A Gαq-Ca2+ Signaling Pathway Promotes Actin-Mediated Epidermal Wound Closure in C. elegans

Abstract

Summary Background Repair of skin wounds is essential for animals to survive in a harsh environment, yet the signaling pathways initiating wound repair in vivo remain little understood. In C. elegans a p38 MAPK cascade promotes innate immune responses to wounding, but is not required for other aspects of wound healing. We therefore set out to identify additional wound response pathways in C. elegans epidermis. Results We show here that wounding the adult C. elegans skin triggers a rapid and sustained rise in epidermal Ca2+ that is critical for survival after wounding. The wound-triggered rise in Ca2+ requires the epidermal TRPM channel GTL-2 and IP3R-stimulated release from internal stores. We identify an epidermal signal transduction pathway that includes the Gαq EGL-30 and its effector PLCβ EGL-8. Loss of function in this pathway impairs survival after wounding. The Gαq-Ca2+ pathway is not required for known innate immune responses to wounding but instead promotes actin-dependent wound closure. Wound closure requires the Cdc42 small GTPase and Arp2/3 dependent actin polymerization, and is negatively regulated by Rho and non-muscle myosin. Finally, we show that the death-associated protein kinase DAPK-1 acts as a negative regulator of wound closure. Conclusions Skin wounding in C. elegans triggers a Ca2+-dependent signaling cascade that promotes wound closure, in parallel to the innate immune response to damage. Wound closure requires actin polymerization and is negatively regulated by non-muscle myosin.

The Electrical Response to Injury: Molecular Mechanisms and Wound Healing

“…10,81 Extracellular calcium flux at the wound is small, 10 but an intracellular calcium wave that passes from cell to cell away from the wound edge is WOUND ELECTRIC MECHANISMS required for normal healing in some systems. 89,91 A G protein (guanine nucleotide binding protein alpha subunit)-Ca 2 + signaling pathway is necessary for actin-dependent wound healing in C. elegans nematode worms, 91 but the intracellular calcium release may also activate calcium-activated CLCs.…”

“…11). 91 The woundinduced rise in calcium requires the epidermal transient receptor potential channel, melastatin family channel gene trap locus 2, and inositol trisphosphate receptor-stimulated release from internal stores. The resultant calcium-dependent signaling cascade promotes wound closure by promoting actin polymerisation at the wound site.…”

Epidermal Wound Healing in the Nematode Caenorhabditis elegans

“…The advent of genetically encoded Ca 2 + sensors such as the GCaMPs 41 has greatly simplified imaging of Ca 2 + dynamics in vivo. In C. elegans, wounding triggers elevation of Ca 2 + at the wound site within less than a second 42 ; the elevated intracellular Ca 2 + spreads out in a wave-like manner through the epidermal syncytium, eventually extending several hundred microns. The elevation in epidermal Ca 2 + persists for 1-2 h after injury before returning to baseline levels.…”

“…A plasma membrane TRPM channel GTL-2 is also required for Ca 2 + influx in C. elegans wounding and might mediate Ca 2 + influx directly. 42 Interestingly, a TRPM channel is also required in Drosophila wound healing, acting upstream of the actin cytoskeleton. 43 In zebrafish, TRPV1 functions in keratinocyte migration, mechanistically relevant to wound healing.…”

“…42 The sustained rise in epidermal Ca 2 + involves ITR-1-dependent Ca 2 + -induced calcium release from internal stores, as Ca 2 + levels are reduced by expression of dominant-negative ITR-1. Wound-triggered Ca 2 + signaling is not required for AMP induction, 42 although as mentioned above it may play a role in ROS production. The epidermal Ca 2 + signal appears to be specifically involved in the formation of actin rings at the wound site.…”