Protein Domain : Peroxisome proliferator-activated receptor, beta IPR003075

Type	Family
Description	Steroid or nuclear hormone receptors (NRs) constitute an important superfamily of transcription regulators that are involved in widely diverse physiological functions, including control of embryonic development, cell differentiation and homeostasis. Members of the superfamily include the steroid hormone receptors and receptors for thyroid hormone, retinoids, 1,25-dihydroxy-vitamin D3 and a variety of other ligands [ ]. The proteins function as dimeric molecules in nuclei to regulate the transcription of target genes in a ligand-responsive manner [, ]. In addition to C-terminal ligand-binding domains, these nuclear receptors contain a highly-conserved, N-terminal zinc-finger that mediates specific binding to target DNA sequences, termed ligand-responsive elements. In the absence of ligand, steroid hormone receptors are thought to be weakly associated with nuclear components; hormone binding greatly increases receptor affinity.NRs are extremely important in medical research, a large number of them being implicated in diseases such as cancer, diabetes, hormone resistance syndromes, etc. While several NRs act as ligand-inducible transcription factors, many do not yet have a defined ligand and are accordingly termed 'orphan' receptors. During the last decade, more than 300 NRs have been described, many of which are orphans, which cannot easily be named due to current nomenclature confusions in the literature. However, a new system has recently been introduced in an attempt to rationalise the increasingly complex set of names used to describe superfamily members.Peroxisome proliferator-activated receptors (PPAR) are ligand-activated transcription factors that belong to the nuclear hormone receptor superfamily. Three cDNAs encoding PPARs have been isolated from Xenopus laevis: xPPAR alpha, beta and gamma [ ]. All three xPPARs appear to be activated by both synthetic peroxisome proliferators and naturally occurring fatty acids, suggesting a common mode of action for all members of this subfamily of receptors []. Furthermore, the multiplicity of the receptors suggests the existence of hitherto unknown cellular signalling pathways for xenobiotics and putative endogenous ligands []. A PPAR alpha-related cDNA from mouse (designated PPAR delta, and subsequently renamed beta) has been cloned and characterised. The alpha, beta and gamma PPAR isoforms display widely divergent patterns of expression during embryogenesis and in the adult []. PPAR gamma and beta are not activated by pirinixic acid, a potent peroxisome proliferator and activator of PPAR alpha; they are, however, activated by the structurally distinct peroxisome proliferator LY-171883 and linoleic acid, respectively, indicating that each isoform can act as a regulated activator of transcription []. Thus tissue-specific responsiveness to peroxisome proliferators, including certain fatty acids, may be partly a consequence of differential expression of multiple, pharmacologically distinct PPAR isoforms [].
Short Name	1Cnucl_rcpt_B