ERBB2 (v-erb-b2 erythroblastic leukemia viral oncogene homolog 2, neuro/glioblastoma derived oncogene homolog (avian))
2011-05-01 Luca Braccioli , Marilena V Iorio , Patrizia CasaliniIdentity
DNA/RNA
Description
Polymorphisms: allelic variations at amino acid positions 654 and 655 of isoform (a) (positions 624 and 625 of isoform (b)) have been reported, with the most common allele B1 (Ile-654/Ile-655); allele B2 (Ile-654/Val-655); allele B3 (Val-654/Val-655). This nucleotide polymorphism could be associated with development of gastric carcinoma and with breast cancer risk, particularly among younger women.
Transcription
- mRNA transcript variant: this variant (1) represents the shorter transcript but encodes the longer isoform (a) (protein: erbB-2 isoform (a)).
- mRNA transcript variant: this variant (2) (protein: erbB-2 isoform (b)) contains additional exons at its 5 end and lacks an alternate 5 noncoding exon, compared to variant (1). These differences result in translation initiation at an in-frame, downstream AUG and an isoform (b) with a shorter N-terminus compared to isoform (a).
- mRNA transcript variant: herstatin HER2-ECD 1300 bp alternative erbB-2 transcript that retains intron 8. This alternative transcript specifies 340 residues identical to subdomains I and II from the extracellular domain of p185erbB-2 followed by a unique C-terminal sequence of 79 aa encoded by intron 8. The herstatin mRNA is expressed in normal human fetal kidney and liver, but is at reduced levels relative to p185erbB-2 mRNA in carcinoma cells that contain an amplified erbB-2 gene.
- mRNA transcript variant: an alternative transcript form of the human homologous gene erbB-2, containing an in-frame deletion encompassing exon 19, has been detected in human breast carcinomas.
- mRNA transcript variant: an alternative transcript form of the human homologous gene erbB-2, called HER2Δ16, has been detected in human breast carcinomas. This splicing variant, contains an in-frame deletion and encodes a receptor lacking exon 16, which immediately precedes the transmembrane domain containing two cysteines. The loss of these cysteine residues might induce a change in the conformation of HER2 receptor extracellular domain that promotes intermolecular disulfide bonding and, in turn, homodimers capable of transforming cells. Ectopic expression of HER2Δ16 promotes receptor dimerization, cell invasion, and trastuzumab resistant tumor cell lines. The potential metastatic and oncogenic properties of HER2Δ16 were mediated through direct coupling of HER2Δ16 to Src kinase.
Proteins
Description
Expression
Localisation
Function
For the other member of the HER family, ligand binding induces receptor homo- or heterodimerization, which is essential for TKs activation and subsequent recruitment of target proteins, in turn initiating a complex signaling cascade that leads into distinct transcriptional programs. There are several HER-specific ligands. HER2, which apparently has no direct or specific ligand, plays a major coordinating role in the HER network because of its ability to enhance and stabilize the dimerization: each receptor with a specific ligand appears in fact to prefer HER-2 as its heterodimeric partner. HER-2-containing heterodimers are characterized by extremely high signaling potency because HER-2 dramatically reduces the rate of ligand dissociation, allowing strong and prolonged activation of downstream signaling pathways.
Signaling and cellular
The most important intracellular pathways activated by HER2 are those involving mitogen activated protein kinase (MAPK) and phosphatidylinositol-3 kinase (PI3K). HER2 expression in cancer, besides its role in proliferation, enhances and prolongs survivals signals, associating up-regulation of this receptor to the malignant phenotype. At the same time, and depending on cellular status, the role of this receptor in controlling cell fate can also lead to differentiation and apoptosis.
Physiological
Role in development and differentiation:
- HER2 has several non-oncogenic roles in regulating growth, differentiation, apoptosis and/or remodeling in normal mammary glands. Dominant-negative forms of HER2 have significant defects in mammary development and lactation.
- HER2 has an important role in development and function of heart. Cre-Lox technology to mutate erbB-2 specifically in ventricular cardiomyocytes leads to a severe cardiomyopathy. This is inferred also by the adverse cardiac side effects observed in breast cancer patients treated with the monoclonal anti-HER2 Ab Trastuzumab.
- HER2 has a role in control of Schwann cell myelination and it has been demonstrated that HER2 signaling is also critical for oligodendrocyte differentiation in vivo.
- HER2 has a dual role in both muscle spindle maintenance and survival of myoblasts. Muscle-specific HER2 KO results in fact in viable mice with a progressive defect in proprioception due to loss of muscles spindles.
Homology
Mutations
Somatic
In non small cell lung cancer (adenocarcinoma) the following erbB-2 mutations were found: insertion/duplication of GCATACGTGATG at nucleotide 2322 of the erbB-2 gene, resulting in a 4-amino acid insertion (AYVM) at codon 774. Insertion of CTGTGGGCT at nucleotide 2335 of the erbB-2 gene, resulting in a 3-amino acid insertion (VGS) starting at codon 779; a 2-bp substitution in the erbB-2 gene, TT-CC at nucleotides 2263 and 2264, resulting in a leu755-to-pro (L755P) substitution.
In lung cancer a C44645G transition in the erbB-2 gene that caused a pro1170-to-ala substitution (P1170A).
In a glioblastoma a 2740G-A transition in the erbB-2 gene that caused a glu914-to-lys substitution (E914K).
In a gastric tumor a 2326G-A transition in the erbB-2 gene that caused a gly776-to-ser (G776S) substitution.
In an ovarian tumor, a 2570A-G transition in the erbB-2 gene that caused an asn857-to-ser (N857S) substitution.
Implicated in
Article Bibliography
Other Information
Locus ID:
NCBI: 2064
MIM: 164870
HGNC: 3430
Ensembl: ENSG00000141736
Variants:
dbSNP: 2064
ClinVar: 2064
TCGA: ENSG00000141736
COSMIC: ERBB2
RNA/Proteins
Expression (GTEx)
Pathways
Protein levels (Protein atlas)
PharmGKB
References
Citation
Luca Braccioli ; Marilena V Iorio ; Patrizia Casalini
ERBB2 (v-erb-b2 erythroblastic leukemia viral oncogene homolog 2, neuro/glioblastoma derived oncogene homolog (avian))
Atlas Genet Cytogenet Oncol Haematol. 2011-05-01
Online version: http://atlasgeneticsoncology.org/gene/162/erbb2
Historical Card
2004-12-01 ERBB2 (v-erb-b2 erythroblastic leukemia viral oncogene homolog 2, neuro/glioblastoma derived oncogene homolog (avian)) by Patrizia Casalini,Marilena V Iorio Affiliation