Related Experiment Videos
Alpha 1-proteinase inhibitor is a neutrophil chemoattractant after proteolytic inactivation by macrophage elastase
M J Banda1, A G Rice, G L Griffin
1Laboratory of Radiobiology and Environmental Health, University of California, San Francisco 94143.
Abstract:
Mouse macrophage elastase, a metalloproteinase, catalytically inactivates human alpha 1-proteinase inhibitor (alpha 1-PI) by attacking a single peptide bond between Pro357 and Met358, resulting in Mr = 4,200 and 47,800 fragments. We show here that this proteolytically inactivated alpha 1-PI is a potent chemotactic factor for human neutrophils at a concentration of 1 nM. The chemotactic response is equivalent to that elicited by formyl-methionyl-leucyl-phenylalanine. Native alpha 1-PI does not stimulate chemotaxis. Purification of the two fragments of alpha 1-PI that result from proteolysis by macrophage elastase indicated that the Mr = 4,200 fragment is responsible for the chemotactic activity. However, the two proteolysis fragments do not dissociate from each other under physiologic conditions. Therefore, the ability of proteolytically inactivated alpha 1-PI to act as a mediator of inflammation is due to rearrangement of the alpha 1-PI molecule rather than to release of a cleavage fragment.
Insights
Proteolytically inactivated human alpha 1-proteinase inhibitor (alpha 1-PI) acts as a potent neutrophil attractant. This inflammatory mediator activity stems from molecular rearrangement, not fragment release.
Area of Science:
- Biochemistry
- Immunology
- Protease activity
Background:
- Human alpha 1-proteinase inhibitor (alpha 1-PI) is a key regulator of protease activity.
- Metalloproteinases, like mouse macrophage elastase, can inactivate alpha 1-PI.
- The biological consequences of alpha 1-PI inactivation are not fully understood.
Purpose of the Study:
- To investigate the biological activity of alpha 1-PI after inactivation by mouse macrophage elastase.
- To determine if inactivated alpha 1-PI can modulate neutrophil behavior.
- To identify the specific component responsible for any observed activity.
Main Methods:
- Incubation of human alpha 1-PI with mouse macrophage elastase.
- Assessment of neutrophil chemotaxis using inactivated alpha 1-PI and its fragments.
- Purification and characterization of alpha 1-PI fragments.
Main Results:
- Proteolytic inactivation of alpha 1-PI by mouse macrophage elastase generates chemotactic activity for human neutrophils at nanomolar concentrations.
- The chemotactic response is comparable to that induced by formyl-methionyl-leucyl-phenylalanine.
- The Mr = 4,200 fragment of inactivated alpha 1-PI mediates the chemotactic activity, although fragments remain associated.
Conclusions:
- Proteolytically inactivated alpha 1-PI, not native alpha 1-PI, functions as a potent chemoattractant for neutrophils.
- The inflammatory mediator role of inactivated alpha 1-PI is attributed to a conformational change or molecular rearrangement within the inhibitor molecule.
- These findings highlight a novel mechanism of inflammation mediated by modified proteinase inhibitors.