SPARC: Atomistic Modeling of Autonomic Stimulation for a Multi‐Scale Neurocardiovascular Simulator.

Abstract

Heart rhythm and vascular tone are modulated by stimulation of the autonomic nervous system, and dysregulation of sympathetic or parasympathetic stimuli is associated with multiple cardiovascular disorders such as arrhythmias and hypertension. At the molecular level, such neuromodulation is established by stimulating myocyte G protein‐coupled receptor (GPCR) mediated signal transduction pathways with neurotransmitters like norepinephrine or acetylcholine. In this study, funded by NIH Common Fund program “Stimulating Peripheral Activity to Relieve Conditions” (SPARC), we used atomistic modeling to identify structural, energetic, and kinetic determinants of several molecular processes crucial for cardiovascular neuromodulation such as neurotransmitter interactions with GPCR / G protein complexes at the neuroeffector junction, as well as G protein interactions with adenylyl cyclase (AC), a key enzyme for downstream subcellular signaling. To determine these parameters, we developed atomistic models of human β1‐ and β2‐adrenergic receptors (β1AR and β2AR) as well as muscarinic acetylcholine receptor M2 (M2R) in different conformational states with and without bound Gs or Gi protein using available structures and Rosetta structural modeling. These models were validated via molecular docking of βAR agonists norepinephrine and isoproterenol and MR agonists acetylcholine and carbachol to compare with experimental crystal structures. Model structural stabilities were assessed via microsecond‐long all‐atom molecular dynamics (MD) simulations with and without bound ligand. Enhanced sampling atomistic MD simulations were used to estimate state‐dependent receptor ‐ ligand binding affinities and association / dissociation rates, which were compared with available experimental values. Also, coarse‐grained and Brownian dynamics implicit‐solvent techniques were utilized to assess G protein interactions with AC and GPCRs. This information will be used to inform functional kinetic models of autonomic control of myocyte subcellular signaling, a crucial component of our predictive multi‐scale neurocardiovascular simulator.Support or Funding InformationNIH SPARC 1OT2OD026580 (C.E.C., I.V.), UC Davis Pharmacology T32GM099608 (J.R.D.D.), AHA career development award 19CDA34770101 (I.V.), NIH NHLBI 5R01HL128537 (C.E.C., V.Y.Y.) and 5U01HL126273 (C.E.C., V.Y.Y.). Computer time allocations: Anton 2 PSCA18077P (I.V., C.E.C., K.R.D.), XSEDE MCB170095 (I.V., K.R.D.), NCSA Blue Waters Broadening Participation Allocation (C.E.C., I.V., K.R.D.).