MMP9 cleavage of the β4 integrin ectodomain leads to recurrent epithelial erosions in mice

Abstract

Integrin α6β4 is an integral membrane protein within hemidesmosomes and it mediates adhesion of epithelial cells to their underlying basement membrane. During wound healing, disassembly of hemidesmosomes must occur for sheet movement-mediated cell migration. The mechanisms of disassembly and reassembly of hemidesmosomes are not fully understood. The current study was initiated to understand the underlying cause of recurrent corneal erosions in the mouse. Here, we show that in vivo: (1) MMP9 levels are elevated and β4 integrin is partially cleaved in epithelial cell extracts derived from debridement wounded corneas; (2) the β4 ectodomain is missing from sites where erosions develop; and (3) β4 cleavage can be reduced by inhibiting MMP activity. Although β4, α3 and β1 integrins were all cleaved by several MMPs, only MMP9 was elevated in cell extracts derived from corneas with erosions. Coimmunoprecipitation studies showed that β4 integrin associates with MMP9, and protein clustering during immunoprecipitation induced proteolytic cleavage of the β4 integrin extracellular domain, generating a 100 kDa β4 integrin cytoplasmic domain fragment. Confocal imaging with three-dimensional reconstruction showed that MMP9 localizes at erosion sites in vivo where the ectodomain of β4 integrin is reduced or absent. MMP activation experiments using cultured corneal and epidermal keratinocytes showed reduced levels of α6β4 and β1 integrins within 20 minutes of phorbol ester treatment. This report is the first to show that β4 integrin associates with MMP9 and that its ectodomain is a target for cleavage by MMP9 in vivo under pathological conditions.

Molecular basis for MMP9 induction and disruption of epithelial cell-cell contacts by galectin-3

“…MMP9 is rapidly expressed as an early response to injury, persisting during healing and declining upon re-epithelialization (Inoue et al, 1995). The increased activity of MMP9 observed in chronic diseases is known to correlate with the clinical severity of the disease and its recurrence (Pal-Ghosh et al, 2011;Rayment et al, 2008). Because the N-terminal domain of galectin-3 is sensitive to MMP9 cleavage (Ochieng et al, 1994;Ortega et al, 2005), it is tempting to speculate that MMP9 can act downstream to prevent the biological activities of full-length galectin-3 and provide protection from the recurrence of epithelial disease.…”

“…Re-epithelialization, which begins immediately after tissue injury, is initiated through the release of a number of factors that cause disassembly of the epithelial junctions and contribute to the movement of the epithelial sheet to cover the wounded area (Gipson et al, 1993;Pal-Ghosh et al, 2011). Matrix metalloproteinases (MMPs), a family of Zn 2+ -dependent endopeptidases that have the combined capacity to degrade adhesion molecules on cell surfaces and extracellular matrices, are central to this process.…”

Functional Characterization of Anopheles Matrix Metalloprotease 1 Reveals Its Agonistic Role during Sporogonic Development of Malaria Parasites

“…MMPs were initially identified as the enzymes that degrade extracellular matrix (ECM) components (12,13) and/or process molecules that mediate cell-cell and cell-ECM interactions (14)(15)(16). As a result of MMP-mediated proteolysis, cells are enabled to glide over ECM (17) or to infiltrate tissues (18,19).…”

Matrix Metalloproteinase 10 Degradomics in Keratinocytes and Epidermal Tissue Identifies Bioactive Substrates With Pleiotropic Functions*

“…Recent results suggest that clipping off these adhesive structures by limited proteolysis might contribute to this process in wound healing as well as during carcinogenesis (62,63). Thereby, MMP9 can cleave ITGB4 (62), and our new data suggest that it may act synergistically with MMP10 upon local activation. Hence, together with desmocollin-3, syndecan-4 (SDC4), perlecan, fibulin-2 and laminin-332 as substrates, our data support the hypothesis that MMP10 is involved in the control of keratinocyte migration by breakdown of adhesion com- (7).…”

“…Upon injury, hemidesmosomes have to be disassembled at the leading wound edge to facilitate migration of keratinocytes along the injured dermis and the newly formed provisional matrix (60,61). Recent results suggest that clipping off these adhesive structures by limited proteolysis might contribute to this process in wound healing as well as during carcinogenesis (62,63). Thereby, MMP9 can cleave ITGB4 (62), and our new data suggest that it may act synergistically with MMP10 upon local activation.…”