The Differentiation-dependent Desmosomal Cadherin Desmoglein 1 Is a Novel Caspase-3 Target That Regulates Apoptosis in Keratinocytes

Abstract

Although a number of cell adhesion proteins have been identified as caspase substrates, the potential role of differentiation-specific desmosomal cadherins during apoptosis has not been examined. Here, we demonstrate that UV-induced caspase cleavage of the human desmoglein 1 cytoplasmic tail results in distinct 17-and 140-kDa products, whereas metalloproteinase-dependent shedding of the extracellular adhesion domain generates a 75-kDa product. In vitro studies identify caspase-3 as the preferred enzyme that cleaves desmoglein 1 within its unique repeating unit domain at aspartic acid 888, part of a consensus sequence not conserved among the other desmosomal cadherins. Apoptotic processing leads to decreased cell surface expression of desmoglein 1 and re-localization of its C terminus diffusely throughout the cytoplasm over a time course comparable with the processing of other desmosomal proteins and cytoplasmic keratins. Importantly, whereas classic cadherins have been reported to promote cell survival, short hairpin RNA-mediated suppression of desmoglein 1 in differentiated keratinocytes protected cells from UV-induced apoptosis. Collectively, our results identify desmoglein 1 as a novel caspase and metalloproteinase substrate whose cleavage likely contributes to the dismantling of desmosomes during keratinocyte apoptosis and also reveal desmoglein 1 as a previously unrecognized regulator of apoptosis in keratinocytes.Desmosomes are vertebrate cell junctions that anchor the intermediate filament cytoskeleton to the plasma membrane at sites of cell-cell contact and in so doing form a supracellular scaffolding that is essential for maintaining tissue integrity (for review, see Ref. 1). The molecular components of the desmosome fall into three main families: desmosomal cadherins, armadillo family proteins, and plakins. The two types of desmosomal cadherins, desmogleins (Dsgs) 4 and desmocollins (Dscs), are thought to mediate calcium dependent cell-cell adhesion at the membrane, which is strengthened through indirect interactions with the intermediate filament cytoskeleton (for review, see Ref.2). The armadillo family protein, plakoglobin (Pg), interacts directly with the cytoplasmic tail of the desmosomal cadherins (3-6), thereby connecting the transmembrane glycoproteins to the obligate desmosomal protein, desmoplakin (DP) (7). DP links the cell surface to the cytoskeleton by associating with Pg at its N terminus and intermediate filaments through its C terminus (8 -10). Plakophilins, additional members of the armadillo family, can interact with desmosomal cadherin cytoplasmic domains (11, 12), enhance recruitment of DP to the membrane, and likely facilitate lateral clustering of the plaque components to enhance the mechanical strength of the junction (13,14).Four isoforms of Dsgs and three isoforms of Dscs have been identified in humans (15-17). The cytoplasmic domains of all of the Dsg isoforms contain regions of unknown function, including a unique repeating unit domain (RUD). Each Dsg isoform includes a RUD c...

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

“…Likewise, removal of these domains blunted the capacity of ectopic DSG1 to inhibit ERK signaling and promote differentiation. These data, and earlier work that identified DSG1 residue 888 as a caspase-3 cleavage site during UV-induced apoptosis, provide the first experimental evidence to our knowledge that the unique domains (PL, RUD, and TD) participate in epidermal signaling (81)(82)(83). In addition, a recent investigation of comparable domains in DSG2 indicates an important role in mediating homodimerization, internalization, and protein stability (84).…”

“…The following primary antibodies were used in this study: M2 mouse anti-FLAG, rabbit anti-FLAG, and rabbit anti-GAPDH (Sigma-Aldrich); 1646 rabbit anti-Erbin and 139 rabbit anti-Erbin were gifts from L. Fontao (Hôpitaux Universitaires de Genève, Geneva, Switzerland); K13 gt anti-Erbin and F234 mouse anti-KRas (Santa Cruz Biotechnology Inc.); goat anti-GST (GE Healthcare Biosciences); 4B2 mouse anti-DSG1 is described in Dusek et al (83); 27B2 mouse anti-DSG1 (Invitrogen); U100 anti-DSC1 (Progen); LH2 anti-K10 was a gift from I. Leigh (University of Dundee, Dundee City, United Kingdom); rabbit anti-K10, rabbit anti-K1, rabbit anti-K5, and rabbit anti-loricrin were gifts from J. Segre…”

Biphasic Activation of p38MAPK Suggests That Apoptosis Is a Downstream Event in Pemphigus Acantholysis

“…3 The potential for caspase-dependent proteolysis to augment the pathogenic response in pemphigus is supported by the observation that components of the desmosome including dsg3, dsg1, plakoglobin, and desmoplakin (38,39), as well as intermediate filaments (40,41), have all been shown to undergo caspase-dependent cleavage. In A431 epithelial cells induced to undergo apoptosis by UV exposure, caspase 3-dependent and matrix metalloproteinase (MMP)-dependent cleavage of dsg1 has been observed (39). In this system, caspase 3 cleavage occurred within the cytoplasmic tail of dsg1, whereas MMP-dependent cleavage resulted in shedding of a 75-kDa fragment of the dsg1 ectodomain.…”

“…In this system, caspase 3 cleavage occurred within the cytoplasmic tail of dsg1, whereas MMP-dependent cleavage resulted in shedding of a 75-kDa fragment of the dsg1 ectodomain. Interestingly, UV-induced MMP cleavage of the dsg1 ectodomain was not only inhibited by the MMP inhibitor TAPI-0 but also by the caspase inhibitor ZVAD-fmk (39). In addition, the pathophysiology of staphylococcal scalded skin syndrome demonstrates that proteolysis of desmosome components can contribute to destabilization of desmosomes (42).…”

Desmosome assembly, homeostasis, and desmosomal disease

“…In one example, knockdown of Pkp3 in colon cancer cells promoted anchorage-independent growth and tumor growth in immunocompromised mice. 158 However, there are instances where desmosomal molecules are overexpressed, 159 although this could represent a compensatory mechanism for the loss of adhesion strength. Alternatively, the desmosomal cadherins may serve as signaling molecules via their adaptor proteins, thus controlling cell cycle and apoptosis.…”