In addition to its well defined role as a transcription factor, liver X receptor β (LXRβ or NR1H2) can directly bind to the C-terminal region of ATP-binding cassette A1 (ABCA1) in the human macrophage-like (THP-1) and human embryonic kidney 293 (HEK293) cell lines to impact ABCA1 protein function (Hozoji M et al. 2008; Hozoji-Inada M et al. 2011). In the absence of cholesterol accumulation in THP-1 cells, the ABCA1:NR1H2 complex stably localizes to the plasma membrane, but apolipoprotein A-I (apoA-I) binding or cholesterol efflux does not occur (Hozoji M et al. 2008; Hozoji-Inada M et al. 2011). Exogenously added NR1H2 ligands, which mimic cholesterol accumulation, cause NR1H2 (LXRβ) to dissociate from ABCA1, thus freeing ABCA1 for apoA-I binding and subsequent cholesterol efflux (Hozoji M et al. 2008; Hozoji-Inada M et al. 2011). Photoaffinity labeling experiments with 8-azido-[α-(32)P]ATP suggested that the interaction of NR1H2 (LXRβ) with ABCA1 inhibits ATP binding by ABCA1 (Hozoji-Inada M et al. 2011).