ICAM1 Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">ICAM1 Protein</th>
</tr>
<tr>
<td class="label">
Protein Name</td>
<td>Intercellular Adhesion Molecule 1</td>
</tr>
<tr>
<td class="label">
Gene Symbol</td>
<td>ICAM1</td>
</tr>
<tr>
<td class="label">
Protein Length</td>
<td>532 amino acids</td>
</tr>
<tr>
<td class="label">
Molecular Weight</td>
<td>~90 kDa (unglycosylated); 110-120 kDa (glycosylated)</td>
</tr>
<tr>
<td class="label">
UniProt ID</td>
<td>P05362</td>
</tr>
<tr>
<td class="label">
PDB Structures</td>
<td>1IC1, 1IAQ, 1P53, 2AYZ</td>
</tr>
<tr>
<td class="label">
Cellular Location</td>
<td>Plasma membrane (type I transmembrane); also secreted as soluble form</td>
</tr>
<tr>
<td class="label">
Protein Family</td>
<td>Immunoglobulin superfamily (IgSF)</td>
</tr>
<tr>
<td class="label">Integrin</td>
<td>Alternative Name</td>
</tr>
<tr>
<td class="label">
ITGAL/CD11a</td>
<td>LFA-1</td>
</tr>
<tr>
<td class="label">
ITGAM/CD11b</td>
<td>Mac-1</td>
</tr>
<tr>
<td class="label">
ITGAX/CD11c</td>
<td>αXβ2</td>
</tr>
<tr>
<td class="label">
ITGAM/CD11d</td>
<td>αDβ2</td>
</tr>
<tr>
<td class="label">Strategy</td>
<td>Agent</td>
</tr>
<tr>
<td class="label">
LFA-1 Antagonists</td>
<td>Lifitegrast (Efalizumab withdrawn)</td>
</tr>
<tr>
<td class="label">
Small Molecules</td>
<td>Variou
...ICAM1 Protein
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">ICAM1 Protein</th>
</tr>
<tr>
<td class="label">
Protein Name</td>
<td>Intercellular Adhesion Molecule 1</td>
</tr>
<tr>
<td class="label">
Gene Symbol</td>
<td>ICAM1</td>
</tr>
<tr>
<td class="label">
Protein Length</td>
<td>532 amino acids</td>
</tr>
<tr>
<td class="label">
Molecular Weight</td>
<td>~90 kDa (unglycosylated); 110-120 kDa (glycosylated)</td>
</tr>
<tr>
<td class="label">
UniProt ID</td>
<td>P05362</td>
</tr>
<tr>
<td class="label">
PDB Structures</td>
<td>1IC1, 1IAQ, 1P53, 2AYZ</td>
</tr>
<tr>
<td class="label">
Cellular Location</td>
<td>Plasma membrane (type I transmembrane); also secreted as soluble form</td>
</tr>
<tr>
<td class="label">
Protein Family</td>
<td>Immunoglobulin superfamily (IgSF)</td>
</tr>
<tr>
<td class="label">Integrin</td>
<td>Alternative Name</td>
</tr>
<tr>
<td class="label">
ITGAL/CD11a</td>
<td>LFA-1</td>
</tr>
<tr>
<td class="label">
ITGAM/CD11b</td>
<td>Mac-1</td>
</tr>
<tr>
<td class="label">
ITGAX/CD11c</td>
<td>αXβ2</td>
</tr>
<tr>
<td class="label">
ITGAM/CD11d</td>
<td>αDβ2</td>
</tr>
<tr>
<td class="label">Strategy</td>
<td>Agent</td>
</tr>
<tr>
<td class="label">
LFA-1 Antagonists</td>
<td>Lifitegrast (Efalizumab withdrawn)</td>
</tr>
<tr>
<td class="label">
Small Molecules</td>
<td>Various inhibitors</td>
</tr>
<tr>
<td class="label">
Antibodies</td>
<td>Anti-ICAM1 monoclonal</td>
</tr>
<tr>
<td class="label">
Gene Therapy</td>
<td>siRNA/shRNA</td>
</tr>
<tr>
<td class="label">
Natural Compounds</td>
<td>Curcumin, resveratrol</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a>, <a href="/wiki/anxiety" style="color:#ef9a9a">Anxiety</a>, <a href="/wiki/atherosclerosis" style="color:#ef9a9a">Atherosclerosis</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">256 edges</a></td>
</tr>
</table>
Introduction
Icam1 Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Overview
Intercellular Adhesion Molecule 1 (ICAM1) is a 532-amino acid type I transmembrane glycoprotein that serves as a critical mediator of leukocyte adhesion, neuroinflammation, and blood-brain barrier (BBB) dysfunction in neurodegenerative diseases[@dustin1986]. ICAM1 is expressed on endothelial cells, epithelial cells, fibroblasts, and immune cells, with its expression dramatically upregulated by proinflammatory cytokines[@collins1995].
Domain Structure
The ICAM1 protein contains four distinct structural domains[@springer1994]:
Extracellular Domain (24-453 aa)
- Ig-like domain D1 (24-117 aa): N-terminal domain containing the primary integrin binding site[@shimaoka2003]
- Ig-like domain D2 (118-212 aa): Stabilizes the protein structure
- Ig-like domain D3 (213-305 aa): Contributes to ligand binding
- Ig-like domain D4 (306-400 aa): Provides structural flexibility
- Ig-like domain D5 (401-453 aa): C-terminal extracellular domain
Transmembrane Domain (454-477 aa)
- Single α-helical membrane-spanning segment
- Anchors the protein in the plasma membrane
Cytoplasmic Tail (478-532 aa)
- Contains serine and threonine residues for phosphorylation
- Involved in intracellular signaling
- Essential for protein localization and function
Molecular Function
Receptor Binding
ICAM1 serves as the primary ligand for leukocyte integrins[@hynes1992]:
The D1 Ig-like domain contains the primary integrin binding site, specifically the "ADMIDAS" and "MIDAS" metal ion-dependent adhesion sites[@shimaoka2003].
Signaling Functions
- Outside-in signaling: Integrin binding triggers intracellular signaling cascades
- Immune synapse formation: Critical for immunological synapse between T cells and antigen-presenting cells[@grakoui1999]
- Leukocyte activation: Co-stimulatory signals for T cell activation
Post-Translational Modifications
Glycosylation
ICAM1 is heavily N-glycosylated with complex-type oligosaccharides at multiple asparagine residues[@diamond1991]:
- N-glycosylation affects protein folding
- Influences ligand binding affinity
- Modulates receptor interactions
Phosphorylation
The cytoplasmic tail is phosphorylated on serine and threonine residues[@volpes1991]:
- Regulates protein-protein interactions
- Affects intracellular trafficking
Soluble ICAM1 (sICAM1)
Alternative splicing and proteolytic cleavage produce soluble forms[@becker2010]:
- Lacks transmembrane domain
- Can function as a decoy receptor
- Elevated in inflammatory conditions
- Used as a biomarker
Structural Insights
Crystal Structures
Several crystal structures reveal the molecular details[@shimaoka2003]:
- 1IC1: ICAM1 D1-D2 domains with LFA-1
- 1IAQ: ICAM1 D1 with LFA-1 I domain
- 1P53: ICAM1 D1-D3
- 2AYZ: ICAM1 D1 with antibodies
The five Ig-like domains are connected by flexible linkers, allowing the protein to adopt multiple conformations and engage multiple ligands simultaneously[@mccloskey1997].
Role in Neurodegenerative Diseases
Alzheimer's Disease (AD)
ICAM1 contributes to AD pathogenesis through multiple mechanisms[@akiyama2000][@grammas2011]:
- [BBB](/entities/blood-brain-barrier) dysfunction: Elevated expression on brain endothelial cells disrupts the blood-brain barrier[@zlokovic2008]
- Immune cell infiltration: Mediates peripheral immune cell trafficking into the brain[@michaud2013]
- Neuroinflammation: Facilitates microglial activation and proinflammatory cytokine production[@liu2018]
- Cerebral amyloid angiopathy (CAA): Associated with vascular amyloid deposits[@weller2009]
- Therapeutic target: ICAM1-LFA-1 antagonists under investigation[@yednock1992]
Parkinson's Disease (PD)
In PD, ICAM1 mediates neuroinflammation[@zerlauth1997][@mcgeer1988]:
- Substantia nigra: Increased expression in dopaminergic regions[@wang2019]
- Microglial activation: Facilitates recruitment of peripheral macrophages[@croisier2005]
- BBB permeability: Contributes to blood-brain barrier breakdown[@kortekaas2005]
- Disease progression: Levels correlate with motor symptom severity[@chen2018]
Multiple Sclerosis (MS)
ICAM1 is crucial for immune cell entry into the CNS[@sobel1993]:
- Leukocyte trafficking: Essential for T cell migration across the BBB[@cannella1998]
- Lesion formation: Elevated in active demyelinating lesions[@lee1999]
- Clinical therapy: Natalizumab blocks α4-integrin, preventing ICAM1-mediated adhesion[@polman2006]
Amyotrophic Lateral Sclerosis (ALS)
ICAM1 is elevated in ALS and contributes to inflammation[@baron2005]:
- Motor [cortex](/brain-regions/cortex): Upregulated in motor cortex blood vessels[@kim2016]
- Spinal cord: Mediates inflammatory cell infiltration[@rossi2012]
- Disease progression: Correlates with rate of functional decline[@fiala2010]
Stroke and TBI
ICAM1 mediates post-injury neuroinflammation[@beschorner2007][@huang2000]:
- Ischemic injury: Rapidly upregulated after stroke[@zhang1998]
- Reperfusion injury: Contributes to secondary damage[@petty2009]
- Therapeutic target: ICAM1 inhibitors show neuroprotective potential[@nimmerjahn2005]
Expression and Regulation
Cellular Expression
- Endothelial cells: High expression at cell junctions
- Epithelial cells: Inducible expression
- Fibroblasts: Cytokine-responsive
- Immune cells: Constitutive on some, inducible on others
- [Neurons](/entities/neurons): Induced under pathological conditions[@andersson2005]
- [Astrocytes](/entities/astrocytes): Variable in reactive states[@saliba2014]
- [Microglia](/entities/microglia): Inducible expression[@lee1993]
Regulatory Mechanisms
- [NF-κB](/entities/nf-kb): Primary transcriptional regulator[@collins1995]
- Cytokines: TNF-α, IL-1β, IFN-γ strongly induce expression
- Shear stress: Mechanical forces modulate expression
- Oxidative stress: Increases ICAM1 expression[@chiu2008]
Therapeutic Targeting
Diagnostic and Prognostic Value
Biomarker Applications
- Soluble ICAM1: Elevated in AD, PD, MS, stroke[@rentzos2009]
- Blood/CSF correlation: Reflects CNS inflammation
- Disease staging: Higher levels with advanced disease[@zetterberg2016]
- Treatment monitoring: Changes with therapy response
Research Applications
- Structural studies: ICAM1-integrin interactions
- Drug screening: High-throughput assays for inhibitors
- Animal models: ICAM1 knockout mice for function studies
See Also
- [VCAM1 Protein](/proteins/vcam1-protein) - Vascular Cell Adhesion Molecule 1
- [PECAM1 Protein](/proteins/pecam1-protein) - Platelet Endothelial Cell Adhesion Molecule 1
- [LFA-1 (ITGAL) Protein](/proteins/itgal-protein) - Integrin Alpha L
- [Mac-1 (ITGAM) Protein](/proteins/itgam-protein) - Integrin Alpha M
- [TNF Protein](/proteins/tnf-protein) - Tumor Necrosis Factor
- [Neuroinflammation Pathway](/mechanisms/neuroinflammation-pathway)
- [Blood-Brain Barrier Dysfunction](/mechanisms/blood-brain-barrier-dysfunction)
- [Leukocyte Extravasation Signaling](/mechanisms/leukocyte-extravasation)
- [TNF Signaling Pathway](/mechanisms/tnf-signaling-pathway)
Background
The study of Icam1 Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
External Links
- [PubMed](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
- [Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
- [Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data
References
[Dustin ML, et al, (1986) (1986)](https://pubmed.ncbi.nlm.nih.gov/2426277/)
[Collins T, et al, (1995) (1995)](https://pubmed.ncbi.nlm.nih.gov/7544006/)
[Unknown, Springer TA (1994) (1994)](https://pubmed.ncbi.nlm.nih.gov/7515918/)
[Shimaoka M, et al, (2003) (2003)](https://pubmed.ncbi.nlm.nih.gov/12530978/)
[Unknown, Hynes RO (1992) (1992)](https://pubmed.ncbi.nlm.nih.gov/1534403/)
[Grakoui A, et al, (1999) (1999)](https://pubmed.ncbi.nlm.nih.gov/10535941/)
[Diamond MS, et al, (1991) (1991)](https://pubmed.ncbi.nlm.nih.gov/1826941/)
[Volpes R, et al, (1991) (1991)](https://pubmed.ncbi.nlm.nih.gov/1712826/)
[Becker M, et al, (2010) (2010)](https://pubmed.ncbi.nlm.nih.gov/20048155/)
[McCloskey N, et al, (1997) (1997)](https://pubmed.ncbi.nlm.nih.gov/9083890/)
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