Related Experiment Videos
Stimulated neutrophils induce myosin light chain phosphorylation and isometric tension in endothelial cells
E A Hixenbaugh1, Z M Goeckeler, N N Papaiya
1Department of Physiology and Cellular Biophysics, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Abstract:
The mechanism or mechanisms by which polymorphonuclear leukocytes (PMN) penetrate junctions between neighboring endothelial cells (EC) to traverse endothelial barriers remain unresolved. We report that chemoattractant-stimulated PMN induce a coordinate increase in both phosphorylation of serine 19 and threonine 18 of EC myosin regulatory light chains and isometric tension generation by EC monolayers. Unstimulated PMN had no effect on either parameter. These findings, coupled with our previous report (Huang et al., J. Cell Biol. 120: 1371-1380, 1993) that chemoattractant-stimulated PMN cause a rise in EC cytosolic free Ca2+, provide strong presumptive evidence that myosin light chain kinase is the EC enzyme responsible for initiating myosin light chain phosphorylation, EC contraction, and isometric tension generation in response to chemoattractant-stimulated PMN. We suggest that, by inducing phosphorylation of EC cytoskeletal proteins, chemoattractant-stimulated PMN induce EC to open their intercellular junctions, thereby facilitating transendothelial movement of these leukocytes.
Insights
Chemoattractant-stimulated polymorphonuclear leukocytes (PMN) trigger endothelial cell (EC) contraction and junction opening. This process, involving myosin light chain phosphorylation, facilitates leukocyte transmigration across endothelial barriers.
Area of Science:
- Cell Biology
- Immunology
- Physiology
Background:
- The transmigration of polymorphonuclear leukocytes (PMN) across endothelial barriers is crucial for immune responses but the underlying mechanisms remain unclear.
- Understanding how PMN interact with endothelial cells (EC) to facilitate their passage is essential for developing targeted therapies.
Purpose of the Study:
- To elucidate the molecular mechanisms by which PMN induce endothelial cells to open their intercellular junctions.
- To investigate the role of endothelial cell cytoskeletal dynamics in PMN transmigration.
Main Methods:
- Measurement of endothelial cell isometric tension generation.
- Assessment of myosin regulatory light chain phosphorylation in endothelial cells.
- Correlation of these changes with chemoattractant-stimulated PMN presence.
Main Results:
- Chemoattractant-stimulated PMN induced a significant increase in myosin regulatory light chain phosphorylation (serine 19 and threonine 18) in endothelial cells.
- PMN stimulation also led to a coordinate increase in isometric tension generation by endothelial cell monolayers.
- Unstimulated PMN did not elicit these responses, indicating a specific, stimulus-dependent mechanism.
Conclusions:
- The findings strongly suggest that myosin light chain kinase is the key enzyme mediating PMN-induced endothelial cell contraction and junction opening.
- PMN-induced phosphorylation of endothelial cytoskeletal proteins facilitates the opening of intercellular junctions.
- This mechanism is critical for enabling leukocyte transmigration across the endothelial barrier.