Extracellular Collagenases and the Endocytic Receptor, Urokinase Plasminogen Activator Receptor-associated Protein/Endo180, Cooperate in Fibroblast-mediated Collagen Degradation

Abstract

The collagens of the extracellular matrix are the most abundant structural proteins in the mammalian body. In tissue remodeling and in the invasive growth of malignant tumors, collagens constitute an important barrier, and consequently, the turnover of collagen is a rate-limiting process in these events. A recently discovered turnover route with importance for tumor growth involves intracellular collagen degradation and is governed by the collagen receptor, urokinase plasminogen activator receptor-associated protein (uPARAP or Endo180). The interplay between this mechanism and extracellular collagenolysis is not known. In this report, we demonstrate the existence of a new, composite collagen breakdown pathway. Thus, fibroblastmediated collagen degradation proceeds preferentially as a sequential mechanism in which extracellular collagenolysis is followed by uPARAP/Endo180-mediated endocytosis of large collagen fragments. First, we show that collagen that has been pre-cleaved by a mammalian collagenase is taken up much more efficiently than intact, native collagen by uPARAP/Endo180-positive cells. Second, we demonstrate that this preference is governed by the acquisition of a gelatin-like structure by the collagen, occurring upon collagenase-mediated cleavage under native conditions. Third, we demonstrate that the growth of uPARAP/Endo180-deficient fibroblasts on a native collagen matrix leads to substantial extracellular accumulation of well defined collagen fragments, whereas, wild-type fibroblasts possess the ability to direct an organized and complete degradation sequence comprising both the initial cleavage, the endocytic uptake, and the intracellular breakdown of collagen.Collagens are the most abundant protein constituents of the extracellular matrix. The sheet-like collagens of the basement membrane and the fibrillar matrix collagens all incorporate into dense, insoluble protein networks that form a critical barrier against processes of cell migration such as those connected to tissue remodeling, including the invasive growth of cancer. Consequently, the degradation of these matrices is one of the rate-limiting steps in cancer invasion (1).The physiological mechanisms responsible for collagen degradation have long been subject to investigation. Due to their unique structural features, collagens can only be degraded by a minority of mammalian extracellular proteases, but certain matrix metalloproteases (MMPs), 3 such as MMP-1, MMP-2, MMP-8, MMP-13, and the membrane-bound MMP-14 and -15, are indeed active against native collagens (2-10). The initial attack of these proteases leads to the generation of well defined collagen fragments, which, while still in the extracellular environment, may be subject to further degradation by gelatinases, MMP-2 or MMP-9, or other types of proteases (11-13).Importantly, however, collagen may also be degraded through an intracellular turnover pathway (11,14). Recent studies have shown that an endocytic route of collagen breakdown, mediated by the collagen internalization recep...

Fibroblast Activation Protein (FAP) Accelerates Collagen Degradation and Clearance from Lungs in Mice

“…The second event involves endocytosis of collagen through interaction with cell surface receptors, in particular ␣ 2 ␤ 1 integrin and uPARAP/Endo180, with subsequent degradation of the internalized collagen within the lysosomal compartment (45, 47, 68 -70). Although intact collagen may be endocytosed, fragmentation of collagen greatly speeds its rate of internalization and clearance (44,71). Collagen internalization through uPARAP/Endo180 has been implicated in both tumorigenesis and the development of fibrosis in the liver and lung in vivo (46,47,72).…”

Survival Outcome and EMT Suppression Mediated by a Lectin Domain Interaction of Endo180 and CD147

“…15). To test whether silencing of MT1-MMP has a similar effect on acinar architecture to Endo180 knockdown, we depleted MT1-MMP from 3D cultures of RWPE-1 and BPH-1 cells ( Supplementary Fig.…”

Three‐dimensional invasion of macrophages is mediated by cysteine cathepsins in protrusive podosomes

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