Figure 1.

Schematic of HER2 signaling system.

Notes: HER2 homo- or heterodimers predominantly activate to major pathways, namely the RAS/MAP kinase and PI3K/AKT pathways, which drive the aberrant proliferation and survival of breast cancer cells. Inset depicts the major tyrosine residues phosphorylated upon HER2 activation, as well as the predominant downstream signaling system coupled to these events. See “Cell signaling mediated by HER” for additional details.

Abbreviations: Bcl-2, B-cell CLL/lymphoma 2; ERK, extracellular signal-regulated kinase; Grb2, growth factor receptor-bound protein 2; HER, human epidermal growth factor receptor; MEK, mitogen-activated protein kinase kinase; mTORC, mammalian target of rapamycin complex; P, phosphorylation site; PI3K, phosphoinositide 3-kinase; PIP₂, phosphatidylinositol-4,5-bisphosphate; PIP₃, phosphatidylinositol-3,4,5-trisphosphate; PTEN, phosphatase and tensin homologue; SOS, son of sevenless.