Activities of the MBL-associated serine proteases (MASPs) and their regulation by natural inhibitors

Wong, Nicky; Kojima, Mayumi; Dobó, József; Ambrus, Géza; Sim, Robert B.

doi:10.1016/s0161-5890(99)00106-6

Cited by 70 publications

(46 citation statements)

References 60 publications

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“…As for C3 cleavage, as judged from the data presented by Matsushita et al (21), the activity exhibited by the MASP-1 fraction purified from serum appears comparable with that obtained with our recombinant material, since only partial cleavage was obtained under the conditions used. In this respect, it should also be mentioned that other studies have reported no detectable C3 cleavage by the total MASP fraction (22,24). In summary, although our data certainly validate previous findings by Matsushita et al (21) that MASP-1 exhibits detectable C2 and C3 cleaving activities, they also clearly show that these activities are quite negligible compared with the very efficient C4 and C2 cleaving activities of MASP-2.…”

Section: Discussionmentioning

confidence: 81%

“…The only available information dealing with the substrate specificity of MASP-1 and MASP-2 has been obtained on proteases isolated from human serum, and is somewhat controversial. Thus, whereas it is now widely accepted that MASP-2 cleaves both C4 and C2 (6,21,22), the observation that MASP-1 can cleave C3 and hence directly trigger complement activation (21, 23) is debated (22,24). In addition, the relative efficiency of MASP-2 with respect to C4 and C2 cleavage has not been assessed.…”

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confidence: 99%

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Substrate Specificities of Recombinant Mannan-binding Lectin-associated Serine Proteases-1 and -2

Rossi¹,

Cseh²,

Bally³

et al. 2001

Journal of Biological Chemistry

166

135

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Mannan-binding lectin (MBL)-associated serine proteases-1 and 2 (MASP-1 and MASP-2) are homologous modular proteases that each interact with MBL, an oligomeric serum lectin involved in innate immunity. To precisely determine their substrate specificity, human MASP-1 and MASP-2, and fragments from their catalytic regions were expressed using a baculovirus/insect cells system. Recombinant MASP-2 displayed a rather wide, C1s-like esterolytic activity, and specifically cleaved complement proteins C2 and C4, with relative efficiencies 3-and 23-fold higher, respectively, than human C1s. MASP-2 also showed very weak C3 cleaving activity. Recombinant MASP-1 had a lower and more restricted esterolytic activity. It showed marginal activity toward C2 and C3, and no activity on C4. The enzymic activity of both MASP-1 and MASP-2 was specifically titrated by C1 inhibitor, and abolished at a 1:1 C1 inhibitor:protease ratio. Taken together with previous findings, these and other data strongly support the hypothesis that MASP-2 is the protease that, in association with MBL, triggers complement activation via the MBL pathway, through combined self-activation and proteolytic properties devoted to C1r and C1s in the C1 complex. In view of the very low activity of MASP-1 on C3 and C2, our data raise questions about the implication of this protease in complement activation.Mannan-binding lectin (MBL) 1 is an oligomeric C-type lectin that recognizes arrays of neutral carbohydrates such as mannose and N-acetylglucosamine on the surface of pathogenic microorganisms (2). This selectivity endows MBL with the ability to discriminate self from infectious non-self, and confers this "ante-antibody" a major role in innate immunity, as underlined by numerous clinical reports indicating that MBL deficiency is linked with increased susceptibility to infectious diseases (3-5). In addition to its role as an opsonin (3), MBL has devised the ability to associate to several modular proteases termed MASPs (MBL-associated serine proteases) (6 -9). A single MASP entity was initially identified, and characterized as a protease with the ability to cleave complement proteins C4, C2, and C3 (7, 10). Further studies by Thiel et al. (6) revealed that MASP was indeed a mixture of two related but distinct proteases, MASP-1 and MASP-2, and that only the latter had the ability to cleave C4. A third protein component MAp19, arising from alternative splicing of the MASP-2 gene (11, 12), and very recently a further protease MASP-3 (13) were also shown to be associated with MBL.MASP-1 and MASP-2 show a domain organization identical to that of C1r and C1s, the enzymatic components of the C1 complex of complement (14), with an N-terminal CUB module (15) followed by an epidermal growth factor-like module, a second CUB module, two contiguous CCP modules (16), and a C-terminal chymotrypsin-like serine protease domain (see Fig. 1). By analogy with human C1s, it may be anticipated that the proteolytic activity and specificity of the MASPs is defined by the two CCP modules ...

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Section: Discussionmentioning

confidence: 81%

mentioning

confidence: 99%

Substrate Specificities of Recombinant Mannan-binding Lectin-associated Serine Proteases-1 and -2

Rossi¹,

Cseh²,

Bally³

et al. 2001

Journal of Biological Chemistry

166

135

View full text Add to dashboard Cite

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“…Previous studies showed that MASP-2 cleaved C2 and C4 efficiently, with rates similar to C1s, a classical pathway enzyme (8,22). However, the contribution of the individual domains to the enzymatic properties of MASP- 2 has not yet been determined.…”

mentioning

confidence: 98%

“…The activation of the complement system results in the sequential activation of serine protease (SP) 4 zymogens. The first step in the lectin and the classical pathways is the binding of a specific recognition molecule (mannan-binding lectin (MBL) or C1q) to activator structures, which is followed by the activation of associated SP (1,2). Although the lectin pathway was discovered more than a decade ago (3), there are many uncertainties concerning the composition of the activation complex and the substrate specificities of the MBL-associated SP (MASPs).…”

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confidence: 99%

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Natural Substrates and Inhibitors of Mannan-Binding Lectin-Associated Serine Protease-1 and -2: A Study on Recombinant Catalytic Fragments

Ambrus

Gál

Kojima

et al. 2003

The Journal of Immunology

202

204

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Mannan-binding lectin-associated serine protease (SP) (MASP)-1 and MASP-2 are modular SP and form complexes with mannan-binding lectin, the recognition molecule of the lectin pathway of the complement system. To characterize the enzymatic properties of these proteases we expressed their catalytic region, the C-terminal three domains, in Escherichia coli. Both enzymes autoactivated and cleaved synthetic oligopeptide substrates. In a competing oligopeptide substrate library assay, MASP-1 showed extreme Arg selectivity, whereas MASP-2 exhibited a less restricted, trypsin-like specificity. The enzymatic assays with complement components showed that cleavage of intact C3 by MASP-1 and MASP-2 was detectable, but was only ∼0.1% of the previously reported efficiency of C3bBb, the alternative pathway C3-convertase. Both enzymes cleaved C3i 10- to 20-fold faster, but still at only ∼1% of the efficiency of MASP-2 cleavage of C2. We believe that C3 is not the natural substrate of either enzyme. MASP-2 cleaved C2 and C4 at high rates. To determine the role of the individual domains in the catalytic region of MASP-2, the second complement control protein module together with the SP module and the SP module were also expressed and characterized. We demonstrated that the SP domain alone can autoactivate and cleave C2 as efficiently as the entire catalytic region, while the second complement control protein module is necessary for efficient C4 cleavage. This behavior strongly resembles C1s. Each MASP-1 and MASP-2 fragment reacted with C1-inhibitor, which completely blocked the enzymatic action of the enzymes. Nevertheless, relative rates of reaction with α-2-macroglobulin and C1-inhibitor suggest that α-2-macroglobulin may be a significant physiological inhibitor of MASP-1.

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Cryoprecipitate of Patients with Cryoglobulinemic Glomerulonephritis Contains Molecules of the Lectin Complement Pathway

Ohsawa

Ohi

Tamano

et al. 2001

Clinical Immunology

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Activities of the MBL-associated serine proteases (MASPs) and their regulation by natural inhibitors

Cited by 70 publications

References 60 publications

Substrate Specificities of Recombinant Mannan-binding Lectin-associated Serine Proteases-1 and -2

Substrate Specificities of Recombinant Mannan-binding Lectin-associated Serine Proteases-1 and -2

Natural Substrates and Inhibitors of Mannan-Binding Lectin-Associated Serine Protease-1 and -2: A Study on Recombinant Catalytic Fragments

Cryoprecipitate of Patients with Cryoglobulinemic Glomerulonephritis Contains Molecules of the Lectin Complement Pathway

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