A Disintegrin and Metalloproteinase 17 (ADAM17) Mediates Inflammation-induced Shedding of Syndecan-1 and -4 by Lung Epithelial Cells

Abstract

Syndecans are cell surface proteoglycans that bind and modulate various proinflammatory mediators and can be proteolytically shed from the cell surface. Within the lung, syndecan-1 and -4 are expressed as transmembrane proteins on epithelial cells and released in the bronchoalveolar fluid during inflammation. We here characterize the mechanism leading to the generation of soluble syndecan-1 and -4 in cultured epithelial cells and murine lung tissue. We show that the bladder carcinoma epithelial cell line ECV304, the lung epithelial cell line A459 and primary alveolar epithelial cells express and constitutively release syndecan-1 and -4. This release involves the activity of the disintegrin-like metalloproteinase ADAM17 as demonstrated by use of specific inhibitors and lentivirally transduced shRNA. Stimulation of epithelial cells with PMA, thrombin, or proinflammatory cytokines (TNF␣/IFN␥) led to the down-regulation of surface-expressed syndecan-1 and -4, which was associated with a significant increase of soluble syndecans and cell-associated cleavage fragments. The enhanced syndecan release was not related to gene induction of syndecans or ADAM17, but rather due to increased ADAM17 activity. Soluble syndecan-1 and -4 were also released into the bronchoalveolar fluid of mice. Treatment with TNF␣/IFN␥ increased ADAM17 activity and syndecan release in murine lungs. Both constitutive and induced syndecan shedding was prevented by the ADAM17 inhibitor. ADAM17 may therefore be an important regulator of syndecan functions on inflamed lung epithelium.Syndecans are a family of cell surface proteoglycans that play regulatory roles in wound healing, inflammation, angiogenesis, and neuronal patterning. There are four members of the syndecan family (syndecan-1, -2, -3, and -4) each consisting of an ectodomain carrying heparan sulfate-or chondroitin sulfaterich glucosaminoglycan chains, a transmembrane domain, and a short cytoplasmic tail (1). Syndecan-1 is predominantly found on endothelial and epithelial cells whereas syndecan-4 is ubiquitously expressed (2). Syndecans are also released as soluble variants that have been found in various body fluids including serum of cancer patients, wound fluid, or bronchoalveolar fluid of inflamed lungs (3-7).Recent research with syndecan-1 Ϫ/Ϫ and syndecan-4mice has demonstrated that syndecans play an important role in the regulation of inflammation and wound healing (1). Syndecans act as coreceptors modulating binding and signaling of cytokines, chemokines, and adhesion molecules. Syndecan-1 deficiency results in increased acute lung inflammation. Syndecan-1 cleavage by matrix metalloproteinase 7 (MMP7) 2 helps to establish a gradient for the chemokine KC guiding transepithelial migration of neutrophils into the airway (8). These activities can be partially reversed by soluble syndecans competing with transmembrane syndecans for their extracellular ligands (9). Soluble syndecans are generated by proteolytic shedding at the cell surface (4, 10, 11). A basal shedding activity results i...

Secretome Signature Identifies ADAM17 as Novel Target for Radiosensitization of Non–Small Cell Lung Cancer

“…ADAM17 regulates shedding of multiple key oncogenic growth factors, cytokines, and adhesion molecules, including ligands of ErbB family members (15,16,19,(25)(26)(27)(28). Thus, ADAM17 drives pleiotropic pathways and might therefore represent a more relevant target for a combined treatment modality in NSCLC.…”

“…Growth and survival of NSCLC cells are often dependent on ectodomain shedding which includes the proteolytic cleavage of the extracellular part of membrane proteins primarily mediated by membrane-anchored metalloproteases, and results in release of various soluble growth factors and cytokines regulating cell proliferation and migration (15,16). ADAMs (a disintegrin and metalloproteinase) are membrane-associated metalloproteinases with modular design and complex multidomain structure (17).…”

Shedding; towards a new paradigm of syndecan function in cancer

“…Similarly, the shedding of syndecan-1 and syndecan-4 is stimulated by the recombinant ADAM17 catalytic domain (37). In addition, siRNA-mediated knockdown of ADAM17 reduced shedding of syndecan-1 and syndecan-4 in ECV304 cells and A549 cells (37). ADAM17 activation also mediates release of soluble syndecan-1 and -4 into the bronchoalveolar fluid of mice, as evidenced by the fact that both constitutive and induced syndecan shedding could be prevented by inhibiting ADAM17 (37).…”

“…Production of soluble syndecan-1 and -4 was reduced in both ECV304 bladder carcinoma epithelial cells and A549 lung carcinoma epithelial cells by treatment with GW280264, an inhibitor of ADAM17 and ADAM10, but not by the ADAM10 inhibitor GI254023 (37). Similarly, the shedding of syndecan-1 and syndecan-4 is stimulated by the recombinant ADAM17 catalytic domain (37). In addition, siRNA-mediated knockdown of ADAM17 reduced shedding of syndecan-1 and syndecan-4 in ECV304 cells and A549 cells (37).…”

“…In addition, siRNA-mediated knockdown of ADAM17 reduced shedding of syndecan-1 and syndecan-4 in ECV304 cells and A549 cells (37). ADAM17 activation also mediates release of soluble syndecan-1 and -4 into the bronchoalveolar fluid of mice, as evidenced by the fact that both constitutive and induced syndecan shedding could be prevented by inhibiting ADAM17 (37). The pseudomonas virulence factor LasA, an M23 metallopeptidase related to autolytic glycylglycine endopeptidases, is known for stimulating ectodomain shedding of syndecan-1 (38,39).…”