ICAM-5 ICAM-5(intracellular adhesion molecule), TLN, TLCN(telencephalin)
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Lineage Restricted Molecule
Type 1 glycoprotein
Neuron
125 / 135
515 / 525

Expression
ICAM-5 is expressed on neurons in the telencephalon of mammalian brain.  No other expression has been observed.

Structure
MOLECULAR FAMILY NAME: intracellular adhesion molecule family -->immunoglobulin supergene family.

ICAM-5 is a type 1 glycoprotein.  It is a nueron-specific adhesion molecule in the telencephalon region of the brain that binds leukocytes.  It is a member of the immunoglobulin superfamily of proteins and is closely related to other members of the ICAM-family.  ICAM-5 is comprised of 9 Ig-like domains, 1 transmembrane region and 1 C-terminal cytoplasmic tail.  The binding regions for leukocytes has been mapped.  The binding region for leukocyte CD11a/CD18 integrin is in the 1st immunoglobulin domain and homophilic binding occurs via binding of the 1st domain to domains 4-5. 

MOLECULAR MASS
Cell Type Unreduced Reduced Comment
Adult brain 520 kDa 130 kDa Apparent tetramer in adult brain
Newborn brain 130 kDa 130 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION

ICAM-5 is N-glycosylated but probably not O-glycosylated.  No details are known about its carbohydrate chains.  HNK-1 carbohydrate antigen is present in ICAM-5.  The possible phosphorylation of ICAM-5 has not been studied.  ICAM-5 is also found in soluble form in the cerebrospinal fluid, evidently due to proteolytic cleavage.

Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH ICAM-5
Molecule Comment
CD11a/CD18 (LFA-1) Mediates cell adhesion
ICAM-5 ICAM-5 shows homophilic binding to itself and evidently forms a tetramer.  The monomer/tetramer transition may be important in the regulation of adhesion




Function
ICAM-5 is a ligand that binds to the leukocyte integrin CD11a/CD18 LFA-1 but it also shows homophilic binding and therefore it may be important in neuron-neuron binding.  ICAM-5 is a stimulatory molecule for dendritic outgrowth.  During development in the rat it shows a monomer/high molecular weight switch, which co-relates with the time of dendrite formation.

BIOCHEMICAL ACTIVITY:

ICAM-5 is not known to have any enzymatic function.  The main activity of ICAM-5 is in cellular adhesion.

DISEASE RELEVANCE AND FUNCTION OF ICAM-5 IN INTACT ANIMAL

Little is known about the in vivo function of ICAM-5.  ICAM-5 may be important for the interaction of microglia cells with neurons and also for neuron-neuron interaction.  Furthermore ICAM-5 may be important for dendritic formation during development and is involved in long term potentiation of synaptic transmission in hippocampus.  A soluble form of ICAM-5 is found in the cerebrospinal fluid, in plasma and the levels increase during inflammation and other conditions in the brain.


Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF ICAM-5: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY ICAM-5: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
Antibodies

Revised June 25, 2008


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