title: Computational and structural evidence for neurotransmitter-mediated modulation of the oligomeric states of human insulin in storage granules.
abstract: Human insulin is a pivotal protein hormone controlling metabolism, growth, and aging and whose malfunctioning underlies diabetes, some cancers, and neurodegeneration. Despite its central position in human physiology, thein vivooligomeric state and conformation of insulin in its storage granules in the pancreas are not known. In contrast, manyin vitrostructures of hexamers of this hormone are available and fall into three conformational states: T6, T3Rf3, and R6As there is strong evidence for accumulation of neurotransmitters, such as serotonin and dopamine, in insulin storage granules in pancreatic β-cells, we probed by molecular dynamics (MD) and protein crystallography (PC) if these endogenous ligands affect and stabilize insulin oligomers. Parallel studies independently converged on the observation that serotonin binds well within the insulin hexamer (site I), stabilizing it in the T3R3conformation. Both methods indicated serotonin binding on the hexamer surface (site III) as well. MD, but not PC, indicated that dopamine was also a good site III ligand. Some of the PC studies also included arginine, which may be abundant in insulin granules upon processing of pro-insulin, and stable T3R3hexamers loaded with both serotonin and arginine were obtained. The MD and PC results were supported further by in solution spectroscopic studies with R-state-specific chromophore. Our results indicate that the T3R3oligomer is a plausible insulin pancreatic storage form, resulting from its complex interplay with neurotransmitters, and pro-insulin processing products. These findings may have implications for clinical insulin formulations.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic.
authors.forename: Vladimír
authors.initials: V
authors.lastname: Palivec
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Viola
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Kozak
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Ganderton
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic.
authors.forename: Květoslava
authors.initials: K
authors.lastname: Křížková
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
authors.forename: Johan P
authors.initials: JP
authors.lastname: Turkenburg
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic.
authors.forename: Petra
authors.initials: P
authors.lastname: Haluŝková
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic.
authors.forename: Lenka
authors.initials: L
authors.lastname: Žáková
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic. Electronic address: jiracek@uochb.cas.cz.
authors.forename: Jiří
authors.initials: J
authors.lastname: Jiráĉek
authors.affiliation: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, v.v.i., Flemingovo nám 2, 166 10 Prague 6, Czech Republic. Electronic address: pavel.jungwirth@uochb.cas.cz.
authors.forename: Pavel
authors.initials: P
authors.lastname: Jungwirth
authors.affiliation: York Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom. Electronic address: marek.brzozowski@york.ac.uk.
authors.forename: Andrzej M
authors.initials: AM
authors.lastname: Brzozowski
mesh_terms: D003198:Computer Simulation; D006801:Humans; D007328:Insulin / Q000737:chemistry / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D056004:Molecular Dynamics Simulation; D018377:Neurotransmitter Agents / Q000378:metabolism*; D055503:Protein Multimerization; D022142:Secretory Vesicles / Q000737:chemistry / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*
chemical_list: D007328:Insulin; D018377:Neurotransmitter Agents; D012701:Serotonin
keywords: crystal structure; dopamine; insulin; pancreatic islet; serotonin; vesicles