What is the Difference Between ICAM-1 and VCAM-1

The key difference between ICAM-1 and VCAM-1 is that ICAM-1 is a cell adhesion molecule that is constitutively expressed in the membranes of leukocytes and endothelial cells, while VCAM1 is a cell adhesion molecule that is expressed in the membranes of vascular endothelial cells only after stimulated by cytokines.

Cell adhesion molecules are a subset of cell surface proteins. Their function is binding cells together with other cells or with the extracellular matrix. Hence, these proteins help cells to stick together and to their surroundings. They are a vital part of maintaining tissue structure. In addition to serving as adhesion molecules, they also play important roles in growth, contact inhibition, and apoptosis. The aberrant expression of these molecules results in many diseases, including cancer. ICAM-1 and VCAM-1 are two types of cell adhesion molecules.

CONTENTS

1. Overview and Key Difference
2. What is ICAM-1 
3. What is VCAM-1
4. Similarities – ICAM-1 and VCAM-1
5. ICAM-1 vs VCAM-1 in Tabular Form
6. Summary – ICAM-1 vs VCAM-1

What is ICAM-1?

Intracellular adhesion molecule-1 (ICAM-1) is a cell adhesion molecule that is constitutively expressed in the membranes of leukocytes and endothelial cells. It is also known as CD54 (cluster differentiation 54) protein. In humans, this protein is encoded by the ICAM-1 gene. It is a surface glycoprotein. ICAM-1 is continuously present in low concentrations in the membranes of leukocytes and endothelial cells.  It usually binds to integrins of type CD11a/CD18 or CD11b/CD18. ICAM-1 is also exploited by the rhinovirus as a receptor for entry into the epithelium of the respiratory system.

ICAM-1 is a member of the immunoglobulin superfamily. This superfamily includes antibodies and T cell receptors as well. Moreover, this protein is a transmembrane protein. It contains an amino-terminus extracellular domain, a single transmembrane domain and a carboxy-terminus cytoplasmic domain. ICAM-1 has heavy glycosylation. The extracellular domain of this protein conations multiple loops created by disulphide bonds. The main function of this protein is stabilizing cell to cell interactions and facilitating leukocyte endothelial transmigration. It also plays an important role in spermatogenesis and signal transduction.

What is VCAM-1?

Vascular cell adhesion molecule-1 (VCAM-1) is a cytokine-inducible cell adhesion molecule that is expressed only in the membranes of vascular endothelial cells. It is also called CD106 (cluster differentiation 106). This cell adhesion molecule is a protein encoded by the VCAM1 gene in humans. VCAM-1 gene contains six or seven immunoglobulin domains.VCAM-1 is expressed on both large and small blood vessels after cytokines stimulate endothelial cells. This protein is a cell surface sialoglycoprotein. Furthermore, it is a type 1 membrane protein that is a member of the Ig superfamily.

The main function of VCAM-1 is mediating the adhesion of lymphocytes, monocytes, eosinophils, and basophils to vascular endothelium. It is also involved in leukocyte-endothelial cell signal transduction. Moreover, it may play a role in the development of atherosclerosis and rheumatoid arthritis.

What are the Similarities Between ICAM-1 and VCAM-1?

• ICAM-1 and VCAM-1 are two types of cell adhesion molecules.
• Both are calcium-independent cell adhesion molecules.
• They belong to the class of Ig superfamily cell adhesion molecules (IgSF CAMs).
• They have extracellular domains containing Ig-like domains.
• Aberrant expression of both adhesion molecules can cause diseases in humans.

What is the Difference Between ICAM-1 and VCAM-1?

ICAM-1 is a cell adhesion molecule that is constitutively expressed in the membranes of leukocytes and endothelial cells, while VCAM1 is a cell adhesion molecule that is expressed in the membranes of vascular endothelial cells only after stimulated by cytokines. So, this is the key difference between ICAM-1 and VCAM-1. Furthermore, ICAM-1 is coded by the ICAM-1 gene in humans, while VCAM-1 is encoded by the VCAM-1 gene in humans.

The following infographic lists the differences between ICAM-1 and VCAM-1 in tabular form for side by side comparison.

Summary – ICAM-1 vs VCAM-1

Cell adhesion molecules are important components in maintaining the tissue structure and function. They are cell-surface proteins. They are involved in the binding of cells with other cells. ICAM-1 and VCAM-1 are two types of cell adhesion molecules. ICAM-1is constitutively expressed in the membranes of leukocytes and endothelial cells, while VCAM1 is expressed in the membranes of vascular endothelial cells only after stimulated by cytokines. Thus, this summarizes the difference between ICAM-1 and VCAM-1.

Reference:

1. “Intercellular Adhesion MOLECULE 1.” An Overview | ScienceDirect Topics.
2. “Vascular Cell Adhesion Molecule 1.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Synapse immunologique” By Tai Yu, Wang Qingtong, Korner Heinrich, Zhang Lingling, Wei WeiMolecular Mechanisms of T Cells Activation by Dendritic Cells in Autoimmune DiseasesFrontiers in Pharmacology Vol 9, 2018, page 642 DOI=10.3389/fphar.2018.00642 – (CC BY-SA 4.0) via Commons Wikimedia
2. “VLA-4 Figure” By Immcarle66 – Own work (CC BY-SA 4.0) via Commons Wikimedia