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Junctional adhesion molecules and interendothelial junctions.

Michel Aurrand-Lions1, Caroline Johnson-Leger, Chrystelle Lamagna

  • 1Department of Pathology, Centre Médical Universitaire, Geneva, Switzerland.

Cells, Tissues, Organs
|December 12, 2002
PubMed
Summary

This study explores how endothelial cells form junctions that allow leukocytes to move through them. Researchers focused on a molecule called JAM-2, which is found in lymphatic endothelial cells and high endothelial venules. They cloned the human version of JAM-2 and found that it belongs to a new family of proteins called CTX. In experiments, overexpression of JAM-2 increased the movement of leukocytes across endothelial cells. This suggests that JAM-2 may help regulate how easily cells can pass through blood vessel walls, especially in areas like lymph nodes where immune cells are constantly moving. The findings support a role for JAM-2 in junctional dynamics and leukocyte trafficking.

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Area of Science:

  • Vascular biology
  • Cell adhesion mechanisms
  • Immunology

Background:

Endothelial cells form junctional complexes similar to those in epithelial cells. These include gap junctions, adherens junctions, and tight junctions. Unlike polarized epithelia, endothelia show random organization of junctions. This adaptability allows endothelia to regulate permeability and leukocyte movement. Lymphoid organs, such as high endothelial venules (HEVs), demonstrate leakier junctions. In contrast, the blood-brain barrier remains tightly regulated. Prior research has shown that endothelial junctions vary in permeability depending on tissue needs. However, the specific molecular mechanisms remain unclear. This gap motivated investigations into junctional adhesion molecules.

Purpose Of The Study:

The study aimed to identify and characterize junctional adhesion molecules in endothelial cells. Specifically, the focus was on lymphatic endothelial cells and HEVs. Researchers sought to understand how these molecules influence leukocyte transmigration. The goal was to determine if JAM-2 plays a role in this process. The study also aimed to clone the human equivalent of JAM-2. By examining its expression and function, the researchers hoped to clarify its role in junctional dynamics. The motivation stemmed from observing increased transmigration in vitro when JAM-2 was overexpressed. This led to the hypothesis that JAM-2 facilitates leukocyte passage through endothelial barriers.

Keywords:
endothelial junctionsleukocyte transmigrationJAM-2vascular permeability

Frequently Asked Questions

The authors propose that JAM-2 facilitates transmigration, as overexpression increases leukocyte passage in vitro.

In vitro transmigration assays showed increased passage when JAM-2 was overexpressed in endothelial cells.

The authors suggest this localization supports a role in constitutive lymphocyte circulation and junctional adaptability.

Belonging to the CTX family indicates a novel classification and potential unique function in junctional regulation.

Related Experiment Videos

Main Methods:

The researchers used molecular cloning techniques to identify JAM-2. They focused on lymphatic endothelial cells and HEVs for analysis. Immunostaining was employed to detect JAM-2 localization at junctions. In vitro transmigration assays measured leukocyte passage across endothelial cells. Overexpression of JAM-2 was achieved using transfection methods. The CTX molecular family was analyzed to classify JAM-2. Comparative analysis with other junctional adhesion molecules was conducted. The study combined molecular biology with functional assays to assess JAM-2's role.

Main Results:

JAM-2 was found to be specifically expressed in lymphatic endothelial junctions and HEVs. The human equivalent of JAM-2 was successfully cloned and characterized. Localization studies showed JAM-2 at sites of constitutive lymphocyte circulation. In vitro experiments revealed increased transmigration when JAM-2 was overexpressed. These findings suggest a functional role for JAM-2 in facilitating leukocyte movement. The molecule belongs to the novel CTX family, indicating a unique classification. Expression patterns suggest JAM-2 is involved in junctional adaptability. The results support a direct link between JAM-2 and transmigration efficiency.

Conclusions:

The study demonstrated that JAM-2 is expressed in lymphatic and HEV junctions. Overexpression of JAM-2 correlates with increased leukocyte transmigration in vitro. The findings suggest JAM-2 facilitates leukocyte passage through endothelial barriers. The molecule's localization supports a role in junctional dynamics. JAM-2's classification within the CTX family adds to its functional significance. The results imply that JAM-2 contributes to junctional adaptability. This adaptability is crucial for regulating permeability and leukocyte trafficking. The authors propose that JAM-2 may be a key player in junctional regulation.

Endothelia show random junction organization, while epithelia display polarized spatial sorting of junctional complexes.

The authors propose that JAM-2 contributes to junctional adaptability, which is essential for regulating permeability and leukocyte trafficking.