TY - JOUR
T1 - Orexin A, an amphipathic α-helical neuropeptide involved in pleiotropic functions in the nervous and immune systems
T2 - Synthetic approach and biophysical studies of the membrane-bound state
AU - Ball, Haydn L.
AU - Said, Hooda
AU - Chapman, Karen
AU - Fu, Riqiang
AU - Xiong, Yawei
AU - Burk, Joshua A.
AU - Rosenbaum, Daniel
AU - Veneziano, Remi
AU - Cotten, Myriam L.
N1 - Publisher Copyright:
© 2023 The Authors
PY - 2023/6
Y1 - 2023/6
N2 - This research reports on the membrane interactions of orexin A (OXA), an α-helical and amphipathic neuropeptide that contains 33 residues and two disulfide bonds in the N-terminal region. OXA, which activates the orexins 1 and 2 receptors in neural and immune cell membranes, has essential pleiotropic physiological effects, including at the levels of arousal, sleep/wakefulness, energy balance, neuroprotection, lipid signaling, the inflammatory response, and pain. As a result, the orexin system has become a prominent target to treat diseases such as sleep disorders, drug addiction, and inflammation. While the high-resolution structure of OXA has been investigated in water and bound to micelles, there is a lack of information about its conformation bound to phospholipid membranes and its receptors. NMR is a powerful method to investigate peptide structures in a membrane environment. To facilitate the NMR structural studies of OXA exposed to membranes, we present a novel synthetic scheme, leading to the production of isotopically-labeled material at high purity. A receptor activation assay shows that the 15N-labeled peptide is biologically active. Biophysical studies are performed using surface plasmon resonance, circular dichroism, and NMR to investigate the interactions of OXA with phospholipid bilayers. The results demonstrate a strong interaction between the peptide and phospholipids, an increase in α-helical content upon membrane binding, and an in-plane orientation of the C-terminal region critical to function. This new knowledge about structure-activity relationships in OXA could inspire the design of novel therapeutics that leverage the anti-inflammatory and neuro-protective functions of OXA, and therefore could help address neuroinflammation, a major issue associated with neurological disorders such as Alzheimer's disease.
AB - This research reports on the membrane interactions of orexin A (OXA), an α-helical and amphipathic neuropeptide that contains 33 residues and two disulfide bonds in the N-terminal region. OXA, which activates the orexins 1 and 2 receptors in neural and immune cell membranes, has essential pleiotropic physiological effects, including at the levels of arousal, sleep/wakefulness, energy balance, neuroprotection, lipid signaling, the inflammatory response, and pain. As a result, the orexin system has become a prominent target to treat diseases such as sleep disorders, drug addiction, and inflammation. While the high-resolution structure of OXA has been investigated in water and bound to micelles, there is a lack of information about its conformation bound to phospholipid membranes and its receptors. NMR is a powerful method to investigate peptide structures in a membrane environment. To facilitate the NMR structural studies of OXA exposed to membranes, we present a novel synthetic scheme, leading to the production of isotopically-labeled material at high purity. A receptor activation assay shows that the 15N-labeled peptide is biologically active. Biophysical studies are performed using surface plasmon resonance, circular dichroism, and NMR to investigate the interactions of OXA with phospholipid bilayers. The results demonstrate a strong interaction between the peptide and phospholipids, an increase in α-helical content upon membrane binding, and an in-plane orientation of the C-terminal region critical to function. This new knowledge about structure-activity relationships in OXA could inspire the design of novel therapeutics that leverage the anti-inflammatory and neuro-protective functions of OXA, and therefore could help address neuroinflammation, a major issue associated with neurological disorders such as Alzheimer's disease.
KW - Anti-inflammatory
KW - Circular dichroism
KW - Hypocretin
KW - Isotopic labeling
KW - Membrane interactions
KW - Neuropeptide
KW - Nuclear magnetic resonance (NMR)
KW - Orexin
KW - Receptor activation
KW - Surface plasmon resonance
KW - Synthesis
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U2 - 10.1016/j.bpc.2023.107007
DO - 10.1016/j.bpc.2023.107007
M3 - Article
C2 - 37037119
AN - SCOPUS:85151698106
SN - 0301-4622
VL - 297
JO - Biophysical Chemistry
JF - Biophysical Chemistry
M1 - 107007
ER -