Is the small heat shock protein HspB1 (Hsp27) a real and predominant target of methylglyoxal modification?

The chemical language of protein glycation

Glycation is a non-enzymatic post-translational modification (PTM) that is correlated with many diseases, including diabetes, cancer and age-related disorders. Although recent work points to the importance of glycation as a functional PTM, it remains an open question whether glycation has a causal role in cellular signaling and/or disease development. In this Review, we contextualize glycation as a specific mechanism of carbon stress and consolidate what is known about advanced glycation end-product (AGE) structures and mechanisms. We highlight the current understanding of glycation as a PTM, focusing on mechanisms for installing, removing or recognizing AGEs. Finally, we discuss challenges that have hampered a more complete understanding of the biological consequences of glycation. The development of tools for predicting, modulating, mimicking or capturing glycation will be essential for interpreting a post-translational glycation network. Therefore, continued insights into the chemistry of glycation will be necessary to advance understanding of glycation biology.

The Glyoxalase System Is a Novel Cargo of Amniotic Fluid Stem-Cell-Derived Extracellular Vesicles

The glyoxalase system is a ubiquitous cellular metabolic pathway whose main physiological role is the removal of methylglyoxal (MG). MG, a glycolysis byproduct formed by the spontaneous degradation of triosephosphates glyceraldehyde-3-phosphate (GA3P) and dihydroxyacetonephosphate (DHAP), is an arginine-directed glycating agent and precursor of the major advanced glycation end product arginine-derived, hydroimidazolone (MG-H1). Extracellular vesicles (EVs) are a heterogeneous family of lipid-bilayer-vesicular structures released by virtually all living cells, involved in cell-to-cell communication, specifically by transporting biomolecules to recipient cells, driving distinct biological responses. Emerging evidence suggests that included in the EVs cargo there are different metabolic enzymes. Specifically, recent research has pointed out that EVs derived from human amniotic fluid stem cell (HASC-EVs) contain glycolytic pay-off phase enzymes, such as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Since GAPDH catalyzes the sixth step of glycolysis using as a substrate GA3P, from which MG spontaneously origins, we wanted to investigate whether MG-derived MG-H1, as well as glyoxalases, could be novel molecule cargo in these EVs. By using immunoassays and spectrophotometric methods, we found, for the first time ever, that HASC-EVs contain functional glyoxalases and MG-H1, pioneering research to novel and exciting roles of these eclectic proteins, bringing them to the limelight once more.

Dicarbonyl derived post-translational modifications: chemistry bridging biology and aging-related disease

In living systems, nucleophilic amino acid residues are prone to non-enzymatic post-translational modification by electrophiles. α-Dicarbonyl compounds are a special type of electrophiles that can react irreversibly with lysine, arginine, and cysteine residues via complex mechanisms to form post-translational modifications known as advanced glycation end-products (AGEs). Glyoxal, methylglyoxal, and 3-deoxyglucosone are the major endogenous dicarbonyls, with methylglyoxal being the most well-studied. There are several routes that lead to the formation of dicarbonyl compounds, most originating from glucose and glucose metabolism, such as the non-enzymatic decomposition of glycolytic intermediates and fructosyl amines. Although dicarbonyls are removed continuously mainly via the glyoxalase system, several conditions lead to an increase in dicarbonyl concentration and thereby AGE formation. AGEs have been implicated in diabetes and aging-related diseases, and for this reason the elucidation of their structure as well as protein targets is of great interest. Though the dicarbonyls and reactive protein side chains are of relatively simple nature, the structures of the adducts as well as their mechanism of formation are not that trivial. Furthermore, detection of sites of modification can be demanding and current best practices rely on either direct mass spectrometry or various methods of enrichment based on antibodies or click chemistry followed by mass spectrometry. Future research into the structure of these adducts and protein targets of dicarbonyl compounds may improve the understanding of how the mechanisms of diabetes and aging-related physiological damage occur.

Bcl-2-associated athanogene 5 overexpression attenuates catecholamine-induced vascular endothelial cell apoptosis

Bcl-2 associated athanogene 5 (Bag5) is a novel endoplasmic reticulum (ER) regulator. However, its role in catecholamine-induced endothelial cells damage has not been fully understood. In our study, catecholamine was used to mimic hypertension-related endothelial cell damage. Then, western blots, enzyme-linked immunosorbent assay, immunofluorescence, quantitative polymerase chain reaction and pathway analysis were conducted to analyze the role of Bag5 in endothelial cell damage in response to catecholamine. Our results indicated that the endothelial cell viability was impaired by catecholamine. Interestingly, Bag5 overexpression significantly reversed endothelial cell viability. Mechanistically, Bag5 overexpression inhibited ER stress, attenuated oxidative stress and repressed inflammation in catecholamine-treated endothelial cells. These beneficial effects finally contributed to endothelial cell survival under catecholamine treatment. Pathway analysis demonstrated that Bag5 was under the control of the mitogen-activated protein kinase (MAPK)-extracellular-signal-regulated kinase (ERK) signaling pathway. Reactivation of the MAPK-ERK pathway could upregulate Bag5 expression and thus promote endothelial cell survival through inhibiting oxidative stress, ER stress, and inflammation. Altogether, our results illustrate that Bag5 overexpression sustains endothelial cell survival in response to catecholamine treatment. This finding identifies Bag5 downregulation and the inactivated MAPK-ERK pathway as potential mechanisms underlying catecholamine-induced endothelial cell damage.

Identifications, Characteristics, and Expression Patterns of Small Heat Shock Protein Genes in a Major Mulberry Pest, Glyphodes pyloalis (Lepidoptera: Pyralidae)

Six candidate sHSP genes were identified from the Glyphodes pyloalis transcriptome. All sHSP genes included full-length open reading frames and shared high similarity with the sequences of other lepidopteran species. These sHSP genes encoded 175-191 amino acid residues, and the predicted proteins had a molecular weight from 19.5 to 21.8 kDa. All GpsHSPs were expressed at lower levels at larval stages. All GpsHSPs were expressed at higher levels at diapaused, prepupal, or pupal stages, suggesting that sHSPs may be involved in metamorphosis in G. pyloalis. In addition to the developmental stage, extreme temperatures can induce variations in the expression of sHSPs genes. All GpsHSPs were significantly upregulated in larvae following exposure to heat shock, except GpHSP21.4 which downregulated at 4 h following exposure to the cold shock treatment. Furthermore, Starvation influenced the expression patterns of GpsHSPs as a function of the duration of food deprivation. Four GpsHSPs increased their expression with time of starvation until reaching to the peak level at 6 d of starvation. Finally, parasitism by the endoparasitoid Aulacocentrum confusum He et van Achterberg (Hymenoptera: Braconidae)-induced fluctuations in the expression of all GpsHSPs, and the expression varied with time after parasitization. Our results from this study strongly suggest functional differentiation within the sHSPs subfamily in G. pyloalis. The present study would provide further insight into the roles of sHSPs in G. pyloalis and novel avenues for promoting integrated management of this pest.