Table 1.

RXRs and heterodimer partners expressed in the osteoblast and osteoclast lineages

NR	Isotypes	Osteoblast	Osteoclast	Natural ligands	Synthetic ligands	DR
RXR	α(NR2B1)	E [51]	E [57]	Retinoids Fatty acids	Rexinoids Tributyltin	DR-1
	β(NR2B2)	E [51]	E [57]
	γ (NR2B3)	E [51]	NE [57]
PPAR	α(NR1C1)	E [51]	E [58]	Arachidonic acid metabolites Linoleic acid	GW7647 Fibrate derivatives	DR-1
	β/δ (NR1C2)	E [51]	E [45, 57]	Prostaglandin I2 Carbaprostacyclin	GW0742 L165041 GW501516
	γ(NR1C3)	E [51]	E [57, 59]	Fatty acids	TZD GW9662 THR0921 CLX-090717 Tributyltin
LXR	α(NR1H1)	E [57, 60]	E [57, 60]	Oxysterols	GW3965 T0901317	DR-4
	β(NR1H2)	E [57, 60]	E [57, 60]
FXR	NR1H4	E [51, 56]	E [61]	Farnesol Bile acids	Fexaramine 6E-CDCA GW4064	IR-1
PXR	NR1I2	E [109]	E [62]	Xenobiotics Vitamin K2 Sterols and their metabolites	Rifampicin Hyperforin Taxol Phenobarbital Ritonavir Carbamazipine	DR-3–5 IR-6 ER-6,8
CAR	NR1I3	E [52]	E [52]	Xenobiotics Endobiotics Steroid hormones	TCPOBOP CITCO	DR-4 DR-5
Nur77	NR4A1	E [51]	E [57, 63]	Not known	DIMs [17] Citosporone B [18]	DR-5
Nurr1	NR4A2	E [51]	NE [63]	Not known	DIMs [19]	DR-5
RAR	α(NR1B1)	E [51]	E [57]	Retinoids	AM580 TTNPB	DR-2 DR-5
	β(NR1B2)	E [51]	E [57]
	γ(NR1B3)	E [51]	E [57]
TR	α(NR1A1)	E [51, 110]	E [57]	Thyroid hormones	GC-1 KB141 GC-24	DR-4
	β(NR1A2)	E [51, 110]	E [57]
VDR	NR1I1	E [54]	NE [54]	1,25(OH)2 VD 3	MC903 EB1089 KH1060	DR-3

Bold: permissive RXR heterodimer partners; italics: non-permissive RXR heterodimer partners; E: expressed; NE: not expressed