CD138 SDC1 (syndecan 1), B-B4
Molecule TypeAntigen ExpressionMolecular Weight
Min / Max
Non-lineage Restricted Molecule
Type 1 glycoprotein
Plasma Cell
Epithelial Cell
Endothelial Cell
B Cell
Neural Cell
Muscle, Smooth
Mesenchymal Cell
Endothelium
Keratinocyte
Breast
Cancer cell
100 / 100
200 / 200

Expression
CD138 is expressed by epithelial cells and B-lineage cells (pre-B cells and immature cells).  In the B lineage, bone marrow B-cell precursors express CD138, which is lost prior to maturation and release B lymphocytes into the circulation.  CD138 is expressed upon plasma cell including the malignant plasma cells of multiple myeloma and on some lymphomas.  It is expressed on endothelial cells and on keratinocytes during wound healing and on malignant keratinocytes.  CD138 is expressed on endothelial during embryogenesis and on the basolateral surfaces of epithelial cells, embryonic mesenchymal cells, vascular smooth muscle cells, endothelium, neural cells, endothelial cells and breast cancer cells.

Structure
MOLECULAR FAMILY NAME: Belongs to the syndecan proteoglycan family.

CD138 is a single-pass type-1 310 aa glycoprotein.  It contains a signal peptide, a 251 aa extracellular domain which contains  5 potential glycosaminoglycan attachment sites, a protease cleavage site at its C-terminus and 2 serine clusters, the proximal cluster bears chondroitin sulfate while the distal cluster bears heparan sulfate, a 34 aa transmembrane domain and a 25 aa intracellular cytoplasmic domain which interacts with cytoskeletal components.

In the mouse, there are 3 distal sites, Ser20, Ser28 and Ser30, which are usually modified by heparan sulfate (HS), whereas the 2 sites close to the membrane, Ser190 and Ser200 which is equivalent to Ser189 and Ser199 in the human, are usually occupied by chrondroitin sulfate (CS).  The structure of the GAG chains may be cell type specific. CD138 is >90% highly conserved between the human and the mouse.  The single N-glycosylation site may serve to regulate the glycanation of the distal cluster.  CD138 is closely related to syndecan-2 fibroglycan, syndecan-3 N-syndecan and syndecan-4 amphiglycan or ryudocan.  Although the extracellular protein cores are different they have very similar transmembrane and cytoplasmic domains.  Their expression patterns also vary, suggesting that they have tissue-specific functions.

MOLECULAR MASS
Cell Type Unreduced Reduced
Immature B cells 92 kDa
Plasma cells 85 kDa

POST-TRANSCRIPTIONAL MODIFICATION: No information.

POST-TRANSLATIONAL MODIFICATION: No information.
    

Ligands
LIGANDS AND MOLECULES ASSOCIATED WITH CD138

CD138-bound heparan sulphate binds growth factors and has been shown to bind many extracellular matrix proteins through its HS side-chains, including fibronectin, collagen types 1, 3 and 5, tenascin, thrombospondin and antithrombin 3.  The cytoplasmic region of CD138 is known to interact with actin-rich microfilaments.  CD138 on the cell surface may be regulated to form oligomeric complexes, since antibody-induced clustering causes CD138 to become insoluble in non-ionic detergents.  This aggregation is mediated by the transmembrane segment. CD138 has been shown to bind fibroblast growth factor 2 (FGF-2).

Function
CD138 is involved in the control of cell shape in mature and developing epithelia.  It is also involved in adhesion with the ligand depending on the cell bearing the molecule.  CD138 is a cell surface proteoglycan that bears both heparan sulfate and chondroitin sulfate and that links the cytoskeleton to the interstitial matrix.  The extracellular heparan sulfate binds growth factors and extracellular matrix constituents including the basic fibroblast growth factor, collagens, thrombospondin and fibronectin.  CD138 thus is though to have roles in growth factor action, extracellular matrix adhesion and cytoskeletal organization that controls cell morphology.  CD138 is an extracellular matrix receptor (ECM). It may serve as a co-receptor for fibroblast growth factor (FGF) and related molecules.  FGF-2 appears to require an association with HS-bearing molecules such as CD138 to transduce signals via the FGF receptor. 

BIOCHEMICAL ACTIVITY: No information.

DISEASE RELEVANCE AND FUNCTION OF CD138 IN INTACT ANIMAL

CD138 mediates hepatocyte growth factor binding and promotes Met signaling in multiple myeloma.  It has been demonstrated that CD138 can function as in trans HIV receptors via binding HIV-1 gp120 to syndecan heparan sulfate chains.  It has been suggested that CD138-rich endothelial cell lining the vasculature can provide a microenvironment that boosts HIV replication in T cells.  CD138 is used as a marker of plasma cells and for Reed-Sternberg cells.  CD138 is potentially useful as a therapeutic agent for destruction of multiple myeloma cells.


Comments
MOLECULAR INTERACTIONS-
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD138: No information.

SUBSTRATES: No information.

ENZYMES WHICH MODIFY CD138: No information.


Database accession numbers
AnimalPIRSWISSPROTEMGBL/GENBANK
 
HumanEntrezgene 6382P18827
MouseS06619P18828X15487
MouseZ22532
Antibodies

Revised June 25, 2008


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