Crystal Structure of the P38α-MAPKAP Kinase 2 Heterodimer

Abstract

The p38 signaling pathway is activated in response to cell stress and induces production of proinflammatory cytokines. P38α is phosphorylated and activated in response to cell stress by MKK3 and MKK6 and in turn phosphorylates a number of substrates, including MAPKAP kinase 2 (MK2). We have determined the crystal structure of the unphosphorylated p38α-MK2 heterodimer. The C-terminal regulatory domain of MK2 binds in the docking groove of p38α, and the ATP-binding sites of both kinases are at the heterodimer interface. The conformation suggests an extra mechanism in addition to the regulation of the p38α and MK2 phosphorylation states that prevents phosphorylation of substrates in the absence of cell stress. Addition of constitutively active MKK6-DD results in rapid phosphorylation of the p38α-MK2 heterodimer. The p38 signaling pathway is activated in response to cell stress and induces production of proinflammatory cytokines. P38α is phosphorylated and activated in response to cell stress by MKK3 and MKK6 and in turn phosphorylates a number of substrates, including MAPKAP kinase 2 (MK2). We have determined the crystal structure of the unphosphorylated p38α-MK2 heterodimer. The C-terminal regulatory domain of MK2 binds in the docking groove of p38α, and the ATP-binding sites of both kinases are at the heterodimer interface. The conformation suggests an extra mechanism in addition to the regulation of the p38α and MK2 phosphorylation states that prevents phosphorylation of substrates in the absence of cell stress. Addition of constitutively active MKK6-DD results in rapid phosphorylation of the p38α-MK2 heterodimer. The p38 signal transduction pathway regulates cellular inflammatory responses. The pathway is activated by proinflammatory cytokines, tumor necrosis factor α, bacterial lipopolysaccharides, or osmotic stress (1Cuenda A. Rouse J. Doza Y.N. Meier R. Cohen P. Gallagher T.F. Young P.R. Lee J.C. FEBS Lett. 1995; 364: 229-233Crossref PubMed Scopus (1985) Google Scholar) and results in increased levels of tumor necrosis factor α, interleukin 1β, interleukin 6, interleukin 10 interferon-γ, and COX-2 (2Lasa M. Mahtani K.R. Finch A. Brewer G. Saklatvala J. Clark A.R. Mol. Cell. Biol. 2000; 20: 4265-4274Crossref PubMed Scopus (372) Google Scholar, 3Winzen R. Kracht M. Ritter B. Wilhelm A. Chen C.Y. Shyu A.B. Muller M. Gaestel M. Resch K. Holtmann H. EMBO J. 1999; 18: 4969-4980Crossref PubMed Scopus (714) Google Scholar). Inhibitors of this pathway have been demonstrated to reduce inflammation (4Saklatvala J. Curr. Opin. Pharmacol. 2004; 4: 372-377Crossref PubMed Scopus (377) Google Scholar). The p38 kinase family has four members: P38α, β, γ, and δ (5Shi Y. Gaestel M. Biol. Chem. 2002; 383: 1519-1536Crossref PubMed Scopus (139) Google Scholar). P38α and β are the main transponders of the inflammatory response (6Salituro F.G. Germann U.A. Wilson K.P. Bemis G.W. Fox T. Su M.S. Curr. Med. Chem. 1999; 6: 807-823PubMed Google Scholar) and have been targets for anti-inflammatory therapy. Several p38α and β inhibitors are in clinical trials for the treatment of chronic obstructive pulmonary disease, psoriasis, and rheumatoid arthritis (7Force T. Kuida K. Namchuk M. Parang K. Kyriakis J.M. Circulation. 2004; 109: 1196-1205Crossref PubMed Scopus (116) Google Scholar). Activated p38α phosphorylates transcription factors such as ATF2, Elk-1, and MEF2A and downstream kinases such as MAPKAP kinase 2 (MK2), 2The abbreviations used are: MK2, MAPKAP kinase 2; MAP, mitogen-activated protein; NLS, nuclear localization signal; NES, nuclear export signal; JNK, c-Jun N-terminal kinase; ERK, extracellular signal-regulated kinase; CD, common docking; ED, glutamate-aspartate. MK3, PRAK, MNK1/2, and MSK1 (8Stokoe D. Campbell D.G. Nakielny S. Hidaka H. Leevers S.J. Marshall C. Cohen P. EMBO J. 1992; 11: 3985-3994Crossref PubMed Scopus (392) Google Scholar, 9Kumar S. Boehm J. Lee J.C. Nat. Rev. Drug. Discov. 2003; 2: 717-726Crossref PubMed Scopus (1087) Google Scholar). Several p38α substrates are phosphorylated in the nucleus, others in the cytoplasm. MK2 also phosphorylates proteins found in both the nucleus (cAMP-response element-binding protein, or CREB) (10Tan Y. Rouse J. Zhang A. Cariati S. Cohen P. Comb M.J. EMBO J. 1996; 15: 4629-4642Crossref PubMed Scopus (569) Google Scholar) and cytoplasm (HSP25/27 and LSP-1) (11Huang C.K. Zhan L. Ai Y. Jongstra J. J. Biol. Chem. 1997; 272: 17-19Abstract Full Text Full Text PDF PubMed Scopus (111) Google Scholar, 12Stokoe D. Engel K. Campbell D.G. Cohen P. Gaestel M. FEBS Lett. 1992; 313: 307-313Crossref PubMed Scopus (475) Google Scholar). Two splice variants of MK2 have been identified. MK2a contains the nuclear localization signal (NLS) and the p38 docking domain, whereas MK2b is a truncated variant of MK2 that lacks the NLS and p38 docking domain (13Zu Y.L. Wu F. Gilchrist A. Ai Y. Labadia M.E. Huang C.K. Biochem. Biophys. Res. Commun. 1994; 200: 1118-1124Crossref PubMed Scopus (44) Google Scholar, 14Zu Y.L. Ai Y. Huang C.K. J. Biol. Chem. 1995; 270: 202-206Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar). MK2b is still phosphorylated by p38α but the signal transduction is less efficient (15Kotlyarov A. Yannoni Y. Fritz S. Laass K. Telliez J.B. Pitman D. Lin L.L. Gaestel M. Mol. Cell. Biol. 2002; 22: 4827-4835Crossref PubMed Scopus (213) Google Scholar). P38α forms a complex with MK2a even when the signaling pathway is not activated (16Lukas S.M. Kroe R.R. Wildeson J. Peet G.W. Frego L. Davidson W. Ingraham R.H. Pargellis C.A. Labadia M.E. Werneburg B.G. Biochemistry. 2004; 43: 9950-9960Crossref PubMed Scopus (46) Google Scholar). This heterodimer is found mainly in the nucleus. Upon activation of the p38α signaling cascade, p38α and MK2a phosphorylate their nuclear substrates before translocating to the cytoplasm. P38α does not have a nuclear export signal (NES) and cannot leave the nucleus by itself but rather needs to be associated with MK2a. The NES of MK2a facilitates the transfer of both kinases from the nucleus to the cytoplasm but only after MK2 has been phosphorylated by p38α (17Ben-Levy R. Hooper S. Wilson R. Paterson H.F. Marshall C.J. Curr. Biol. 1998; 8: 1049-1057Abstract Full Text Full Text PDF PubMed Scopus (295) Google Scholar, 18Engel K. Kotlyarov A. Gaestel M. EMBO J. 1998; 17: 3363-3371Crossref PubMed Scopus (237) Google Scholar). P38α phosphorylates MK2 at four sites, Thr25, Thr222, Ser272, and Thr334. The phosphorylation of Thr334 has been demonstrated to be critical for the nuclear export of the p38α-MK2 complex, whereas the kinase activity of MK2 is not (18Engel K. Kotlyarov A. Gaestel M. EMBO J. 1998; 17: 3363-3371Crossref PubMed Scopus (237) Google Scholar). Phosphorylation of Thr334 is believed to induce a conformational change in the complex prior to interaction with the leptomycin B-sensitive nuclear export receptor (19Neininger A. Thielemann H. Gaestel M. EMBO Rep. 2001; 2: 703-708Crossref PubMed Scopus (50) Google Scholar). In this report, we present a structural analysis of the p38α-MK2 heterodimer. Crystal structures were determined for both the full-length p38α-MK2 heterodimer and the p38α-MK2 peptide (residues 370–400) complex. The structures reveal that the heterodimer conformation buries the substrate binding grooves of both p38α and MK2a, thus preventing both kinases from phosphorylating their respective substrates. The structure suggests that substrate phosphorylation is dependent on the phosphorylation states of both kinases and the heterodimer conformation. Protein Purification and Generation of Protein-Protein Complex—Human p38α was expressed and purified as described (20Wilson K.P. Fitzgibbon M.J. Caron P.R. Griffith J.P. Chen W. McCaffrey P.G. Chambers S.P. Su M.S. J. Biol. Chem. 1996; 271: 27696-27700Abstract Full Text Full Text PDF PubMed Scopus (218) Google Scholar). Full-length MK2 was expressed and purified according to the protocol used for N-terminal-truncated MK2 (residues 46–400) (21Meng W. Swenson L.L. Fitzgibbon M.J. Hayakawa K. Ter Haar E. Behrens A.E. Fulghum J.R. Lippke J.A. J. Biol. Chem. 2002; 277: 37401-37405Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar). P38α-MK2 heterodimer samples were prepared by incubating the purified proteins in equimolar concentrations (25 μm each) for 1 h on ice. The p38α-MK2 complex was separated from the monomers by Q-Sepharose anion exchange chromatography using a linear NaCl gradient (100–500 mm), and the fractions containing the p38α-MK2 heterodimer were pooled. Finally, the buffer was exchanged into 20 mm Tris-Cl, pH 7.8, 50 mm NaCl, and 2 mm dithiothreitol, and the protein sample was concentrated to 20 mg/ml for crystallization set-ups. Crystallization and Data Collection—Crystals were grown with the hanging drop method over a reservoir containing 3.75% polyethylene glycol 2000, 100 mm Hepes, pH 7.5. Prior to the crystallization set up, 1-s-nonyl-1-β-d-thioglucoside (1× critical micelle concentration) and heptanetriol (1.5%) were added to the protein sample. The crystallization drop was prepared by mixing the reservoir solution with the protein solution in a 1:1 ratio. Crystals grew overnight and were typically harvested after 72 h. The crystals were transferred for 1 min to a solution consisting of reservoir solution and before in Data at and the of a set to The crystals of full-length p38α-MK2 heterodimer to with cell of Crystals of p38α-MK2 peptide (residues 370–400) were grown with the hanging drop method over a reservoir containing polyethylene glycol and mm The crystallization drop was prepared by mixing the protein solution with the reservoir solution in a 1:1 ratio. The crystals grew in a of and were harvested after h. The crystals were transferred for 1 min to a solution consisting of reservoir solution and before in at of to The crystals of the p38α-MK2 peptide complex to with cell of The were and with The structure was determined by A. A. Biol. 2000; PubMed Scopus Google Scholar) using a of p38α R. Mol. Cell. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar) as the The p38α peptide The crystal structure was with of and using the E. P. C. C. S.M. G. Biol. 2004; PubMed Scopus Google Scholar). The p38α and and MK2a peptide The and of the p38α-MK2 peptide complex were and p38α-MK2 peptide complex and the MK2 were used to the structure of the full-length p38α-MK2 heterodimer. This structure was using only the protocol of and was to the and of the MK2 activation Phosphorylation of the p38α-MK2 and of the p38α-MK2 complex in the absence or of the p38α was by mixing the p38α-MK2 complex and MKK6-DD in a ratio. The phosphorylation was in 20 mm Tris-Cl, pH 7.8, 50 mm NaCl, 10 mm and 2 mm The complex was with for min on prior to The was by addition of mm and were at and and with sample were using kinase and and were with an at and the were to the of of the and MK2 are both protein The structures of both P38α and MK2 have been determined as monomers (20Wilson K.P. Fitzgibbon M.J. Caron P.R. Griffith J.P. Chen W. McCaffrey P.G. Chambers S.P. Su M.S. J. Biol. Chem. 1996; 271: 27696-27700Abstract Full Text Full Text PDF PubMed Scopus (218) Google Scholar, W. Swenson L.L. Fitzgibbon M.J. Hayakawa K. Ter Haar E. Behrens A.E. Fulghum J.R. Lippke J.A. J. Biol. Chem. 2002; 277: 37401-37405Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar, E. L. T. M. K. Y. S. M. K. Telliez J.B. Lin L.L. J. 2003; 11: Full Text Full Text PDF PubMed Scopus Google Scholar). structures have kinase with a N-terminal domain by a C-terminal domain consisting of and an ATP-binding the The ATP-binding is by the the that the N-terminal domain with the domain, and the The kinase of p38α and MK2 also have a substrate binding This groove is at the of the and C-terminal and binds the of the substrate protein that contains the phosphorylation p38α and MK2 have P38α has an extra docking groove for substrate and The docking groove contains the and common docking and is kinases such as and JNK, but not in The kinase domain of MK2a is by a (residues that is not present in the crystal structures D. B. Cohen Cohen P. Biochem. J. PubMed Scopus Google Scholar). the kinase domain has a C-terminal regulatory domain (residues that of and and a The C-terminal regulatory domain contains an NES and the NLS (17Ben-Levy R. Hooper S. Wilson R. Paterson H.F. Marshall C.J. Curr. Biol. 1998; 8: 1049-1057Abstract Full Text Full Text PDF PubMed Scopus (295) Google Scholar, 18Engel K. Kotlyarov A. Gaestel M. EMBO J. 1998; 17: 3363-3371Crossref PubMed Scopus (237) Google Scholar). The the MK2a substrate binding groove in an conformation in of the crystal structures of the (21Meng W. Swenson L.L. Fitzgibbon M.J. Hayakawa K. Ter Haar E. Behrens A.E. Fulghum J.R. Lippke J.A. J. Biol. Chem. 2002; 277: 37401-37405Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar). We have determined the crystal structure of a p38α-MK2 heterodimer that contains full-length p38α and MK2a, and we have also determined a structure of with only the docking peptide (residues 370–400) of The p38α and MK2a that the heterodimer are to that the ATP-binding sites of both kinases are at the heterodimer The C-terminal of MK2 (residues the p38α and into the docking including the C-terminal of the NLS, into an the of the p38α docking groove The (residues of the C-terminal regulatory domain is the p38α and MK2a kinase the MK2a substrate binding as does in the crystals of the MK2a kinase domain (21Meng W. Swenson L.L. Fitzgibbon M.J. Hayakawa K. Ter Haar E. Behrens A.E. Fulghum J.R. Lippke J.A. J. Biol. Chem. 2002; 277: 37401-37405Abstract Full Text Full Text PDF PubMed Scopus (104) Google Scholar). The C-terminal of the and that contains the NES of MK2a (residues is the kinase in to the p38α ATP-binding The MK2a activation (residues also to binding with In the crystal the activation is whereas in the p38α-MK2 heterodimer the MK2a activation be the as is by with the domain of p38α The phosphorylation in the MK2a activation does not with The C-terminal regulatory domain and the activation of MK2a of the p38α and MK2a in the heterodimer The C-terminal regulatory domain both the N-terminal and the of The C-terminal of the the of the and the but only and are less The C-terminal of the C-terminal regulatory domain the docking groove of p38α and is for the interaction and MK2a (16Lukas S.M. Kroe R.R. Wildeson J. Peet G.W. Frego L. Davidson W. Ingraham R.H. Pargellis C.A. Labadia M.E. Werneburg B.G. Biochemistry. 2004; 43: 9950-9960Crossref PubMed Scopus (46) Google Scholar). This interaction be in The activation of MK2a with p38α in the heterodimer and a MK2a The conformation of the C-terminal of the activation (residues is by the the and in p38α, but only the is in the is an the MK2a of and and the p38α and The in the heterodimer is for MK2a and for p38α The p38α activation contains phosphorylation sites and that when activated conformation and the substrate binding In the heterodimer described p38α is not phosphorylated and the p38α activation is were from the to of This was in to a from MK2a (residues The MK2a are in a crystal structure (21Meng W. Swenson L.L. Fitzgibbon M.J. Hayakawa K. Ter Haar E. Behrens A.E. Fulghum J.R. Lippke J.A. J. Biol. Chem. 2002; 277: 37401-37405Abstract Full Text Full Text PDF PubMed Scopus (104) Google but their are not with the p38α-MK2 heterodimer conformation. The P38α and the kinases have a docking groove for binding with their and substrates R. Mol. Cell. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar, T. M. T. E. Nat. Cell. Biol. 2000; 2: PubMed Scopus Google Scholar, K. J. L. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, D. D. K. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar, T. R. M. E. EMBO J. 2001; 20: PubMed Scopus Google Scholar, T. T. E. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, T. E. Pharmacol. 2002; PubMed Scopus Google Scholar, M. L. Biochem. J. 2003; PubMed Google Scholar, M. L. J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, T. E. Cell. 2003; 15: PubMed Scopus Google Scholar, T. T. R. E. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). The docking groove is not to be with the substrate binding groove at the phosphorylation The groove was by as the and the T. M. T. E. Nat. Cell. Biol. 2000; 2: PubMed Scopus Google Scholar). The is of a groove by the and the and The is of a groove by at and and at the The C-terminal of the regulatory domain of MK2a (residues binds in the docking groove of p38α and with the and are a of and the kinase binding as in and the and of p38α are mainly was that structure that this is the The docking groove are with the binding of (16Lukas S.M. Kroe R.R. Wildeson J. Peet G.W. Frego L. Davidson W. Ingraham R.H. Pargellis C.A. Labadia M.E. Werneburg B.G. Biochemistry. 2004; 43: 9950-9960Crossref PubMed Scopus (46) Google Scholar). and that the docking groove to the of the heterodimer. also that the binding of the MK2a to p38α on the of the with the p38α and MK2a that we in the heterodimer. The of the kinase binding is proteins that p38α, ERK, or The main is the of the with to the In kinases and the of the kinase binding before the whereas for the substrate kinases such as MK2a the binding after the kinase Two crystal structures of p38α in complex with have been determined peptide is from the p38α and the peptide is from the transcription R. Mol. Cell. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). also in the p38α docking but the with the p38α-MK2 complex is the of the peptide The in have with or with MK2a, but the the peptide and p38α at the domain are the of the peptide The is but at the of MK2a both also have an with the in the with an of the peptide and both into the from The also have a at the of that is by the of p38α consisting of and a that MKK6-DD the ATP-binding sites and substrate binding grooves of p38α and MK2a are at the of the to substrates. the conformation of the heterodimer does not a p38α phosphorylation complex but rather a conformation for the activity of p38α and MK2a are from substrates. the complex and the of both kinases when the cell does not their phosphorylation when the cell does not stress as stress at the we the p38α-MK2 heterodimer to such that both kinases are to their substrates. The p38α-MK2 heterodimer is a complex with a of (16Lukas S.M. Kroe R.R. Wildeson J. Peet G.W. Frego L. Davidson W. Ingraham R.H. Pargellis C.A. Labadia M.E. Werneburg B.G. Biochemistry. 2004; 43: 9950-9960Crossref PubMed Scopus (46) Google Scholar). the p38 signaling pathway is activated to cell the kinases MKK6 or MKK3 phosphorylate the p38α-MK2 heterodimer is the conformation for both p38α and MK2a still be phosphorylated when activated MKK6 is added to the complex. to is the p38α signaling activated MKK6 phosphorylate and p38α and p38α phosphorylate MK2a. MKK6-DD is a constitutively activated of MKK6 in the the phosphorylated and M. T. H. EMBO J. 1998; 17: PubMed Scopus Google Scholar) and is a efficient of a of MKK6-DD was added to the p38α-MK2 complex, both p38α and MK2a phosphorylated over Phosphorylation of p38α was by analysis using an that phosphorylated and phosphorylated Phosphorylation of MK2a was with that phosphorylated and phosphorylated Thr334. The that when MKK6-DD was added to the p38α-MK2 heterodimer the of phosphorylated p38α increased the the levels of phosphorylated p38α were but min a of phosphorylated p38α and the levels increased the of the The MK2a of the heterodimer also phosphorylated in at sites MK2a has four phosphorylation sites, and phosphorylated MK2a with a unphosphorylated MK2a. a of MK2a was but with that the protein was not was not phosphorylated at The levels of phosphorylated Thr334 in MK2a increased whereas the levels of phosphorylated increased the of the In addition of constitutively activated MKK6 to phosphorylation at both p38α and MK2a in the p38α-MK2 and we that both kinases activated when activated MKK6 is The signaling pathway of p38α and MK2a has been and is that MKK6 phosphorylates p38α and p38α phosphorylates MK2a. we have that MKK6-DD to the p38α-MK2 heterodimer to the phosphorylation of p38α and MK2a, we to the phosphorylation was MKK6-DD phosphorylated p38α and p38α in turn phosphorylated MK2a. is a and of p38α that has been used to the p38α signaling pathway J.C. Gallagher T.F. S. D. D. M.J. J.R. S.M. J.R. Young P.R. 1994; PubMed Scopus Google Scholar, S. Lee J.C. Young P.R. Biochem. Biophys. Res. Commun. 1997; PubMed Scopus Google Scholar, A. Cohen P. M. EMBO J. 1997; PubMed Scopus Google Scholar). was added to the p38α-MK2 heterodimer min in of the addition of phosphorylation of MK2a was Phosphorylation of Thr334 not the levels in the 20 min of the and after min the levels of MK2a were less a of that in the absence of The of phosphorylated was also in the of the the activity of MKK6-DD was not by the addition of as the levels of phosphorylated p38α not change not does not phosphorylate MK2 when MKK6-DD is added to the p38α-MK2 heterodimer in the of and the in the signaling is the of We have determined the crystal structure of the p38α-MK2 complex. This is the structure of full-length kinases associated in a complex. the of the full-length p38α-MK2 complex was only we also determined the structure of the p38α-MK2 peptide complex, and with the structures of the MK2a we the docking groove p38α and MK2a. We that the crystal structure the conformation of p38α and MK2a as is present in the nucleus when the cell is of stress. MK2a is a phosphorylation substrate of p38α, the conformation of the heterodimer does not the phosphorylation but rather prevents both p38α and MK2a from phosphorylating their substrates in the absence of stress regulation of the p38α signal transduction is for the of a as activation of this pathway the levels of proinflammatory and induces cell is that the of unphosphorylated and phosphorylated The of the unphosphorylated p38α-MK2 heterodimer is whereas the of the phosphorylated heterodimer is 10 (16Lukas S.M. Kroe R.R. Wildeson J. Peet G.W. Frego L. Davidson W. Ingraham R.H. Pargellis C.A. Labadia M.E. Werneburg B.G. Biochemistry. 2004; 43: 9950-9960Crossref PubMed Scopus (46) Google Scholar). conformational change has also been in MK2a with transfer analysis and is by the phosphorylation of Thr334 (19Neininger A. Thielemann H. Gaestel M. EMBO Rep. 2001; 2: 703-708Crossref PubMed Scopus (50) Google Scholar). The conformational change the NES thus the heterodimer to be to the cytoplasm. The heterodimer structure is not the complex in the kinases from the nucleus to the cytoplasm. The MK2a NES is the kinase of the heterodimer and not to The NLS is of the p38α binding and is in the domain of the docking groove and not to from the cytoplasm to the nucleus. stress the p38α-MK2 signaling have for the heterodimer. kinases be p38α by MKK3 or MKK6 and MK2a by kinases in turn phosphorylate transcription factors in the nucleus, to the and phosphorylate substrates. the kinases be by a kinase We have that MK2a binds p38α in the docking proteins that with p38α also in this groove T. M. T. E. Nat. Cell. Biol. 2000; 2: PubMed Scopus Google Scholar, T. R. M. E. EMBO J. 2001; 20: PubMed Scopus Google Scholar, T. T. E. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, M. L. Biochem. J. 2003; PubMed Google Scholar, T. T. R. E. J. Biol. Chem. 2001; Full Text Full Text PDF PubMed Scopus Google Scholar). proteins be p38α substrates such as PRAK, and MK2a, p38α MKK3 and or be the kinase that substrates for the binding in p38α and the stress response and of p38α We have also that constitutively active MKK6 phosphorylate the p38α in the heterodimer and that p38α in turn phosphorylates MK2a. We the for that when the p38α signaling pathway is activated and the nucleus. In the nucleus of a p38α and MK2a are in the described Activated MK2a from p38α to phosphorylate and p38α Activated p38α has on the protein of nuclear substrates such as transcription factor and in response to cell stress. The binding is a in the kinase has for the for the the transcription factor is and p38α a p38α a kinase This in and of The p38α a heterodimer with MK2a and this heterodimer in the nucleus Activated p38α binds and MK2a at phosphorylation sites, including Thr334 MK2a a conformational change and nuclear export The activated heterodimer of p38α and MK2a the nucleus and phosphorylate substrates in the cytoplasm of the p38α and MK2a to the nucleus. is not as a heterodimer or as monomers but p38α is found in the nucleus (17Ben-Levy R. Hooper S. Wilson R. Paterson H.F. Marshall C.J. Curr. Biol. 1998; 8: 1049-1057Abstract Full Text Full Text PDF PubMed Scopus (295) Google that p38α the nucleus the of MK2a. The NLS of MK2a is also the p38α docking that binding by p38α prevents the binding of and to the nucleus. a the MK2a NLS is and MK2a and with to the nucleus. The p38α signaling pathway is a for anti-inflammatory therapy. of the p38α signaling pathway the levels of proinflammatory cytokines, and p38 inhibitors have in the treatment of rheumatoid psoriasis, and chronic obstructive pulmonary (7Force T. Kuida K. Namchuk M. Parang K. Kyriakis J.M. Circulation. 2004; 109: 1196-1205Crossref PubMed Scopus (116) Google Scholar). In this we have that p38α forms a heterodimer with MK2a that is the conformation of both kinases in the nucleus of a cell that is not stress The crystal structures of the p38α signaling pathway that be for anti-inflammatory We and Namchuk for their critical of the We Hayakawa and for their with