Requirement for and polarized localization of integrin proteins duringDrosophilawound closure

Abstract

Wound reepithelialization is an evolutionarily conserved process in which skin cells migrate as sheets to heal the breach and is critical to prevent infection but impaired in chronic wounds. Integrin heterodimers mediate attachment between epithelia and underlying extracellular matrix and also act in large signaling complexes. The complexity of the mammalian wound environment and evident redundancy among integrins has impeded determination of their specific contributions to reepithelialization. Taking advantage of the genetic tools and smaller number of integrins in Drosophila, we undertook a systematic in vivo analysis of integrin requirements in the reepithelialization of skin wounds in the larva. We identify αPS2-βPS and αPS3-βPS as the crucial integrin dimers and talin as the only integrin adhesion component required for reepithelialization. The integrins rapidly accumulate in a JNK-dependent manner in a few rows of cells surrounding a wound. Intriguingly, the integrins localize to the distal margin in these cells, instead of the frontal or lamellipodial distribution expected for proteins providing traction and recruit nonmuscle myosin II to the same location. These findings indicate that signaling roles of integrins may be important for epithelial polarization around wounds and lay the groundwork for using Drosophila to better understand integrin contributions to reepithelialization.

cdc37 is essential for JNK pathway activation and wound closure in Drosophila

“…Because JNK up-regulates protein levels of the integrin β subunit βPS and integrins are essential for wound closure in Drosophila (Lee et al , 2017; Park et al , 2018), we also measured βPS and talin protein levels. βPS levels were greatly reduced in the epidermis of cdc37 -knockdown larvae compared with wild-type controls, whereas talin levels did not differ between the two groups of larvae (Figure 6, A, G, and H).…”

“…In Drosophila, JNK mediates diverse wound healing responses, including gene expression, cell shape change and polarization, reepithelialization, and cell fusion (Ramet et al , 2002; Galko and Krasnow, 2004; Bosch et al , 2005; Mattila et al , 2005; Campos et al , 2010; Kwon et al , 2010; Lesch et al , 2010; Brock et al , 2012; Losick et al , 2016; Lee et al , 2017; Park et al , 2018). The present study suggests that the JNK pathway also mediates wound-induced endoreplication and cell growth.…”

“…The larvae were then placed on cornmeal–agar media for recovery. Epidermal tissues were dissected in phosphate-buffered saline (PBS), as described in Park et al (2018). Samples were fixed in 4% paraformaldehyde for 15 min.…”

“…Of these, c-Jun N-terminal kinase (JNK), which is required for a broad range of wound healing processes, is the most crucial. Without JNK, cells cannot properly polarize, change shape, orient toward the wound center, or migrate to close the wound (Ramet et al , 2002; Galko and Krasnow, 2004; Kwon et al , 2010; Park et al , 2018). Conversely, some proteins acting upstream of JNK appear to be redundant in a pathway that includes both canonical and noncanonical factors in regard to the embryonic dorsal closure process (Lesch et al , 2010; Rios-Barrera and Riesgo-Escovar, 2013).…”

Casein kinase 1α decreases β-catenin levels at adherens junctions to facilitate wound closure inDrosophilalarvae

“…What accounts for this stage-dependent difference? Occluding (septate) junctions are also required for efficient WC in fly embryos (Carvalho et al, 2018) as are some Integrin complex components in fly larvae (Park et al, 2018). A specific role for occluding junctions in larval WC has not yet been tested.…”