|CD340||ERBB2 (erythroblastic leukemia viral oncogene homolog 2), HER-2/neu|
|Molecule Type||Antigen Expression||Molecular Weight|
Min / Max
|Non-lineage Restricted Molecule|
Type 1 glycoprotein
|185 / 185|
CD340 is expressed by bone marrow CD271+ mesenchymal stem cells, subsets of C-ALL blasts and B lymphoblastis leukemia. Several types of epithelial cells express CD340 and many cancers including neuroblastomas and carcinomas of the breast, stomach, lung, ovary, colon, cervix and ovarian tumors.
|MOLECULAR FAMILY NAME: Belongs to the tyrosine kinase protein family.|
CD340 is a single-pass type-1 1233 aa glycoprotein. It contains a 630 aa extracellular domain which contains 4 domains (I-IV) and domain II and IV are cysteine-rich and 7 potential N-linked glycosylation sites, 23 aa transmembrane domain and a 580 aa intracellular cytoplasmic domain which contains a protein tyrosine kinase domain. CD340 encodes a member of the tyrosine kinase family of the epidermal growth factor (EGF) receptor subfamily. CD340 has 1 protein kinase domain has no ligand binding domain of its own and therefore cannot bind growth factors. However, it does bind tightly to other ligand-bound EGF receptor family members to form a heterodimer, stabilizing ligand binding and enhancing kinase-mediated activation of downstream signaling pathways, such as those involving mitogen-activated protein kinase and phosphatidylinositol-3 kinase.
Alternative splicing yields several isoforms but all of which have not been characterized.
CD340 has 7 potential N-linked glycosylation sites.
|LIGANDS AND MOLECULES ASSOCIATED WITH CD340|
Ligand binding increases phosphorylation of tyrosine kinases.
|Although no direct ligand has been observed for CD340, it forms heterodimers with ligand-bound ERBB family members and plexin-1. Heterodimerization stabilizes ligand binding and contributes to kinase-mediated activation of MAPK, phospholipase-Cγ and PI-3K signaling pathways. ERBB-heterodimers play a role in a wide range of cellular responses that vary depending on the ligand and the cell type. CD340 forms a stable complex with plexin-B1 bound to its ligand CD100 (Sema4D). CD340-mediated phosphorylation of plexin-B1 is involved in RhoA activation and ultimately in axonal growth cone collapse. |
BIOCHEMICALACTIVITY: No information.
DISEASE RELEVANCE AND FUNCTION OF CD340 IN INTACT ANIMAL
Homodimerization and receptor activation occurs when CD340 is overexpressed as occurs in several cancers. In most cases overexpression is the result of gene amplification and increased promoter activity rather than mutations. CD340 is a therapeutic target in the treatment of HER2-positive breast cancer with Trastuzumab (Herceptin). Overexpression by carcinoma cells correlates with aggressive disease and a poor prognosis. CD340 is a marker for bone marrow-MSC.
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD340: No information.
SUBSTRATES: No information.
ENZYMES WHICH MODIFY CD340: No information.
Database accession numbers
Revised June 25, 2008