Consequently, we analyzed tissue from naive WT and ERK1 KO mice by European blot to size separate the isoforms and quantify the basal phosphorylation state of each isoform individually (Fig
December 7, 2021
Consequently, we analyzed tissue from naive WT and ERK1 KO mice by European blot to size separate the isoforms and quantify the basal phosphorylation state of each isoform individually (Fig. ERK1 KO mice. Additionally, systemic MEK inhibition with SL327 (-[amino[(4-aminophenyl)thio]methylene]-2-(trifluoromethyl)benzeneacetonitrile) attenuated formalin-induced spontaneous behaviors similarly in wild-type and ERK1 KO mice, indicating that unrelated signaling pathways do not functionally compensate for the loss of ERK1. Together, these results suggest that ERK1 takes on a limited part in ADL5747 nociceptive sensitization and support a predominant part for ERK2 in these processes. Intro Extracellular signal-regulated kinases (ERKs), ERK1 and ERK2, are mitogen-activated protein kinases (MAPKs) (Pearson et al., 2001) that have been identified as crucial players in sensitization to noxious stimuli after peripheral swelling and nerve damage (Ji et al., 1999, 2002; Karim et al., 2001; Ciruela et al., 2003; Obata et al., 2003; Track et al., 2005). A variety of acute noxious stimuli and chronic pain models result in ERK1/2 activation (phosphorylation) at many levels of the nociceptive sensory system including dorsal root ganglion (DRG), spinal cord, and amygdala (Ji et al., 2009). The use of inhibitors that block activation of both ERK1 and ERK2 by inhibiting their shared upstream MAP kinase kinases (MEK1/2) and transgenic manifestation in neurons of a dominant-negative form of MEK1, which suppresses MEK1/2CERK1/2 signaling, have shown that ERK1/2 is necessary for nociceptive sensitization (Ji et al., 1999, 2002, 2009; Karim et al., 2001, 2006; Track et al., 2005; Hu et al., 2006; Seino et al., 2006). Although much is known about MEK1/2CERK1/2 signaling, little is known about the specific functions of each ERK isoform. Functional redundancy has been a operating model because the isoforms are 90% homologous (Boulton et al., 1991) and no isoform-specific inhibitors currently exist. However, there is growing evidence that ERK1 and ERK2 may be functionally unique. ERK1 knock-outs (ERK1 KOs) are viable but show behavioral abnormalities correlated with modified synaptic plasticity in striatum (Pags et al., 1999; Selcher et al., 2001; Mazzucchelli et al., 2002), whereas ERK2 knock-outs are embryonic lethal at embryonic day time 8.5 (Krens et al., 2006). Alternative methods for focusing on ERK2, including reduced manifestation from a hypomorphic mutant allele and conditional deletion ADL5747 in telencephalon, have revealed a requirement for ERK2 in several learning and memory space paradigms (Satoh et al., 2007; Samuels et al., 2008). In cell tradition, genetic focusing on or RNA interference (RNAi) experiments suggest specific functions for ERK1 and ERK2 (Mazzucchelli et al., 2002; Vantaggiato et al., 2006). Evidence to support this hypothesis includes the observations that ERK1 specifically interacts with the MEKCERK signaling scaffold MP1 (Schaeffer Rabbit Polyclonal to EDG7 et al., 1998) and the fact that variations in amino acid sequence between ERK1 and ERK2 occur in domains that may impact MEK1/2 binding, ERK dimerization, and subcellular localization (Boulton et al., 1991; Zhang et al., 1994; Cobb and Goldsmith, 2000). Indeed, ERK1 and ERK2 have different rates of shuttling between the cytoplasm and nucleus because of sequence variations in the N terminus (Marchi et al., 2008). Currently, the importance of ERK1 in nociceptive sensitization remains unknown. Consequently, we tested the necessity of ERK1 in acute noxious sensitization and in models of chronic inflammatory and neuropathic pain using ADL5747 ERK1 KO mice. Although ERK1 is definitely triggered in these models, genetic deletion of ERK1 experienced a minimal impact on these ERK-dependent behaviors. Interestingly, ERK1 deletion improved basal ERK2 phosphorylation without influencing inflammation-induced changes in ERK2 phosphorylation. Our observations show that ERK1 is not required for nociceptive sensitization and suggest that ERK2 takes on a.