Targeting Aminoacyl tRNA Synthetases for Antimalarial Drug Development.

Infections caused by malaria parasites place an enormous burden on the world's poorest communities. Breakthrough drugs with novel mechanisms of action are urgently needed. As an organism that undergoes rapid growth and division, the malaria parasite Plasmodium falciparum is highly reliant on protein synthesis, which in turn requires aminoacyl-tRNA synthetases (aaRSs) to charge tRNAs with their corresponding amino acid. Protein translation is required at all stages of the parasite life cycle; thus, aaRS inhibitors have the potential for whole-of-life-cycle antimalarial activity. This review focuses on efforts to identify potent plasmodium-specific aaRS inhibitors using phenotypic screening, target validation, and structure-guided drug design. Recent work reveals that aaRSs are susceptible targets for a class of AMP-mimicking nucleoside sulfamates that target the enzymes via a novel reaction hijacking mechanism. This finding opens up the possibility of generating bespoke inhibitors of different aaRSs, providing new drug leads.

De novo missense variants in exon 9 of SEPHS1 cause a neurodevelopmental condition with developmental delay, poor growth, hypotonia, and dysmorphic features.

Selenophosphate synthetase (SEPHS) plays an essential role in selenium metabolism. Two mammalian SEPHS paralogues, SEPHS1 and SEPHS2, share high sequence identity and structural homology with SEPHS. Here, we report nine individuals from eight families with developmental delay, growth and feeding problems, hypotonia, and dysmorphic features, all with heterozygous missense variants in SEPHS1. Eight of these individuals had a recurrent variant at amino acid position 371 of SEPHS1 (p.Arg371Trp, p.Arg371Gln, and p.Arg371Gly); seven of these variants were known to be de novo. Structural modeling and biochemical assays were used to understand the effect of these variants on SEPHS1 function. We found that a variant at residue Trp352 results in local structural changes of the C-terminal region of SEPHS1 that decrease the overall thermal stability of the enzyme. In contrast, variants of a solvent-exposed residue Arg371 do not impact enzyme stability and folding but could modulate direct protein-protein interactions of SEPSH1 with cellular factors in promoting cell proliferation and development. In neuronal SH-SY5Y cells, we assessed the impact of SEPHS1 variants on cell proliferation and ROS production and investigated the mRNA expression levels of genes encoding stress-related selenoproteins. Our findings provided evidence that the identified SEPHS1 variants enhance cell proliferation by modulating ROS homeostasis. Our study supports the hypothesis that SEPHS1 plays a critical role during human development and provides a basis for further investigation into the molecular mechanisms employed by SEPHS1. Furthermore, our data suggest that variants in SEPHS1 are associated with a neurodevelopmental disorder.

Loss of NF-κB1 Causes Gastric Cancer with Aberrant Inflammation and Expression of Immune Checkpoint Regulators in a STAT-1-Dependent Manner.

Polymorphisms in NFKB1 that diminish its expression have been linked to human inflammatory diseases and increased risk for epithelial cancers. The underlying mechanisms are unknown, and the link is perplexing given that NF-κB signaling reportedly typically exerts pro-tumorigenic activity. Here we have shown that NF-κB1 deficiency, even loss of a single allele, resulted in spontaneous invasive gastric cancer (GC) in mice that mirrored the histopathological progression of human intestinal-type gastric adenocarcinoma. Bone marrow chimeras revealed that NF-κB1 exerted tumor suppressive functions in both epithelial and hematopoietic cells. RNA-seq analysis showed that NF-κB1 deficiency resulted in aberrant JAK-STAT signaling, which dysregulated expression of effectors of inflammation, antigen presentation, and immune checkpoints. Concomitant loss of STAT1 prevented these immune abnormalities and GC development. These findings provide mechanistic insight into how polymorphisms that attenuate NFKB1 expression predispose humans to epithelial cancers, highlighting the pro-tumorigenic activity of STAT1 and identifying targetable vulnerabilities in GC.

Cryo-EM structure of an essential Plasmodium vivax invasion complex.

Plasmodium vivax is the most widely distributed malaria parasite that infects humans1. P. vivax invades reticulocytes exclusively, and successful entry depends on specific interactions between the P. vivax reticulocyte-binding protein 2b (PvRBP2b) and transferrin receptor 1 (TfR1)2. TfR1-deficient erythroid cells are refractory to invasion by P. vivax, and anti-PvRBP2b monoclonal antibodies inhibit reticulocyte binding and block P. vivax invasion in field isolates2. Here we report a high-resolution cryo-electron microscopy structure of a ternary complex of PvRBP2b bound to human TfR1 and transferrin, at 3.7 Å resolution. Mutational analyses show that PvRBP2b residues involved in complex formation are conserved; this suggests that antigens could be designed that act across P. vivax strains. Functional analyses of TfR1 highlight how P. vivax hijacks TfR1, an essential housekeeping protein, by binding to sites that govern host specificity, without affecting its cellular function of transporting iron. Crystal and solution structures of PvRBP2b in complex with antibody fragments characterize the inhibitory epitopes. Our results establish a structural framework for understanding how P. vivax reticulocyte-binding protein engages its receptor and the molecular mechanism of inhibitory monoclonal antibodies, providing important information for the design of novel vaccine candidates.

In limb or pelvic fracture, aspirin was noninferior to enoxaparin for reducing all-cause death.

SOURCE CITATION: Major Extremity Trauma Research Consortium (METRC); O'Toole RV, Stein DM, O'Hara NN, et al. Aspirin or low-molecular-weight heparin for thromboprophylaxis after a fracture. N Engl J Med. 2023;388:203-213. 36652352.

Design of proteasome inhibitors with oral efficacy in vivo against Plasmodium falciparum and selectivity over the human proteasome.

The Plasmodium falciparum proteasome is a potential antimalarial drug target. We have identified a series of amino-amide boronates that are potent and specific inhibitors of the P. falciparum 20S proteasome (Pf20S) ß5 active site and that exhibit fast-acting antimalarial activity. They selectively inhibit the growth of P. falciparum compared with a human cell line and exhibit high potency against field isolates of P. falciparum and Plasmodium vivax They have a low propensity for development of resistance and possess liver stage and transmission-blocking activity. Exemplar compounds, MPI-5 and MPI-13, show potent activity against P. falciparum infections in a SCID mouse model with an oral dosing regimen that is well tolerated. We show that MPI-5 binds more strongly to Pf20S than to human constitutive 20S (Hs20Sc). Comparison of the cryo-electron microscopy (EM) structures of Pf20S and Hs20Sc in complex with MPI-5 and Pf20S in complex with the clinically used anti-cancer agent, bortezomib, reveal differences in binding modes that help to explain the selectivity. Together, this work provides insights into the 20S proteasome in P. falciparum, underpinning the design of potent and selective antimalarial proteasome inhibitors.

Molecular Basis of Functional Effects of Phosphorylation of the C-Terminal Domain of the Rabies Virus P Protein.

The rabies virus (RABV) phosphoprotein (P protein) is expressed as several isoforms, which differ in nucleocytoplasmic localization and microtubule (MT) association, mediated by several sequences, including nuclear localization (NLS) and export (NES) sequences. This appears to underpin a functional diversity enabling multiple functions in viral replication and modulation of host biology. Mechanisms regulating trafficking are poorly defined, but phosphorylation by protein kinase C (PKC) in the P protein C-terminal domain (PCTD) regulates nuclear trafficking, mediated by PCTD-localized NLS/NES sequences, indicating that phosphorylation contributes to functional diversity. The molecular mechanism underlying the effects of PKC, and potential roles in regulating other host-cell interactions are unresolved. Here, we assess effects of phosphorylation on the P3 isoform, which differs from longer isoforms through an ability to localize to the nucleus and associate with MTs, which are associated with antagonism of interferon (IFN) signaling. We find that phosphomimetic mutation of the PKC site S210 inhibits nuclear accumulation and MT association/bundling. Structural analysis indicated that phosphomimetic mutation induces no significant structural change to the NLS/NES but results in the side chain of N226 switching its interactions from E228, within the NES, to E210. Intriguingly, N226 is the sole substituted residue between the PCTD of the pathogenic IFN-resistant RABV strain Nishigahara and a derivative attenuated IFN-sensitive strain Ni-CE, inhibiting P3 nuclear localization and MT association. Thus, S210 phosphorylation appears to impact on N226/E228 to regulate P protein localization, with N226 mutation in Ni-CE mimicking a constitutively phosphorylated state resulting in IFN sensitivity and attenuation. IMPORTANCE Rabies virus P protein is a multifunctional protein with critical roles in replication and manipulation of host-cell processes, including subversion of immunity. This functional diversity involves interactions of several P protein isoforms with the cell nucleus and microtubules. Previous studies showed that phosphorylation of the P protein C-terminal domain (PCTD) at S210, near nuclear trafficking sequences, regulates nucleocytoplasmic localization, indicating key roles in functional diversity. The molecular mechanisms of this regulation have remained unknown. Here, we show that phosphomimetic mutation of S210 regulates nuclear localization and MT association. This regulation does not appear to result from disrupted PCTD structure, but rather from a switch of specific side chain interactions of N226. Intriguingly, N226 was previously implicated in P protein nuclear localization/MT association, immune evasion, and RABV pathogenesis, through undefined mechanisms. Our data indicate that the S210-N226 interface is a key regulator of virus-host interactions, which is significant for pathogenesis.

Exploring Predictors of Sleep State Misperception in Women with Posttraumatic Stress Disorder.

OBJECTIVES: Insomnia is a common symptom of posttraumatic stress disorder (PTSD) that is resistant to first-line cognitive behavioral interventions. However, research suggests that, among individuals with PTSD, self-reported sleep impairment is typically more severe than what is objectively observed, a phenomenon termed sleep state misperception. Relatively little research has examined which individuals with PTSD are most likely to exhibit sleep state misperception. This study explored clinical predictors of sleep state misperception in a sample of 43 women with PTSD and clinically significant sleep impairment. METHOD: During a baseline assessment, participants' PTSD symptoms were assessed using a clinical interview and their sleep was assessed using the Pittsburgh Sleep Quality Index (PSQI). Objective sleep, self-reported sleep, and PTSD symptoms were then assessed over a 1-week period using actigraphy and daily diaries. RESULTS: Consistent with previous research, women in the study exhibited total sleep time (TST), sleep efficiency (SE), and sleep onset latency (SOL) sleep state misperception. For TST and SE, but not SOL, discrepancies between actigraphy and the PSQI were associated with each clinician-rated PTSD symptom cluster, whereas discrepancies between actigraphy and daily diary were only associated with clinician-rated reexperiencing symptoms. The only self-reported PTSD symptom that was uniquely associated with sleep state misperception was nightmares. This association was no longer significant after controlling for sleep-related anxiety. CONCLUSIONS: Results suggest that women with more severe reexperiencing symptoms of PTSD, particularly nightmares, may be more likely to exhibit TST and SE sleep state misperception, perhaps due to associated sleep-related anxiety.

Rescue Transesophageal Echocardiography: A Narrative Review of Current Knowledge and Practice.

Perioperative transesophageal echocardiography (TEE) has been part of clinical activity for more than 40 years. During this period, TEE has evolved in terms of technology and clinical applications beyond the initial fields of cardiology and cardiac surgery. The benefits of TEE in the diagnosis and management of acute hemodynamic and respiratory collapse have been recognized in noncardiac surgery and by other specialties too. This natural progress led to the development of rescue TEE, a relatively recent clinical application that extends the use of TEE and makes it accessible to a large group of clinicians and patients requiring acute care. In this review, the authors appraise the current clinical applications and evidence base around this topic. The authors provide a thorough review of the various image acquisition protocols, clinical benefits, and compare it with the more frequently used transthoracic echocardiography. Furthermore, the authors have reviewed the current training and credentialing pathways. Overall, rescue TEE is a highly attractive and useful point-of-care examination, but the current evidence base is limited and the technical protocols, training, and credentialing processes are not standardized. There is a need for adequate guidelines and high-quality research to support its application as a bedside rescue tool.

The utility of a symptom model to predict the risk of oesophageal cancer.

OBJECTIVE: To assess whether extra-oesophageal symptoms are predictive of oesophageal malignancy. METHODS: A prospective, single-centre cross-sectional questionnaire study at a tertiary referral unit for oesophageal cancer using the Comprehensive Reflux Symptoms Scale (CReSS) questionnaire tool. Respondents with oesophageal malignancy were compared with historical cohorts undergoing airway examination or upper gastrointestinal endoscopy and found to have benign diagnoses. We developed a model for predicting oesophageal cancer using linear discriminant analysis and logistic regression, assessed by Monte Carlo cross validation. RESULTS: Respondents with oesophageal malignancy (n = 146; mean age 70.5; male: female, 71:29) were compared with those undergoing airway examination (n = 177) and upper gastrointestinal endoscopy (n = 351), found to have benign diagnoses. No single questionnaire item, or group of co-varying items (factors), reliably discriminated oesophageal cancer from other diagnoses. Individual items which suggested higher risk of oesophageal malignancy included dysphagia (area under the curve (AUC) 0.68), low appetite (AUC 0.66), and early satiety (AUC 0.58). Conversely, throat pain (AUC 0.38), bloating (AUC 0.38) and heartburn (AUC 0.37) were inversely related to cancer risk. A forward stepwise regression analysis including a subset of 12 CReSS questionnaire items together with age and sex derived a model predictive of oesophageal malignancy in this cohort (AUC 0.89). CONCLUSION: We demonstrate a model comprised of 12 questionnaire items and 2 demographic parameters as a potential predictive tool for oesophageal malignancy diagnosis in this study population. Translating this model for predicting oesophageal malignancy in the general population is a valuable topic for future research.

Dissociation as a Distinct Peritraumatic Coping Response: A Preliminary Analysis.

Research examining physiological responses to trauma cues in PTSD has identified a subset of "nonresponders" showing suppressed physiological reactivity. The defense cascade model posits that individuals respond to stressors by progressing through a series of defensive reactions, with nonresponders having advanced to a shutdown response. It remains unclear whether dissociation is at the end of a continuum of passive behavior, indicating full shutdown, or if it comprises a distinct response. The present study aimed to address this uncertainty, using EFA to compare a two-factor (active, passive) and three-factor (active, passive, dissociative) model of defensive responding. Eighty-nine female physical and sexual assault survivors reported their peritraumatic reactions within 1 month of their assault, which were entered into the EFA. The three-factor model was superior, suggesting dissociation is a distinct category of peritraumatic coping. Peritraumatic use of both passive and dissociative coping strategies were each significantly associated with ongoing use of passive coping and increased PTSD symptoms 1-month posttrauma; surprisingly, the use of passive peritraumatic coping strategies was a better indicator than peritraumatic dissociation. The inclusion of depression as a covariate removed the association of passive (but not dissociative) coping with PTSD symptom severity. Active coping use was not significantly associated with any outcome, suggesting that the presence of shutdown responses is more informative than the presence or absence of any active coping. These findings highlight the importance of differentiating peritraumatic coping responses and the need for increased attention to the comparatively neglected topic of passive coping.

Emerging roles for IL-11 in inflammatory diseases.

Interleukin-11 (IL-11) is a cytokine that has been strongly implicated in the pathogenesis of fibrotic diseases and solid malignancies. Elevated IL-11 expression is also associated with several non-malignant inflammatory diseases where its function remains less well-characterized. Here, we summarize current literature surrounding the contribution of IL-11 to the pathogenesis of autoimmune inflammatory diseases, including rheumatoid arthritis, multiple sclerosis, diabetes and systemic sclerosis, as well as other chronic inflammatory conditions such as periodontitis, asthma, chronic obstructive pulmonary disease, psoriasis and colitis.

Multi-Site Concordance of Diffusion-Weighted Imaging Quantification for Assessing Prostate Cancer Aggressiveness.

BACKGROUND: Diffusion-weighted imaging (DWI) is commonly used to detect prostate cancer, and a major clinical challenge is differentiating aggressive from indolent disease. PURPOSE: To compare 14 site-specific parametric fitting implementations applied to the same dataset of whole-mount pathologically validated DWI to test the hypothesis that cancer differentiation varies with different fitting algorithms. STUDY TYPE: Prospective. POPULATION: Thirty-three patients prospectively imaged prior to prostatectomy. FIELD STRENGTH/SEQUENCE: 3 T, field-of-view optimized and constrained undistorted single-shot DWI sequence. ASSESSMENT: Datasets, including a noise-free digital reference object (DRO), were distributed to the 14 teams, where locally implemented DWI parameter maps were calculated, including mono-exponential apparent diffusion coefficient (MEADC), kurtosis (K), diffusion kurtosis (DK), bi-exponential diffusion (BID), pseudo-diffusion (BID*), and perfusion fraction (F). The resulting parametric maps were centrally analyzed, where differentiation of benign from cancerous tissue was compared between DWI parameters and the fitting algorithms with a receiver operating characteristic area under the curve (ROC AUC). STATISTICAL TEST: Levene's test, P < 0.05 corrected for multiple comparisons was considered statistically significant. RESULTS: The DRO results indicated minimal discordance between sites. Comparison across sites indicated that K, DK, and MEADC had significantly higher prostate cancer detection capability (AUC range = 0.72-0.76, 0.76-0.81, and 0.76-0.80 respectively) as compared to bi-exponential parameters (BID, BID*, F) which had lower AUC and greater between site variation (AUC range = 0.53-0.80, 0.51-0.81, and 0.52-0.80 respectively). Post-processing parameters also affected the resulting AUC, moving from, for example, 0.75 to 0.87 for MEADC varying cluster size. DATA CONCLUSION: We found that conventional diffusion models had consistent performance at differentiating prostate cancer from benign tissue. Our results also indicated that post-processing decisions on DWI data can affect sensitivity and specificity when applied to radiological-pathological studies in prostate cancer. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 3.

Image Quality Evaluation in Dual-Energy CT of the Chest, Abdomen, and Pelvis in Obese Patients With Deep Learning Image Reconstruction.

OBJECTIVE: The aim of this study was to evaluate image quality in vascular and oncologic dual-energy computed tomography (CT) imaging studies performed with a deep learning (DL)-based image reconstruction algorithm in patients with body mass index of ≥30. METHODS: Vascular and multiphase oncologic staging dual-energy CT examinations were evaluated. Two image reconstruction algorithms were applied to the dual-energy CT data sets: standard of care Adaptive Statistical Iterative Reconstruction (ASiR-V) and TrueFidelity DL image reconstruction at 2 levels (medium and high). Subjective quality criteria were independently evaluated by 4 abdominal radiologists, and interreader agreement was assessed. Signal-to-noise ratio (SNR) and contrast-to-noise ratio were compared between image reconstruction methods. RESULTS: Forty-eight patients were included in this study, and the mean patient body mass index was 39.5 (SD, 7.36). TrueFidelity-High (DL-High) and TrueFidelity-Medium (DL-Med) image reconstructions showed statistically significant higher Likert scores compared with ASiR-V across all subjective image quality criteria ( P < 0.001 for DL-High vs ASiR-V; P < 0.05 for DL-Med vs ASiR-V), and SNRs for aorta and liver were significantly higher for DL-High versus ASiR-V ( P < 0.001). Contrast-to-noise ratio for aorta and SNR for aorta and liver were significantly higher for DL-Med versus ASiR-V ( P < 0.05). CONCLUSIONS: TrueFidelity DL image reconstruction provides improved image quality compared with ASiR-V in dual-energy CTs obtained in obese patients.

Perioperative Management of the Fontan Patient for Cardiac and Noncardiac Surgery.

The Fontan circulation is the single-ventricle approach to surgical palliation of complex congenital heart disease wherein biventricular separation and function cannot be safely achieved. Incremental improvements in this surgical technique, along with improvements in the long-term medical management of these patients, have led to greater survival of these patients and a remarkably steady increase in the number of adults living with this unusual circulation and physiology. This has implications for healthcare providers who now have a greater chance of encountering Fontan patients during the course of their practice. This has particularly important implications for anesthesiologists because the effects of their interventions on the finely balanced Fontan circulation may be profound. The American Heart Association and American College of Cardiology recommend that, when possible, elective surgery should be performed in an adult congenital heart disease center, although this may not be feasible in the provision of true emergency care. This review article summarizes the pathophysiology pertinent to the provision of anesthesia in this complex patient group and describes important modifications to anesthetic technique and perioperative management.

Jensen polynomials for the Riemann zeta function and other sequences.

In 1927, Pólya proved that the Riemann hypothesis is equivalent to the hyperbolicity of Jensen polynomials for the Riemann zeta function [Formula: see text] at its point of symmetry. This hyperbolicity has been proved for degrees [Formula: see text] We obtain an asymptotic formula for the central derivatives [Formula: see text] that is accurate to all orders, which allows us to prove the hyperbolicity of all but finitely many of the Jensen polynomials of each degree. Moreover, we establish hyperbolicity for all [Formula: see text] These results follow from a general theorem which models such polynomials by Hermite polynomials. In the case of the Riemann zeta function, this proves the Gaussian unitary ensemble random matrix model prediction in derivative aspect. The general theorem also allows us to prove a conjecture of Chen, Jia, and Wang on the partition function.

Undifferentiated carcinoma with osteoclast-like giant cells: A pathologic-radiologic correlation of a rare histologic subtype of pancreatic ductal adenocarcinoma.

Undifferentiated carcinoma with osteoclast-like giant cells (UC-OGC) is an exceedingly rare subtype of pancreatic ductal adenocarcinoma. Histologically, UC-OGC is characterized by three cell types namely, a neoplastic mononuclear cell component, non-neoplastic osteoclast-like giant cells, and a non-neoplastic mononuclear histiocytic component. The behavior of this tumor is unpredictable; but many patients survive many years after diagnosis. UC-OGC may have a better prognosis compared to conventional pancreatic adenocarcinoma due to its slower local spread, less aggressive nature, better response to surgical resection and/or chemotherapy, and fewer metastases. Due to likely differences in prognosis and significant impact on patient management, it is important to distinguish this subtype from other types of pancreatic adenocarcinoma. We report a case of a small (<1 cm) undifferentiated carcinoma with osteoclast-like giant cells of the posterior pancreatic body discovered incidentally on magnetic resonance image (MRI) scan of a middle-aged man. The radiologic and pathologic findings are presented along with a discussion of the differential diagnosis of this exceedingly rare entity.

Functional and structural analysis of cytokine-selective IL6ST defects that cause recessive hyper-IgE syndrome.

BACKGROUND: Biallelic variants in IL6ST, encoding GP130, cause a recessive form of hyper-IgE syndrome (HIES) characterized by high IgE level, eosinophilia, defective acute phase response, susceptibility to bacterial infections, and skeletal abnormalities due to cytokine-selective loss of function in GP130, with defective IL-6 and IL-11 and variable oncostatin M (OSM) and IL-27 levels but sparing leukemia inhibitory factor (LIF) signaling. OBJECTIVE: Our aim was to understand the functional and structural impact of recessive HIES-associated IL6ST variants. METHODS: We investigated a patient with HIES by using exome, genome, and RNA sequencing. Functional assays assessed IL-6, IL-11, IL-27, OSM, LIF, CT-1, CLC, and CNTF signaling. Molecular dynamics simulations and structural modeling of GP130 cytokine receptor complexes were performed. RESULTS: We identified a patient with compound heterozygous novel missense variants in IL6ST (p.Ala517Pro and the exon-skipping null variant p.Gly484_Pro518delinsArg). The p.Ala517Pro variant resulted in a more profound IL-6- and IL-11-dominated signaling defect than did the previously identified recessive HIES IL6ST variants p.Asn404Tyr and p.Pro498Leu. Molecular dynamics simulations suggested that the p.Ala517Pro and p.Asn404Tyr variants result in increased flexibility of the extracellular membrane-proximal domains of GP130. We propose a structural model that explains the cytokine selectivity of pathogenic IL6ST variants that result in recessive HIES. The variants destabilized the conformation of the hexameric cytokine receptor complexes, whereas the trimeric LIF-GP130-LIFR complex remained stable through an additional membrane-proximal interaction. Deletion of this membrane-proximal interaction site in GP130 consequently caused additional defective LIF signaling and Stüve-Wiedemann syndrome. CONCLUSION: Our data provide a structural basis to understand clinical phenotypes in patients with IL6ST variants.

N- and C-terminal regions of αB-crystallin and Hsp27 mediate inhibition of amyloid nucleation, fibril binding, and fibril disaggregation.

Small heat-shock proteins (sHSPs) are ubiquitously expressed molecular chaperones that inhibit amyloid fibril formation; however, their mechanisms of action remain poorly understood. sHSPs comprise a conserved α-crystallin domain flanked by variable N- and C-terminal regions. To investigate the functional contributions of these three regions, we compared the chaperone activities of various constructs of human αB-crystallin (HSPB5) and heat-shock 27-kDa protein (Hsp27, HSPB1) during amyloid formation by α-synuclein and apolipoprotein C-II. Using an array of approaches, including thioflavin T fluorescence assays and sedimentation analysis, we found that the N-terminal region of Hsp27 and the terminal regions of αB-crystallin are important for delaying amyloid fibril nucleation and for disaggregating mature apolipoprotein C-II fibrils. We further show that the terminal regions are required for stable fibril binding by both sHSPs and for mediating lateral fibril-fibril association, which sequesters preformed fibrils into large aggregates and is believed to have a cytoprotective function. We conclude that although the isolated α-crystallin domain retains some chaperone activity against amyloid formation, the flanking domains contribute additional and important chaperone activities, both in delaying amyloid formation and in mediating interactions of sHSPs with amyloid aggregates. Both these chaperone activities have significant implications for the pathogenesis and progression of diseases associated with amyloid deposition, such as Parkinson's and Alzheimer's diseases.