Regulation of cutaneous wound healing by GCN2

NIH RePORTER · VA · I01 · · view on reporter.nih.gov ↗

Abstract

Approximately 6.5 million Americans are diagnosed with a cutaneous chronic wound each year, costing the healthcare system in the United States over 20 billion dollars annually. Often these chronic wounds are found in geriatric individuals, up to 85% of patients with chronic wounds are over 65 years old, or in patients with concurrent diseases such as diabetes, obesity, malnutrition, or substance abuse. Similarly, the failure to properly heal wounds is a major problem for the Veteran population as presently there are over 9 million Veterans over the age of 65, or about 38% of the total Veteran population. Often these patients are subjected to a litany of various treatments, frequently without mechanistic justification, and they still lack adequate resolution of their wounds. Therefore, a better understanding of specific causes of chronic wounds and a better menu of treatment options is needed to address this unmet need. Once any type of chronic wound appears, whether it is a diabetic ulcer, decubitus ulcer, or venous stasis ulcer, one of the primary limiting factors in wound closure is the inability of epidermal cells to re-epithelialize the wound bed. Chronic wounds remain arrested in the inflammatory phase with little to no migration of keratinocytes across the wound bed. Recent data have demonstrated that an evolutionarily-conserved mechanism, called the Integrated Stress Response (ISR), is crucial for normal re-epithelialization in human skin. The ISR consists of four distinct but related protein kinases are activated by various types of environmental stress leading to the phosphorylation of the same target protein, eukaryotic initiation factor 2 on its alpha subunit (eIF2α~P). The consequences of eIF2α~P include a global inhibition of protein translation, which conserves vital cellular energy stores, and the selective translation of genes associated with responding to the stress. Importantly, it was recently demonstrated that the ISR is activated in differentiating keratinocytes in normal skin. Furthermore, keratinocytes deficient for one of the eIF2α~P protein kinases (GCN2, which phosphorylates eIF2α~P during epidermal differentiation) form abnormal, dyskeratotic skin lacking a normal barrier function. If GCN2 expression is knocked-out in human keratinocytes (an exon 12 deletion using CRISPR/CAS9), keratinocytes are deficient in epithelial sheet migration without affecting individual cell motility. These data led to the hypothesis that GCN2 is a critical component of the cutaneous wounding response, and that manipulation of the ISR via pharmaceutical agents will improve wound healing. This last point is particularly intriguing, because several drugs that regulate the ISR (either positively or negatively) are already in human clinical trials for unrelated diseases which could accelerate bringing any drugs that showed promise rapidly into human trials. The initial studies into the role of the ISR on wound healing in this proposal use model sy...

Key facts

NIH application ID
10124987
Project number
5I01CX001956-02
Recipient
RLR VA MEDICAL CENTER
Principal Investigator
DAN F SPANDAU
Activity code
I01
Funding institute
VA
Fiscal year
2021
Award amount
Award type
5
Project period
2020-01-01 → 2023-12-31