Neurons express ABC transporters, namely ABCA1, ABCG1, and ABCG4 (Kim et al., 2008), to mediate cellular sterol efflux at the plasma membrane.
Functional defects in the ABCA1 protein that impair its ability to mediate cellular cholesterol efflux can thus result in deposition of cholesterol within the tissues.
The MRP1 mediates the cellular efflux of various xenobiotics including heavy metals and mediates cellular resistance to heavy metals.
Furthermore, resistant nematodes may show increased expression of ABC (ATP-binding cassette) transporters, a group of membrane proteins with members capable of mediating the cellular efflux of drugs [ 17, 18].
Interestingly, of the MDR proteins induced by NRF2, at least ABCG2 has been confirmed to facilitate cytoprotection against PDT by mediating the cellular efflux of photosensitizers PPIX, pyropheophorbide A, and benzoporphyrin deri-vative monoacid ring A [ 129] but not meso-tetrahydroxyphenylchloride and porfimer sodium [ 130].
Thus, we investigated whether mutations of Asn316 and Phe320 affected the ability of ABCG1 to mediate cellular 7-ketocholesterol efflux, the most abundant nonenzymatic oxysterol in the atherosclerotic lesions.
CO can protect neurones from oxidative stress-induced apoptosis by inhibiting Kv2.1 channels, which mediates cellular K+ efflux as an early step in the apoptotic cascade.
Additionally, resistance could also be directly or indirectly caused by an increase in cellular efflux of imatinib, mediated mainly by the drug transporter P-gp (P-glycoprotein) (Mahon et al, 2003; Widmer et al, 2007), or by a decrease in cellular influx, mediated by the uptake carrier hOCT1 (organic cation transporter) (Thomas et al, 2004; Crossman et al, 2005; Wang et al, 2008).
Gene ectopic expression of AthPHO1 in leaves [ 5] and in mesophyll protoplasts [ 6] mediates cellular specific phosphate efflux.
To determine cellular efflux, 0.3 × 106 89Zr-labeled cells were plated into each well of a six-well culture plate.
