Table 2.
Amino acid transporter systems in the placenta
| Human gene name (protein/system) | Expression and localisation of mRNA expression from Simner et al. (2017) | Mechanism | Substrates |
|---|---|---|---|
|
SLC1A1 (EAAT3/XAG) SLC1A2 (EAAT2/XAG) SLC1A3 (EAAT1/XAG) SLC1A6 (EAAT4/XAG) SLC1A3 (EAAT5/XAG) |
mRNA; activity on MVM and BM (cannot distinguish family member); SLCA1,2,3 protein expressed but location unclear (Moe & Smith, 1989; Hoeltzli et al. 1990; Noorlander et al. 2004) | 3Na+/H+/AA cotransport/K+ exchange | D, E (Kanai et al. 2013) |
| SLC1A4 (ASCT1/ASC) | A, S, C, T | ||
| mRNA; activity on BM (Cleal et al. 2011) | Na+ dependant exchanger | ||
| SLC1A5 (ASCT2/ASC) | A, C, Q, S, T, N (Kanai et al. 2013) | ||
|
SLC3A1 (rBAT) SLC3A2 (4F2hc) |
mRNA mRNA; protein on MVM and BM (Palacin & Kanai, 2004) |
Chaperone subunit for specific SLC7 transporters | |
| SLC6A6 (TAUT) | mRNA; activity and protein on MVM (Roos et al. 2004; Desforges et al. 2013) | Na+/Cl− dependant cotransporter | Taurine (Pramod et al. 2013) |
|
SLC7A1 (CAT1/y+) SLC7A2 (CAT2B/y+) SLC7A3P (CAT3/y+) |
mRNA; activity on MVM and BM; CAT1 protein on BM (Speake et al. 2003). | Electrogenic uniporter | R, H, K (Fotiadis et al. 2013) |
|
SLC7A5 (LAT1/L) SLC7A8 (LAT2/L) |
mRNA; LAT2 activity on MVM and LAT1 activity on BM; both proteins on MVM and BM (Cleal et al. 2011; Widdows et al. 2015) | Exchanger; requires 4F2hc (SLC3A2) | F, Y, W, M, V, I, L, H, BCH L, A, S, T, C, F, Y, W, BCH, N, H, I, M, V, Q, G (Fotiadis et al. 2013) |
|
SLC7A7 (y+LAT1/y+L) SLC7A6 (y+LAT2/y+L) |
mRNA; activity on MVM and BM but cannot distinguish family member (Ayuk et al. 2000; Cleal et al. 2011) | Exchanger; requires 4F2hc (Na+ dependant for neutral amino acids) | R, H, K, M, AL (Fotiadis et al. 2013) |
| SLC7A9 (b0,+AT) | mRNA; activity inconclusive. | Requires rBAT (SLC3A1) | R, H, K, F, Y, W, T, M, V, I, L (Fotiadis et al. 2013) |
| SLC7A10 (asc1/asc) | mRNA; no activity on BM (Cleal et al. 2011) | Exchanger; requires 4F2hc (SLC3A2) | G, A, S, T, C (Fotiadis et al. 2013) |
| SLC7A11 (xCT/Xc‐) | mRNA | Exchanger; requires 4F2hc (SLC3A2) | Cystine, E (Fotiadis et al. 2013) |
| SLC16A10 (TAT1) | mRNA; activity and protein on BM (Cleal et al. 2011) | Facilitated diffusion | F, W, Y A, L (Ramadan et al. 2006) |
|
SLC38A1 (SNAT1/A) SLC38A2 (SNAT2/A) SLC38A4 (SNAT4/A) |
mRNA; activity and protein on MVM (Desforges et al. 2009) | Na+/AA cotransporter; Na/AA cotransport, H antiport | Q, A, N, C, H, S A, N, C, Q, G, H, M, P, S A, N, C, G, S, T (Schioth et al. 2013) |
| SLC38A3 (SNAT3/N) | mRNA | Na/AA cotransport, H antiport | Q, H, A, N |
| SLC38A5 (SNAT5/N) | mRNA; activity and protein on MVM (Day et al. 2013) | Q, H, N, S (Schioth et al. 2013) | |
|
SLC43A1 (LAT3) SLC43A2 (LAT4) |
mRNA; activity and protein on BM (Cleal et al. 2011) | Facilitated diffusion | L, I, V, F, M, BCH (Bodoy et al. 2013) |
BCH, 2‐aminobicyclo‐(2,2,1)‐heptane‐2‐carboxylic acid. l‐Alanine (A), l‐arginine (R), l‐asparagine (N), l‐aspartate (D), l‐cysteine (C), l‐glutamate (E), l‐glutamine (Q), glycine (G), l‐histidine (H), l‐isoleucine (I), l‐leucine (L), l‐lysine (K), l‐methionine (M), l‐phenylalanine (F), l‐proline (P), l‐serine (S), l‐threonine (T), l‐tryptophan (W), l‐tyrosine (Y), l‐valine (V). AL: y+L, influx but not efflux of l‐Leucine (Chillaron et al.).