title: Molecular interactions of the physiological anti-hypertensive peptide catestatin with the neuronal nicotinic acetylcholine receptor.
abstract: Catestatin (CST), a chromogranin-A-derived peptide, is a potent endogenous inhibitor of the neuronal nicotinic acetylcholine receptor (nAChR). It exerts an anti-hypertensive effect by acting as a 'physiological brake' on transmitter release into the circulation. However, the mechanism of interaction of CST with nAChR is only partially understood. To unravel molecular interactions of the wild-type human CST (CST-WT) as well as its naturally occurring variants (CST-364S and CST-370L, which have Gly→Ser and Pro→Leu substitutions, respectively) with the human α3β4 nAChR, we generated a homology-modeled human α3β4 nAChR structure and solution structures of CST peptides. Docking and molecular dynamics simulations showed that ~90% of interacting residues were within 15 N-terminal residues of CST peptides. The rank order of binding affinity of these peptides with nAChR was: CST-370L>CST-WT>CST-364S; the extent of occlusion of the receptor pore by these peptides was also in the same order. In corroboration with computational predictions, circular dichroism analysis revealed significant differences in global structures of CST peptides (e.g. the order of α-helical content was: CST-370L>CST-WT>CST-364S). Consistently, CST peptides blocked various stages of nAChR signal transduction, such as nicotine- or acetylcholine-evoked inward current, rise in intracellular Ca(2+) and catecholamine secretion in or from neuron-differentiated PC12 cells, in the same rank order. Taken together, this study shows molecular interactions between human CST peptides and human α3β4 nAChR, and demonstrates that alterations in the CST secondary structure lead to the gain of potency for CST-370L and loss of potency for CST-364S. These findings have implications for understanding the nicotinic cholinergic signaling in humans.
authors.affiliation: Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences Building, Indian Institute of Technology Madras, Chennai, India.
authors.forename: Bhavani S
authors.initials: BS
authors.lastname: Sahu
authors.forename: Jagan
authors.initials: J
authors.lastname: Mohan
authors.forename: Jagan M
authors.initials: JM
authors.lastname: Obbineni
authors.forename: Giriraj
authors.initials: G
authors.lastname: Sahu
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Singh
authors.forename: Parshuram J
authors.initials: PJ
authors.lastname: Sonawane
authors.forename: Binu K
authors.initials: BK
authors.lastname: Sasi
authors.forename: Prasanna K R
authors.initials: PK
authors.lastname: Allu
authors.forename: Samir K
authors.initials: SK
authors.lastname: Maji
authors.forename: Amal K
authors.initials: AK
authors.lastname: Bera
authors.forename: Sanjib
authors.initials: S
authors.lastname: Senapati
authors.forename: Nitish R
authors.initials: NR
authors.lastname: Mahapatra
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D019943:Amino Acid Substitution; D000818:Animals; D000959:Antihypertensive Agents / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D053379:Chromogranin A / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D002942:Circular Dichroism; D006801:Humans; D008564:Membrane Potentials / Q000187:drug effects*; D056004:Molecular Dynamics Simulation; D009538:Nicotine / Q000494:pharmacology; D016716:PC12 Cells; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D051381:Rats; D011978:Receptors, Nicotinic / Q000737:chemistry* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D040681:Structural Homology, Protein; D013329:Structure-Activity Relationship
chemical_list: D000959:Antihypertensive Agents; D002395:Catecholamines; D053379:Chromogranin A; D010446:Peptide Fragments; D011978:Receptors, Nicotinic; C109084:chromogranin A (344-364); C403530:nicotinic receptor alpha3beta4; D009538:Nicotine; D000109:Acetylcholine; D002118:Calcium