Tumor Necrosis Factor-α Regulates Transforming Growth Factor-β-dependent Epithelial-Mesenchymal Transition by Promoting Hyaluronan-CD44-Moesin Interaction

Abstract

Aberrant epithelial-mesenchymal transition (EMT) is involved in development of fibrotic disorders and cancer invasion.Alterations of cell-extracellular matrix interaction also contribute to those pathological conditions. However, the functional interplay between EMT and cell-extracellular matrix interactions remains poorly understood. We now show that the inflammatory mediator tumor necrosis factor-␣ (TNF-␣) induces the formation of fibrotic foci by cultured retinal pigment epithelial cells through activation of transforming growth factor-␤ (TGF-␤) signaling in a manner dependent on hyaluronan-CD44-moesin interaction. TNF-␣ promoted CD44 expression and moesin phosphorylation by protein kinase C, leading to the pericellular interaction of hyaluronan and CD44. Formation of the hyaluronan-CD44-moesin complex resulted in both cell-cell dissociation and increased cellular motility through actin remodeling. Furthermore, this complex was found to be associated with TGF-␤ receptor II and clathrin at actin microdomains, leading to activation of TGF-␤ signaling. We established an in vivo model of TNF-␣-induced fibrosis in the mouse eye, and such ocular fibrosis was attenuated in CD44-null mice. The production of hyaluronan and its interaction with CD44, thus, play an essential role in TNF-␣-induced EMT and are potential therapeutic targets in fibrotic disorders. The epithelial-mesenchymal transition (EMT)2 of epithelial cells is characterized by the loss of epithelial characteristics and the gain of mesenchymal attributes. During this transition, epithelial cells down-regulate cell-cell adhesion systems, lose their polarity, and acquire a mesenchymal phenotype associated with increased interaction with the extracellular matrix (ECM) and enhanced migratory capacity. The EMT is considered a critical event in metazoan embryogenesis as well as in physiological processes such as wound healing. However, it also plays an important role in pathological settings such as fibrotic disorders in various organs as well as cancer invasion and metastasis.The EMT associated with physiological processes is triggered by members of the transforming growth factor-␤ (TGF-␤) family of proteins that function as morphogens (1). In vitro studies have also shown that TGF-␤ is the major inducer of the EMT in epithelial cells (2). Fibrotic disorders associated with pathological EMT result from a series of events including inflammation, leukocyte infiltration, and the production of cytokines and growth factors. TGF-␤ is one of the cytokines produced during inflammation and is, therefore, thought to heavily contribute to EMT-associated fibrosis (3). However, given that TGF-␤ also possesses anti-inflammatory properties, the mechanism of pathological EMT induced by the inflammatory response may be multifactorial and differ from that of physiological EMT.In addition to growth factors, changes in the ECM microenvironment contribute to the EMT. Epithelial cells cultured in a type I collagen gel were found to undergo the EMT (4). Furthermore, collagen-induce...

Hyaluronic Acid Promotes Angiogenesis by Inducing RHAMM-TGFβ Receptor Interaction via CD44-PKCδ

“…TNF-α regulates TGFβ-promoted epithelial mesenchymal transition (EMT) by inducing HA-CD44-moesin interaction (Takahashi et al, 2010), suggesting transactivation of TGFβRI by TNF-α. We hypothesized that HA would activate TGFβ receptor signaling to induce expression of PAI-1.…”

Interleukin-1β-induced Reduction of CD44 Ser-325 Phosphorylation in Human Epidermal Keratinocytes Promotes CD44 Homomeric Complexes, Binding to Ezrin, and Extended, Monocyte-adhesive Hyaluronan Coats

“…In different cell types, the binding is mediated by various linker proteins like ERM (ezrin, radixin, moesin, merlin), ankyrin, and IQGAP (1,46,58,(61)(62)(63)(64)(65) (Fig. 7A).…”

4-Methylumbelliferone Diminishes Catabolically Activated Articular Chondrocytes and Cartilage Explants via a Mechanism Independent of Hyaluronan Inhibition

“…Additionally, 4-MU effects a pronounced reduction of HA synthase 2 (HAS2) transcription but by mechanisms that are currently unknown (32)(33)(34). As a potent inhibitor of HA, 4-MU has been used to examine the role of HA in epithelial-mesenchymal transitions (35), collagen-induced arthritis (36), invasion and metastasis of osteosarcoma (37) and breast cancer cells (38), inflammation and autoimmunity (31), chondrogenic differentiation (39), myofibroblast differentiation (40,41), and keratinocyte activation (42). We have shown that 4-MU blocks the assembly of pericellular coats on bovine, rat, and mouse chondrocytes and diminishes the responsiveness of chondrocytes to bone morphogenetic protein-7 similar to results obtained by hyaluronidase treatment (43).…”