T. Neubert - Academia.edu (original) (raw)

Papers by T. Neubert

Research paper thumbnail of The CD26-Related Dipeptidyl Aminopeptidase-like Protein DPPX Is a Critical Component of Neuronal A-Type K Channels importance of the somatodendritic I SA in regu- lating firing frequency was recently highlighted by the demonstration that the pacemaker frequency of individ

ual dopaminergic neurons in the substantia nigra, and 1 Department of Physiology and Neuroscience... more ual dopaminergic neurons in the substantia nigra, and 1 Department of Physiology and Neuroscience and hence their levels of dopamine release, is directly corre

Research paper thumbnail of Multi-site assessment of the precision and reproducibility of multiple reaction monitoring–based measurements of proteins in plasma

Nature Biotechnology, 2009

Verification of candidate biomarkers relies upon specific, quantitative assays optimized for sele... more Verification of candidate biomarkers relies upon specific, quantitative assays optimized for selective detection of target proteins, and is increasingly viewed as a critical step in the discovery pipeline that bridges unbiased biomarker discovery to preclinical validation. Although individual laboratories have demonstrated that multiple reaction monitoring (MRM) coupled with isotope dilution mass spectrometry can quantify candidate protein biomarkers in plasma, reproducibility and transferability of these assays between laboratories have not been demonstrated. We describe a multilaboratory study to assess reproducibility, recovery, linear dynamic range and limits of detection and quantification of multiplexed, MRM-based assays, conducted by NCI-CPTAC. Using common materials and standardized protocols, we demonstrate that these assays can be highly reproducible within and across laboratories and instrument platforms, and are sensitive to low µg/ml protein concentrations in unfractionated plasma. We provide data and benchmarks against which individual laboratories can compare their performance and evaluate new technologies for biomarker verification in plasma.

Research paper thumbnail of The CD26-Related Dipeptidyl Aminopeptidase-like Protein DPPX Is a Critical Component of Neuronal A-Type K+ Channels

Neuron, 2003

Subthreshold-activating somatodendritic A-type potassium channels have fundamental roles in neuro... more Subthreshold-activating somatodendritic A-type potassium channels have fundamental roles in neuronal signaling and plasticity which depend on their unique cellular localization, voltage dependence, and kinetic properties. Some of the components of A-type K(+) channels have been identified; however, these do not reproduce the properties of the native channels, indicating that key molecular factors have yet to be unveiled. We purified A-type K(+) channel complexes from rat brain membranes and found that DPPX, a protein of unknown function that is structurally related to the dipeptidyl aminopeptidase and cell adhesion protein CD26, is a novel component of A-type K(+) channels. DPPX associates with the channels' pore-forming subunits, facilitates their trafficking and membrane targeting, reconstitutes the properties of the native channels in heterologous expression systems, and is coexpressed with the pore-forming subunits in the somatodendritic compartment of CNS neurons.

Research paper thumbnail of Sequencing of oxidized methionine-containing peptides for protein identification

Rapid Communications in Mass Spectrometry, 2000

Research paper thumbnail of Characterization of phosphopeptides from protein digests using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nanoelectrospray quadrupole time-of-flight mass spectrometry

Rapid Communications in Mass Spectrometry, 2001

A two-step mass spectrometric method for characterization of phosphopeptides from peptide mixture... more A two-step mass spectrometric method for characterization of phosphopeptides from peptide mixtures is presented. In the first step, phosphopeptide candidates were identified by matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) based on their higher relative intensities in negative ion MALDI spectra than in positive ion MALDI spectra. The detection limit for this step was found to be 18 femtomoles or lower in the case of unfractionated in-solution digests of a model phosphoprotein, b-casein. In the second step, nanoelectrospray tandem mass (nES-MS/MS) spectra of doubly or triply charged precursor ions of these candidate phosphopeptides were obtained using a quadrupole time-of-flight (Q-TOF) mass spectrometer. This step provided information about the phosphorylated residues, and ruled out nonphosphorylated candidates, for these peptides. After [ 32 P] labeling and reverse-phase high-performance liquid chromatography (RP-HPLC) to simplify the mixtures and to monitor the efficiency of phosphopeptide identification, we used this method to identify multiple autophosphorylation sites on the PKRlike endoplasmic reticulum kinase (PERK), a recently discovered mammalian stress-response protein.

Research paper thumbnail of Crystal Structure of the MuSK Tyrosine Kinase

Structure, 2002

receptor and creates binding sites for other signaling proteins [8]. In the proper sequence conte... more receptor and creates binding sites for other signaling proteins [8]. In the proper sequence context, phospho-New York, New York 10016 tyrosines recruit proteins containing phosphotyrosine binding (PTB) or Src homology 2 (SH2) domains to propagate downstream signaling events [9].

Research paper thumbnail of Proteome analysis reveals roles of L-DOPA in response to oxidative stress in neurons

BMC Neuroscience, 2014

Background: Parkinson's disease (PD) is the second most common neurodegenerative movement disorde... more Background: Parkinson's disease (PD) is the second most common neurodegenerative movement disorder, caused by preferential dopaminergic neuronal cell death in the substantia nigra, a process also influenced by oxidative stress. L-3,4-dihydroxyphenylalanine (L-DOPA) represents the main treatment route for motor symptoms associated with PD however, its exact mode of action remains unclear. A spectrum of conflicting data suggests that L-DOPA may damage dopaminergic neurons due to oxidative stress whilst other data suggest that L-DOPA itself may induce low levels of oxidative stress, which in turn stimulates endogenous antioxidant mechanisms and neuroprotection. Results: In this study we performed a two-dimensional gel electrophoresis (2DE)-based proteomic study to gain further insight into the mechanism by which L-DOPA can influence the toxic effects of H 2 O 2 in neuronal cells. We observed that oxidative stress affects metabolic pathways as well as cytoskeletal integrity and that neuronal cells respond to oxidative conditions by enhancing numerous survival pathways. Our study underlines the complex nature of L-DOPA in PD and sheds light on the interplay between oxidative stress and L-DOPA.

Research paper thumbnail of The CD26-Related Dipeptidyl Aminopeptidase-like Protein DPPX Is a Critical Component of Neuronal A-Type K Channels importance of the somatodendritic I SA in regu- lating firing frequency was recently highlighted by the demonstration that the pacemaker frequency of individ

ual dopaminergic neurons in the substantia nigra, and 1 Department of Physiology and Neuroscience... more ual dopaminergic neurons in the substantia nigra, and 1 Department of Physiology and Neuroscience and hence their levels of dopamine release, is directly corre

Research paper thumbnail of Multi-site assessment of the precision and reproducibility of multiple reaction monitoring–based measurements of proteins in plasma

Nature Biotechnology, 2009

Verification of candidate biomarkers relies upon specific, quantitative assays optimized for sele... more Verification of candidate biomarkers relies upon specific, quantitative assays optimized for selective detection of target proteins, and is increasingly viewed as a critical step in the discovery pipeline that bridges unbiased biomarker discovery to preclinical validation. Although individual laboratories have demonstrated that multiple reaction monitoring (MRM) coupled with isotope dilution mass spectrometry can quantify candidate protein biomarkers in plasma, reproducibility and transferability of these assays between laboratories have not been demonstrated. We describe a multilaboratory study to assess reproducibility, recovery, linear dynamic range and limits of detection and quantification of multiplexed, MRM-based assays, conducted by NCI-CPTAC. Using common materials and standardized protocols, we demonstrate that these assays can be highly reproducible within and across laboratories and instrument platforms, and are sensitive to low µg/ml protein concentrations in unfractionated plasma. We provide data and benchmarks against which individual laboratories can compare their performance and evaluate new technologies for biomarker verification in plasma.

Research paper thumbnail of The CD26-Related Dipeptidyl Aminopeptidase-like Protein DPPX Is a Critical Component of Neuronal A-Type K+ Channels

Neuron, 2003

Subthreshold-activating somatodendritic A-type potassium channels have fundamental roles in neuro... more Subthreshold-activating somatodendritic A-type potassium channels have fundamental roles in neuronal signaling and plasticity which depend on their unique cellular localization, voltage dependence, and kinetic properties. Some of the components of A-type K(+) channels have been identified; however, these do not reproduce the properties of the native channels, indicating that key molecular factors have yet to be unveiled. We purified A-type K(+) channel complexes from rat brain membranes and found that DPPX, a protein of unknown function that is structurally related to the dipeptidyl aminopeptidase and cell adhesion protein CD26, is a novel component of A-type K(+) channels. DPPX associates with the channels' pore-forming subunits, facilitates their trafficking and membrane targeting, reconstitutes the properties of the native channels in heterologous expression systems, and is coexpressed with the pore-forming subunits in the somatodendritic compartment of CNS neurons.

Research paper thumbnail of Sequencing of oxidized methionine-containing peptides for protein identification

Rapid Communications in Mass Spectrometry, 2000

Research paper thumbnail of Characterization of phosphopeptides from protein digests using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and nanoelectrospray quadrupole time-of-flight mass spectrometry

Rapid Communications in Mass Spectrometry, 2001

A two-step mass spectrometric method for characterization of phosphopeptides from peptide mixture... more A two-step mass spectrometric method for characterization of phosphopeptides from peptide mixtures is presented. In the first step, phosphopeptide candidates were identified by matrixassisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) based on their higher relative intensities in negative ion MALDI spectra than in positive ion MALDI spectra. The detection limit for this step was found to be 18 femtomoles or lower in the case of unfractionated in-solution digests of a model phosphoprotein, b-casein. In the second step, nanoelectrospray tandem mass (nES-MS/MS) spectra of doubly or triply charged precursor ions of these candidate phosphopeptides were obtained using a quadrupole time-of-flight (Q-TOF) mass spectrometer. This step provided information about the phosphorylated residues, and ruled out nonphosphorylated candidates, for these peptides. After [ 32 P] labeling and reverse-phase high-performance liquid chromatography (RP-HPLC) to simplify the mixtures and to monitor the efficiency of phosphopeptide identification, we used this method to identify multiple autophosphorylation sites on the PKRlike endoplasmic reticulum kinase (PERK), a recently discovered mammalian stress-response protein.

Research paper thumbnail of Crystal Structure of the MuSK Tyrosine Kinase

Structure, 2002

receptor and creates binding sites for other signaling proteins [8]. In the proper sequence conte... more receptor and creates binding sites for other signaling proteins [8]. In the proper sequence context, phospho-New York, New York 10016 tyrosines recruit proteins containing phosphotyrosine binding (PTB) or Src homology 2 (SH2) domains to propagate downstream signaling events [9].

Research paper thumbnail of Proteome analysis reveals roles of L-DOPA in response to oxidative stress in neurons

BMC Neuroscience, 2014

Background: Parkinson's disease (PD) is the second most common neurodegenerative movement disorde... more Background: Parkinson's disease (PD) is the second most common neurodegenerative movement disorder, caused by preferential dopaminergic neuronal cell death in the substantia nigra, a process also influenced by oxidative stress. L-3,4-dihydroxyphenylalanine (L-DOPA) represents the main treatment route for motor symptoms associated with PD however, its exact mode of action remains unclear. A spectrum of conflicting data suggests that L-DOPA may damage dopaminergic neurons due to oxidative stress whilst other data suggest that L-DOPA itself may induce low levels of oxidative stress, which in turn stimulates endogenous antioxidant mechanisms and neuroprotection. Results: In this study we performed a two-dimensional gel electrophoresis (2DE)-based proteomic study to gain further insight into the mechanism by which L-DOPA can influence the toxic effects of H 2 O 2 in neuronal cells. We observed that oxidative stress affects metabolic pathways as well as cytoskeletal integrity and that neuronal cells respond to oxidative conditions by enhancing numerous survival pathways. Our study underlines the complex nature of L-DOPA in PD and sheds light on the interplay between oxidative stress and L-DOPA.