Table 1.

EGF signaling family.

Ligands	Receptors	Signaling protiens
EGF	ErbB1	Akt
TGFα	ErbB2*	GAP/Ras
HB-EGF	ErbB3#	HB-EGF
Amphiregulin	ErbB4	Jak
β-cellulin		PKC
Epiregulin		PLCγ
NRG1		Shp2
Glial growth factor (GGF2)		STAT
Heregulin (HRG)		PAK-JNKK-JNK
SMDF		RAF-MEK-MAPK
ARIA
NDF
NRG2
NRG3
NRG4

Ligands: List of known ErbB ligands. Receptors: ErbBI (EGFR, HER1), ErbB2 (neu or HER2),

^*binds no ligand with high affinity, ErbB3 (HER3),

^#inactive catalytic domain, and ErbB4 (HER4). Signaling proteins: Only some of the pathways and transcription factors are represented in this table.

Abbreviations: Epidermal growth factor (EGF), Transforming growth factor-α, (TGFα), Heparin-binding EGF (HB-EGF), Neuregulin (NRG), Sensory and motor neuron-derived factor (SMDF), Acetylcholine receptor inducing activity (ARIA), and neu-differentiation factor (NDF). Akt, a serine/threonine kinase; GAP, GTPase activating protein; HB-EGF, heparin-binding EGF; Jak, janus kinase; PKC, protein kinase C; PLCγ, phospholipase Cγ, Shp2; Src homology domain-2-containing protein tyrosine phosphatase 2; STAT, signal transducer and activator of transcription; RAF-MEK-MAPK and PAK-JNKK-JNK, serine/threonine kinases. (Adapted from Yarden and Sliwkowski, 2001).