CD108 JMH(John-Milton-Hagen) human blood group antigen, SEMA7A (semaphorin 7A), GPI-gp80, Sema L, Sema K1, CDw108
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
GPI anchor
T Cell
Stromal Cell
Myeloid Cell
Erythrocyte
Lymphoblast
76 / 76
80 / 80

Expression
CD108, formally was CDw108, is expressed on erythrocytes, at low levels on circulating lymphocytes, myeloid and stromal cells, and at moderately high levels on lymphoblasts and lymphoblastic cell lines.  It is highly expressed on the leukemic T cell line HPB-ALL.


Structure
MOLECULAR FAMILY NAME: Belongs to the semaphoris family.

CD108 is a GPI-anchored 602 aa glycoprotein but the primary structure remains unknown.  It contains a 44 aa N-terminal signal sequence, a 500 aa extracellular domain which contains a semaphorin domain, 1 Ig-like C2-type domain, a RGD (Arg-Gly-Asp) cell attachment sequence and 5 potential N-linked glycosylation sites and a 19 aa C-terminal hydrophobic tail for the GPI-anchor that lacks a significant intracellular cytoplamsic tail.  CD108 is a member of the semaphorin family within the Ig superfamily.  Proteolytic release of CD108 from the cell surface is possible, however soluble CD108 is not normally present in plasma.

MOLECULAR MASS
Cell Type Unreduced Reduced Comment
Lymphocytes 76 kDa 80 kDa
Erythrocytes 76 kDa 80 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION

CD108 has 5 N-glycosylated sites which can estimate Mr of unglycolated form of 68 kDa.  Approximately 20% of the apparent molecular weight is accounted for by N-linked carbohydrate, as determined by endoglycosidase F treatment.

Ligands
Plexin C1, (CD232 and also known as VESPR), is a receptor for and binds to CD108.

LIGANDS AND MOLECULES ASSOCIATED WITH CD108
Molecule Comment
Tyrosine kinases Antibodies to CD108 coprecipitate protein kinases, most likely tyrosine kinases belonging to the Src family



Function
The function of CD108 is not clearly demonstrated but is thought to play a role in inflammation and may have a role monocyte activation and in regulating immune cells.  It is a member of semaphorin K1 family of proteins that are involved in neuronal growth cone guidance.  An adhesion function has been postulated but not proven for CD108.  Recombinant soluble CD108 was found to induces production of inflammatory cytokines such as TNF╬▒, IL-6 and IL-8 and is a chemotactic for monocytes.

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD108 IN INTACT ANIMAL

CD108 carries the John Milton Hagen (JMH) blood group antigen.  In a preliminary report, the deficiency of erythroid CD108 has been reported as associated with a rare form of congenital dyserythropoietic anemia.  CD108 is thought to play an important role in the nervous system and in modulating immune function.

Comments
The CD108 antigen is identical to the JMH erythrocyte blood group antigen.

MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD108: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD108: No information.

ADDITIONAL INSIGHTS:

Autoantibodies to this protein are relatively common and often associate with the loss of JMH antigen expression by circulating red cells.  CD108 can also be released from cells as a 67 kDa protein through proteolysis, however, soluble CD108 is not normally present in plasma.

Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 8482O75326
Antibodies

Revised June 25, 2008


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