Self-assembled GLP-1/glucagon peptide nanofibrils prolong inhibition of food intake

Introduction

Oxyntomodulin (Oxm) hormone peptide has a number of beneficial effects on nutrition and metabolism including increased energy expenditure and reduced body weight gain. Despite its many advantages as a potential therapeutic agent, Oxm is subjected to rapid renal clearance and protease degradation limiting its clinical application. Previously, we have shown that subcutaneous administration of a fibrillar Oxm formulation can significantly prolong its bioactivity in vivo from a few hours to a few days.

Methods

We used a protease resistant analogue of Oxm, Aib2-Oxm, to form nanfibrils depot and improve serum stability of released peptide. The nanofibrils and monomeric peptide in solution were characterized by spectroscopic, microscopic techniques, potency assay, QCM-D and in vivo studies.

Results

We show that in comparison to Oxm, Aib2-Oxm fibrils display a slower elongation rate requiring higher ionic strength solutions, and a higher propensity to dissociate. Upon subcutaneous administration of fibrillar Aib2-Oxm in rodents, a 5-fold increase in bioactivity relative to fibrillar Oxm and a significantly longer bioactivity than free Aib2-Oxm were characterized. Importantly, a decrease in food intake was observed up to 72-hour post-administration, which was not seen for free Aib2-Oxm.

Conclusion

Our findings provides compelling evidence for the development of long-lasting peptide fibrillar formulations that yield extended plasma exposure and enhanced in vivo pharmacological response.

Polymeric nanobiotics as a novel treatment for mycobacterial infections

Mycobacterium tuberculosis (Mtb) remains a major challenge to global health, made worse by the spread of multi-drug resistance. Currently, the efficacy and safety of treatment is limited by difficulties in achieving and sustaining adequate tissue antibiotic concentrations while limiting systemic drug exposure to tolerable levels. Here we show that nanoparticles generated from a polymer-antibiotic conjugate (‘nanobiotics’) deliver sustained release of active drug upon hydrolysis in acidic environments, found within Mtb-infected macrophages and granulomas, and can, by encapsulation of a second antibiotic, provide a mechanism of synchronous drug delivery. Nanobiotics are avidly taken up by infected macrophages, enhance killing of intracellular Mtb, and are efficiently delivered to granulomas and extracellular mycobacterial cords in vivo in an infected zebrafish model. We demonstrate that isoniazid (INH)-derived nanobiotics, alone or with additional encapsulation of clofazimine (CFZ), enhance killing of mycobacteria in vitro and in infected zebrafish, supporting the use of nanobiotics for Mtb therapy and indicating that nanoparticles generated from polymer-small molecule conjugates might provide a more general solution to delivering co-ordinated combination chemotherapy.

Two-Step Membrane Binding of NDPK-B Induces Membrane Fluidity Decrease and Changes in Lipid Lateral Organization and Protein Cluster Formation

Nucleoside diphosphate kinases (NDPKs) are crucial elements in a wide array of cellular physiological or pathophysiological processes such as apoptosis, proliferation, or metastasis formation. Among the NDPK isoenzymes, NDPK-B, a cytoplasmic protein, was reported to be associated with several biological membranes such as plasma or endoplasmic reticulum membranes. Using several membrane models (liposomes, lipid monolayers, and supported lipid bilayers) associated with biophysical approaches, we show that lipid membrane binding occurs in a two-step process: first, initiation by a strong electrostatic adsorption process and followed by shallow penetration of the protein within the membrane. The NDPK-B binding leads to a decrease in membrane fluidity and formation of protein patches. The ability of NDPK-B to form microdomains at the membrane level may be related to protein-protein interactions triggered by its association with anionic phospholipids. Such accumulation of NDPK-B would amplify its effects in functional platform formation and protein recruitment at the membrane.

Two-Step Membrane Binding of NDPK-B Induces Membrane Fluidity Decrease and Changes in Lipid Lateral Organization and Protein Cluster Formation

Nucleoside diphosphate kinases (NDPKs) are crucial elements in a wide array of cellular physiological or pathophysiological processes such as apoptosis, proliferation, or metastasis formation. Among the NDPK isoenzymes, NDPK-B, a cytoplasmic protein, was reported to be associated with several biological membranes such as plasma or endoplasmic reticulum membranes. Using several membrane models (liposomes, lipid monolayers, and supported lipid bilayers) associated with biophysical approaches, we show that lipid membrane binding occurs in a two-step process: first, initiation by a strong electrostatic adsorption process and followed by shallow penetration of the protein within the membrane. The NDPK-B binding leads to a decrease in membrane fluidity and formation of protein patches. The ability of NDPK-B to form microdomains at the membrane level may be related to protein-protein interactions triggered by its association with anionic phospholipids. Such accumulation of NDPK-B would amplify its effects in functional platform formation and protein recruitment at the membrane.

Conserved Amphipathic Helices Mediate Lipid Droplet Targeting of Perilipins 1-3

Perilipins (PLINs) play a key role in energy storage by orchestrating the activity of lipases on the surface of lipid droplets. Failure of this activity results in severe metabolic disease in humans. Unlike all other lipid droplet-associated proteins, PLINs localize almost exclusively to the phospholipid monolayer surrounding the droplet. To understand how they sense and associate with the unique topology of the droplet surface, we studied the localization of human PLINs inSaccharomyces cerevisiae,demonstrating that the targeting mechanism is highly conserved and that 11-mer repeat regions are sufficient for droplet targeting. Mutations designed to disrupt folding of this region into amphipathic helices (AHs) significantly decreased lipid droplet targetingin vivoandin vitro Finally, we demonstrated a substantial increase in the helicity of this region in the presence of detergent micelles, which was prevented by an AH-disrupting missense mutation. We conclude that highly conserved 11-mer repeat regions of PLINs target lipid droplets by folding into AHs on the droplet surface, thus enabling PLINs to regulate the interface between the hydrophobic lipid core and its surrounding hydrophilic environment.

Serum protein layers on parylene-C and silicon oxide: effect on cell adhesion

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We studied how cell adhesion is affected by serum protein adsorbed on parylene-C.

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Serum proteins form distinct layers when adsorbed onto parylene-C or silicon oxide.

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Biosensing technique elucidates contrasting protein layer densities and thicknesses.

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Fibronectin supports cell adhesion on both surfaces.

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Albumin outcompetes fibronectin on parylene-C and vice versa on silicon oxide.

Among the range of materials used in bioengineering, parylene-C has been used in combination with silicon oxide and in presence of the serum proteins, in cell patterning. However, the structural properties of adsorbed serum proteins on these substrates still remain elusive. In this study, we use an optical biosensing technique to decipher the properties of fibronectin (Fn) and serum albumin adsorbed on parylene-C and silicon oxide substrates. Our results show the formation of layers with distinct structural and adhesive properties. Thin, dense layers are formed on parylene-C, whereas thicker, more diffuse layers are formed on silicon oxide. These results suggest that Fn acquires a compact structure on parylene-C and a more extended structure on silicon oxide. Nonetheless, parylene-C and silicon oxide substrates coated with Fn host cell populations that exhibit focal adhesion complexes and good cell attachment. Albumin adopts a deformed structure on parylene-C and a globular structure on silicon oxide, and does not support significant cell attachment on either surface. Interestingly, the co-incubation of Fn and albumin at the ratio found in serum, results in the preferential adsorption of albumin on parylene-C and Fn on silicon oxide. This finding is supported by the exclusive formation of focal adhesion complexes in differentiated mouse embryonic stem cells (CGR8), cultured on Fn/albumin coated silicon oxide, but not on parylene-C. The detailed information provided in this study on the distinct properties of layers of serum proteins on substrates such as parylene-C and silicon oxide is highly significant in developing methods for cell patterning.

α-Synuclein senses lipid packing defects and induces lateral expansion of lipids leading to membrane remodeling

There is increasing evidence for the involvement of lipid membranes in both the functional and pathological properties of α-synuclein (α-Syn). Despite many investigations to characterize the binding of α-Syn to membranes, there is still a lack of understanding of the binding mode linking the properties of lipid membranes to α-Syn insertion into these dynamic structures. Using a combination of an optical biosensing technique and in situ atomic force microscopy, we show that the binding strength of α-Syn is related to the specificity of the lipid environment (the lipid chemistry and steric properties within a bilayer structure) and to the ability of the membranes to accommodate and remodel upon the interaction of α-Syn with lipid membranes. We show that this interaction results in the insertion of α-Syn into the region of the headgroups, inducing a lateral expansion of lipid molecules that can progress to further bilayer remodeling, such as membrane thinning and expansion of lipids out of the membrane plane. We provide new insights into the affinity of α-Syn for lipid packing defects found in vesicles of high curvature and in planar membranes with cone-shaped lipids and suggest a comprehensive model of the interaction between α-Syn and lipid bilayers. The ability of α-Syn to sense lipid packing defects and to remodel membrane structure supports its proposed role in vesicle trafficking.

A comprehensive study of lysozyme adsorption using dual polarization interferometry and quartz crystal microbalance with dissipation

Protein adsorption plays a crucial role in biomaterial surface science as it is directly linked to the biocompatibility of artificial biomaterial devices. Here, elucidation of protein adsorption mechanism is effected using dual polarization interferometry and a quartz crystal microbalance to characterize lysozyme layer properties on a silica surface at different coverage values. Lysozyme is observed to adsorb from sparse monolayer to multilayer coverage. At low coverage an irreversibly adsorbed layer is formed with slight deformation consistent with side-on orientation. At higher coverage values dynamic re-orientation effects are observed which lead to monolayer surface coverages of 2-3 ng/mm² corresponding to edge-on or/and end-on orientations. These monolayer thickness values ranged between 3 and 4.5 nm with a protein density value of 0.60 g/mL and with 50 wt% solvent mass. Further increase of coverage results formation of a multilayer structure. Using the hydration content and other physical layer properties a tentative model lysozyme adsorption is proposed.