Elucidation of the substrate specificity of the MASP-2 protease of the lectin complement pathway and identification of the enzyme as a major physiological target of the serpin, C1-inhibitor

Kerr, Felicity Kate; Thomas, Adele R.; Wijeyewickrema, Lakshmi C.; Whisstock, James C.; Boyd, Sarah; Kaiserman, Dion; Matthews, Antony Y.; Bird, Phillip I.; Thielens, Nicole M.; Rossi, Véronique; Pike, Robert N.

doi:10.1016/j.molimm.2007.07.008

Cited by 70 publications

(53 citation statements)

References 26 publications

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“…Although MASP-2 concentrations in the blood were normal, the enzymatic activity was much lower in oncology patients (irrespective of treatment and/or MBL substitution) than the MASP-2 activity determined in 100 healthy controls (30,38). The explanation may be related to the presence of protein inhibitors such as C1 esterase inhibitor, ␣ 2 -macroglobulin, or as yet unidentified modulators of its activity (39). Also, the reduction of alternative pathway activation in samples from several of the oncology patients, when these patients were neutropenic as a consequence of the chemotherapy, may have had an effect.…”

Section: Discussionmentioning

confidence: 87%

Mannose-Binding Lectin (MBL) Substitution: Recovery of Opsonic Function In Vivo Lags behind MBL Serum Levels

Brouwer

Frakking

Wetering

et al. 2009

The Journal of Immunology

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Mannose-binding lectin (MBL) deficiency is often associated with an increased risk of infection or worse prognosis in immunocompromised patients. MBL substitution in these patients might diminish these risks. We therefore performed an open, uncontrolled safety and pharmacokinetic MBL-substitution study in 12 pediatric oncology patients with chemotherapy-induced neutropenia. Twice weekly MBL infusions with plasma-derived MBL yielded MBL trough levels >1.0 μg/ml. We tested whether MBL substitution in vivo increased MBL-dependent complement activation and opsonophagocytosis of zymosan in vitro. Upon MBL substitution, opsonophagocytosis by control neutrophils increased significantly (p < 0.001) but remained suboptimal, although repeated MBL infusions resulted in improvement over time. The MBL-dependent MBL-associated serine protease (MASP)-mediated complement C3 and C4 activation also showed a suboptimal increase. To explain these results, complement activation was studied in detail. We found that in the presence of normal MASP-2 blood levels, MASP-2 activity (p < 0.0001) was reduced as well as the alternative pathway of complement activation (p < 0.05). This MBL-substitution study demonstrates that plasma-derived MBL infusions increase MBL/MASP-mediated C3 and C4 activation and opsonophagocytosis, but that higher circulating levels of plasma-derived MBL are required to achieve MBL-mediated complement activation comparable to healthy controls. Other patient cohorts should be considered to demonstrate clinical efficacy in phase II/III MBL-substitution studies, because we found a suboptimal recovery of (in vitro) biological activity upon MBL substitution in our neutropenic pediatric oncology cohort.

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Section: Discussionmentioning

confidence: 87%

Mannose-Binding Lectin (MBL) Substitution: Recovery of Opsonic Function In Vivo Lags behind MBL Serum Levels

Brouwer

Frakking

Wetering

et al. 2009

The Journal of Immunology

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“…In contrast, only one report showed that AT inhibits MASP-1, but only in the presence of heparin (15). Because of the discussed dual role of MASP-1, both in complement and coagulation, we undertook to quantitatively examine the reaction between rMASP-1 and AT in the absence and presence of different concentrations of heparin, and compared it with the rMASP-1/C1-inh reaction and data presented in the literature (35,41,42) regarding the thrombin/AT and rMASP-2/C1-inh reaction (Table II). We found that AT was the fastest inhibitor of rMASP-1 in the presence of heparin, and in contrast to Presanis et al (15), the reaction took place in the absence of heparin as well, although without heparin AT inhibited rMASP-1 slower than C1-inh did.…”

Section: Inhibition By C1-inh and At In The Presence And Absence Of Hmentioning

confidence: 99%

“…C1-inh was used at 0 or 200-2000 nM and AT at 0 or 200-2000 nM, whereas heparin was applied at 0 or 0.1-1000 g ml Ϫ1 final concentration. The second order rate constants of inhibition (k ass ) were determined under pseudo-first-order conditions as described (35,36). Data were fitted by nonlinear regression using the A ϭ a Ϫ b ϫ e Ϫkobsϫt ϩ c ϫ t equation, where A is the absorbance; a, b, and c are fitting parameters; and k obs is the observed association rate constant.…”

mentioning

confidence: 99%

MASP-1, a Promiscuous Complement Protease: Structure of Its Catalytic Region Reveals the Basis of Its Broad Specificity

Dobó

Harmat

Beinrohr

et al. 2009

The Journal of Immunology

112

104

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Mannose-binding lectin (MBL)-associated serine protease (MASP)-1 is an abundant component of the lectin pathway of complement. The related enzyme, MASP-2 is capable of activating the complement cascade alone. Though the concentration of MASP-1 far exceeds that of MASP-2, only a supporting role of MASP-1 has been identified regarding lectin pathway activation. Several non-complement substrates, like fibrinogen and factor XIII, have also been reported. MASP-1 belongs to the C1r/C1s/MASP family of modular serine proteases; however, its serine protease domain is evolutionary different. We have determined the crystal structure of the catalytic region of active MASP-1 and refined it to 2.55 Å resolution. Unusual features of the structure are an internal salt bridge (similar to one in factor D) between the S1 Asp189 and Arg224, and a very long 60-loop. The functional and evolutionary differences between MASP-1 and the other members of the C1r/C1s/MASP family are reflected in the crystal structure. Structural comparison of the protease domains revealed that the substrate binding groove of MASP-1 is wide and resembles that of trypsin rather than early complement proteases explaining its relaxed specificity. Also, MASP-1’s multifunctional behavior as both a complement and a coagulation enzyme is in accordance with our observation that antithrombin in the presence of heparin is a more potent inhibitor of MASP-1 than C1 inhibitor. Overall, MASP-1 behaves as a promiscuous protease. The structure shows that its substrate binding groove is accessible; however, its reactivity could be modulated by an unusually large 60-loop and an internal salt bridge involving the S1 Asp.

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“…It also allows for fusion to nonpermissive cells, such as follicular dendritic cells. The complement cascade is also regulated by many antiproteases, including serpins, so lowered levels may be a result of this relationship [50]. Rho dissociation inhibitor has been implicated in mediating HIV-1-infected cell migration though tight junctions [51].…”

Section: Investigating the Proteome Of Eu Womenmentioning

confidence: 99%

Systems Biology-Based Approaches to Understand HIV-Exposed Uninfected Women

Burgener¹,

Sainsbury²,

Plummer³

et al. 2010

Curr HIV/AIDS Rep

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Worldwide HIV infects women more frequently than men, and it is clear that not all exposed to HIV become infected. Several populations of HIV-exposed uninfected (EU) women have been identified, including discordant couples and sex workers. Understanding what provides natural protection in EU women is critical in vaccine or microbicide development. However, correlates of protection in these women are still unclear. Most studies have used classical methods, examining single genes or cellular factors, a mainstay for traditional immunobiology. This reductionist approach may be limited in the information it can provide. Novel technologies are now available that allow us to take a "systems biology" approach, which allows the study of a complex biological system and identifies factors that may provide protection against HIV infection. Herein we report developments in discovery-based systems biology approaches in EU women and how this broadens our understanding of natural protection against HIV-1.

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Elucidation of the substrate specificity of the MASP-2 protease of the lectin complement pathway and identification of the enzyme as a major physiological target of the serpin, C1-inhibitor

Cited by 70 publications

References 26 publications

Mannose-Binding Lectin (MBL) Substitution: Recovery of Opsonic Function In Vivo Lags behind MBL Serum Levels

Mannose-Binding Lectin (MBL) Substitution: Recovery of Opsonic Function In Vivo Lags behind MBL Serum Levels

MASP-1, a Promiscuous Complement Protease: Structure of Its Catalytic Region Reveals the Basis of Its Broad Specificity

Systems Biology-Based Approaches to Understand HIV-Exposed Uninfected Women

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