CD44R CD44v, CD44v9
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
Epithelial Cell
Monocyte
Leukocyte
80 / 80
250 / 250

Expression
CD44R is expressed on a heterogeneous group of CD44 variant isoforms expressed constitutively on epithelial cells and monocyte lineage cells and can be upregulated in activated leukocytes.



Structure
MOLECULAR FAMILY NAME:  Belongs to the hyaladherin family.

CD44Ris a single-pass type-1 glycoprotein.  It contains an extracellular and has the same transmembrane and cytoplasmic domains as the standard form of CD44.  They contain almost all of the 341 aa of the major form of CD44 with an insertion of a variable number of aa, encoded by exons 6-14 in humans and in the membrane proximal region of the extracellular domain.  CD44R is a member of the cartilage link protein family.

MOLECULAR MASS
Cell Type Unreduced Reduced
Lymphocyte 85-200 kDa
Epithelial 85-250 kDa

POST-TRANSCRIPTIONAL MODIFICATION

CD44 exons 6-14, v2-v10, in humans can be variably spliced into the standard CD44 encoded by exons 1-5, 15-17, and 19 leading to the production of CD44 variant isoforms.

POST-TRANSLATIONAL MODIFICATION

Insertion of a variable number of aa in the membrane-proximal region of the extracellular domain due to alternative splicing gives additional sites for N- and O-linked carbohydrate modification.  Exon 8, a variant exon 3, containing CD44 isoforms can also be modified by heparin sulfate (HS).

Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD44R: No information.




Function
CD44R, and in particular CD44v6-containing isoforms, may be involved in leukocyte, aggregation, attachment to and rolling on endothelial cells, homing to peripheral lymphoid organs and to sites of inflammation.

BIOCHEMICAL ACTIVITY

The activity of many isoforms of CD44R remains to be clarified.  The expression of variant isoforms of CD44 appear to correlate with hyaluronan (HA)-binding, but this is not yet clear.

DISEASE RELEVANCE AND FUNCTION OF CD44R IN INTACT ANIMAL

Expression of CD44v6 in a non-metastatic rat pancreatic adenocarcinoma conferred metastatic potential, and mAbs to CD44v6 inhibited metastasis, suggesting a role for CD44v6-containing isoforms in tumor metastasis and uterine smooth muscle tumors.  Variant isoforms are involved in plasma adhesion to bone marrow stromal cells and in the multiple myeloma disease process.

Comments
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD44R: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD44R

Protein kinase C.

ADDITIONAL INSIGHTS

Isoforms of CD44 containing inserts of variant exons may be referred to by the various exons, 1-10 for mouse and rat and 2-10 for human, that they contain.  For example, a CD44 isoform containing variant exon 6 may be referred to as CD44v6 and an isoform containing CD44 variant exons 8, 9 and 10 may be referred to as CD44v8-10.

Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
Antibodies

Revised June 25, 2008


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