Glycoprotein | EPFL Graph Search

Glycoproteins are proteins which contain oligosaccharide chains covalently attached to amino acid side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. Secreted extracellular proteins are often glycosylated. In proteins that have segments extending extracellularly, the extracellular segments are also often glycosylated. Glycoproteins are also often important integral membrane proteins, where they play a role in cell–cell interactions. It is important to distinguish endoplasmic reticulum-based glycosylation of the secretory system from reversible cytosolic-nuclear glycosylation. Glycoproteins of the cytosol and nucleus can be modified through the reversible addition of a single GlcNAc residue that is considered reciprocal to phosphorylation and the functions of these are likely to be an additional regulatory mechanism that controls phosphorylation-based signalling. In contrast, classica

Evaluation of oxidation-sensitive polymersomes as vaccine nanocarriers to enhance humoral responses against arenavirus envelope glycoproteins

Clara Galan Navarro

Vaccines currently represent one of the most effective means to control and prevent infectious diseases affecting humans and animals and have dramatically improved public health, quality of life, and life expectancy. Over the last years several conceptual and technological advances in the field of bioengineering and immunology have allowed the development of new vaccines designs. Expanding novel domains such as structural biology, human monoclonal antibody isolation, high throughput sequencing, and design of new nanocarrier delivery platforms have changed the landscape of vaccinology. These new vaccine formulations allow the design of tailor-made antigens and particulate vehicles which allow better and fine-tuned protective immune responses against known and newly emerging pathogens. Over the past decades emerging human pathogens with the potential to cause severe epidemics have become a major public health problem. The last Ebola and Zika virus epidemics demonstrated in a dramatic manner that there is an urgent need to develop prophylactic and therapeutic approaches against pathogenic emerging viruses. Most successful vaccines rely on attenuated live microorganisms to induce protective immunity. However, changed demographics and associated safety concerns makes the development of a safer alternative a priority. Subunit vaccines composed of microbial components and proteins have emerged as a suitable alternative, however they are generally less immunogenic. To address this problematic our laboratory works on the development of immunization platforms which allow 1) the development of safe recombinant subunit vaccines and 2) the rapid generation of specific monoclonal antibodies using biosynthetic immunogens without the need for prior isolation and culture of the agent. The approach evaluated in the present studies is based on a novel polymersome (PS) platform serving as nanocarrier for efficient antigen delivery and the induction of humoral immunity. The potential of PS was assessed in the context of two important human emerging pathogens form the arenavirus family that cause severe hemorrhagic fevers and of which there are neither FDA-approved vaccines not prophylactic treatments: Lassa virus (LASV), endemic in Western Africa, and Machupo virus (MACV), the causative agent of Bolivian hemorrhagic fever. In a first part, we evaluated the PS platformâs capacity to enhance humoral immunity against the envelope glycoprotein 1 of LASV, (LASV GP1) that is notorious for its weak immunogenicity and poor antibody response. Immunization of mice with adjuvanted PS (LASV GP1) enhanced the quality of the humoral response to LASV GP1, eliciting antibodies with higher binding affinity to virion GP1, increased levels of polyfunctional anti-viral CD4 T cells, and the frequency of IgG-secreting B cells. PS (LASV GP1) elicited a more diverse epitope repertoire of anti-viral IgG. In a second part, we employed the PS platform in combination with single cell B cell sorting and cloning of recombinant IgG to generate a first set of species-specific mAbs against MACV. These new mAbs show exquisite specificity and negligible cross-reactivity to closely related arenaviruses in relevant techniques making them a unique and powerful tool for research and diagnostics purposes.

EPFL2017

Real-time monitoring of single-cell secretion with a high-throughput nanoplasmonic microarray

Hatice Altug, Saeid Ansaryan, Xiaokang Li, Yen-Cheng Liu, Eduardo Romero Arvelo

Proteins secreted by cells play significant roles in mediating many physiological, developmental, and pathological processes due to their functions in intra/intercellular communication and signaling. Conventional end-point methods are insufficient for understanding the temporal response in cell secretion process, which is often highly dynamic. Furthermore, cellular heterogeneity makes it essential to analyze secretory proteins from single cells. To uncover individual cellular activities and the underlying kinetics, new technologies are needed for real-time analysis of the secretomes of many cells at single-cell resolution. This study reports a high-throughput biosensing microarray platform, which is capable of label-free and real-time secretome monitoring from a large number of living single cells using a biochip integrating ultrasensitive nanoplasmonic substrate and microwell compartments having volumes of ∼0.4 nL. Precise synchronization of image acquisition and microscope stage movement of the developed optical platform enables spectroscopic analysis with high temporal and spectral resolution. In addition, our system allows simultaneous optical imaging of cells to track morphology changes for a comprehensive understanding of cellular behavior. We demonstrated the platform performance by detecting interleukin-2 secretion from hundreds of single lymphoma cells in real-time over many hours. Significantly, the analysis of the secretion kinetics allows us to study cellular response to the stimulations in a statistical way. The new platform is a promising tool for the characterization of single-cell functionalities given its versatility, throughput and label-free configuration.

2022

Nutritional Intervention for Developmental Brain Damage: Effects of Lactoferrin Supplementation in Hypocaloric Induced Intrauterine Growth Restriction Rat Pups

Camille Larpin, Yohan Van de Looij

Introduction: Intrauterine Growth Restriction (IUGR) refers to an impaired development of the fetus and hence results in adverse neurodevelopmental and psychiatric consequences later in life. Lactoferrin (Lf) is a glycoprotein present in milk that has already shown neuroprotective effects through its anti-inflammatory and antioxidant properties on impaired developing brains. The aim of this study was to characterize a rat model of IUGR and assess the neuroprotective effect of a nutritional supplementation with bovine Lf during pregnancy and lactation on this model. Methods: A model of 50% gestational caloric restriction (CR) was used. Three groups were designed, and pregnant rats had either ad libitum access to food (control group, CTL) or 50% of the controls' intake (restricted group, IUGR). The diet was isocaloric and supplemented with bovine Lf for the caloric restricted dams (restricted-Lf, IUGR_Lf). At postnatal day 7 and 21, advanced ex-vivo diffusion MRI techniques at 9.4T were used to investigate brain cortical and white matter microstructure. Further, genes and proteins involved in structure (synaptophysin, MBP), microglia (Iba-1), metabolism (MCT2, betaCaMKII) and apoptosis (Bcl-2) were analyzed in the cortex and striatum. In the cortex, the number of parvalbumin immunoreactive interneurons and their perineuronal nets were quantified. Behavioral tests were performed at P31. Results: Effects of the CR were significant in the cortex and striatum with reduction of synaptophysin (marker of synaptogenesis) at P7 and MBP (marker of myelin) at P21 in the cortex. Indeed, MCT2 (energy metabolism), Bcl-2 (anti-apoptotic protein) and betaCaMKII (synapse activity) expressions were reduced in IUGR groups at P7. In the striatum NG2 (marker of oligodendrocyte precursor cells) and Bcl-2 at P7 as well as betaCaMKII at P21 were decreased following IUGR and restored by Lf. Cortical microstructure was impaired following CR with partial effect of Lf. Lf prevented oxidative stress induced parvalbumin interneurons impairments whereas striatum and external capsule showed alterations in microstructure depicted by diffusion MRI, which were also partially reversed by Lf. Discussion and Conclusion: The model of 50% caloric restriction induced mild impairment partially reversed by nutritional intervention using Lf during pregnancy and lactation.

2019