation of these signalling pathways in TAB1(-/-) and MEKK3(-/-) MEFs.
authors.affiliation: MRC Protein Phosphorylation Unit, University of Dundee, Dundee DD1 5EH, Scotland, UK.
authors.forename: Heidi
authors.initials: H
authors.lastname: Mendoza
authors.forename: David G
authors.initials: DG
authors.lastname: Campbell
authors.forename: Kerry
authors.initials: K
authors.lastname: Burness
authors.forename: James
authors.initials: J
authors.lastname: Hastie
authors.forename: Natalia
authors.initials: N
authors.lastname: Ronkina
authors.forename: Jae-Hyuck
authors.initials: JH
authors.lastname: Shim
authors.forename: J Simon C
authors.initials: JS
authors.lastname: Arthur
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Davis
authors.forename: Matthias
authors.initials: M
authors.lastname: Gaestel
authors.forename: Gary L
authors.initials: GL
authors.lastname: Johnson
authors.forename: Sankar
authors.initials: S
authors.lastname: Ghosh
authors.forename: Philip
authors.initials: P
authors.lastname: Cohen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D020134:Catalytic Domain; D002460:Cell Line; D007375:Interleukin-1 / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D000099151:MAP Kinase Kinase Kinase 7
chemical_list: D000906:Antibodies; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D021122:Protein Subunits; D014409:Tumor Necrosis Factor-alpha; D000099151:MAP Kinase Kinase Kinase 7