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. Mitogen-activated protein kinase (MAPK)2 phosphorylation cascades play important roles in the regulation of diverse cellular functions such as cell proliferation, differentiation, migration, and apoptosis (1, 2). 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 (p38␣/␤/␥/␦), and ERK5 (3-7). 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).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...

Identification of the Atypical MAPK Erk3 as a Novel Substrate for p21-activated Kinase (Pak) Activity

“…We also believe that the similarity in subcellular localization of the GFP-Erk3S189A variant to that seen for GFP-Erk3 in cells co-expressing mRFP-PID (Fig. 6, C and D (33). This interface is distinct from the common docking domain used by classical Erks to bind to both their respective MAP2Ks and their cognate substrates (34).…”

“…This interface is distinct from the common docking domain used by classical Erks to bind to both their respective MAP2Ks and their cognate substrates (34). Molecular modeling suggests that Erk4 Ser 186 phosphorylation (analogous the Erk3 Ser 189 ) might promote a conformational change that increases the solvent accessibility of isoleucine 330 (within the conserved FRIEDE motif) allowing for efficient interaction with the C terminus of Prak (33).…”

IGF2BP1 promotes cell migration by regulating MK5 and PTEN signaling

“…MAPK4 and its homolog, ERK3, are classified as atypical MAPKs, both of which activate MK5 (Seternes et al 2004;Aberg et al 2006Aberg et al , 2009Gaestel 2006;Kant et al 2006;Deleris et al 2008;Perander et al 2008). Notably, ERK3 protein is rapidly turned over, whereas MAPK4 is not (Aberg et al 2006).…”

“…MAPK4 activates MK5 by phosphorylating the latter at T182, resulting in cytoplasmic accumulation of MK5 (Kant et al 2006;Coulombe and Meloche 2007;Deleris et al 2008;Perander et al 2008;Aberg et al 2009). MK5, in turn, phosphorylates HSP27 (HSPB1) and was suggested to thereby induce altered microfilament organization Doshi et al 2010).…”

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