The Discovery and Characterization of [18F]MK‐8553, a Novel PET Tracer for Imaging O‐GlcNAcase (OGA)

[18F]MK-8553 is a high affinity, selective OGA inhibitor with properties suitable for imaging OGA and determining central enzyme occupancy in both preclinical and clinical studies. Currently [18F]MK‐8553 is being utilized in humans as a PET tracer to assess CNS target engagement to select a dose for clinical proof of concept trials with a small molecule [...]

July 14th, 2016|Tags: , , , |

Discovery of [18F]-MK-6240: A Positron Emission Tomography (PET) Imaging Agent for Quantification of Neurofibrillary Tangles (NFTs)

Neurofibrillary tangles (NFTs) made up of aggregated tau protein have been identified as the pathologic hallmark of several neurodegenerative diseases including Alzheimer's disease. In vivo detection of NFTs using PET imaging represents a unique opportunity to develop a pharmacodynamic tool to accelerate discovery of new disease modifying therapeutics targeting tau pathology. Herein we present the [...]

April 18th, 2016|Tags: , , , , , |

Analysis of transition state mimicry by tight binding aminothiazoline inhibitors provides insight into catalysis by human O-GlcNAcase

The modification of nucleocytoplasmic proteins with O-linked N-acetylglucosamine (O-GlcNAc) plays diverse roles in multicellular organisms. Inhibitors of O-GlcNAc hydrolase (OGA), the enzyme that removes O-GlcNAc from proteins, lead to increased O-GlcNAc levels in cells and are seeing widespread adoption in the field as a research tool used in cells and in vivo. Here we synthesize [...]

February 15th, 2016|Tags: , , |

O-GlcNAc modification blocks the aggregation and toxicity of the protein α-synuclein associated with Parkinson’s disease

Several aggregation-prone proteins associated with neurodegenerative diseases can be modified by O-linked N-acetyl-glucosamine (O-GlcNAc) in vivo. One of these proteins, α-synuclein, is a toxic aggregating protein associated with synucleinopathies, including Parkinson's disease. However, the effect of O-GlcNAcylation on α-synuclein is not clear. Here, we use synthetic protein chemistry to generate both unmodified α-synuclein and α-synuclein [...]

October 12th, 2015|Tags: , , |

Structures of lactate dehydrogenase A (LDHA) in apo, ternary and inhibitor-bound forms

Lactate dehydrogenase (LDH) is an essential metabolic enzyme that catalyzes the interconversion of pyruvate and lactate using NADH/NAD(+) as a co-substrate. Many cancer cells exhibit a glycolytic phenotype known as the Warburg effect, in which elevated LDH levels enhance the conversion of glucose to lactate, making LDH an attractive therapeutic target for oncology. Two known [...]

January 23rd, 2015|Tags: , , , |

Fluorescence-quenched substrates for live cell imaging of human glucocerebrosidase activity

Deficiency of the lysosomal glycoside hydrolase glucocerebrosidase (GCase) leads to abnormal accumulation of glucosyl ceramide in lysosomes and the development of the lysosomal storage disease known as Gaucher's disease. More recently, mutations in the GBA1 gene that encodes GCase have been uncovered as a major genetic risk factor for Parkinson's disease (PD). Current therapeutic strategies [...]

January 15th, 2015|Tags: , , |

Pharmacological inhibition of O-GlcNAcase (OGA) prevents cognitive decline and amyloid plaque formation in bigenic tau/APP mutant mice

BACKGROUND: Amyloid plaques and neurofibrillary tangles (NFTs) are the defining pathological hallmarks of Alzheimer's disease (AD). Increasing the quantity of the O-linked N-acetylglucosamine (O-GlcNAc) post-translational modification of nuclear and cytoplasmic proteins slows neurodegeneration and blocks the formation of NFTs in a tauopathy mouse model. It remains unknown, however, if O-GlcNAc can influence the formation of [...]

October 26th, 2014|Tags: , , , , , , , |

The emerging link between O-GlcNAc and Alzheimer disease

Regional glucose hypometabolism is a defining feature of Alzheimer disease (AD). One emerging link between glucose hypometabolism and progression of AD is the nutrient-responsive post-translational O-GlcNAcylation of nucleocytoplasmic proteins. O-GlcNAc is abundant in neurons and occurs on both tau and amyloid precursor protein. Increased brain O-GlcNAcylation protects against tau and amyloid-β peptide toxicity. Decreased O-GlcNAcylation [...]

October 21st, 2014|Tags: , , , , , , , , , , |

Chronic O-β-N-acetylglucosaminylase inhibition with Thiamet-G prevents tau pathology and hyperactivity in rTg4510 mice

Background: The abnormal hyperphosphorylation of the microtubule-associated protein tau plays a crucial role in neurodegeneration in Alzheimer's disease (AD) and aggregation of hyperphosphorylated tau into neurofibrillary tangles is a hallmark brain lesion in AD. Besides kinases and phosphatases tau phosphorylation is regulated by O-GlcNAcylation, a posttranslational modification of proteins on the serine or threonine residues with [...]

September 6th, 2014|Tags: , , , , , |

O-GlcNAcylation regulates cancer metabolism and survival stress signaling via regulation of the HIF-1 pathway

The hexosamine biosynthetic pathway elevates posttranslational addition of O-linked β-N-acetylglucosamine (O-GlcNAc) on intracellular proteins. Cancer cells elevate total O-GlcNAcylation by increasing O-GlcNAc transferase (OGT) and/or decreasing O-GlcNAcase (OGA) levels. Reducing O-GlcNAcylation inhibits oncogenesis. Here, we demonstrate that O-GlcNAcylation regulates glycolysis in cancer cells via hypoxia-inducible factor 1 (HIF-1α) and its transcriptional target GLUT1. Reducing O-GlcNAcylation [...]

May 22nd, 2014|Tags: , , |