Nur (nuclear receptor subfamily 4) is a family of orphan nuclear receptors which act as transcription factors in neuron development and maintenance. Recently, members of the NR4A family have been implicated in the control of skeletal muscle metabolism.
Three members have been identified in humans:
- nerve Growth factor IB (Nur77, or NR4A1),
- nuclear receptor related 1 protein (Nurr1, or NR4A2), and
- neuron-derived orphan receptor 1 (Nor-1, or NR4A3).