Classes of PI 3-kinases
| PI 3-kinase . | Subunit composition . | In vivo substrate . | Activated by . |
|---|---|---|---|
| Class IA | Catalytic (p110α,β,δ) | PtdIns(4,5)P2 | RTKs, FcγR, Ras |
| Regulatory (p85α,β, p55γ) | |||
| Class IB | Catalytic (p110γ) | PtdIns(4,5)P2 | GPCRs, Ras |
| Regulatory (p101) | |||
| Class II | Catalytic (PI3K-C2α,β,γ) | PtdIns | LPA, insulin receptors |
| Class III | Catalytic (Vps34/hVps34) | PtdIns | Constitutive† |
| Regulatory (Vps15/p150) | |||
| Accessory (Vps30/Beclin1) | |||
| Accessory (Vps38 or Vps14)* |
| PI 3-kinase . | Subunit composition . | In vivo substrate . | Activated by . |
|---|---|---|---|
| Class IA | Catalytic (p110α,β,δ) | PtdIns(4,5)P2 | RTKs, FcγR, Ras |
| Regulatory (p85α,β, p55γ) | |||
| Class IB | Catalytic (p110γ) | PtdIns(4,5)P2 | GPCRs, Ras |
| Regulatory (p101) | |||
| Class II | Catalytic (PI3K-C2α,β,γ) | PtdIns | LPA, insulin receptors |
| Class III | Catalytic (Vps34/hVps34) | PtdIns | Constitutive† |
| Regulatory (Vps15/p150) | |||
| Accessory (Vps30/Beclin1) | |||
| Accessory (Vps38 or Vps14)* |
FcγR, receptor for immunoglobulin G; RTK, receptor tyrosine kinase; GPCR, G-protein-coupled receptor; LPA, lysophosphatidic acid.
Vps38 is part of the PI 3-kinase complex that mediates vacuolar protein sorting, whereas Vps14 is part of the PI 3-kinase complex that mediates autophagy. So far, mammalian homologs of these proteins have not been identified.
Stimulated to some extent by amino-acid-rich medium (Byfield et al., 2005). The h Vps34/p150 complex is also activated by the small GTPase Rab5, which can be activated by RTKs (Christoforidis et al., 1999; Murray et al., 2002; Barbieri et al., 2000).