Table 1.
The ligand preference and G-protein-dependent signaling pathways of the free fatty acid receptors (FFARs). AC, adenylate cyclase; Akt (PKB), protein kinase B, DAG, diacylglycerol; IP3, inositol trisphosphate; PI3K, phosphatidylinositol 3-kinase; PKC, protein kinase C; PKD, protein kinase D; PLC, phospholipase C, ω3 PUFAs (ω3 polyunsaturated fatty acids: α-linolenic acid, eicosatrienoic acid, eicosapentenoic acid, docosahexaenoic acid), ω6 PUFAs (ω6 polyunsaturated fatty acids: linoleic acid, γ-linolenic acid, dihomo- γ-linolenic acid, arachidonic acid, docosatetraenoic acid).
| Type | Ligands | G-Protein Subunits | Primary Effector | Secondary Effectors, Effects |
|---|---|---|---|---|
| FFAR1 | MCFAs | Gs | AC | cAMP↑ |
| LCFAs | Gi | AC | cAMP↓ | |
| ω3 PUFAs | Gq | PLC | IP3 (Ca2+↑) | |
| ω6 PUFAs | DAG, PKC↑ | |||
| FFAR2 | SCFAs | Gi | PLC | PKC↑, ERK1/2↑ |
| AC | cAMP↓ | |||
| Gq | PLC | IP3 (Ca2+↑) | ||
| FFAR3 | SCFAs | Gi | AC | cAMP↓ |
| FFAR4 | LCFAs | Gq | PI3K | Akt↑ |
| ω3 PUFAs | PLC | IP3 (Ca2+↑) | ||
| ω6 PUFAs | DAG, PKC↑, ERK1/2↑ |