Project

Endothelium; cell adhesion; leukocyte migration; adhesion molecule; cell junctions; angiogenesis

Lead
Lay summary
LEAD Adhesion molecules stabilize the cell-cell contacts in endothelial barriers. Junctional adhesion molecules B and C (JAMB, JAMC)are part of a network of proteins controlling this physical barrier by preserving endothetial polarity between the luminal and abluminal membrane domains. The Jam interactions will be studied in leukocyte migration during inflammation, autoimmunity and neovessel formation. RESUME The vascular molecules JAM-B and-C, previously cloned by our laboratory, are expressed by vascular endothelial cells and they control vascular permeability, cell polarity, inflammatory leukocyte transmigration and angiogenic neovessel formation. We found that JAM-B and -C interact with high affinity. However, our trustable techniques did not confirm several described other binding partners such as the leukocyte integrins and others. As we are convinced that such complex interactions between leukocytes andothelial JAMs exist, we will search for Jam ligands by various methods including the so called two hybrid system. We hope that these novel ligands will be of help to explain why JAMs contribute to the one-way traffic of leukocytes into inflamed tissue and what signal transduction mechanisms prevail. Using our valuable reagents we then will study the role of the JAMs in models for multiple sclerosis (MS), B cell leukemia and tumor angiogenesis. BUT This project will elucidate novel molecular machanisms leading to understand chronic inflammatory reactions and in particular leukocyte migration across the vascular barrier. As JAMs control endothelial junctions our work should also be able to explain their role in the angiogenic formation of novel blood vessels, for example during tumor progression and embryogenesis SIGNIFICATION This type of research investigates the basic molecular mechanisms how JAM-B and_c determine vital vascular functions. They include vascular permeability, leukocyte transmigration during inflammation and angiogenesis. The project then turns towards investigations of more complex pathologies such as multiple sclerosis or leukemia . Data collected with animal models not only should explain basic mechanisms but rather will guide us towards developing therapies in human.

Direct link to Lay Summary

Last update: 21.02.2013

Number	Title	Start	Funding scheme

This is a continuation of our project aiming to understand how the junction adhesion molecules B and C (JAM-B, JAM-C) interfere in inflammatory and immune reactions. The two molecules, previously cloned by our laboratory, are expressed by vascular endothelial cells and they control vascular permeability, cell polarity and leukocyte transmigration.During the last grant period, we investigated molecular interactions of JAM-B and -C by Plasmon resonance technology and gene mutation of potential binding sites. Thereby we found JAM-B/JAM-C interaction of high affinity. However, the trustable techniques did not confirm the described interactions with JAM ligands such as the leukocyte integrin Mac-1. As most lymphocytes/leukocytes do not express JAM-B or -C and interact with vascular JAM-C, searching for novel, unknown ligands is in need. This will be performed by biochemistry and the so-called yeast two-hybrid system using extracellular JAM domains as baits. The suggested experiments should clarify how JAM-C and its novel ligands contribute to the one-way traffic of leukocytes into inflamed tissue and what signal transduction mechanisms prevail. Video microscopy and two photon technology will continue to be used to visualize JAM interactions in vivo.Antibodies against JAMs and soluble recombinant molecules will potentially make valuable tools for treatment of inflammatory pathologies. For testing of JAM-C we used several experimental systems with promising outcome. However, JAM-B testing has just started with one of the models (glomerulonephritis) during our last period. As we found JAM-B expressed in brain endothelium, we wish to learn whether it played a role in multiple sclerosis (MS), since MS triggering lymphocytes express and use integrin alpha 4 for which JAM-B is a ligand. The chosen testing system will be experimental autoimmune encephalomyelitis (EAE) for which our department has ample expertise.Recently we found JAM-C prominently expressed by human T cells after in vitro TCR activation. The functional role of this expression is unknown. Therefore we will investigate the effect of lymphocyte JAM-C in vitro on migration behavior, survival and cytokine secretion of these T-cells. Furthermore we will transfer these cells into immunodeficient NOD/Scid animals in order to study in vivo behavior. The latter experiments have been successfully applied in our laboratory using human B lymphocytes and leukemia cells. Clearly JAM-C expression by a B-cell subpopulation changes its migration behavior (manuscript in preparation).As JAMs are clearly polarity proteins, their expression may affect tissue specific differentiation of embryonic stem cells (ESC). We will use ESC lines, manipulate the expression levels of the JAMs by knock down and over expression technologies and investigate VEGF driven differentiation of these ESCs into polarized endothelial cells. The aim of these experiments will be vascular repair avoiding teratocarcinoma tumor formation and better understanding of the vascular differentiation process.In conclusion: We will largely extend work on JAM-B in addition to JAM-C. Both molecules are involved in essential steps in inflammatory diseases and tissue differentiation and we are looking forward to further clarify the molecular mechanisms.