Docking of PRAK/MK5 to the Atypical MAPKs ERK3 and ERK4 Defines a Novel MAPK Interaction Motif

Abstract

ERK3 and ERK4 are atypical MAPKs in which the canonical TXY motif within the activation loop of the classical MAPKs is replaced by SEG. Both ERK3 and ERK4 bind, translocate, and activate the MAPK-activated protein kinase (MK) 5. The classical MAPKs ERK1/2 and p38 interact with downstream MKs (RSK1–3 and MK2–3, respectively) through conserved clusters of acidic amino acids, which constitute the common docking (CD) domain. In contrast to the classical MAPKs, the interaction between ERK3/4 and MK5 is strictly dependent on phosphorylation of the SEG motif of these kinases. Here we report that the conserved CD domain is dispensable for the interaction of ERK3 and ERK4 with MK5. Using peptide overlay assays, we have defined a novel MK5 interaction motif (FRIEDE) within both ERK4 and ERK3 that is essential for binding to the C-terminal region of MK5. This motif is located within the L16 extension lying C-terminal to the CD domain in ERK3 and ERK4 and a single isoleucine to lysine substitution in FRIEDE totally abrogates binding, activation, and translocation of MK5 by both ERK3 and ERK4. These findings are the first to demonstrate binding of a physiological substrate via this region of the L16 loop in a MAPK. Furthermore, the link between activation loop phosphorylation and accessibility of the FRIEDE interaction motif suggests a switch mechanism for these atypical MAPKs in which the phosphorylation status of the activation loop regulates the ability of both ERK3 and ERK4 to bind to a downstream effector. ERK3 and ERK4 are atypical MAPKs in which the canonical TXY motif within the activation loop of the classical MAPKs is replaced by SEG. Both ERK3 and ERK4 bind, translocate, and activate the MAPK-activated protein kinase (MK) 5. The classical MAPKs ERK1/2 and p38 interact with downstream MKs (RSK1–3 and MK2–3, respectively) through conserved clusters of acidic amino acids, which constitute the common docking (CD) domain. In contrast to the classical MAPKs, the interaction between ERK3/4 and MK5 is strictly dependent on phosphorylation of the SEG motif of these kinases. Here we report that the conserved CD domain is dispensable for the interaction of ERK3 and ERK4 with MK5. Using peptide overlay assays, we have defined a novel MK5 interaction motif (FRIEDE) within both ERK4 and ERK3 that is essential for binding to the C-terminal region of MK5. This motif is located within the L16 extension lying C-terminal to the CD domain in ERK3 and ERK4 and a single isoleucine to lysine substitution in FRIEDE totally abrogates binding, activation, and translocation of MK5 by both ERK3 and ERK4. These findings are the first to demonstrate binding of a physiological substrate via this region of the L16 loop in a MAPK. Furthermore, the link between activation loop phosphorylation and accessibility of the FRIEDE interaction motif suggests a switch mechanism for these atypical MAPKs in which the phosphorylation status of the activation loop regulates the ability of both ERK3 and ERK4 to bind to a downstream effector. Mitogen-activated protein kinase (MAPK) 2The abbreviations used are: MAPKmitogen-activated protein kinaseCDcommon dockingERKextracellular signal-regulated kinaseMEKMAPK/ERK kinaseMK or MAPKAPKMAPK-activated protein kinasesGFPgreen fluorescent proteinGSTglutathione S-transferaseWTwild typeCDmCD mutantEGFPenhanced GFP. phosphorylation cascades play important roles in the regulation of diverse cellular functions such as cell proliferation, differentiation, migration, and apoptosis (1.Raman M. Chen W. Cobb M.H. Oncogene. 2007; 26: 3100-3112Crossref PubMed Scopus (1142) Google Scholar, 2.Avruch J. Biochim. Biophys. Acta. 2007; 1773: 1150-1160Crossref PubMed Scopus (208) Google Scholar). A characteristic and conserved feature of this family of signaling pathways is their organization into modules comprising a sequential three-tiered kinase cascade. This contains a MAPK kinase kinase, a MEK, and the MAPK itself. Four such MAPK signaling modules have been described in mammals: ERK1 and ERK2, the c-Jun N-terminal kinases 1–3, the p38 kinases (p38α/β/γ/δ), and ERK5 (3.Bogoyevitch M.A. Court N.W. Cell Signal. 2004; 16: 1345-1354Crossref PubMed Scopus (109) Google Scholar, 4.Roux P.P. Blenis J. Microbiol. Mol. Biol. Rev. 2004; 68: 320-344Crossref PubMed Scopus (1936) Google Scholar, 5.Turjanski A.G. Vaqué J.P. Gutkind J.S. Oncogene. 2007; 26: 3240-3253Crossref PubMed Scopus (352) Google Scholar, 6.Qi M. Elion E.A. J. Cell Sci. 2005; 118: 3569-3572Crossref PubMed Scopus (421) Google Scholar, 7.Cuenda A. Rousseau S. Biochim. Biophys. Acta. 2007; 1773: 1358-1375Crossref PubMed Scopus (1026) Google Scholar). The MAPK kinase kinases phosphorylate and activate the MEKs, which in turn activate the MAPKs by dual phosphorylation on both the threonine and the tyrosine residue of a highly conserved TXY motif in the kinase activation loop. MAPKs are Ser/Thr kinases, which phosphorylate a wide range of substrates with the minimal consensus sequence (S/T)P (2.Avruch J. Biochim. Biophys. Acta. 2007; 1773: 1150-1160Crossref PubMed Scopus (208) Google Scholar). mitogen-activated protein kinase common docking extracellular signal-regulated kinase MAPK/ERK kinase MAPK-activated protein kinases green fluorescent protein glutathione S-transferase wild type CD mutant enhanced GFP. ERK4 and its close relative ERK3 are regarded as atypical members of the MAPK family. In contrast to the classical MAPKs, ERK3 and ERK4 harbor an SEG motif in the activation loop and thus lack a second phosphoacceptor site. In addition, protein kinases all possess a conserved APE motif located just C-terminal to the phosphoacceptor sites within subdomain VIII, in which the conserved glutamate is important for maintaining the stability of the kinase domain. In both ERK3 and ERK4, this motif is substituted by SPR, and ERK3 and ERK4 are the only two protein kinases in the human genome with an arginine residue in this position (8.Kostich M. English J. Madison V. Gheyas F. Wang L. Qiu P. Greene J. Laz T.M. Genome Biol.2002Google Scholar). Although they display significant sequence homology (44% identity) with ERK1 and ERK2 within their kinase domains, both ERK3 and ERK4 have unique C-terminal extensions, which account for the large differences in size observed between ERK1/2 (∼360 amino acids) and ERK3/ERK4 (721/587 amino acids). Whereas classical MAPKs have been highly conserved throughout evolution, with examples found in both unicellular and multicellular organisms, ERK3 and ERK4 are only present in vertebrates. Finally, in contrast to many of the classical MAPKs, the regulation, substrate specificity, and physiological functions of ERK3 and ERK4 are poorly understood. Although ERK3 and ERK4 are very similar to each other, there are significant differences between them. For instance, whereas ERK4, like most classical MAPKs, is a stable protein, ERK3 is highly unstable and subject to rapid proteosomal degradation. Thus, ERK3 activity may be regulated at the level of cellular abundance, and taken together these features indicate that ERK3 and ERK4 may perform specialized functions and enjoy different modes of regulation when compared with classical MAPKs (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, 10.Coulombe P. Rodier G. Pelletier S. Pellerin J. Meloche S. Mol. Cell. Biol. 2003; 23: 4542-4558Crossref PubMed Scopus (113) Google Scholar, 11.Seternes O.M. Mikalsen Johansen B. E. B. Meloche S. Keyse S.M. J. 2004; 23: PubMed Scopus Google Scholar). the differences between ERK3 and ERK4 and the classical MAPKs, they with the and the ability to interact with a of downstream Ser/Thr protein kinases, MAPK-activated protein kinases or M. Rev. Mol. Cell Biol. 2006; PubMed Scopus Google Scholar, A. Cobb M.H. Biophys. 2006; PubMed Scopus Google Scholar). In the of ERK3 and ERK4, both interact translocate, and activate the MK5 protein have to the of docking that to both substrate and regulation in MAPK pathways Chem. Rev. 2007; PubMed Scopus Google Scholar, A. Sci. Full Text Full Text PDF PubMed Scopus Google Scholar, E. Cell Signal. 2003; PubMed Scopus Google Scholar, J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google Scholar). These docking domains, which peptide docking located on MAPK downstream as as and The docking domains, located within the kinase domains, are the site. the which these docking are the phosphoacceptor sites within protein substrates A. Rev. 2006; PubMed Scopus Google Scholar). are of The found in kinases MK5 have the consensus sequence is amino M. Rev. Mol. Cell Biol. 2006; PubMed Scopus Google Scholar). The docking within the MAPKs have been E. Cell Signal. 2003; PubMed Scopus Google Scholar, M. E. Cell Biol. PubMed Scopus Google Scholar, M. E. J. PubMed Scopus Google Scholar). The common docking (CD) domain is a of amino located in the L16 extension C-terminal to the kinase domain in the MAPK A second domain to binding This is located the CD domain in the MAPK Whereas the CD domain is important for all docking the is to be important for the of E. Cell Signal. 2003; PubMed Scopus Google Scholar). and the and CD have been to be important for Cobb M.H. Mol. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar, J. B. J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, B. B. G. M. PubMed Scopus Google Scholar, M. Cobb M.H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, B. S. Cobb M.H. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). This been to of the classical MAPKs, and is the of substrate or docking for the atypical and (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, 11.Seternes O.M. Mikalsen Johansen B. E. B. Meloche S. Keyse S.M. J. 2004; 23: PubMed Scopus Google Scholar, S. S. A. A. M. J. Biol. Chem. 2006; 281: Full Text Full Text PDF PubMed Scopus Google have that the region within both ERK3 and ERK4 is for their ability to interact with and activate MK5. Furthermore, a mutant of which the C-terminal to bind to ERK4 the that its domain. Finally, in contrast to MAPKs, the interaction between ERK3 and ERK4 and MK5 activation loop phosphorylation of ERK3 and ERK4 P. Rousseau J. P. Rodier G. Meloche S. J. Cell. PubMed Scopus Google Scholar, M. E. Johansen B. B. Keyse S.M. Seternes O.M. J. PubMed Scopus Google Scholar). together these that the mechanism by which the atypical MAPKs and bind to at important of kinases may be to that found in the classical MAPKs such as ERK1/2 and Here we demonstrate that two C-terminal and are for MK5 to interact with both ERK3 and ERK4. These are the motif within that binding to ERK3 and ERK4 may be by a different mechanism to that in the classical In of the conserved CD within ERK3 and ERK4 are to be dispensable for MK5 Using peptide overlay assays, we have defined a minimal MK5 interaction motif FRIEDE in ERK4. Furthermore, we demonstrate that a single or ERK4 within this FRIEDE motif is to the binding of both ERK3 and ERK4 to MK5 and their ability to both and activate MK5. The FRIEDE motif is located within the L16 extension C-terminal to the CD domain in both ERK3 and ERK4. of the region in ERK2 suggests that a significant as a of activation loop this of the L16 extension A. Cobb M.H. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). that the FRIEDE motif a novel MAPK interaction the of which is to activation loop phosphorylation and MAPK and A and an by P. of and and The and The by Johansen of in essential with amino and used to the to the of the of and ERK4 and the of cell as described O.M. Mikalsen Johansen B. E. B. Meloche S. Keyse S.M. J. 2004; 23: PubMed Scopus Google Scholar). The a and of (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google and been described The by of the of MK5 and into The by of or the and into the or Perander M. A. E. G. Johansen J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google and for of MK5 by and into into the to and used to and with as on their are of the described by the of the to the For of ERK4, and MK5 in and the by to a and with or and with or by or or and the The the protein protein in E. and as and used to both the and of the on a peptide as described A. J. Mol. Biol. Google Scholar). The in with and peptide with and by the with of protein for at in the with The of the of the PubMed Scopus Google and and of ERK2 and respectively) as and (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, S. S. A. A. M. J. Biol. Chem. 2006; 281: Full Text Full Text PDF PubMed Scopus Google Scholar, S. S. A. A. M. J. 2004; 23: PubMed Scopus Google have ERK4 as a interaction for MK5. binding to ERK4, MK5 is and and the of MK5 the to the The C-terminal amino of MK5 are essential for this a C-terminal mutant comprising of MK5 is to bind to ERK4 (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar). the within MK5 that are for its interaction with ERK4, a of and N-terminal MK5 the minimal we first the N-terminal MK5 with ERK4 in and to binding that of MK5 are for both ERK3 and ERK4 In the of the of this protein its ability to bind to ERK3 and ERK4 and the C-terminal with ERK3 or ERK4 in of by for ERK3 or ERK4 that of the amino of MK5 interaction with both ERK3 and ERK4 and In of only the of MK5 the ability of MK5 to bind to ERK3 or ERK4 and both of these C-terminal are in the cell when as and of ERK4 with wild type MK5 or the C-terminal of MK5 protein only to of these MK5 to and In the C-terminal mutant of MK5 is on of ERK5 with observed in both and and that and of MK5 to ERK3 and ERK4 have the CD and of MAPKs as important for interaction with binding M. E. Cell Biol. PubMed Scopus Google Scholar, M. E. J. PubMed Scopus Google Scholar). The CD domain is a of amino located in the L16 extension C-terminal to the kinase domain in the MAPK Although this domain is present in all MAPKs, is docking within the ERK3/4 homology with MAPKs, the ERK3 and ERK4 CD between and The lying between and in ERK3 and and in ERK4. the of these two with to with we ERK4 in within both the CD and The ERK4 CD mutant by substitution of with and with The substitution is to the mutant found in the MAPK J. E. Cell. Full Text PDF PubMed Scopus Google whereas been in CD domain M. E. J. PubMed Scopus Google Scholar). two C-terminal ERK4 ERK4 (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, S. S. A. A. M. J. Biol. Chem. 2006; 281: Full Text Full Text PDF PubMed Scopus Google and ERK4 (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, S. S. A. A. M. J. Biol. Chem. 2006; 281: Full Text Full Text PDF PubMed Scopus Google to be to both binding to MK5 and its translocation the to the both of these the CD This suggests that the CD domain is for In with these we found that ERK4 with MK5 in and this mutant MK5 to the of as as the wild type protein the of the ERK4 domain by an ERK4 mutant in which both the CD domain and the these on the ability of ERK4 to MK5 within the CD domain of ERK3 on its ability to interact with MK5 that conserved within both the CD and of both ERK3 and ERK4 are essential for docking with MK5. that ERK4 bind to ERK3 and ERK4 which a of the L16 MK5 These the region lying C-terminal to the ERK3 and ERK4 CD in the interaction with MK5 (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, S. S. A. A. M. J. Biol. Chem. 2006; 281: Full Text Full Text PDF PubMed Scopus Google Scholar). a sequence of MAPKs the region to of ERK4. the binding of MK5 to this region at we a peptide through amino of ERK4 by a peptide on of at This with or and with an to In with the this the binding of MK5 to ERK4 in a region C-terminal to the CD domain. in with a of to amino of ERK4 with that these are the of this with and C-terminal and with These and as for MK5 binding and a binding motif defined by the sequence The essential of this sequence in a in which and in the FRIEDE motif as for MK5 binding Using these we an to of ERK4, for a peptide in which residue of the ERK4 sequence substituted by each of the amino these with the of all of the at this position the interaction with only amino or to for the at this this that lysine of through in for MK5. substitution of into to the on sequence and the ability to bind we a the region in of the ERK3 sequence to for ERK4 that similar for MK5 binding by both these that ERK3 and ERK4 bind to MK5 of the CD domain and that within the L16 extension a interaction essential for this the of MK5 for the FRIEDE motif in ERK3 and ERK4, we the of different human MAPKs, the p38 MAPK of and on a and with the of this MK5 to ERK3 and ERK4 with only a interaction observed for ERK5 and ERK1 and binding to the the of these in a of the that binding to MK5 into the FRIEDE motif of ERK4. ERK4 ERK4 ERK4 and ERK4 for binding to in of in In with the peptide ERK4 the a ability to bind to whereas the of the ERK4 substitution In contrast to and substitution of isoleucine for lysine binding to as as to MK5 A and the isoleucine in ERK3 to lysine by and as in this ERK3 mutant to interact with MK5. ERK3 is a highly unstable protein with a of in P. Rodier G. Pelletier S. Pellerin J. Meloche S. Mol. Cell. Biol. 2003; 23: 4542-4558Crossref PubMed Scopus (113) Google Scholar). of MK5 by or its by to a in ERK3 protein O.M. Mikalsen Johansen B. E. B. Meloche S. Keyse S.M. J. 2004; 23: PubMed Scopus Google Scholar, S. S. A. A. M. J. 2004; 23: PubMed Scopus Google Scholar). the of MK5 into or the ERK3 protein that MK5 as a for MK5 a mutant of ERK3 that to bind we or mutant of ERK3 with and MK5 in the of at different the of and the of ERK3 by In with ERK3 unstable significant within of of MK5 in significant of ERK3 or on the stability of ERK3 have that a mutant of ERK3 or ERK4 the FRIEDE region to interact with or to activate MK5 (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar). Thus, the activation of MK5 by ERK3 or ERK4 is dependent on between these Furthermore, we that the activation of MK5 or phosphorylation of within the activation loop of MK5 (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar). Using phosphorylation to MK5 we the ability of the ERK3 and ERK4 FRIEDE to bind to MK5 by a ability to activate MK5 in this we wild type MK5 with of the ERK3 or ERK4 FRIEDE in MK5 the and a A between binding and of MK5 phosphorylation of wild type or the or of ERK3 and ERK4, both of which bind to of phosphorylation by ERK3 or ERK4 which bind to MK5 with a a ability to phosphorylate wild type whereas ERK3 or ERK4 both of which are to interact with to of In this we have defined and the interaction between ERK3/4 and MK5. The of between classical MAPKs and their are to be through the conserved CD domain in the MAPKs, which found in the The CD domain is conserved in both ERK3 and ERK4, and MK5 a motif O.M. Johansen B. B. M. Keyse S.M. Mol. Cell. Biol. PubMed Scopus Google Scholar). that these are in the interaction between ERK3/4 and MK5 (9.Aberg E. Perander M. Johansen B. Julien C. Meloche S. Keyse S.M. Seternes O.M. J. Biol. Chem. 2006; 281: 35499-35510Abstract Full Text Full Text PDF PubMed Scopus (60) Google Scholar, 11.Seternes O.M. Mikalsen Johansen B. E. B. Meloche S. Keyse S.M. J. 2004; 23: PubMed Scopus Google Scholar, S. S. A. A. M. J. Biol. Chem. 2006; 281: Full Text Full Text PDF PubMed Scopus Google Scholar, S. S. A. A. M. J. 2004; 23: PubMed Scopus Google Scholar). The we have in the present within the CD of both ERK3 and ERK4 this The domain an of important for the interaction between MAPKs and kinases M. E. J. PubMed Scopus Google Scholar). This is in the docking close to the CD domain in the of the MAPKs M. E. J. PubMed Scopus Google Scholar). of two characteristic within this motif of ERK3 or ERK4 with MK5. Thus, the CD domain the of ERK3 and ERK4 to be in the interaction with their downstream MK5. This the as to the CD domain is highly conserved in ERK3 and The is to be that is important in binding to ERK3/ERK4 binding and we have to that this may be the S. M. and M. defined the minimal domain in the of MK5 in the binding to ERK3 and ERK4. Although of as as the of MK5 the interaction with ERK4, this peptide is for interaction with MK5. The of peptide MK5 to ERK3/4 interaction is by the peptide overlay we to MK5 that interaction with ERK4 or ERK3 This with MAPK in which motif as as are for interaction J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The minimal domain of MK5 for the interaction with ERK4 to be the C-terminal extension of MK5. This extension is unique to MK5 and is found in and and may the of MK5 for ERK3 and ERK4. the C-terminal of MK5 that binding in this they are for together they are to and stable interaction with both ERK3 and ERK4. the of a peptide we a minimal motif in ERK4 for interaction with MK5. A peptide in which the in position in the peptide to each of the in the of amino that only amino in position of ERK4 in in position within the region comprising to to for have that this of the L16 loop of MAPKs may be a interaction motif in A. Cobb M.H. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar, M. J. Mol. Biol. 2007; PubMed Scopus Google Scholar). this is the first to demonstrate that a MAPK this region for binding to important characteristic of the interaction between both ERK3 and ERK4 and MK5 is that the interaction by the FRIEDE motif is dependent on phosphorylation of the SEG motif within the activation loop of these atypical MAPKs P. Rousseau J. P. Rodier G. Meloche S. J. Cell. PubMed Scopus Google Scholar, M. E. Johansen B. B. Keyse S.M. Seternes O.M. J. PubMed Scopus Google Scholar). This that activation loop phosphorylation may or the L16 region of ERK3 and ERK4 the FRIEDE thus its interaction with MK5. as to this of the in the classical MAPK This in the in the FRIEDE motif be the of and ERK2 This suggests a between the phosphorylation status of the activation loop and the binding of downstream to the FRIEDE motif within ERK3 and ERK4. In the the residue is the phosphorylation of the activation loop to a in the region of the FRIEDE which in the of and may its in with MK5. In ERK2, the L16 region of ERK2 is important for the of this MAPK B. J. M. M. E. Cobb M.H. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). phosphorylation of the TXY motif in the activation loop. This in turn to interaction with with this in of the the residue to of ERK4, to the is important for through a interaction between its and of the activation loop. the that the activation of both ERK3 and ERK4 are in to that found in ERK2, these atypical MAPKs lack conserved found in ERK2 that In of this we have been to demonstrate the of ERK3/ERK4 or in important between the of binding between ERK3/ERK4 and MK5 and of ERK2 is that a single amino substitution within the FRIEDE motif in ERK3 and in ERK4 to is to MK5 In single or amino to ERK2 B. J. M. M. E. Cobb M.H. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). This the of a or of the ERK2 activation loop B. J. M. M. E. Cobb M.H. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar, E. Cobb M.H. 2006; PubMed Scopus Google Scholar). Although dual phosphorylation of ERK2 to in binding of or of this region may the of the activation loop as E. 2005; PubMed Scopus Google have that of p38 which to of ERK4, is a novel phosphorylation site. of this by in in and activation of p38 MAPK. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus Google to kinases by of p38 MAPK in the region to the FRIEDE motif of ERK4. of these that in the L16 loop region kinase activation M. J. Mol. Biol. 2007; PubMed Scopus Google Scholar). on these the that the L16 may as a switch that these there is a level of between the activation loop of the MAPKs and the L16 which contains the FRIEDE motif in both ERK3 and ERK4. within this region activation loop phosphorylation may binding to MK5 as in 5. the of ERK4 which observed MK5 binding and which of MK5 kinase be to in the activation loop by MK5 binding to the FRIEDE region P. Rousseau J. P. Rodier G. Meloche S. J. Cell. PubMed Scopus Google Scholar, M. E. Johansen B. B. Keyse S.M. Seternes O.M. J. PubMed Scopus Google Scholar). This the to a protein or to the ERK3/4 In we have that both ERK3 and ERK4 the classical CD domain and motif to bind to and activate their downstream substrate MK5. we have that a novel MAPK docking the FRIEDE motif that is located in the L16 loop of ERK4 C-terminal to the CD domain is for interaction with the unique C-terminal extension of MK5. the region in ERK2 that this region phosphorylation of the activation loop A. Cobb M.H. Cell. Full Text Full Text PDF PubMed Scopus Google and a between activation loop status and binding of downstream to the FRIEDE be and of the ERK3/4 domain this motif and its ability to bind to MK5. The of this conserved region may the of and of ERK3 and ERK4 in and the physiological of between these two signaling and MK5. and the protein and of of by and and Johansen of for