Characterising metamorphic moonlighting CLIC proteins within ageing epidermal tissue

Turkewitz DR1, Gorrie CA1, Bishop DP2 and Valenzuela SM1

  1. School of Life Sciences, University of Technology Sydney, NSW, Australia.
  2. Elemental Bio-imaging Facility, University of Technology Sydney, NSW, Australia.

The chloride intracellular ion channel (CLIC) family consists of six evolutionarily conserved protein members in vertebrates with evidence emerging that CLICs exhibit enzymatic properties in addition to their traditional ion channel roles. This could serve as an important component for the protection of the intracellular environment against oxidation. We aim to confirm the presence of CLIC proteins in human and mice skin tissue and examine their role in aging and cell cycle processes. CLIC family expression and localisation in 5µm thick commercially available human (n=1; Ages=17 male, 55, female, and 96 female years) and donated mice (n=3; Ages=1 male, 4 female, 8 female months), skin tissue was determined using a combination of classical histology and immunohistochemistry. Spatiotemporal analysis of human skin tissue reveals a thinner epidermis with age, due to a flattened interface between the dermis and epidermis. CLIC1 and CLIC4 stained throughout the epidermis. CLIC1 had slight stratum corneum staining while CLIC4 had much stronger staining with co-localisation in the stratum corneum and granulosum. As the donor tissue ages, there is a significant decrease in CLIC4 protein levels and a change in localisation. CLIC4 with ageing relocates from a strong presence across the entire epidermal network to a more restricted localisation, focused in the stratum corneum and granulosum, where differentiation of keratinocytes to corneocytes occur. A spatiotemporal study shows that CLIC1 and CLIC4 proteins are present within the epidermal network of human and mice skin in high concentrations with CLIC4’s expression level and localisation changing with age regardless of the donor’s species and sex.