Desmosomes, complex structures found at intercellular junctions, are important for the development, structural integrity, and immune barrier of the skin. Extracellular components of the desmosome connect neighboring cells and intracellular interactions amongst cadherin, armadillo, and plakin proteins anchor the desmosome to intermediate filaments. Beyond their canonical role as “spot welds” or adhesion structures, desmosomes have recently been found to exert multiple functions and regulate signaling pathways in skin cells or keratinocytes. The desmosomal cadherin desmoglein 1 (Dsg1) has been shown to promote differentiation of suprabasal keratinocytes by suppressing Erk/MAPK signaling. This is achieved via interactions with a protein partner named Erbin; the Dsg1-Erbin complex disrupts the Ras-Raf scaffold upstream of Erk activation. Dsg1 was also found to be sensitive to oxidative stress in the form of ultraviolet radiation that trigger its cleavage via caspase 3 and dampen its ability to regulate signaling pathways and promote epidermal differentiation. Given that Dsg1 is involved in multiple key functions of keratinocytes, namely adhesion and differentiation, and that it may be perturbed by oxidative stress, the question arose as to how the protein is stabilized and protected to carry out those functions in keratinocytes that face many environmental stressors. This dissertation focuses on testing the hypothesis that antioxidant machineries are involved in promoting Dsg1 stability by protecting it from oxidative stress. The antioxidant enzyme, peroxiredoxin 1 (PRDX1), was identified as a putative binding partner of Dsg1 via yeast two-hybrid screen. While Dsg1 likely scaffolds other redox proteins, interactions between PRDX1 and Dsg1 are the main focus of this thesis. Loss of PRDX1 in submerged and 3D organotypic keratinocytes as well as in mice epidermis results in a reduction of Dsg1 protein, accompanied by structural and biochemical defects in epidermal differentiation. These defects are due at least in part to loss of Dsg1, as ectopically expressed Dsg1 is sufficient to rescue markers of differentiation in PRDX1-deficient keratinocytes. Expression of wild-type but not catalytically dead PRDX1 in PRDX1-deficient cells, or treatment with the antioxidant N-acetylcysteine, restores Dsg1 expression and membrane localization. These data indicate that the antioxidant function of PRDX1 is necessary to stabilize Dsg1. Imaging and biochemical studies show that downregulation of Dsg1 from the loss of PRDX1 and oxidative stress occurs via lysosomal degradation. The findings presented here reveal novel protein interactors of Dsg1 that promote its stability and the program of epidermal differentiation and shed light on degradation machineries Dsg1 is targeted to, which advance our current understanding of how Dsg1 is regulated in normal keratinocytes and potentially in Dsg1-associated skin diseases.

Creator

• Lee, Sherry

DOI

• https://doi.org/10.21985/n2-t4y6-6448

Subject

• Health sciences
• Cellular biology

Language

• en

Alternate Identifier

• etdadmin_upload_572406
• http://dissertations.umi.com/northwestern:14076

Date created

• 2018-01-01

Resource type

• Dissertation

Rights statement

• In Copyright