Intercellular adhesion molecule-5 induces dendritic outgrowth by homophilic adhesion

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Intercellular adhesion molecule-5 (ICAM-5) is a glycoprotein found in telencephalic neurons.
• ICAM-5 is known to bind to leukocyte beta(2)-integrins in a heterophilic manner.

Purpose of the Study:

• To investigate the homophilic binding properties of ICAM-5.
• To understand the role of ICAM-5 in dendritic development and adhesion.
• To elucidate the regulatory mechanisms of ICAM-5's adhesive functions.

Main Methods:

• Analysis of human ICAM-5 protein interactions using binding assays.
• Experimental manipulation of ICAM-5-Fc on cultured hippocampal neurons.
• Investigation of ICAM-5's molecular form during rat brain development using electrophoresis.

Main Results:

• Human ICAM-5 exhibits homophilic binding via its immunoglobulin domain 1 to domains 4-5.
• Surface-bound ICAM-5-Fc significantly enhanced dendritic outgrowth and arborization in hippocampal neurons.
• ICAM-5 exists as a monomer during early development and forms high molecular weight complexes in mature neurons, correlating with binding activity.

Conclusions:

• ICAM-5 possesses homophilic binding capabilities, distinct from its known heterophilic interactions.
• The transition between monomeric and complex forms of ICAM-5 regulates its homophilic binding activity.
• ICAM-5 mediates both neuron-neuron (homophilic) and neuron-leukocyte (heterophilic) adhesion.