Selective Processing and Metabolism of Disease-Causing Mutant Prion Proteins

Prion diseases are fatal neurodegenerative disorders caused by aberrant metabolism of the cellular prion protein (PrPC). In genetic forms of these diseases, mutations in the globular C-terminal domain are hypothesized to favor the spontaneous generation of misfolded PrP conformers (including the transmissible PrPSc form) that trigger downstream pathways leading to neuronal death. A mechanistic understanding of these diseases therefore requires knowledge of the quality control pathways that recognize and degrade aberrant PrPs. Here, we present comparative analyses of the biosynthesis, trafficking, and metabolism of a panel of genetic disease-causing prion protein mutants in the C-terminal domain. Using quantitative imaging and biochemistry, we identify a misfolded subpopulation of each mutant PrP characterized by relative detergent insolubility, inaccessibility to the cell surface, and incomplete glycan modifications. The misfolded populations of mutant PrPs were neither recognized by ER quality control pathways nor routed to ER-associated degradation despite demonstrable misfolding in the ER. Instead, mutant PrPs trafficked to the Golgi, from where the misfolded subpopulation was selectively trafficked for degradation in acidic compartments. Surprisingly, selective re-routing was dependent not only on a mutant globular domain, but on an additional lysine-based motif in the highly conserved unstructured N-terminus. These results define a specific trafficking and degradation pathway shared by many disease-causing PrP mutants. As the acidic lysosomal environment has been implicated in facilitating the conversion of PrPC to PrPSc, our identification of a mutant-selective trafficking pathway to this compartment may provide a cell biological basis for spontaneous generation of PrPSc in familial prion disease

Deficiency of Cartilage-Associated Protein in Recessive Lethal Osteogenesis Imperfecta

Classic osteogenesis imperfecta, an autosomal dominant disorder associated with osteoporosis and bone fragility, is caused by mutations in the genes for type I collagen. A recessive form of the disorder has long been suspected. Since the loss of cartilage-associated protein (CRTAP), which is required for post-translational prolyl 3-hydroxylation of collagen, causes severe osteoporosis in mice, we investigated whether CRTAP deficiency is associated with recessive osteogenesis imperfecta. Three of 10 children with lethal or severe osteogenesis imperfecta, who did not have a primary collagen defect yet had excess post-translational modification of collagen, were found to have a recessive condition resulting in CRTAP deficiency, suggesting that prolyl 3-hydroxylation of type I collagen is important for bone formation

An Overview of Stem Cell Therapies for Parkinson’s Disease

Parkinson’s disease (PD) is referred to as a neurodegenerative disease which is a disease that targets specific brain regions and is characterized by neuronal death. PD is believed to be caused by the loss of nerve cells in the substantia nigra (SN), a dopamine releasing area (Dickson, 2012). Current treatments are directed at alleviating pain symptoms and slowing down the progression of disease, however, no cure currently exists. Recent advances in stem cell therapies raise new possibilities to treat neurodegenerative diseases. Stem cells have the ability to differentiate into neural cells, and thus, could potentially be used to restore neurogenesis and neuroplasticity (Lunn et al., 2011). There exist several cell types that can be applied in therapy including embryonic stem cells (ESCs), neural stem cells (NSCs), induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs). PD which has localized neural degeneration to the SN may serve as a better model for stem cell therapy and displays greater success when compared to other neurodegenerative diseases that spread to several brain regions (Vasic et al., 2019). This review aims to discuss the several approaches used in stem cell therapy as well as the current challenges and shortcomings of this cell-based therapy

Designing an Audiocast Assignment: A Primary-Literature-Based Approach that Promotes Student Learning of Cell and Molecular Biology through Conversations with Scientist Authors

We believe that conversations between students and scientist authors that link recently published research to fundamental concepts taught in undergraduate biology courses can serve to engage students and enhance learning. To explore this hypothesis, we designed an assignment in a 2nd year cell and molecular biology course in which students read a scientific article, conduct an interview with the corresponding author of the publication, and then produce an audiocast (or videocast). The audiocast summarizes the paper’s findings and describes how the research advance links back to fundamental concepts discussed in the course and its implications for the field. Feedback from student surveys has been positive and suggests that students felt they developed important analytical skills and a better understanding of the process of science through participation in this assignment. Students enjoyed the interactions with scientists and reported on how their learning from primary literature was enriched by asking questions of the authors. Importantly, the assignment had a very positive influence on student attitudes towards research; this is increasingly important at a time when public involvement in debates about scientific funding cuts is critical. We hope this assignment will be of interest to other instructors that teach undergraduate foundation courses in the life sciences

Investigating Anti-Vaccination Stances on Social Media: an Assignment To Promote Science Literacy

ABSTRACT In this digital age in which social media use among young adults continues to rise, consideration of the impact of these platforms on our students and on science literacy pedagogy is essential. This has been highlighted during the 2019 coronavirus disease pandemic, when mis- and disinformation surrounding the pandemic and vaccinations were so prevalent on social media platforms that it provoked a cautionary announcement from the World Health Organization. We describe here the structure of an assignment aimed to promote science literacy by encouraging students to explore antivaccination stances on social media and evaluate the scientific validity of such claims using scientific literature. To comprehensively analyze these antivaccination sentiments, we encouraged students to develop succinct arguments to demonstrate the social, economic, or other cultural influences likely contributing to antivaccination stances. In alignment with the philosophical-educational concept of Bildung, we hope to nurture an understanding of scientific literacy that focuses on both evidence-based critical thinking as well as empathetic understanding of the socio-political circumstances that influence public opinion on scientific matters. Student work provided compelling evidence for the success of our field-tested assignment in fostering students to be authoritative voices of science in everyday life and highlighted the importance of efforts to explicitly focus on science literacy within biology curricula

Contrasting Roles of Endosomal pH and the Cytoskeleton in Infection of Human Glial Cells by JC Virus and Simian Virus 40

Infection of eukaryotic cells by pathogens requires the efficient use of host cell endocytic and cytoplasmic transport mechanisms. Understanding how these cellular functions are exploited by microorganisms allows us to better define the basic biology of pathogenesis while providing better insight into normal cellular functions. In this report we compare and contrast intracellular transport and trafficking of the human polyomavirus JC virus (JCV) with that of simian virus 40 (SV40). We have previously shown that infection of human glial cells by JCV requires clathrin-dependent endocytosis. In contrast, infection of cells by SV40 proceeds by caveola-dependent endocytosis. We now examine the roles of endosomal pH and the cellular cytoskeleton during infection of glial cells by both viruses. Our results demonstrate that JCV infection is sensitive to disruption of endosomal pH, whereas SV40 infection is pH independent. Infection by JCV is inhibited by treatment of glial cells with cytochalasin D, nocodazole, and acrylamide, whereas SV40 infection is affected only by nocodazole. These data point to critical differences between JCV and SV40 in terms of endocytosis and intracellular trafficking of their DNA genomes to the nucleus. These data also suggest a unique sequential involvement of cytoskeletal elements during infection of glial cells by JCV

Examining the Relationship Between a Rapidly Evolving Diet, Physiological Constraints, and Increasing Incidence of Illnesses in Humans

There is a speculated relationship between the rapidly changing human diet, physiology and an upward trend in chronic illness incidence. Better understanding the relationship between these variables is of high importance as it not only allows one to understand current trends in chronic illness incidence but also future trends and possibly how an upward trend in illness incidence can be averted. This literature review attempts to explore the aforementioned relationship through comparison of paleolithic and modern-day human diets with a primary focus on understanding how differences amidst the two diets contribute to upward trends in cardiovascular disease, diabetes, cancer and Alzheimer’s incidence. The need for diversification of study populations to increase generalizability, further studies to remove discrepancy in findings and understanding how socioeconomic status may impact diet are also discussed

Glucose transporter expression in an avian nectarivore: the ruby-throated hummingbird (Archilochus colubris).

Glucose transporter (GLUT) proteins play a key role in the transport of monosaccharides across cellular membranes, and thus, blood sugar regulation and tissue metabolism. Patterns of GLUT expression, including the insulin-responsive GLUT4, have been well characterized in mammals. However, relatively little is known about patterns of GLUT expression in birds with existing data limited to the granivorous or herbivorous chicken, duck and sparrow. The smallest avian taxa, hummingbirds, exhibit some of the highest fasted and fed blood glucose levels and display an unusual ability to switch rapidly and completely between endogenous fat and exogenous sugar to fuel energetically expensive hovering flight. Despite this, nothing is known about the GLUT transporters that enable observed rapid rates of carbohydrate flux. We examined GLUT (GLUT1, 2, 3, & 4) expression in pectoralis, leg muscle, heart, liver, kidney, intestine and brain from both zebra finches (Taeniopygia guttata) and ruby-throated hummingbirds (Archilochus colubris). mRNA expression of all four transporters was probed using reverse-transcription PCR (RT-PCR). In addition, GLUT1 and 4 protein expression were assayed by western blot and immunostaining. Patterns of RNA and protein expression of GLUT1-3 in both species agree closely with published reports from other birds and mammals. As in other birds, and unlike in mammals, we did not detect GLUT4. A lack of GLUT4 correlates with hyperglycemia and an uncoupling of exercise intensity and relative oxidation of carbohydrates in hummingbirds. The function of GLUTs present in hummingbird muscle tissue (e.g. GLUT1 and 3) remain undescribed. Thus, further work is necessary to determine if high capillary density, and thus surface area across which cellular-mediated transport of sugars into active tissues (e.g. muscle) occurs, rather than taxon-specific differences in GLUT density or kinetics, can account for observed rapid rates of sugar flux into these tissues