Sphingosine 1-Phosphate, Present in Serum-derived Lipoproteins, Activates Matriptase

Abstract

We describe here a novel biological function of sphingosine 1-phosphate (S1P): the activation of a serine protease, matriptase. Matriptase is a type II integral membrane serine protease, expressed on the surface of a variety of epithelial cells; it may play an important role in tissue remodeling. We have previously reported that the activation of matriptase is regulated by serum. We have now identified the bioactive component from serum. First, the activity was observed to co-purify with lipoproteins by conventional liquid chromatography and immunoaffinity chromatography. The ability of lipoproteins to induce the activation of matriptase was further confirmed with commercial preparations of low density lipoprotein (LDL) and very low density lipoprotein (VLDL). Next, we observed that the bioactive component of LDL is associated with the phospholipid components of LDL. Fractionation of lipid components of LDL by thin layer chromatography (TLC) revealed that the bioactive component of LDL comigrates with S1P. Nanomolar concentrations of commercially obtained S1P were then observed to induce the rapid activation of matriptase on the surfaces of nontransformed human mammary epithelial cells. Other structurally related sphingolipids, including dihydro-S1P, ceramide 1-phosphates, and sphingosine phosphocholine as well as lysophosphatidic acid, can also induce the activation of matriptase, but at significantly higher concentrations than S1P. Furthermore, S1P-dependent matriptase activation is dependent on Ca 2؉ but not via G i protein-coupled receptors. Our results demonstrate that bioactive phospholipids can function as nonprotein activators of a cell surface protease, suggesting a possible mechanistic link between S1P and normal and possibly pathologic tissue remodeling.Physiologic and pathologic tissue remodeling involve an interplay of processes involving proteases and growth factors. Whereas growth factors induce cell proliferation and motility and function as chemoattractants, proteases directly promote cell migration by degrading the surrounding extracellular matrix barrier. However, the participation of proteases in physiologic and pathologic tissue remodeling is more complex, since proteolytic cleavage also serves to expose cryptic sites of extracellular matrix molecules, to activate latent growth factors, and to activate other protease cascades (1, 2). This complexity is exemplified by the epithelium-derived serine protease, matriptase (3, 4) (also known as membrane type serine protease-1 (5) or as epithin, its mouse homologue (6)). Matriptase has been demonstrated to activate the extracellular matrixdegrading protease, urokinase-type plasminogen activator, the potent, motility-inducing hepatocyte growth factor/scatter factor, and the calcium-regulating protease-activated receptor-2 (7, 8). Therefore, matriptase may play an important role in tissue remodeling (7).In addition to its catalytic serine protease domain, matriptase contains a transmembrane domain and two putative regulatory domains: two tandem repea...

Matriptase Activation, an Early Cellular Response to Acidosis

“…Consistent with this observation, no protein bands were detected using the activated matriptase-specific mAb (Fig. 1B, M69, lanes 1 and 3) (28,31). The inhibitor HAI-1 was detected in its uncomplexed form at 55 kDa, again consistent with the lack of active matriptase in these lysates (Fig.…”

“…Activated matriptase was detected using the M69 mouse mAb, which recognizes an epitope present only on the activated form of the enzyme (28,31). Human HAI-1 was detected using the HAI-1-specific mouse mAb M19 (32).…”

Tissue Expression, Protease Specificity, and Kunitz Domain Functions of Hepatocyte Growth Factor Activator Inhibitor-1B (HAI-1B), a New Splice Variant of HAI-1

“…Matriptase is a type II transmembrane serine protease (21) expressed as a single-chain form on epithelial cell types (5,22). It has been suggested that sphingosine 1-phosphate, a serumderived lipoprotein, is able to convert matriptase zymogen into its enzymatically active two chain form (23). In addition to HGFA and matriptase, there are a number of other serine proteases that, at least in vitro, convert pro-HGF into its active form.…”

Matriptase Activation in Breast Cancer Progression

“…These observations suggest that matriptase could act as a cell surface activator to recruit and activate stromal-derived ECM-degrading proteases and motiUty factors. Furthermore, activation of matriptase in nontumorogenic human mammary epithelial cells (HMEC) seems to be tightly regulated by bioactive lipids, mainly sphingosine 1-phosphate (SIP) (3,4). Surprisingly, this SIP-based, physiological regulatory mechanism may be lost during breast cancer progression (5).…”