Related Experiment Videos
Secretion of plasminogen activator by stimulated macrophages
Abstract:
Cultured thioglycollate-stimulated peritoneal macrophages synthesize, accumulate, and continuously release high levels of plasminogen activators for at least 4 days whereas cultures of unstimulated macrophages do not; the higher specific catalytic activity of released vs. cell-associated enzyme suggests that the plasminogen activators are actively secreted. The major macrophage plasminogen activator is a serine protease of mol wt 48,000, and thus resembles the comparable enzyme released by virally transformed fibroblasts. Macrophages release a second plasminogen activator of mol wt 28,000 that is also a serine enzyme. The secretion products released by stimulated and unstimulated macrophages have been compared by SDS-polyacrylamide gel electrophoresis after chemical labeling with (3)H-DFP or biosynthetic labeling with (14)C-amino acids. These procedures show that some proteins are formed in both cultures, whereas others are uniquely secreted by each type of macrophage. The serine enzymes released by the two kinds of macrophages differ in specificity and electrophoretic mobility.
Insights
Stimulated macrophages release high levels of plasminogen activators, unlike unstimulated cells. These secreted serine proteases, differing in size and specificity, suggest active secretion by macrophages.
Area of Science:
- Cell Biology
- Biochemistry
- Immunology
Background:
- Macrophages are key immune cells involved in tissue remodeling and inflammation.
- Plasminogen activators are crucial enzymes in the fibrinolytic system, regulating blood clot breakdown.
- Understanding macrophage secretory function is vital for comprehending their role in physiological and pathological processes.
Purpose of the Study:
- To investigate the synthesis, accumulation, and release of plasminogen activators by cultured macrophages.
- To characterize the molecular properties and secretion patterns of macrophage-derived plasminogen activators.
- To compare the secretory products of stimulated versus unstimulated macrophages.
Main Methods:
- Culturing thioglycollate-stimulated and unstimulated peritoneal macrophages.
- Measuring plasminogen activator activity in cell-associated and released fractions.
- Characterizing enzyme properties using SDS-polyacrylamide gel electrophoresis.
- Labeling proteins with (3H)-DFP and (14C)-amino acids to analyze secreted products.
Main Results:
- Stimulated macrophages continuously release high levels of plasminogen activators for at least 4 days.
- Macrophages secrete two major serine protease plasminogen activators, with molecular weights of 48,000 and 28,000.
- Secreted enzymes exhibit higher specific catalytic activity than cell-associated enzymes, indicating active secretion.
- Proteomic analysis revealed distinct secreted proteins between stimulated and unstimulated macrophages.
- The secreted serine enzymes differ in specificity and electrophoretic mobility.
Conclusions:
- Thioglycollate stimulation induces macrophages to actively secrete significant amounts of plasminogen activators.
- Macrophages release distinct serine proteases, including a 48 kDa enzyme similar to that from fibroblasts.
- Differential protein secretion by stimulated and unstimulated macrophages highlights their distinct functional states.