Table 1. Mammalian TGF-β family members and receptors.
(*) TGFBR1 is also known as TβRI or ALK5; ACVR1A as ActR1A or ALK2; ACVR1B as ActR1B or ALK4; ACVR1C as ALK7; BMPR1A and BMPR1B as ALK3 and ALK6, respectively; ACVR2 and ACVR2B as ActRII and ActRIIB, respectively; and ACVRL1 as ALK1 or TSR1. (**) Inhibin, lefty, and BMP3 block the receptors for Activins, Nodal, and BMPs, respectively. Not included is GDF15, a distant member of the TGF-β family that binds to GDNF receptor α-like (GFRAL). GFRAL and related receptors for artemin, neurturin, persephin, and glial-derived neurotrophic factor (GDNF) signal through the receptor tyrosine kinase RET257
| Ligand | Type I Receptor | Type II Receptor | Co-receptor | Smad |
|---|---|---|---|---|
| TGFβ-1 | TGFBR1 * | TGFBR2 | Betaglycan | SMAD2/3 |
| TGFβ-2 | TGFBR1 | TGFBR2 | Betaglycan | SMAD2/3 |
| TGFβ-3 | TGFBR1 | TGFBR2 | Betaglycan | SMAD2/3 |
| Activin A | ACVR1B, ACVR1C | ACVR2A, ACVR2B | SMAD2/3 | |
| Activin B | ACVR1B, ACVR1C | ACVR2A, ACVR2B | SMAD2/3 | |
| Activin C | ACVR1B, ACVR1C | ACVR2A, ACVR2B | SMAD2/3 | |
| Activin E | ACVR1B, ACVR1C | ACVR2B | SMAD2/3 | |
| Nodal | ACVR1B, ACVR1C | ACVR2A, ACVR2B | Cripto, Cryptic | SMAD2/3 |
| GDF1 | ACVR1B, ACVR1C | ACVR2A, ACVR2B | Cripto, Cryptic | SMAD2/3 |
| GDF3 | ACVR1B, ACVR1C | ACVR2A, ACVR2B | Cripto, Cryptic | SMAD2/3 |
| GDF8/Myostatin | ACVR1B, ACVR1C | ACVR2A | SMAD2/3 | |
| GDF9 | ACVR1B | BMPR2 | SMAD2/3 | |
| GDF11 | ACVR1B, TGFBR1 | ACVR2A, ACVR2B | SMAD2/3 | |
| Inhibin ** | –– | ACVR2A | Betaglycan | –– |
| Lefty-1 ** | –– | –– | Cripto, Cryptic | –– |
| Lefty-2 ** | –– | –– | Cripto, Cryptic | –– |
| BMP2 | BMPR1A BMPR1B | ACVR2A, ACVR2B, BMPR2 | RGM | SMAD1/5 |
| BMP4 | BMPR1A BMPR1B | ACVR2A, ACVR2B, BMPR2 | SMAD1/5 | |
| BMP5 | ACVR1A, BMPR1A, BMPR1B | ACVR2A, ACVR2B, BMPR2 | SMAD1/5 | |
| BMP6 | ACVR1A, BMPR1A, BMPR1B | ACVR2A, ACVR2B, BMPR2 | RGM | SMAD1/5 |
| BPM7 | ACVR1A, BMPR1A, BMPR1B | ACVR2A, ACVR2B, BMPR2 | SMAD1/5 | |
| BPM8 | ACVR1A, BMPR1A, BMPR1B | ACVR2A, ACVR2B, BMPR2 | SMAD1/5 | |
| BPM8B | BMPR1A, BMPR1B | ACVR2A, BMPR2 | SMAD1/5 | |
| BMP9/GDF2 | ACVRL1 | ACVR2, BMPR2 | Endoglin | SMAD1/5 |
| BMP10 | ACVRL1 | ACVR2, BMPR2 | Endoglin | SMAD1/5 |
| BMP15 | BMPR1B | BMPR2 | SMAD1/5 | |
| GDF5 | BMPR1A, BMPR1B | ACVR2, ACVR2B, BMPR2 | SMAD1/5 | |
| GDF6 | BMPR1A, BMPR1B | ACVR2, ACVR2B, BMPR2 | SMAD1/5 | |
| GDF7 | BMPR1A, BMPR1B | ACVR2, ACVR2B, BMPR2 | SMAD1/5 | |
| GDF10 | BMPR1A, BMPR1B | ACVR2, ACVR2B, BMPR2 | SMAD1/5 | |
| AMH | ACVR1A, BMPR1A, | AMHR2 | SMAD1/5 | |
| BMP3 ** | –– | ACVR2B | –– |