Phosphorylation of Grainy head by ERK is essential for wound-dependent regeneration but not for development of an epidermal barrier

Abstract

Grainy head (GRH) is a key transcription factor responsible for epidermal barrier formation and repair, whose function is highly conserved across diverse animal species. However, it is not known how GRH function is reactivated to repair differentiated epidermal barriers after wounding. Here, we show that GRH is directly regulated by extracellular signal-regulated kinase (ERK) phosphorylation, which is required for wound-dependent expression of GRH target genes in epidermal cells. Serine 91 is the principal residue in GRH that is phosphorylated by ERK. Although mutations of the ERK phosphorylation sites in GRH do not impair its DNA binding function, the ERK sites in GRH are required to activate Dopa decarboxylase (Ddc) and misshapen (msn) epidermal wound enhancers as well as functional regeneration of an epidermal barrier upon wounding. This result indicates that the phosphorylation sites are essential for damaged epidermal barrier repair. However, GRH with mutant ERK phosphorylation sites can still promote barrier formation during embryonic epidermal development, suggesting that ERK sites are dispensable for the GRH function in establishing epidermal barrier integrity. These results provide mechanistic insight into how tissue repair can be initiated by posttranslational modification of a key transcription factor that normally mediates the developmental generation of that tissue.embryo | Drosophila | cuticle

P2Y2 nucleotide receptor activation enhances the aggregation and self-organization of dispersed salivary epithelial cells

“…It is well-established that MAPKs, including JNK and ERK1/2, regulate cell proliferation, migration, and differentiation (15,18,21,36,63,72,86,102,120), processes important for salivary gland morphogenesis (60,70) and regeneration of a wide variety of tissues (19,24,50,53,54,56,65,71,80,100,105,107,111,122,124). The P2Y 2 R-mediated activation of ERK1/2 has been reported in HSG cells (94), corneal epithelial cells (13), and human coronary artery endothelial cells (HCAEC) (29).…”

Stable Binding of the Conserved Transcription Factor Grainy Head to its Target Genes ThroughoutDrosophila melanogasterDevelopment

“…It is possible that Grh activity during development is directly regulated through post-translational modification, cofactor binding, or a combination of both. It is known that Grh is phosphorylated both in vivo and in vitro, and that the mitogen activated kinase (MAPK) pathway can regulate Grh activity Hemphala et al 2003;Zhai et al 2008;Wang et al 2009;Kim and McGinnis 2011). Grh has also been found to interact with Polycomb and Trithorax group proteins, suggesting that Grh may function to recruit corepressors or coactivators to distinct loci (Tuckfield et al 2002;Blastyak et al 2006;Strubbe et al 2011;Hopkin et al 2012).…”

Src kinases and ERK activate distinct responses to Stitcher receptor tyrosine kinase signaling during wound healing in Drosophila

“…Because the overexpression of the constitutively active version of Src42A can induce the transcriptional activation of woundresponse genes without inducing detectable accumulation of dpERK, we suggest that Drk is the major linker between Stit and ERK. ERK phosphorylates Grh in vitro, and this phosphorylation is important for the Grh-dependent activation of wound reporters (Kim and McGinnis, 2011). This suggests that the binding of Drk to phosphorylated Stit induces ERK-mediated Grh phosphorylation and Ddc activation.…”

“…Grh is phosphorylated by ERK, and this modification is necessary for its function following wounding (Kim and McGinnis, 2011). Therefore, we tested the ability of Src42A CA to activate ERK in the embryonic epidermis.…”

“…Wounding also initiates inflammation and activates ERK to induce the expression of barrier-repair genes in epithelial cells at the wound site (Mace et al, 2005;Pearson et al, 2009;Wood et al, 2006). The evolutionarily conserved transcription factor Grainy head (Grh) is phosphorylated by ERK and lies at the heart of wound healing (Kim and McGinnis, 2011). It activates the barrier-repair genes Dopa decarboxylase (Ddc) and pale (ple, encoding tyrosine hydroxylase) in Drosophila and transglutaminase-1 in mice (Ting et al, 2005;Wang and Samakovlis, 2012).…”