Desmoglein-1/Erbin interaction suppresses ERK activation to support epidermal differentiation
Robert M. Harmon, Cory L. Simpson, Jodi L. Johnson, Jennifer L. Koetsier, Adi D. Dubash, Nicole A. Najor, Ofer Sarig, Eli Sprecher, Kathleen J. Green
Robert M. Harmon, Cory L. Simpson, Jodi L. Johnson, Jennifer L. Koetsier, Adi D. Dubash, Nicole A. Najor, Ofer Sarig, Eli Sprecher, Kathleen J. Green
View: Text | PDF
Research Article

Desmoglein-1/Erbin interaction suppresses ERK activation to support epidermal differentiation

Abstract

Genetic disorders of the Ras/MAPK pathway, termed RASopathies, produce numerous abnormalities, including cutaneous keratodermas. The desmosomal cadherin, desmoglein-1 (DSG1), promotes keratinocyte differentiation by attenuating MAPK/ERK signaling and is linked to striate palmoplantar keratoderma (SPPK). This raises the possibility that cutaneous defects associated with SPPK and RASopathies share certain molecular faults. To identify intermediates responsible for executing the inhibition of ERK by DSG1, we conducted a yeast 2-hybrid screen. The screen revealed that Erbin (also known as ERBB2IP), a known ERK regulator, binds DSG1. Erbin silencing disrupted keratinocyte differentiation in culture, mimicking aspects of DSG1 deficiency. Furthermore, ERK inhibition and the induction of differentiation markers by DSG1 required both Erbin and DSG1 domains that participate in binding Erbin. Erbin blocks ERK signaling by interacting with and disrupting Ras-Raf scaffolds mediated by SHOC2, a protein genetically linked to the RASopathy, Noonan-like syndrome with loose anagen hair (NS/LAH). DSG1 overexpression enhanced this inhibitory function, increasing Erbin-SHOC2 interactions and decreasing Ras-SHOC2 interactions. Conversely, analysis of epidermis from DSG1-deficient patients with SPPK demonstrated increased Ras-SHOC2 colocalization and decreased Erbin-SHOC2 colocalization, offering a possible explanation for the observed epidermal defects. These findings suggest a mechanism by which DSG1 and Erbin cooperate to repress MAPK signaling and promote keratinocyte differentiation.

Authors

Robert M. Harmon, Cory L. Simpson, Jodi L. Johnson, Jennifer L. Koetsier, Adi D. Dubash, Nicole A. Najor, Ofer Sarig, Eli Sprecher, Kathleen J. Green

×

Figure 8

PLA of DSG1-deficient epidermis indicates reduced Erbin-SHOC2 colocalization and enhanced SHOC2-Ras colocalization.

Options: View larger image (or click on image) Download as PowerPoint
PLA of DSG1-deficient epidermis indicates reduced Erbin-SHOC2 colocaliza...
(A) Erbin-SHOC2 PLA. Palmoplantar tissue from controls or patients with SPPK with mutant DSG1 (p.D644fs shown) was incubated with indicated primary antibody pairs. Colocalization allows for hybridization, ligation, and amplification of oligonucleotide adducts fused to secondary antibodies, ultimately producing a fluorescent spot in situ (pseudocolored yellow). Blue DAPI staining marks nuclei. (B) SHOC2-Ras PLA was performed as in A (DSG1 mutation: R219X shown). mIgG, mouse IgG. (C) Quantitation of PLA. PLA spots were counted and divided by area analyzed (mm2) to determine PLA density. Analysis included all nucleated epidermal layers (bounded basally and suprabasally by large and small dashed lines, respectively, in A and B). Each data point represents a ratio of the SPPK PLA density (DSG1 mutation indicated) over the value for 1 out of 3 control samples analyzed in parallel. All control values equal 1. Error bars represent SEM. Unanalyzed areas outside of the nucleated epidermis, including the dermis and stratum corneum, are dimmed in A and B for clarity. PLA spots in A and B were enlarged to enhance visibility at low magnification. Scale bars: 30 μm.