TABLE 1.
Oxysterol-binding protein-related proteins (ORPs) that mediate transport or countertransport of lipids at membrane contact sites (MCSs).
| ORPs | Lipid transfer activity in vitro A | Localization at ER MCS (lipids transferred or exchanged)B | References |
| OSBP | PI4P/DHE | ER-Golgi (PI4P/Sterol), ER-endosome (PI4P), ER-LE/Ly (PI4P/Cholesterol) | Mesmin et al. (2013, 2017), Dong et al. (2016), Goto et al. (2016), Lim et al. (2019) |
| ORP1 | DHE | ER-LE/Ly (Cholesterol), ER-phagosome (PI4P) | Eden et al. (2016), Zhao and Ridgway (2017), Dong et al. (2019), Levin-Konigsberg et al. (2019) |
| ORP2 | PI(4,5)P2/DHE | ER-LD | Weber-Boyvat et al. (2015b) |
| ORP3 | ? | ER-PM (PI4P) | Weber-Boyvat et al. (2015a), D’Souza et al. (2020), Gulyás et al. (2020) |
| ORP4 | Cholesterol | ER-Golgi | Wyles et al. (2007), Charman et al. (2014), Pietrangelo and Ridgway (2018) |
| ORP5 | PI4P/PS, PI(4,5)P2/PS, DHE | ER-PM (PI4P/PS), ER-PM (PI(4, 5)P2/PS), ER-LD (PI4P/PS), ER-Mito | Chung et al. (2015b), Galmes et al. (2016), Ghai et al. (2017), Sohn et al. (2018) |
| ORP6 | ? | ER-PM (PI4P) | Mochizuki et al. (2018) |
| ORP7 | ? | ? | |
| ORP8 | PI4P/PS, PI(4,5)P2/PS | ER-PM (PI4P/PS), ER-PM (PI(4,5)P2/PS), ER-Mito | Chung et al. (2015b), Galmes et al. (2016), Ghai et al. (2017), Sohn et al. (2018) |
| ORP9 | Cholesterol | ER-Golgi | Ngo and Ridgway (2009), Venditti et al. (2019b) |
| ORP10 | ? | ER-Golgi (PS) | Venditti et al. (2019b) |
| ORP11 | ? | ? |
ALipids were transported or exchanged between liposomes in vitro. The exchanged lipids are separated by slash (/).
BLipids demonstrated to be transported or exchanged in intact cells are shown in parentheses. The exchanged lipids are separated by slash (/).
BLipids shown in bold font: transport or exchange of the indicated lipids has been demonstrated in loss-of-function or gain-of-function analysis in an acute manner (e.g., acute inhibition or manipulation of ORP proteins).
BLipids shown in regular font: transport or exchange of the indicated lipids has been suggested in loss-of-function or gain-of-function analysis in a chronic manner [e.g., chronic inhibition (knock-down or knock-out) or overexpression of ORP proteins].
?, Unknown.