Desmoglein 3 regulates membrane trafficking of cadherins, an implication in cell-cell adhesion

Abstract

E-cadherin mediated cell-cell adhesion plays a critical role in epithelial cell polarization and morphogenesis. Our recent studies suggest that the desmosomal cadherin, desmoglein 3 (Dsg3) cross talks with E-cadherin and regulates its adhesive function in differentiating keratinocytes. However, the underlying mechanism remains not fully elucidated. Since E-cadherin trafficking has been recognized to be a central determinant in cell-cell adhesion and homeostasis we hypothesize that Dsg3 may play a role in regulating E-cadherin trafficking and hence the cell-cell adhesion. Here we investigated this hypothesis in cells with loss of Dsg3 function through RNAi mediated Dsg3 knockdown or the stable expression of the truncated mutant Dsg3DC. Our results showed that loss of Dsg3 resulted in compromised cell-cell adhesion and reduction of adherens junction and desmosome protein expression as well as the cortical F-actin formation. As a consequence, cells failed to polarize but instead displayed aberrant cell flattening. Furthermore, retardation of Ecadherin internalization and recycling was consistently observed in these cells during the process of calcium induced junction assembling. In contrast, enhanced cadherin endocytosis was detected in cells with overexpression of Dsg3 compared to control cells. Importantly, this altered cadherin trafficking was found to be coincided with the reduced expression and activity of Rab proteins, including Rab5, Rab7 and Rab11 which are known to be involved in E-cadherin trafficking. Taken together, our findings suggest that Dsg3 functions as a key in cell-cell adhesion through at least a mechanism of regulating E-cadherin membrane trafficking.

The desmosomal cadherin Desmoglein-3 regulates YAP and phospho-YAP in keratinocyte responses to mechanical forces

“…This could be due to Dsg3's ability to activate various signal pathways, including Src, as well as c-Jun, that regulate the actin and actomyosin cytoskeleton [7,35,43,54,55]. Dsg3 depletion has a negative impact on the formation and tension of F-actin [35,53,54] that may attenuate YAP, as supported by our qPCR data indicating reduction of YAP1 target gene expression. In our study, however, cyclic strain did not affect the YAP1 target gene expression nor cell proliferation for up to 3 days in confluent cultures.…”

“…7C,D). Diffuse cytoplasmic Dsg3 staining with enhanced cell spreading like the Dsg3 knockdown cells [35] was also observed in cells with PKP1 depletion (Fig. 7C).…”

“…Many studies have indicated that AJs, in association with the cytoskeleton, serve as mechanosensors/mechanotransducers and are adaptable to various tension and tugging forces by modifying the cell adhesion strength, size, and protein concentration as well as causing molecular conformational changes at the junctions [12,13,26,29,30,32,57]. Emerging evidence reveals that the extra-junctional Dsg3 cross-talks with E-cadherin and regulates AJ assembly and adhesion [7,35,43,54,55]. This study demonstrated that the loss of Dsg3 action had a major impact on the junction assembly of E-cadherin and Myosin IIa in response to mechanical loading.…”

“…We have not examined putative mechanisms but such inhibition of YAP might be caused by pronounced attenuation when expression levels fall below the threshold values [16,39] or when localization of YAP/TAZ is controlled by additional factors such as cell density and geometry [37,39]. Our previous studies have shown that Dsg3 silencing results in cell morphological changes with flattening due to defects in F-actin organization and cell polarization [35]. Thus the YAP nuclear retention in Dsg3 knockdown cells could be caused, partly at least, by cell flattening that potentiates the ECM-nuclear mechanical coupling leading to YAP nuclear location [17].…”

Desmoplakin is required for epidermal integrity and morphogenesis in theXenopus laevisembryo

“…For example, adherens junction associated proteins, e-cadherin and actin are both required for desmosome assembly (Lowndes et al, 2014;Shafraz et al, 2018). Further, disruption of the desmosomal protein, Desmoglein 3, decreased e-cadherin at the junction and perturbed actin organization in cultured epithelial cells (Moftah et al, 2017). Therefore, our results and the work of others demonstrate that disruption of the desmosome can affect the adherens junctions and associated cytoskeleton.…”