DSG1

DSG1 is a desmosomal cadherin that mediates Ca²⁺-dependent cell–cell adhesion in stratified epithelia and coordinates epidermal differentiation and barrier homeostasis. Its cytoplasmic domain binds plakoglobin via a conserved 19-amino-acid motif and interacts with plakophilin 1 and plakophilin 2, anchoring keratin intermediate filaments through desmoplakin to form the desmosomal plaque (PMID:8188687, PMID:9606214, PMID:11790773). Beyond adhesion, DSG1 suppresses EGFR–ERK1/2 signaling through a mechanism independent of its adhesive ectodomain to promote keratinocyte terminal differentiation, and its ectodomain is proteolytically cleaved by KLK5 at acidic pH to drive corneodesmosome dissolution during desquamation (PMID:19546243, PMID:15140227). Biallelic loss-of-function mutations in DSG1 cause SAM syndrome (severe dermatitis, multiple allergies, metabolic wasting), linking primary desmosomal disruption to barrier failure and pro-inflammatory cytokine induction (PMID:23974871).

1. 1991 High

   Establishing DSG1 as a cadherin family member resolved how desmosomal glycoprotein DGI relates to classical Ca²⁺-dependent adhesion molecules and identified its unique cytoplasmic repeat architecture.

   Evidence cDNA cloning with sequence homology analysis

   PMID:1711210

   Open questions at the time

   • Binding partners of the unique cytoplasmic repeats were unknown
   • Functional significance of the Arg-Ala-Leu substitution in the adhesion recognition sequence was untested
2. 1994 High

   Mapping the plakoglobin-binding site to a 19-residue cytoplasmic motif homologous to the catenin-binding domain of classical cadherins established how DSG1 connects to the desmosomal plaque via a conserved mechanism.

   Evidence Blot overlay assays with systematic deletion series of DSG1 cytoplasmic domain fusion proteins

   PMID:8188687

   Open questions at the time

   • Stoichiometry and affinity of plakoglobin–DSG1 interaction in intact cells were not determined
   • Role of additional cytoplasmic partners beyond plakoglobin remained open
3. 1998 High

   Demonstrating that plakophilin 1 and plakoglobin both bind DSG1 and desmoplakin established the ordered molecular hierarchy of the desmosomal plaque linking cadherins to intermediate filaments.

   Evidence In vitro overlay assays with deletion and site-directed mutagenesis of desmosomal components

   PMID:9606214

   Open questions at the time

   • In vivo validation of the plaque assembly order was lacking
   • Contribution of individual interactions to adhesive strength was unknown
4. 1999 High

   Identifying a DSG1 splice-site mutation in striate palmoplantar keratoderma proved that the N-terminal ectodomain — required for trans-dimerization and Ca²⁺ binding — is essential for epidermal integrity in humans.

   Evidence Genetic linkage and mutation analysis in a keratoderma family with splicing characterization

   PMID:10332028

   Open questions at the time

   • Whether haploinsufficiency alone fully explained the keratoderma or whether dominant-negative effects contributed was unclear
   • Structural basis of DSG1 trans-dimerization awaited atomic-resolution data
5. 2002 High

   Showing that plakophilin 2 directly binds DSG1 via its head domain expanded the set of cytoplasmic partners bridging desmosomal cadherins to the plaque and identified PKP2 as a second plakophilin interactor.

   Evidence Reciprocal co-immunoprecipitation and yeast two-hybrid assay with domain-mapping constructs

   PMID:11790773

   Open questions at the time

   • Relative contributions of PKP1 versus PKP2 to DSG1-dependent adhesion in different tissues were not resolved
   • Whether PKP2 and plakoglobin binding to DSG1 is competitive or cooperative was undetermined
6. 2004 High

   Reconstituting KLK5-mediated DSG1 degradation at acidic pH identified the protease responsible for corneodesmosome dissolution during desquamation and clarified that KLK7 requires KLK5-dependent activation.

   Evidence In vitro protease activity assays with recombinant KLK5 and KLK7 on epidermal and recombinant DSG1 substrates

   PMID:15140227

   Open questions at the time

   • Exact KLK5 cleavage sites on DSG1 were not mapped
   • In vivo regulation of KLK5 activity at the desmosome surface was not addressed
7. 2006 High

   Demonstrating premature DSG1 degradation by hyperactive KLK5/KLK7 in Netherton syndrome skin established a direct pathological link between dysregulated protease activity and corneodesmosome failure in human disease.

   Evidence Immunostaining of patient biopsies correlated with protease activity assays and LEKTI expression

   PMID:16628198

   Open questions at the time

   • Whether therapeutic protease inhibition could rescue DSG1 levels and barrier function was untested
   • Relative contribution of DSG1 degradation versus other corneodesmosomal target cleavage was unresolved
8. 2009 High

   Revealing that DSG1 suppresses EGFR–ERK1/2 signaling to promote differentiation — independently of its adhesive ectodomain and plakoglobin binding — uncovered a signaling function separable from its structural adhesion role.

   Evidence RNAi knockdown, adhesion-defective DSG1 mutant overexpression, EGFR/ERK western blotting, and organotypic keratinocyte cultures

   PMID:19546243

   Open questions at the time

   • The molecular intermediary connecting DSG1 cytoplasmic domain to EGFR suppression was not identified
   • Whether this signaling function operates in non-epidermal epithelia was unknown
9. 2013 High

   Discovery that biallelic DSG1 loss-of-function mutations cause SAM syndrome — with absent membrane DSG1, adhesion failure, and upregulation of allergy-related cytokines — established DSG1 as essential for human epidermal barrier integrity and immune homeostasis.

   Evidence Homozygous mutation identification in affected families, immunofluorescence, and transcriptomic analysis of patient skin

   PMID:23974871

   Open questions at the time

   • Mechanism by which DSG1 loss activates pro-inflammatory cytokine transcription was not delineated
   • Whether residual desmosomal adhesion via DSG3 partially compensates in SAM was not tested
10. 2013 High

    Showing that DSG1 knockdown in esophageal epithelium weakens barrier integrity and induces an EoE-like transcriptional program (including periostin) connected DSG1 to mucosal immune disease beyond skin.

    Evidence siRNA knockdown with TEER, permeability assays, transcriptomics, and IL-13 treatment in esophageal epithelial cells

    PMID:24220297

    Open questions at the time

    • Whether DSG1 loss is a primary driver or secondary consequence in EoE pathogenesis was unresolved
    • Direct transcriptional regulators of DSG1 downstream of IL-13 were not identified
11. 2019 High

    Using CRISPR knockout of Dsg2/Dsg3, anti-DSG1 autoantibodies were shown to cause loss of cohesion via Ca²⁺ influx independent of EGFR and of other desmogleins, delineating a DSG1-specific pathogenic signaling axis in pemphigus foliaceus.

    Evidence CRISPR/Cas9-generated Dsg2- and Dsg3-deficient HaCaT cells with Ca²⁺ imaging, EGFR/ERK blotting, and dissociation assays

    PMID:31178865

    Open questions at the time

    • Source and mechanism of Ca²⁺ influx triggered by anti-DSG1 antibodies were not identified
    • Whether Ca²⁺ influx is necessary or sufficient for loss of cohesion was not formally tested
12. 2022 Medium

    Super-resolution imaging revealed that extradesmosomal DSG1–plakoglobin complexes exist across all epidermal layers and are disrupted in pemphigus skin, suggesting a non-desmosomal DSG1 pool contributes to disease pathogenesis.

    Evidence STED/STORM microscopy with co-localization analysis using desmoplakin as a desmosome marker in normal and pemphigus patient skin

    PMID:35711465

    Open questions at the time

    • Functional role of the extradesmosomal DSG1–plakoglobin pool was not experimentally tested
    • Whether extradesmosomal DSG1 mediates the EGFR-suppressive signaling function is unknown
    • Single study awaiting independent replication

• The molecular mechanism by which the DSG1 cytoplasmic domain suppresses EGFR–ERK signaling remains unidentified, and the functional significance of extradesmosomal DSG1 pools and the precise KLK5 cleavage sites on DSG1 are unresolved.
• No direct intermediary linking DSG1 to EGFR suppression has been identified
• Atomic-resolution structure of DSG1 ectodomain trans-dimer is lacking
• In vivo requirement for specific DSG1 cytoplasmic motifs in differentiation versus adhesion has not been genetically dissected