Oligosaccharyltransferase Inhibition Induces Senescence in RTK-Driven Tumor Cells

Asparagine (N)-linked glycosylation is a protein modification critical for glycoprotein folding, stability, and cellular localization. To identify small molecules that inhibit new targets in this biosynthetic pathway, we initiated a cell-based high throughput screen and lead compound optimization campaign that delivered a cell permeable inhibitor (NGI-1). NGI-1 targets the oligosaccharyltransferase (OST), a hetero-oligomeric enzyme that exists in multiple isoforms and transfers oligosaccharides to recipient proteins. In non-small cell lung cancer cells NGI-1 blocks cell surface localization and signaling of the EGFR glycoprotein, but selectively arrests proliferation in only those cell lines that are dependent on EGFR (or FGFR) for survival. In these cell lines OST inhibition causes cell cycle arrest accompanied by induction of p21, autofluorescence, and changes in cell morphology; all hallmarks of senescence. These results identify OST inhibition as a potential therapeutic approach for treating receptor tyrosine kinase-dependent tumors and provides a chemical probe for reversibly regulating N-linked glycosylation in mammalian cells

LDLR Expression and Localization Are Altered in Mouse and Human Cell Culture Models of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most common form of dementia. The major molecular risk factor for late-onset AD is expression of the ε-4 allele of apolipoprotein E (apoE), the major cholesterol transporter in the brain. The low-density lipoprotein receptor (LDLR) has the highest affinity for apoE and plays an important role in brain cholesterol metabolism.Using RT-PCR and western blotting techniques we found that over-expression of APP caused increases in both LDLR mRNA and protein levels in APP transfected H4 neuroglioma cells compared to H4 controls. Furthermore, immunohistochemical experiments showed aberrant localization of LDLR in H4-APP neuroglioma cells, Aβ-treated primary neurons, and in the PSAPP transgenic mouse model of AD. Finally, immunofluorescent staining of LDLR and of γ- and α-tubulin showed a change in LDLR localization preferentially away from the plasma membrane that was paralleled by and likely the result of a disruption of the microtubule-organizing center and associated microtubule network.These data suggest that increased APP expression and Aβ exposure alters microtubule function, leading to reduced transport of LDLR to the plasma membrane. Consequent deleterious effects on apoE uptake and function will have implications for AD pathogenesis and/or progression

Diversity in Protein Glycosylation among Insect Species

status: publishe

Innateness as genetic adaptation: Lorenz redivivus (and revised)

In 1965, Konrad Lorenz grounded the innate–acquired distinction in what he believed were the only two possible sources of information that can underlie adaptedness: phylogenetic and individual experience. Phylogenetic experience accumulates in the genome by the process of natural selection. Individual experience is acquired ontogenetically through interacting with the environment during the organism's lifetime. According to Lorenz, the adaptive information underlying innate traits is stored in the genome. Lorenz erred in arguing that genetic adaptation is the only means of accumulating information in phylogenetic (i.e., intergenerational) experience. Cultural adaptation also occurs over a phylogenetic time scale, and cultural tradition is a third source from which adaptive information can be extracted. This paper argues that genetic adaptation can be distinguished from individual and cultural adaptation in a species like Homo sapiens, in which even adaptations with a genetic component require cultural inputs and scaffolding to develop and be expressed. Examination of the way in which innateness is used in science suggests that scientists use the term, as Lorenz suggested, to designate genetic adaptations. The search for innate traits plays an essential role in generating hypotheses in ethology and psychology. In addition, designating a trait as innate establishes important facts that apply at the information-processing level of description