Departments of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA; Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA; Department of Dermatology, "Emek" Medical Center, Afula, Israel; Bruce and Ruth Rappaport Faculty of Medicine, Technion, Haifa, Israel.
Departments of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA; Department of Pathology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.
J Invest Dermatol. 2020 Mar;140(3):556-567.e9. doi: 10.1016/j.jid.2019.08.433. Epub 2019 Aug 26.
An effective epidermal barrier requires structural and functional integration of adherens junctions, tight junctions, gap junctions (GJ), and desmosomes. Desmosomes govern epidermal integrity while GJs facilitate small molecule transfer across cell membranes. Some patients with severe dermatitis, multiple allergies, and metabolic wasting (SAM) syndrome, caused by biallelic desmoglein 1 (DSG1) mutations, exhibit skin lesions reminiscent of erythrokeratodermia variabilis, caused by mutations in connexin (Cx) genes. We, therefore, examined whether SAM syndrome-causing DSG1 mutations interfere with Cx expression and GJ function. Lesional skin biopsies from SAM syndrome patients (n = 7) revealed decreased Dsg1 and Cx43 plasma membrane localization compared with control and nonlesional skin. Cultured keratinocytes and organotypic skin equivalents depleted of Dsg1 exhibited reduced Cx43 expression, rescued upon re-introduction of wild-type Dsg1, but not Dsg1 constructs modeling SAM syndrome-causing mutations. Ectopic Dsg1 expression increased cell-cell dye transfer, which Cx43 silencing inhibited, suggesting that Dsg1 promotes GJ function through Cx43. As GJA1 gene expression was not decreased upon Dsg1 loss, we hypothesized that Cx43 reduction was due to enhanced protein degradation. Supporting this, PKC-dependent Cx43 S368 phosphorylation, which signals Cx43 turnover, increased after Dsg1 depletion, while lysosomal inhibition restored Cx43 levels. These data reveal a role for Dsg1 in regulating epidermal Cx43 turnover.
有效的表皮屏障需要黏附连接、紧密连接、间隙连接 (GJ) 和桥粒的结构和功能整合。桥粒控制表皮完整性，而 GJ 促进小分子跨细胞膜转移。一些由双等位基因桥粒蛋白 1 (DSG1) 突变引起的严重皮炎、多种过敏和代谢消耗 (SAM) 综合征患者表现出类似于连接蛋白 (Cx) 基因突变引起的红斑角化病变的皮肤损伤。因此，我们检查了 SAM 综合征致病 DSG1 突变是否干扰 Cx 表达和 GJ 功能。SAM 综合征患者的皮损皮肤活检（n=7）显示与对照和非皮损皮肤相比，Dsg1 和 Cx43 质膜定位减少。培养的角质形成细胞和去 Dsg1 的器官型皮肤等效物表现出 Cx43 表达减少，野生型 Dsg1 再引入可挽救，但 SAM 综合征致病突变建模的 Dsg1 构建体则不可挽救。异位 Dsg1 表达增加了细胞间染料转移，而 Cx43 沉默抑制了这种转移，表明 Dsg1 通过 Cx43 促进 GJ 功能。由于 Dsg1 丢失时 GJA1 基因表达没有降低，我们假设 Cx43 减少是由于蛋白降解增强所致。支持这一假设的是，Dsg1 耗尽后 PKC 依赖性 Cx43 S368 磷酸化增加，该磷酸化信号提示 Cx43 周转增加，而溶酶体抑制则恢复 Cx43 水平。这些数据揭示了 Dsg1 在调节表皮 Cx43 周转中的作用。
