Cryo-electron microscopy of adipose tissue extracellular vesicles in obesity and type 2 diabetes mellitus.

Extracellular vesicles (EVs) are cell-derived membrane vesicles which play an important role in cell-to-cell communication and physiology. EVs deliver biological information from producing to recipient cells by transport of different cargo such as proteins, mRNAs, microRNAs, non-coding RNAs and lipids. Adipose tissue EVs could regulate metabolic and inflammatory interactions inside adipose tissue depots as well as distal tissues. Thus, adipose tissue EVs are assumed to be implicated in obesity-associated pathologies, notably in insulin resistance and type 2 diabetes mellitus (T2DM). In this study we for the first time characterize EVs secreted by visceral (VAT) and subcutaneous adipose tissue (SAT) of patients with obesity and T2DM with standard methods as well as analyze their morphology with cryo-electron microscopy. Cryo-electron microscopy allowed us to visualize heterogeneous population of EVs of various size and morphology including single EVs and EVs with internal membrane structures in samples from obese patients as well from the control group. Single vesicles prevailed (up to 85% for SAT, up to 75% for VAT) and higher proportion of EVs with internal membrane structures compared to SAT was typical for VAT. Decreased size of single and double SAT EVs compared to VAT EVs, large proportion of multilayered EVs and all EVs with internal membrane structures secreted by VAT distinguished obese patients with/without T2DM from the control group. These findings could support the idea of modified biogenesis of EVs during obesity and T2DM.

Structural Features of the Peptide Homologous to 6-25 Fragment of Influenza A PB1 Protein.

A mirror-symmetry motif was discovered in the N-terminus of the influenza virus PB1 protein. Structure of peptide comprised of the corresponding part of PB1 (amino acid residues 6-25) was investigated by circular dichroism and in silico modeling. We found that peptide PB1 (6-25) in solution assumes beta-hairpin conformation. A truncated peptide PB1 (6-13), containing only half of the mirror-symmetry motif, appeared to stabilize the beta-structure of the original peptide and, at high concentrations, was capable of reacting with peptide to form insoluble aggregates in vitro. Ability of PB1 (6-13) peptide to interact with the N-terminal domain of PB1 protein makes it a potential antiviral agent that inhibits PA-PB1 complex formation by affecting PB1 N-terminus structure.