title: Tyrosine Hydroxylase Binding to Phospholipid Membranes Prompts Its Amyloid Aggregation and Compromises Bilayer Integrity.
abstract: Tyrosine hydroxylase (TH), a rate-limiting enzyme in the synthesis of catecholamine neurotransmitters and hormones, binds to negatively charged phospholipid membranes. Binding to both large and giant unilamellar vesicles causes membrane permeabilization, as observed by efflux and influx of fluorescence dyes. Whereas the initial protein-membrane interaction involves the N-terminal tail that constitutes an extension of the regulatory ACT-domain, prolonged membrane binding induces misfolding and self-oligomerization of TH over time as shown by circular dichroism and Thioflavin T fluorescence. The gradual amyloid-like aggregation likely occurs through cross-β interactions involving aggregation-prone motives in the catalytic domains, consistent with the formation of chain and ring-like protofilaments observed by atomic force microscopy in monolayer-bound TH. PC12 cells treated with the neurotoxin 6-hydroxydopamine displayed increased TH levels in the mitochondrial fraction, while incubation of isolated mitochondria with TH led to a decrease in the mitochondrial membrane potential. Furthermore, cell-substrate impedance and viability assays showed that supplementing the culture media with TH compromises cell viability over time. Our results revealed that the disruptive effect of TH on cell membranes may be a cytotoxic and pathogenic factor if the regulation and intracellular stability of TH is compromised.
authors.affiliation: Department of Biomedicine, University of Bergen, 5009 Bergen, Norway.|Division of Psychiatry, Haukeland University Hospital, 5021 Bergen, Norway.
authors.forename: Anne
authors.initials: A
authors.lastname: Baumann
authors.affiliation: Department of Biomedicine, University of Bergen, 5009 Bergen, Norway.|K.G. Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, 5009 Bergen, Norway.
authors.forename: Ana
authors.initials: A
authors.lastname: Jorge-Finnigan
authors.affiliation: Department of Biomedicine, University of Bergen, 5009 Bergen, Norway.
authors.forename: Kunwar
authors.initials: K
authors.lastname: Jung-Kc
authors.affiliation: Department of Biomedicine, University of Bergen, 5009 Bergen, Norway.|Department of Clinical Dentistry, University of Bergen, 5009 Bergen, Norway.
authors.forename: Alexander
authors.initials: A
authors.lastname: Sauter
authors.affiliation: Department of Medical Biochemistry and Biophysics, Umeå University, 90187 Umeå, Sweden.
authors.forename: Istvan
authors.initials: I
authors.lastname: Horvath
authors.affiliation: Department of Medical Biochemistry and Biophysics, Umeå University, 90187 Umeå, Sweden.
authors.forename: Ludmilla A
authors.initials: LA
authors.lastname: Morozova-Roche
authors.affiliation: Department of Biomedicine, University of Bergen, 5009 Bergen, Norway.|K.G. Jebsen Centre for Neuropsychiatric Disorders, University of Bergen, 5009 Bergen, Norway.
authors.forename: Aurora
authors.initials: A
authors.lastname: Martinez
mesh_terms: D000682:Amyloid / Q000737:chemistry*; D000818:Animals; D052160:Benzothiazoles; D020134:Catalytic Domain; D002462:Cell Membrane / Q000737:chemistry*; D002470:Cell Survival; D002942:Circular Dichroism; D005434:Flow Cytometry; D015972:Gene Expression Regulation, Neoplastic; D057809:HEK293 Cells; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000378:metabolism; D008968:Molecular Conformation; D016716:PC12 Cells; D010539:Permeability; D010713:Phosphatidylcholines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D051381:Rats; D013347:Subcellular Fractions; D013844:Thiazoles / Q000737:chemistry*; D014446:Tyrosine 3-Monooxygenase / Q000737:chemistry*
chemical_list: D000682:Amyloid; D052160:Benzothiazoles; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; D013844:Thiazoles; C009462:thioflavin T; D014446:Tyrosine 3-Monooxygenase; C017251:1,2-oleoylphosphatidylcholine