Interdisciplinary collaborative eye examinations to protect preterm infant neurodevelopment: a quality improvement project.

Introduction: Infants born <31 weeks gestational age with birth weight ≤ 1,500 grams receive routine eye examinations to screen for Retinopathy of Prematurity (ROP) while in the Neonatal Intensive Care Unit (NICU) to help prevent vision threatening complications; however, preterm infants' sensory systems are underdeveloped, and repeated exposure to painful stimuli is associated with worse developmental outcomes. Methods: An interdisciplinary NICU team designed a collaborative eye exam model (CEEM) incorporating best practice recommendations for infant pain control during exams. Pain scores and vital signs were recorded before, during, and after exams. Two sets of mixed-effects regression models with a random intercept on infants were established to investigate relationships between the intervention, birth gestational age (BGA), postmenstrual age (PMA), and outcomes associated with painful stimuli. Survey feedback was elicited from NICU stakeholders about the CEEM. Results: Thirty standard of care (SC) and 35 CEEM exams of 37 infants were included in final analysis. In infants of the same BGA, the number of desaturation events was significantly reduced in the CEEM group (p = 0.003) and became 1.53 times smaller with each additional week of BGA (p = 0.009). Probability of heart rate recovery within 15 min lowered significantly in the CEEM group (p = 0.04). In SC or CEEM or between infants of the same PMA, no differences were observed for bradycardia, heart rate range, chance of heart rate recovery, or pain scores. Increases in tachycardia (p < 0.001) events and desaturations p = 0.006 were discovered in the CEEM group. When considering interaction effects, the CEEM appeared to reduce the number of desaturations to a greater degree for infants at earliest BGAs with attenuation of this effect with greater BGA. Regarding PMA, bradycardia and tachycardia events were reduced for infants across PMAs in the CEEM, but the effect for tachycardia improves with age, while the effect for bradycardia diminishes with age. Stakeholders agreed that the infant's eye exam experience and the staff experience was "very much" improved by the CEEM. Discussion: Despite variable findings in selected outcome measures, the CEEM was positively viewed by staff. Infants may benefit from the CEEM differently based on BGA and PMA.

Retinal injury identified by overhead-mounted optical coherence tomography in two young children with infantile-onset glaucoma.

PURPOSE: To report and characterize unexpected retinal findings identified by imaging with overhead-mounted optical coherence tomography (OCT) in 2 young children with infantile-onset glaucoma. METHODS: Children with glaucoma were imaged during clinically indicated examinations under anesthesia using overhead-mounted HRA+OCT Spectralis with Flex module (Flex-OCT, Heidelberg, Germany) from February 2017 through February 2022. Imagers prioritized scans of the peripapillary retinal nerve fiber layer (pRNFL), optic nerve head, and macula. Children imaged before age 2 years with images adequate for evaluation were included. Age at glaucoma diagnosis, glaucoma type, highest intraocular pressure (IOP), corneal diameter (CD), and axial length (AL) were recorded. RESULTS: A total of 41 children (71 eyes with glaucoma) were imaged before age 2 years. Macular imaging identified both inner and outer retinal thinning in 3 eyes of 2 young children (both eyes of a child with newborn primary congenital glaucoma (PCG) and 1 eye of a child with glaucoma following cataract surgery), which remained stable over time. These findings were present in 2 of 41 children (4.9%) and 3 of 71 eyes (4.2%) imaged with Flex-OCT. Neither highest IOP, CD, nor AL at imaging differentiated the 3 eyes with retinal changes from the larger group. CONCLUSIONS: Three eyes of 2 young children with refractory glaucoma of different etiologies and highly elevated IOP demonstrated areas of inner and outer retinal thinning, consistent with retinal injury from probable prior macular ischemia. Unexpected retinal pathology identified on Flex-OCT imaging in infantile-onset glaucomas highlights the need for continued study of the pathophysiology of this disease.

Intraoperative Mounted Optical Coherence Tomography Findings Following Reversal of Optic Nerve Head Cupping in Childhood Glaucoma.

PURPOSE: To examine the structural changes occurring in the optic nerve head (ONH) and macula in infants with childhood glaucoma and clinically observed ONH cupping reversal following intraocular pressure (IOP)-reducing glaucoma surgery, as captured by intra-operative spectral-domain optical coherence tomography (SD-OCT). DESIGN: Retrospective observational case series from an ongoing prospective cohort study. METHODS: Included were 18 eyes of 14 patients with childhood glaucoma. All eyes had SD-OCT imaging pre- and post-glaucoma intervention and clinically identified ONH cupping reversal. Patients with poor quality images or persistent optic nerve swelling following IOP reduction were excluded. Outcome measurements included IOP, cup-to-disc ratio, axial length and SD-OCT measurements of the peripapillary retinal nerve fiber layer (pRNFL), transverse horizontal diameter of Bruch membrane opening (BMO-D), cup depth, and macula. RESULTS: Mean age at surgery was 1.14±0.93 years and mean interval between pre- and post-operative imaging was 127 days (range 35-595). Following intervention, mean IOP reduction was 45%, accompanied by significant reductions in the cup-to-disc ratio (0.30±0.12, p<0.001), axial length (0.43±0.28mm, p<0.001) and cup depth (46%, p<0.001). Mean global pRNFL thickness pre- vs. post-treatment was 93.1±14.7µm vs. 93.1±17.1µm, respectively, p=1.0. There was no significant difference in pre- and post-treatment global or sectoral pRNFL, 3mm macular total and segmented retinal layer volumes, or the BMO-D. CONCLUSIONS: Clinical ONH cupping reversal after IOP-lowering surgery was associated with axial length reduction and decrease in cup depth, but no significant change in the pRNFL or macular volume measures. ONH cupping reversal likely marks stabilization but any pre-intervention ONH damage persists.

OCULAR MANIFESTATIONS OF PORETTI-BOLTSHAUSER SYNDROME: FINDINGS FROM MULTIMODAL IMAGING AND ELECTROPHYSIOLOGY.

BACKGROUND/PURPOSE: Poretti-Boltshauser syndrome is a rare, nonprogressive neurologic syndrome with characteristic cerebellar cysts on neuroimaging due to mutations in LAMA1. The ophthalmic findings in Poretti-Boltshauser syndrome are not well described. Here, we report the ophthalmic findings from multimodal imaging and electrophysiology of a patient with genetically confirmed Poretti-Boltshauser syndrome. METHODS: A 3-year-old boy with confirmed mutations in LAMA1 underwent examination under anesthesia with electroretinography and multimodal imaging including fundus photography, fluorescein angiography, optical coherence tomography, and optical coherence tomography angiography. RESULTS: Dilated fundus examination was notable for retinal vascular anomalies, including a large area of nonperfusion in the temporal macula with corresponding retinal thinning on optical coherence tomography. There was an absence of a distinct foveal avascular zone and decreased density of both the superficial and deep vascular plexuses in the macula on optical coherence tomography angiography. There was diffuse loss of choriocapillaris architecture and decreased choroidal thickness. CONCLUSION: Patients with Poretti-Boltshauser syndrome may possess chorioretinal thinning and retinal vascular abnormalities appreciable on examination and multimodal imaging. These findings suggest a role for LAMA1 in retinal and choroidal vascular development.

Minimally invasive glaucoma surgery in childhood glaucoma.

PURPOSE OF REVIEW: Minimally invasive glaucoma surgery (MIGS) has been shown to be safe and effective in treatment of mild to moderate glaucoma in adults, but reports in childhood glaucoma are limited. We review the available data concerning MIGS and discuss its potential role in childhood glaucoma management. RECENT FINDINGS: Ab interno counterparts to circumferential ab externo trabeculotomy such as gonioscopy-assisted transluminal trabeculotomy (GATT) and Trab360 show promise in treatment of primary glaucomas as reported in a few retrospective case series. Kahook Dual Blade (KDB) and Trabectome have demonstrated mixed results in few published case reports in children. Small case series and reports suggest that the Xen gel stent can be a safer alternative to traditional filtration surgery, though data on long-term implant and bleb stability are unavailable. Newer devices are being investigated and early results are encouraging. SUMMARY: GATT and Trab360 seem to be safe, effective methods of achieving circumferential trabeculotomy in childhood glaucoma. KDB, Trabectome, and Xen gel stent have shown some success in selected cases with short-term follow-up. Surgeons must determine the risks and benefits of MIGS over more established methods of intraocular pressure reduction for each individual child. Further research is needed to validate initial findings regarding MIGS in childhood glaucoma.

Lipopolysaccharide-Induced Exosomal miR-146a Is Involved in Altered Expression of Alzheimer's Risk Genes Via Suppression of TLR4 Signaling.

Repeated exposure to toll-like receptor 4 (TLR4) ligands, such as lipopolysaccharide (LPS), reduces responses of monocytes/macrophages to LPS (LPS/endotoxin tolerance). Microglial exposure to Aß deposits, a TLR4 ligand, may cause "Aß/LPS tolerance," leading to decreased Aß clearance. We demonstrated that microglial activation by LPS is diminished in Aß deposit-bearing 12-month-old model mice of Alzheimer's disease (AD), compared with non-AD mice and Aß deposit-free 2-month-old AD mice. Because miR-146a plays a predominant role in inducing TLR tolerance in macrophages and because miR-146a in extracellular vesicles (EVs) shed by inflammatory macrophages increases in circulation, we investigated potential roles of miR-146a and inflammatory EVs in inducing TLR tolerance in microglia and in altering expression of inflammatory AD risk genes. We found that miR-146a upregulation induces TLR tolerance and alters expression of inflammatory AD risk genes in response to LPS treatment in BV2 microglia. LPS brain injection altered expression of the AD risk genes in 12-month-old AD mice but not in non-AD littermates. EVs from inflammatory macrophages polarize BV2 microglia to M1 phenotype and induce TLR tolerance. Microglia exposed to Aß in the brain show reduced cytokine responses to systemic inflammation due to peripheral LPS injection, indicating TLR/Aß tolerance in microglia. Our results suggest that increased miR-146a induces microglial Aß/LPS tolerance and that circulating EVs shed by inflammatory macrophages contribute to microglial Aß/LPS tolerance, leading to reduced Aß clearance. Our study also suggests that altered expression of inflammatory AD risk genes may contribute to AD development via the same molecular mechanism underlying LPS tolerance.

Periocular infantile hemangioma masquerading as dacryocele.

A 2-month-old boy developed a protuberant, blue nodule inferomedial to the left medial canthus. It was unresponsive to oral and intramuscular antibiotics. After developing difficulty breathing, he was admitted, with the diagnosis of a dacryocele, and, after an inconclusive ultrasound, underwent probing and irrigation with nasal endoscopy. Intraoperatively, the lesion appeared discontinuous with the nasolacrimal system and could not be decompressed. Postoperative magnetic resonance imaging suggested a hemangioma or possible collapsed dacryocele. Doppler ultrasound confirmed a perinasolacrimal duct hemangioma. Systemic propranolol treatment was initiated.

Overhead Mounted Optical Coherence Tomography in Childhood Glaucoma Evaluation.

PRéCIS:: Overhead mounted spectral-domain optical coherence tomography (OCT) enables high-quality imaging of the optic nerve and macula in childhood glaucoma, and is particularly useful when standard tabletop OCT has failed or is not possible. PURPOSE: Tabletop OCT, integral to adult glaucoma management, can be limited in childhood glaucoma patients because of young age, poor cooperation, and/or technical challenges. To address these imaging difficulties, we determined the feasibility and quality of an overhead mounted unit in childhood glaucoma. Secondary aims included evaluation of peripapillary retinal nerve fiber layer (pRNFL), parafoveal total retinal thickness, and parafoveal ganglion cell complex (GCC) thickness. MATERIALS AND METHODS: Children and adults with a diagnosis of childhood glaucoma were imaged with an overhead mounted spectral-domain OCT as part of a prospective cross-sectional study. Participants had poor quality or unobtainable tabletop OCT and were scheduled for an examination under anesthesia and/or surgery as part of standard care. RESULTS: A total of 88 affected eyes in 60 of 65 (92.3%) enrolled patients (mean age, 5.9±5.9 y; range, 0.2 to 24.5) were successfully imaged. The mean image quality for analyzed scans was 22.9±6.0 dB (n=236 images). Mean values for pRNFL (80.5±31.0 µm; n=86), parafoveal total retinal thickness (301.10±39.9 µm; n=79), and parafoveal GCC thickness (96.0±21.6 µm; n=74) were calculated. CONCLUSIONS: Overhead mounted OCT allowed high-quality image acquisition and analysis in childhood glaucoma patients unable to be imaged with the tabletop counterpart, presenting an opportunity for improved clinical management and study of childhood glaucoma-related pathophysiology. pRNFL, parafoveal total retinal thickness, and parafoveal GCC thickness were decreased for affected eyes of children under 6 years of age compared with age-matched controls from a companion normative study.

Metabolic, Hormonal, Immunologic, and Genetic Factors Associated With the Incidence of Thyroid Disorders in Polycystic Ovarian Syndrome Patients.

Many endocrinopathies have been increasingly affecting females of reproductive age. Polycystic ovary syndrome (PCOS) and hypothyroidism are some of the most common endocrinopathies seen in females. The aim of this study is to find a relationship between the incidence of thyroiditis in polycystic ovarian syndrome patients. Literature review search was conducted via a series of systematic searches using multiple databases which lead to cross-referencing of articles within assigned criteria. Our study resulted in a review of 42 articles pertaining to our study. In this literature review article, factors were identified associating PCOS with thyroiditis. A viable relationship was found between the incidence of PCOS and thyroiditis. The combination of factors seen in this study proposes that clinicians may need to focus on certain markers regarding the screening of the incidence of thyroiditis. We also recommend future cohort studies to be conducted to further confirm the associations identified in this article.

Structural and mechanistic insights into Hsp104 function revealed by synchrotron X-ray footprinting.

Hsp104 is a hexameric AAA+ ring translocase, which drives protein disaggregation in nonmetazoan eukaryotes. Cryo-EM structures of Hsp104 have suggested potential mechanisms of substrate translocation, but precisely how Hsp104 hexamers disaggregate proteins remains incompletely understood. Here, we employed synchrotron X-ray footprinting to probe the solution-state structures of Hsp104 monomers in the absence of nucleotide and Hsp104 hexamers in the presence of ADP or ATPγS (adenosine 5'-O-(thiotriphosphate)). Comparing side-chain solvent accessibilities between these three states illuminated aspects of Hsp104 structure and guided design of Hsp104 variants to probe the disaggregase mechanism in vitro and in vivo We established that Hsp104 hexamers switch from a more-solvated state in ADP to a less-solvated state in ATPγS, consistent with switching from an open spiral to a closed ring visualized by cryo-EM. We pinpointed critical N-terminal domain (NTD), NTD-nucleotide-binding domain 1 (NBD1) linker, NBD1, and middle domain (MD) residues that enable intrinsic disaggregase activity and Hsp70 collaboration. We uncovered NTD residues in the loop between helices A1 and A2 that can be substituted to enhance disaggregase activity. We elucidated a novel potentiated Hsp104 MD variant, Hsp104-RYD, which suppresses α-synuclein, fused in sarcoma (FUS), and TDP-43 toxicity. We disambiguated a secondary pore-loop in NBD1, which collaborates with the NTD and NBD1 tyrosine-bearing pore-loop to drive protein disaggregation. Finally, we defined Leu-601 in NBD2 as crucial for Hsp104 hexamerization. Collectively, our findings unveil new facets of Hsp104 structure and mechanism. They also connect regions undergoing large changes in solvation to functionality, which could have profound implications for protein engineering.

The Effects of Mental Stress on Non-insulin-dependent Diabetes: Determining the Relationship Between Catecholamine and Adrenergic Signals from Stress, Anxiety, and Depression on the Physiological Changes in the Pancreatic Hormone Secretion.

Non-insulin-dependent diabetes or type II diabetes is prevalent around the world. A high-fat diet and chronic inactivity are often responsible for this chronic ailment. However, it is suspected that a high level of stress can also exacerbate diabetes. High anxiety can result in the release of sympathetic hormones that can elevate both cortisol and glucose levels, decrease insulin release, or affect the sensitivity and resistant of the insulin hormone. We have analyzed three research articles to see how stress and anxiety can affect non-insulin-dependent diabetes. In the first article, we selected participants with type II diabetes and injected them with saline or norepinephrine. The results indicated that participants with norepinephrine had experienced a decrease in glucose disposal and reduction in insulin secretion rate. Our second article utilizes African-American adults with type II diabetes. We provide them with a survey to determine how stress, anxiety, and depression can affect adherence to lifestyle modifications such as exercise and eating a proper diet. We find that subjects with higher stress levels tend to have lower compliance with their lifestyle regimes. Our third article focuses on female participants and divides them into two categories which are high chronic stress (HCS) and low chronic stress (LCS). We use an MRI to observe their brain activity while they stare at a picture of high-caloric type food. Our results indicate that there are different responses in various brain structure activities between subjects with HCS and LCS group. With these analyses, it can improve on the way healthcare providers can consult with their patients who have exacerbated type II diabetes despite proper medication and lifestyle modification.

Home Tonometry Assists Glaucoma Drainage Device Management in Childhood Glaucoma.

PRéCIS:: Home tonometry is useful in detecting tube-opening and alarming intraocular pressures (IOPs) after Baerveldt glaucoma drainage device (GDD) implantation in childhood glaucoma, allowing for timely physician response and individualized patient care. PURPOSE: The postoperative management of the nonvalved Baerveldt GDD presents challenges in pediatric patients due to widely variable IOP often occurring perioperatively. We evaluated the use of home tonometry in the management of Baerveldt implants for refractory childhood glaucoma. MATERIALS AND METHODS: As part of an ongoing prospective study involving home rebound tonometry, the families of patients receiving Baerveldt implants were trained to use the Icare TA01i rebound tonometer and asked to document IOP, relevant symptoms, and ocular medication changes outside of the clinic setting. Data were analyzed for time to tube-opening, multiple-day fluctuations, and various IOP trends. Clinician response to IOP fluctuations detected by home tonometry was also evaluated. RESULTS: Included were 19 patients (mean age: 16.1±9.6 y) having Baerveldt implantation from 2015 to 2018 by 1 attending physician. Home tonometry detected 92.3% (12/13) of spontaneous tube-openings, which occurred at a mean of 6.0±0.5 weeks. By home tonometry, mean IOP decreased 32.7% (24 vs. 15 mm Hg, P<0.01); 5-day IOP fluctuation decreased from 15 mm Hg preoperatively to 8 mm Hg after tube-opening (P<0.05). Preoperative, postimplantation, and post-tube-opening IOP ranged from 10 to 59, 3 to 61, and 1 to 51 mm Hg, respectively. Home tonometry prompted 94 documented medication changes and validated 1 surgical decision among 14 patients. CONCLUSIONS: Home rebound tonometry accurately detected tube-opening and alarming IOP fluctuations, allowing clinicians to promptly and appropriately respond to these events. Home tonometry-augmented GDD management in childhood glaucoma may improve the care of these challenging patients.

Strabismus surgery in the setting of glaucoma drainage devices in the pediatric population.

PURPOSE: To evaluate outcomes of strabismus surgery performed subequent to or concomitant with glaucoma drainage device (GDD) implantation for refractory childhood glaucoma. METHODS: The medical records of children who underwent strabismus surgery after or concomitantly with GDD implantation were reviewed retrospectively. Included were surgeries with motility and alignment data measured preoperatively and ≥3 months postoperatively. The following data were collected: demographics, visual acuity, glaucoma diagnosis, GDD type/location, pre- and postoperative sensorimotor/alignment measurements, and surgical details. Motor success was defined as ≤10Δ horizontal and ≤4Δ vertical residual heterotropia postoperatively. RESULTS: A total of 25 children were included: 11 in the post-GDD group and 14 in the concomitant-GDD group. In the former, peri-GDD capsule dissection was required in 9 of 11 patients (82%). All cases had preoperative motility restriction or intraoperative scarring. Mean preoperative deviation (26.7Δ ± 14.6Δ) decreased by 41% postoperatively, with improved alignment in 7 patients (64%). No patients met strict motor alignment criteria for success. In the concomitant-GDD group, mean preoperative deviation (28.5Δ ± 10.0Δ) decreased by 39% postoperatively, with improved alignment in 11 of 14 patients (79%). Four patients (29%) met strict criteria for success. There were no surgical complications in either group. CONCLUSIONS: Strabismus surgery in eyes with existing or planned GDDs for childhood glaucoma usually improves alignment but often does not result in success based on strict motor alignment criteria. Eyes with childhood glaucoma pose surgical technical challenges related to small orbits and exuberant GDD capsule-muscle scarring and postoperative challenges of poor vision and limited binocular function, that likely limit succcess.

Intraocular and extraocular hemorrhage associated with ligature release of non-valved glaucoma drainage implant.

PURPOSE: To report a rare complication of non-valved glaucoma drainage device surgery. OBSERVATIONS: An 85-year-old pseudophakic white male presented with painless vision loss and bloody tears. He was 5 weeks removed from uncomplicated non-valved glaucoma drainage device (Baerveldt 101-350, [AMO, Santa Clara, CA]). There was serosanguinous discharge without apparent source and a 25% layering hyphema in the anterior chamber. The tube was unobstructed in the anterior chamber and not abutting the iris. There was no presence of neovascularization or other abnormal vessels in the angle. After clearing of the hyphema, the patient had persistent vitreous hemorrhage necessitating pars plana vitrectomy. No source of hemorrhage was identified. CONCLUSIONS AND IMPORTANCE: This is the first report of a rare occurrence of intraocular and extraocular hemorrhage associated following spontaneous release of ligature of a non-valved glaucoma drainage implant. The presumed mechanism was sudden shallowing of the anterior chamber resulting in the tube irritating uveal vasculature. We do not have an explanation for the extraocular blood.

Microglial response to LPS increases in wild-type mice during aging but diminishes in an Alzheimer's mouse model: Implication of TLR4 signaling in disease progression.

Microglia-mediated clearance of amyloid beta-protein (Aß) via Toll-like receptor 4 (TLR4) signaling may play an important role in the pathogenesis of Alzheimer's disease (AD). However, as the disease progresses, activated microglia appear to become incapable of clearing Aß deposits. Because repeated exposure to a TLR4 ligand leads to a diminished response of monocytes/macrophages to lipopolysaccharide (LPS) and because aggregated Aß is a TLR4 ligand, we hypothesize that chronic exposure of microglia to Aß deposits may induce a state of Toll-like receptor (TLR) signaling dysfunction, leading to decreased Aß clearance and accelerated disease progression. LPS or phosphate-buffered saline (PBS) was injected into the hippocampus of AD-model (TgAPP/PS1) and wild-type (non-Tg) mice before and after the onset of Aß deposition, at age 2 and 12 months, respectively. Brain specimens were collected 7 days post-injection and analyzed for microglial activation and Aß load. While LPS-injected 2-month-old non-Tg mice showed 48-fold and 11-fold greater Iba1 immunoreactivity in the neocortex and hippocampus, respectively, compared with PBS-injected mice, LPS-injected 2-month-old TgAPP/PS1 mice had 61-fold and 13-fold increases in the neocortex and hippocampus, respectively. LPS injection activated microglia more strongly in TgAPP/PS1 mice than in non-Tg mice at 2 months of age. In contrast, at 12 months of age, Iba1 immunoreactivity of microglia was increased 541-fold and 38-fold in the neocortex and hippocampus, respectively, in LPS-injected non-Tg mice and 2.7-fold and 3.3-fold in the neocortex and hippocampus, respectively, in LPS-injected TgAPP/PS1 mice. Surprisingly, LPS injection decreased CD45 immunoreactivity in TgAPP/PS1 mice but increased it in non-Tg mice at 12 months. Although microglia in 12-month-old non-Tg mice showed stronger response to LPS than 2-month-old non-Tg mice, microglia in TgAPP/PS1 mice exhibited diminished immune response to LPS during aging. Our data indicate that microglial TLR4 signaling is altered in an AD mouse model and suggest that altered TLR4 signaling may contribute to Aß accumulation in the brain.

Mechanistic Insights into Hsp104 Potentiation.

Potentiated variants of Hsp104, a protein disaggregase from yeast, can dissolve protein aggregates connected to neurodegenerative diseases such as Parkinson disease and amyotrophic lateral sclerosis. However, the mechanisms underlying Hsp104 potentiation remain incompletely defined. Here, we establish that 2-3 subunits of the Hsp104 hexamer must bear an A503V potentiating mutation to elicit enhanced disaggregase activity in the absence of Hsp70. We also define the ATPase and substrate-binding modalities needed for potentiated Hsp104(A503V) activity in vitro and in vivo. Hsp104(A503V) disaggregase activity is strongly inhibited by the Y257A mutation that disrupts substrate binding to the nucleotide-binding domain 1 (NBD1) pore loop and is abolished by the Y662A mutation that disrupts substrate binding to the NBD2 pore loop. Intriguingly, Hsp104(A503V) disaggregase activity responds to mixtures of ATP and adenosine 5'-(γ-thio)-triphosphate (a slowly hydrolyzable ATP analogue) differently from Hsp104. Indeed, an altered pattern of ATP hydrolysis and altered allosteric signaling between NBD1 and NBD2 are likely critical for potentiation. Hsp104(A503V) variants bearing inactivating Walker A or Walker B mutations in both NBDs are inoperative. Unexpectedly, however, Hsp104(A503V) retains potentiated activity upon introduction of sensor-1 mutations that reduce ATP hydrolysis at NBD1 (T317A) or NBD2 (N728A). Hsp104(T317A/A503V) and Hsp104(A503V/N728A) rescue TDP-43 (TAR DNA-binding protein 43), FUS (fused in sarcoma), and α-synuclein toxicity in yeast. Thus, Hsp104(A503V) displays a more robust activity that is unperturbed by sensor-1 mutations that greatly reduce Hsp104 activity in vivo. Indeed, ATPase activity at NBD1 or NBD2 is sufficient for Hsp104 potentiation. Our findings will empower design of ameliorated therapeutic disaggregases for various neurodegenerative diseases.

The Hsp104 N-terminal domain enables disaggregase plasticity and potentiation.

The structural basis by which Hsp104 dissolves disordered aggregates and prions is unknown. A single subunit within the Hsp104 hexamer can solubilize disordered aggregates, whereas prion dissolution requires collaboration by multiple Hsp104 subunits. Here, we establish that the poorly understood Hsp104 N-terminal domain (NTD) enables this operational plasticity. Hsp104 lacking the NTD (Hsp104(ΔN)) dissolves disordered aggregates but cannot dissolve prions or be potentiated by activating mutations. We define how Hsp104(ΔN) invariably stimulates Sup35 prionogenesis by fragmenting prions without solubilizing Sup35, whereas Hsp104 couples Sup35 prion fragmentation and dissolution. Volumetric reconstruction of Hsp104 hexamers in ATPγS, ADP-AlFx (hydrolysis transition state mimic), and ADP via small-angle X-ray scattering revealed a peristaltic pumping motion upon ATP hydrolysis, which drives directional substrate translocation through the central Hsp104 channel and is profoundly altered in Hsp104(ΔN). We establish that the Hsp104 NTD enables cooperative substrate translocation, which is critical for prion dissolution and potentiated disaggregase activity.

Conserved distal loop residues in the Hsp104 and ClpB middle domain contact nucleotide-binding domain 2 and enable Hsp70-dependent protein disaggregation.

The homologous hexameric AAA(+) proteins, Hsp104 from yeast and ClpB from bacteria, collaborate with Hsp70 to dissolve disordered protein aggregates but employ distinct mechanisms of intersubunit collaboration. How Hsp104 and ClpB coordinate polypeptide handover with Hsp70 is not understood. Here, we define conserved distal loop residues between middle domain (MD) helix 1 and 2 that are unexpectedly critical for Hsp104 and ClpB collaboration with Hsp70. Surprisingly, the Hsp104 and ClpB MD distal loop does not contact Hsp70 but makes intrasubunit contacts with nucleotide-binding domain 2 (NBD2). Thus, the MD does not invariably project out into solution as in one structural model of Hsp104 and ClpB hexamers. These intrasubunit contacts as well as those between MD helix 2 and NBD1 are different in Hsp104 and ClpB. NBD2-MD contacts dampen disaggregase activity and must separate for protein disaggregation. We demonstrate that ClpB requires DnaK more stringently than Hsp104 requires Hsp70 for protein disaggregation. Thus, we reveal key differences in how Hsp104 and ClpB coordinate polypeptide handover with Hsp70, which likely reflects differential tuning for yeast and bacterial proteostasis.