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Interaction of laminin with Entamoeba histolytica cysteine proteinases and its effect on amebic pathogenesis
1Department of Medicine, Washington University School of Medicine, Saint Louis, Missouri 63110, USA.
Abstract:
The Entamoeba histolytica 27-kDa cysteine proteinases exhibit striking binding specificities for immobilized laminin over other components of the extracellular matrix, such as collagen and fibronectin. Inactivation of the proteinase with the active-site inhibitor L-trans-epoxysuccinyl-leucylamido(4-guanidino)butane abolishes laminin binding by the enzyme, and conversely, laminin inhibits cleavage of a fluorogenic dipeptide substrate of the amebic cysteine proteinase, suggesting that the substrate binding pocket of the enzyme is involved in the binding of laminin. The addition of laminin but not fibronectin or collagen to E. histolytica trophozoites significantly reduces amebic liver abscess formation in severe combined immunodeficient mice, further supporting the hypothesis that E. histolytica cysteine proteinases play an important role in amebic pathogenesis. The specific interaction of amebic proteinases with laminin may be exploited in designing new inhibitors of these enzymes.
Insights
Entamoeba histolytica cysteine proteinases bind specifically to laminin, a key factor in amebic liver abscess formation. Targeting this interaction may lead to new therapeutic inhibitors for amebiasis.
Area of Science:
- Microbiology
- Parasitology
- Biochemistry
Background:
- Entamoeba histolytica (E. histolytica) causes amebiasis, a significant global health concern.
- Extracellular matrix (ECM) components are crucial in parasitic infections and tissue invasion.
- Cysteine proteinases are virulence factors in many protozoan parasites, including E. histolytica.
Purpose of the Study:
- To investigate the binding specificities of E. histolytica 27-kDa cysteine proteinases.
- To determine the role of these proteinases in amebic pathogenesis, particularly liver abscess formation.
- To explore the potential of targeting the proteinase-laminin interaction for therapeutic development.
Main Methods:
- Enzyme-inhibition assays using specific inhibitors.
- Binding assays with immobilized ECM proteins (laminin, collagen, fibronectin).
- In vivo studies using severe combined immunodeficient (SCID) mice to assess liver abscess formation.
- Inhibition of substrate cleavage assays.
Main Results:
- E. histolytica 27-kDa cysteine proteinases show high affinity for laminin compared to collagen and fibronectin.
- Inactivation of the proteinase active site abolished laminin binding.
- Laminin inhibited the cleavage of a fluorogenic substrate by the amebic cysteine proteinase.
- Addition of laminin to E. histolytica trophozoites significantly reduced liver abscess formation in SCID mice.
Conclusions:
- E. histolytica cysteine proteinases specifically bind to laminin, suggesting a role for the enzyme's substrate-binding pocket in this interaction.
- The interaction between E. histolytica proteinases and laminin is critical for amebic liver abscess formation.
- Targeting the specific interaction between E. histolytica cysteine proteinases and laminin presents a promising strategy for developing novel anti-amebiasis therapies.