Search

Biomolecular condensates, membrane-less entities arising from liquid–liquid phase separation, hold dichotomous roles in health and disease. Alongside their physiological functions, these condensates can transition to a solid phase, producing amyloid-like structures implicated in degenerative diseases and cancer. This review thoroughly examines the dual nature of biomolecular condensates, spotlighting their role in cancer, particularly concerning the p53 tumor suppressor. Given that over half of the malignant tumors possess mutations in the TP53 gene, this topic carries profound implications for future cancer treatment strategies. Notably, p53 not only misfolds but also forms biomolecular condensates and aggregates analogous to other protein-based amyloids, thus significantly influencing cancer progression through loss-of-function, negative dominance, and gain-of-function pathways. The exact molecular mechanisms underpinning the gain-of-function in mutant p53 remain elusive. However, cofactors like nucleic acids and glycosaminoglycans are known to be critical players in this intersection between diseases. Importantly, we reveal that molecules capable of inhibiting mutant p53 aggregation can curtail tumor proliferation and migration. Hence, targeting phase transitions to solid-like amorphous and amyloid-like states of mutant p53 offers a promising direction for innovative cancer diagnostics and therapeutics. [ABSTRACT FROM AUTHOR]

Hydrostatic pressure is considered as a robust tool for studying the thermodynamics of protein folding and protein interactions, as well as the dynamics and structure of folding intermediates. The prospect of understanding protein misfolding diseases by using pressure to populate partially folded intermediates at the junction between productive and off-pathway folding, which may give rise to misfolded proteins, aggregates and amyloids is equally important.

Results show that exposure of the coiled-coil tropomyosin to hydrostatic pressure leads to the formation of a denatured dimer and substantial unfolding of the protein. Data indicate that the denatured coiled coil exhibits several independent folding subdomains that play a role in the folding pathway of tropomyosin.

Examination of the stability of the ribonucleoprotein particles of cowpea mosaic virus (CPMV) as a function of pressure and subzero temperatures indicates that presence of urea is not essential for denaturation of CPMV at -20 degree Celsius. Denaturation at room temperature is reversible, while that at subzero temperatures is irreversible. The irreversibly is correlated with the release of protein from RNA. Entropy controls the assembly of ribonucleoprotein and the assembly of CPMV involves the burial of nonpolar side chains.

Analysis of the influence of single-site amino acid substitutions in a viral coat proteins on the stability of the capsid of bacteriophage P22 by light-scattering and fluorescence emission methods reveals that the substitution leads to significant loss of capsid stability. Decrease in the level of entropic stabilization of the shell accounts for the instability of a W48Q mutant, while a volume related effect accounts for the instability of a G232D mutant. Coat proteins subunit is not affected by the substitution, and substitution of a polar amino acid for a nonpolar amino acid leads to significant loss of entropic stabilization.

The study of the stability of three forms of the P equals 3 icosahedral virus CPHV reveals that the presence of viral RNA stabilizes the capsid against disturbances by pressure and urea and promotes reinstatement of the denatured capsids. The reversibility of pressure disruption of RNA occurs at low protein concentrations and the interaction between protein and RNA offers resistance to degradation by cell ribonucleases. A specific RNA sequence initiates the formation of a subparticle and releases this unit to coordinate the assembly of others from the capsid protein.

The study of pre-dissociation phenomena during pressure-induced dissociation, temperature-induced denaturation and chemical-induced denaturation of Arc repressor by high resolution one dimensional and two dimensional NMR techniques reveals the presence of dissociated monomers between the native dimer and the dissociated globule state of Arc repressor. The alteration of pressure permits a less rapid turbulence of proteins than temperature or chemical agents.

Stable intermediate states of assembly, which cannot reassemble into didecamers and decamers, are produced during the pressure-induced dissociation of gastropod hemocyanin that occurs in the absence of calcium at pH values greater than 7.2. The half-dissociation pressure reveals a 1.3 kbar increase when the pH decreases from 7.6 to 6.6, which correlates with the stabilization of 1.35 kcal per mole of subunit.

The thermodynamic properties of the C- domain of TnC in its apo, [Mg.sub.2+] and [Ca.sub.2+] states are studied using a fluorescent mutant. The N-domain of TnC did not seem to have any effect on the C- domain, while a blue shift was observed in the Trp emission on binding with [Mg.sub.2+] and [Ca.sub.2+].

The structural and thermodynamic studies about the folding and dimerization of Smac/DIABLO, dimeric protein which plays a significant role in regulation of apoptosis by removing the inhibitory activity of IAPs (inhibitor of apoptosis proteins) are reported. The results indicate that the loss of both Smac/DIABLO activity and its affinity for IAP in the monomeric form is associated with the unstable state of monomers.

A study was conducted to evaluate the effects of dopamine (DA) on the stability of the in vitro grown PF and F composed of the wild type or variant (A53T and A30P) [alpha]-syn. The mesencephalic neurons seem to be more sensitive than cortical neurons to the presence of either (A53T and A30P) [alpha]-syn aggregate although the percentage of dopaminergic neurons in these cultures is in the range of 17-21%.

The first structural characterization of prion protein (PrP) compelxed to a small double-stranded oligonuclotide (E2DBS) that binds PrP with high affinity is described. The small-angle X-ray scattering (SAXS) data show that formation of the PrP-DNA complex leads to larger values of the maximum dimension and radius of gyration and the globular domain of PrP participates importantly in the formation of the complex.

Research has been conducted on tumor suppressor protein p53. The authors report that the core domain of this protein produces fibrillar aggregates which are rich in beta-sheet, and that these aggregates are toxic to cells and may be responsible for the p53 function loss in some types of cancer.

Results reveal that the homotrimeric vesicular stomatitis virus G protein undergoes pressure-induced conformational change that preserves the fusion properties of the virus as seen in an increase in light scattering. This represents a 'fusion-intermediate state' and contain minor changes in secondary structure.

Results show that hydration of the protein is very critical for the troponin C stability and its affinity for calcium. Data indicate that glycerol counteracts urea-induced troponin N-domain unfolding and that increased stability with glycerol decreases calcium affinity of the troponin N-domain. Furthermore, the calcium binding mediated opening of the N-domain is inhibited by glycerol, indicating that water is involved in wetting the exposed surface of the N-domain.

Prion-like behavior of several amyloidogenic proteins has been demonstrated in recent years. Despite having functional roles in some cases, irregular aggregation can have devastating consequences. The most commonly known amyloid diseases are Alzheimer's, Parkinson's, and Transmissible Spongiform Encephalopathies (TSEs). The pathophysiology of prion-like diseases involves the structural transformation of wild-type (wt) proteins to transmissible forms that can convert healthy proteins, generating aggregates. The mutant form of tumor suppressor protein, p53, has recently been shown to exhibit prion-like properties. Within the context of p53 aggregation and the search for ways to avert it, this review emphasizes discoveries, approaches, and research from our laboratory and others. Although its standard functions are strongly connected to tumor suppression, p53 mutants and aggregates are involved in cancer progression. p53 aggregates are heterogeneous assemblies composed of amorphous aggregates, oligomers, and amyloid-like fibrils. Evidence of these structures in tumor tissues, the in vitro capability for p53 mutants to coaggregate with wt protein, and the detection of cell-to-cell transmission indicate that cancer has the basic characteristics of prion and prion-like diseases. Various approaches aim to restore p53 functions in cancer. Methods include the use of small-molecule and peptide stabilizers of mutant p53, zinc administration, gene therapy, alkylating and DNA intercalators, and blockage of p53-MDM2 interaction. A primary challenge in developing small-molecule inhibitors of p53 aggregation is the large number of p53 mutations. Another issue is the inability to recover p53 function by dissociating mature fibrils. Consequently, efforts have emerged to target the intermediate species of the aggregation reaction. Φ-value analysis has been used to characterize the kinetics of the early phases of p53 aggregation. Our experiments using high hydrostatic pressure (HHP) and chemical denaturants have helped to clarify excited conformers of p53 that are prone to aggregation. Molecular dynamics (MD) and phasor analysis of single Trp fluorescence signals point toward the presence of preamyloidogenic conformations of p53, which are not observed for p63 or p73. Exploring the features of competent preamyloidogenic states of wt and different p53 mutants may provide a framework for designing personalized drugs for the restoration of p53 function. Protection of backbone hydrogen bonds (BHBs) has been shown to be an important factor for the stability of amyloidogenic proteins and was employed to identify and stabilize the structural defect resulting from the p53 Y220C mutation. Using MD simulations, we compared BHB protection factors between p53 family members to determine the donor-acceptor pairs in p53 that exhibit lower protection. The identification of structurally vulnerable sites in p53 should provide new insights into rational designs that can rapidly be screened using our experimental methodology. Through continued and combined efforts, the outlook is positive for the development of strategies for regulating p53 amyloid transformation. [ABSTRACT FROM AUTHOR]

The article discusses hydrostatic pressure which is used as a physicochemical method for conducting the research on biological macromolecules. Issues further discussed includes effects of pressure on macromolecules, perturbation of protein equilibrium reactions and protective effect of the osmolyte trimethylamine- N-oxide (TMAO) in denaturation.

The gene encoding the p53 tumor suppressor protein is the most frequently mutated oncogene in cancer patients; yet, generalized strategies for rescuing the function of different p53 mutants remain elusive. This work investigates factors that may contribute to the low inherent stability of the wild-type p53 core domain (p53C) and structurally compromised Y220C mutant. Pressure-induced unfolding of p53C was compared to p63C, the p53 family member with the highest stability, the engineered superstable p53C hexamutant (p53C HM), and lower stability p53C Y220C cancer-associated mutant. The following pressure unfolding values (P50% bar) were obtained: p53C 3346, p53C Y220C 2217, p53C HM 3943, and p63C 4326. Molecular dynamics (MD) simulations revealed that p53C Y220C was most prone to water infiltration, followed by p53C, whereas the interiors of p53C HM and p63C remained comparably dry. A strong correlation ( r 2 = 0.92) between P50% and extent of interior hydration was observed. The pathways of individual water molecule entry and exit were mapped and analyzed, revealing a common route preserved across the p53 family involving a previously reported pocket, along with a novel surface cleft, both of which appear to be targetable by small molecules. Potential determinants of propensity to water incursion were assessed, including backbone hydrogen bond protection and combined sequence and structure similarity. Collectively, our results indicate that p53C has an intrinsic susceptibility to water leakage, which is exacerbated in a structural class mutant, suggesting that there may be a common avenue for rescuing p53 function.

Human respiratory syncytial virus (hRSV) is a worldwide distributed pathogen that causes respiratory disease mostly in infants and the elderly. The M2-1 protein of hRSV functions as a transcription antiterminator and partakes in virus particle budding. It is present only in Pneumovirinae, namely, Pneumovirus (RSV) and Metapneumovirus, making it an interesting target for specific antivirals. hRSV M2-1 is a tight tetramer bearing a Cys3-His1 zinc-binding motif, present in Ebola VP30 protein and some eukaryotic proteins, whose integrity was shown to be essential for protein function but without a biochemical mechanistic basis. We showed that removal of the zinc atom causes dissociation to a monomeric apo-M2-1 species. Surprisingly, the secondary structure and stability of the apo-monomer is indistinguishable from that of the M2-1 tetramer. Dissociation reported by a highly sensitive tryptophan residue is much increased at pH 5.0 compared to pH 7.0, suggesting a histidine protonation cooperating in zinc removal. The monomeric apo form binds RNA at least as well as the tetramer, and this interaction is outcompeted by the phosphoprotein P, the RNA polymerase cofactor. The role of zinc goes beyond stabilization of local structure, finely tuning dissociation to a fully folded and binding competent monomer. Removal of zinc is equivalent to the disruption of the motif by mutation, only that the former is potentially reversible in the cellular context. Thus, this process could be triggered by a natural chelator such as glutathione or thioneins, where reversibility strongly suggests a modulatory role in the participation of M2-1 in the assembly of the polymerase complex or in virion budding.