26RFa, Human

26RFa, also known as QRFP, is a hypothalamic member of the RFamide peptide family and the endogenous ligand of GPR103. The supplied human sequence ends in the arginine-phenylalanine-amide motif that defines the family, and that C-terminal motif is the receptor-recognition element: antagonist development programmes have explicitly designed small molecules to mimic the C-terminal Arg-Phe of QRFP26.

Functionally it is orexigenic, increasing food intake, and work in mice established that its receptor GPR103 also mediates effects on behavioural arousal and blood pressure. The orexigenic action is not direct at the level of the effector neurons but is mediated through neuropeptide Y and proopiomelanocortin neurons of the arcuate nucleus, placing the peptide upstream of the classical feeding circuitry. Later work has also implicated orexin receptors in its effects on feeding and locomotor activity, so the pathway is not exclusive to GPR103.

This is the human sequence. Structural studies on 26RFa established the conformational features underlying its activity, and the amidated C-terminus is essential rather than incidental. For rodent in vivo work the species-matched rat sequence is offered separately as LT9238, and the two differ at several positions outside the conserved C-terminal motif.

• GPR103 receptor binding and functional assays in human systems
• Food intake and energy balance studies
• Arcuate nucleus NPY and POMC neuron circuit experiments
• Behavioural arousal, locomotor activity and blood pressure research
• Antagonist screening against the C-terminal Arg-Phe pharmacophore

Sequence length, species, terminal chemistry and analog substitutions define the exact reagent. Use sequence-matched controls and consistent preparation conditions.

1. Selected peer-reviewed publication

1. Takayasu S, et al. A neuropeptide ligand of the G protein-coupled receptor GPR103 regulates feeding, behavioral arousal, and blood pressure in mice. PNAS (2006). PNAS 2006

2. The hypothalamic RFamide, QRFP, increases feeding and locomotor activity: the role of Gpr103 and orexin receptors. PLOS ONE (2022). PLOS ONE 2022

3. The orexigenic activity of the hypothalamic neuropeptide 26RFa is mediated by the neuropeptide Y and proopiomelanocortin neurons of the arcuate nucleus. (2009). PMID 19164468

4. Structural studies on 26RFa, a novel human RFamide-related peptide with orexigenic activity. (2005). PMID 15808908