Biomedical subjects

Daryl A Bosco

Publications and source records attributed to Daryl A Bosco.

6 recordsLinked to original sources

PubMed2006

Elevated levels of oxidized cholesterol metabolites in Lewy body disease brains accelerate alpha-synuclein fibrilization.

Oxidative stress, inflammation and alpha-synuclein overexpression confer risk for development of alpha-synucleinopathies-neurodegenerative diseases that include Parkinson disease and Lewy body dementia. Dopaminergic neurons undergo degeneration in these diseases and are particularly susceptible to oxidative stress because dopamine metabolism itself creates reactive oxygen species. Intraneuronal deposition of alpha-synuclein as amyloid fibrils or Lewy bodies is the hallmark of these diseases. Herein, we demonstrate that concentrations of oxidative cholesterol metabolites derived from reactive oxygen species are elevated in the cortices of individuals with Lewy body dementia relative to those of age-matched controls, and we show that these metabolites accelerate alpha-synuclein aggregation in vitro. The increase in the production of these cytotoxic cholesterol metabolites is also observed in a dopaminergic cell line that overexpresses alpha-synuclein. By extension, these data lead to the hypothesis that oxidative stress produces cholesterol aldehydes that enable alpha-synuclein aggregation, leading to a pathologic cycle.

Brain↗

PubMed2006

Small molecule oxidation products trigger disease-associated protein misfolding.

Oxidative stress and inflammation are risk factors for both the development of alpha-synucleinopathies, such as Parkinson's disease and dementia with Lewy bodies, and Alzheimer's disease, the two most common neurodegenerative disorders. These diseases are associated with the neurotoxic deposition of misassembled alpha-synuclein and amyloid-beta (Abeta) peptides, respectively. Both occur sporadically, that is, without detectable disease-related mutations, in the vast majority of cases. Small molecule oxidation products, especially secosterols derived from cholesterol and 4-hydroxynonenal derived from lipid peroxidation, found in afflicted brains, accelerate the misassembly of both Abeta and alpha-synuclein. This Account explores the mechanism of small molecule oxidation product-mediated protein misassembly and possible intervention strategies.

Aldehydes↗

PubMed2005

Intrinsic dynamics of an enzyme underlies catalysis.

A unique feature of chemical catalysis mediated by enzymes is that the catalytically reactive atoms are embedded within a folded protein. Although current understanding of enzyme function has been focused on the chemical reactions and static three-dimensional structures, the dynamic nature of proteins has been proposed to have a function in catalysis. The concept of conformational substates has been described; however, the challenge is to unravel the intimate linkage between protein flexibility and enzymatic function. Here we show that the intrinsic plasticity of the protein is a key characteristic of catalysis. The dynamics of the prolyl cis-trans isomerase cyclophilin A (CypA) in its substrate-free state and during catalysis were characterized with NMR relaxation experiments. The characteristic enzyme motions detected during catalysis are already present in the free enzyme with frequencies corresponding to the catalytic turnover rates. This correlation suggests that the protein motions necessary for catalysis are an intrinsic property of the enzyme and may even limit the overall turnover rate. Motion is localized not only to the active site but also to a wider dynamic network. Whereas coupled networks in proteins have been proposed previously, we experimentally measured the collective nature of motions with the use of mutant forms of CypA. We propose that the pre-existence of collective dynamics in enzymes before catalysis is a common feature of biocatalysts and that proteins have evolved under synergistic pressure between structure and dynamics.

Binding Sites↗

PubMed2004

Catalysis and binding of cyclophilin A with different HIV-1 capsid constructs.

The prolyl isomerase cyclophilin A (CypA) is required for efficient HIV-1 replication and is incorporated into virions through a binding interaction at the Gly-Pro(222) bond located within the capsid domain of the HIV-1 Gag precursor polyprotein (Pr(gag)). It has recently been shown that CypA efficiently catalyzes the cis/trans isomerization of Gly-Pro(222) within the isolated N-terminal domain of capsid (CA(N)). To address the proposal that CypA interacts with Gly-Pro sequences in the C-terminal domain of a mature capsid, the interaction between CypA and the natively folded, full-length capsid protein (CA(FL)) has been investigated here using nuclear magnetic resonance spectroscopy. In addition, a fragment of the Pr(gag) protein encoding the full-matrix protein and the N-terminal domain of capsid (MA-CA(N)) has been used to probe the catalytic interaction between CypA and an immature form of the capsid. The results discussed herein strongly suggest that Gly-Pro(222) located within the N-terminal domain of the capsid is the preferential site for CypA binding and catalysis and that catalysis of Gly-Pro(222) is unaffected by maturational processing at the N-terminus of the capsid.

Amino Acid Sequence↗

PubMed2002

Catalysis of cis/trans isomerization in native HIV-1 capsid by human cyclophilin A.

Packaging of cyclophilin A (CypA) into HIV-1 virions is essential for efficient replication; however, the reason for this is unknown. Incorporation is mediated through binding to the Gly-89-Pro-90 peptide bond of the N-terminal domain of HIV-1 capsid (CA(N)). Despite the fact that CypA is a peptidyl-prolyl cis/trans isomerase, catalytic activity on CA(N) has not been observed previously. We show here, using NMR exchange spectroscopy, that CypA does not only bind to CA(N) but also catalyzes efficiently the cis/trans isomerization of the Gly-89-Pro-90 peptide bond. In addition, conformational changes in CA(N) distal to the CypA binding loop are observed on CypA binding and catalysis. The results provide experimental evidence for efficient CypA catalysis on a natively folded and biologically relevant protein substrate.

Capsid↗

PubMed2002

Enzyme dynamics during catalysis.

Internal protein dynamics are intimately connected to enzymatic catalysis. However, enzyme motions linked to substrate turnover remain largely unknown. We have studied dynamics of an enzyme during catalysis at atomic resolution using nuclear magnetic resonance relaxation methods. During catalytic action of the enzyme cyclophilin A, we detect conformational fluctuations of the active site that occur on a time scale of hundreds of microseconds. The rates of conformational dynamics of the enzyme strongly correlate with the microscopic rates of substrate turnover. The present results, together with available structural data, allow a prediction of the reaction trajectory.

Binding Sites↗