The roles of molecular chaperones in regulating cell metabolism

Cellular oxidants and the proteostasis network: balance between activation and destruction

Loss of protein homeostasis (proteostasis) is a common hallmark of aging and age-associated diseases. Considered as the guardian of proteostasis, the proteostasis network (PN) acts to preserve the functionality of proteins during their lifetime. However, its activity declines with age, leading to disease manifestation. While reactive oxygen species (ROS) were traditionally considered culprits in this process, recent research challenges this view. While harmful at high concentrations, moderate ROS levels protect the cell against age-mediated onset of proteotoxicity by activating molecular chaperones, stress response pathways, and autophagy. This review explores the nuanced roles of ROS in proteostasis and discusses the most recent findings regarding the redox regulation of the PN and its potential in extending healthspan and delaying age-related pathologies.

A Systematic Review of Proteomics in Obesity: Unpacking the Molecular Puzzle

PURPOSE OF REVIEW

The present study aims to review the existing literature to identify pathophysiological proteins in obesity by conducting a systematic review of proteomics studies. Proteomics may reveal the mechanisms of obesity development and clarify the links between obesity and related diseases, improving our comprehension of obesity and its clinical implications.

RECENT FINDINGS

Most of the molecular events implicated in obesity development remain incomplete. Proteomics stands as a powerful tool for elucidating the intricate interactions among proteins in the context of obesity. This methodology has the potential to identify proteins involved in pathological processes and to evaluate changes in protein abundance during obesity development, contributing to the identification of early disease predisposition, monitoring the effectiveness of interventions and improving disease management overall. Despite many non-targeted proteomic studies exploring obesity, a comprehensive and up-to-date systematic review of the molecular events implicated in obesity development is lacking. The lack of such a review presents a significant challenge for researchers trying to interpret the existing literature. This systematic review was conducted following the PRISMA guidelines and included sixteen human proteomic studies, each of which delineated proteins exhibiting significant alterations in obesity. A total of 41 proteins were reported to be altered in obesity by at least two or more studies. These proteins were involved in metabolic pathways, oxidative stress responses, inflammatory processes, protein folding, coagulation, as well as structure/cytoskeleton. Many of the identified proteomic biomarkers of obesity have also been reported to be dysregulated in obesity-related disease. Among them, seven proteins, which belong to metabolic pathways (aldehyde dehydrogenase and apolipoprotein A1), the chaperone family (albumin, heat shock protein beta 1, protein disulfide-isomerase A3) and oxidative stress and inflammation proteins (catalase and complement C3), could potentially serve as biomarkers for the progression of obesity and the development of comorbidities, contributing to personalized medicine in the field of obesity. Our systematic review in proteomics represents a substantial step forward in unravelling the complexities of protein alterations associated with obesity. It provides valuable insights into the pathophysiological mechanisms underlying obesity, thereby opening avenues for the discovery of potential biomarkers and the development of personalized medicine in obesity.

The Role of Heat Shock Protein 70 (HSP70) in the Pathogenesis of Ocular Diseases-Current Literature Review

Heat shock proteins (HSPs) have been attracting the attention of researchers for many years. HSPs are a family of ubiquitous, well-characterised proteins that are generally regarded as protective multifunctional molecules that are expressed in response to different types of cell stress. Their activity in many organs has been reported, including the heart, brain, and retina. By acting as chaperone proteins, HSPs help to refold denatured proteins. Moreover, HSPs elicit inhibitory activity in apoptotic pathways and inflammation. Heat shock proteins were originally classified into several subfamilies, including the HSP70 family. The aim of this paper is to systematise information from the available literature about the presence of HSP70 in the human eye and its role in the pathogenesis of ocular diseases. HSP70 has been identified in the cornea, lens, and retina of a normal eye. The increased expression and synthesis of HSP70 induced by cell stress has also been demonstrated in eyes with pathologies such as glaucoma, eye cancers, cataracts, scarring of the cornea, ocular toxpoplasmosis, PEX, AMD, RPE, and diabetic retinopathy. Most of the studies cited in this paper confirm the protective role of HSP70. However, little is known about these molecules in the human eye and their role in the pathogenesis of eye diseases. Therefore, understanding the role of HSP70 in the pathophysiology of injuries to the cornea, lens, and retina is essential for the development of new therapies aimed at limiting and/or reversing the processes that cause damage to the eye.

Mechanisms of adaptation and evolution in Toxoplasma gondii

Toxoplasma has high host flexibility, infecting all nucleated cells of mammals and birds. This implies that during its infective process the parasite must constantly adapt to different environmental situations, which in turn leads to modifications in its metabolism, regulation of gene transcription, translation of mRNAs and stage specific factors. There are conserved pathways that support these adaptations, which we aim to elucidate in this review. We begin by exploring the widespread epigenetic mechanisms and transcription regulators, continue with the supportive role of Heat Shock Proteins (Hsp), the translation regulation, stress granules, and finish with the emergence of contingency genes in highly variable genomic domains, such as subtelomeres. Within epigenetics, the discovery of a new histone variant of the H2B family (H2B.Z), contributing to T. gondii virulence and differentiation, but also gene expression regulation and its association with the metabolic state of the parasite, is highlighted. Associated with the regulation of gene expression are transcription factors (TFs). An overview of the main findings on TF and development is presented. We also emphasize the role of Hsp90 and Tgj1 in T. gondii metabolic fitness and the regulation of protein translation. Translation regulation is also highlighted as a mechanism for adaptation to conditions encountered by the parasite as well as stress granules containing mRNA and proteins generated in the extracellular tachyzoite. Another important aspect in evolution and adaptability are the subtelomeres because of their high variability and gene duplication rate. Toxoplasma possess multigene families of membrane proteins and contingency genes that are associated with different metabolic stresses. Among them parasite differentiation and environmental stresses stand out, including those that lead tachyzoite to bradyzoite conversion. Finally, we are interested in positioning protozoa as valuable evolution models, focusing on research related to the Extended Evolutionary Synthesis, based on models recently generated, such as extracellular adaptation and ex vivo cyst recrudescence.

The components of the AhR-molecular chaperone complex differ depending on whether the ligands are toxic or non-toxic

The aryl hydrocarbon receptor (AhR) forms a complex with the HSP90-XAP2-p23 molecular chaperone when the cells are exposed to toxic compounds. Recently, 1,4-dihydroxy-2-naphthoic acid (DHNA) was reported to be an AhR ligand. Here, we investigated the components of the molecular chaperone complex when DHNA binds to AhR. Proteins eluted from the 3-Methylcolanthrene-affinity column were AhR-HSP90-XAP2-p23 complex. The AhR-molecular chaperone complex did not contain p23 in the eluents from the DHNA-affinity column. In 3-MC-treated cells, AhR formed a complex with HSP90-XAP2-p23 and nuclear translocation occurred within 30 min, while in DHNA-treated cells, AhR formed a complex with AhR-HSP90-XAP2, and translocation was slow from 60 min. Thus, the AhR activation mechanism may differ when DHNA is the ligand compared to toxic ligands.

A journey into the regulatory secrets of the de novo purine nucleotide biosynthesis

De novo purine nucleotide biosynthesis (DNPNB) consists of sequential reactions that are majorly conserved in living organisms. Several regulation events take place to maintain physiological concentrations of adenylate and guanylate nucleotides in cells and to fine-tune the production of purine nucleotides in response to changing cellular demands. Recent years have seen a renewed interest in the DNPNB enzymes, with some being highlighted as promising targets for therapeutic molecules. Herein, a review of two newly revealed modes of regulation of the DNPNB pathway has been carried out: i) the unprecedent allosteric regulation of one of the limiting enzymes of the pathway named inosine 5'-monophosphate dehydrogenase (IMPDH), and ii) the supramolecular assembly of DNPNB enzymes. Moreover, recent advances that revealed the therapeutic potential of DNPNB enzymes in bacteria could open the road for the pharmacological development of novel antibiotics.

Ab initio protein structure prediction: the necessary presence of external force field as it is delivered by Hsp40 chaperone

BACKGROUND

The aqueous environment directs the protein folding process towards the generation of micelle-type structures, which results in the exposure of hydrophilic residues on the surface (polarity) and the concentration of hydrophobic residues in the center (hydrophobic core). Obtaining a structure without a hydrophobic core requires a different type of external force field than those generated by a water. The examples are membrane proteins, where the distribution of hydrophobicity is opposite to that of water-soluble proteins. Apart from these two extreme examples, the process of protein folding can be directed by chaperones, resulting in a structure devoid of a hydrophobic core.

RESULTS

The current work presents such example: DnaJ Hsp40 in complex with alkaline phosphatase PhoA-U (PDB ID-6PSI)-the client molecule. The availability of WT form of the folding protein-alkaline phosphatase (PDB ID-1EW8) enables a comparative analysis of the structures: at the stage of interaction with the chaperone and the final, folded structure of this biologically active protein. The fuzzy oil drop model in its modified FOD-M version was used in this analysis, taking into account the influence of an external force field, in this case coming from a chaperone.

CONCLUSIONS

The FOD-M model identifies the external force field introduced by chaperon influencing the folding proces. The identified specific external force field can be applied in Ab Initio protein structure prediction as the environmental conditioning the folding proces.