Target-locked: A mechanism for disaggregase binding to aggregated proteins.

ClpG is a novel autonomous disaggregase found in Pseudomonas aeruginosa that confers resistance to lethal heat stress. The mechanism by which ClpG specifically targets protein aggregates for disaggregation is unknown. In their recent work published in JBC, Katikaridis et al. (2023) identify an avidity-based mechanism by which four or more ClpG subunits, through specific N-terminal hydrophobic residues located on an exposed ß-sheet loop, interact with multiple hydrophobic patches on an aggregated protein substrate. This study establishes a model for substrate binding to a prokaryotic disaggregase that should inform further investigations into other autonomous disaggregases.

Assessing the impact of a health navigator on improving access to care and addressing the social needs of palliative care patients experiencing homelessness: A service evaluation.

BACKGROUND: Health navigators are healthcare professionals who specialize in care coordination, case management, navigating transitions, and reducing barriers to care. There is limited literature on the impact of health navigators on community-based palliative care for people experiencing homelessness. AIM: We devised key performance indicators in nine categories with the aim to quantify the impact of a health navigator on the delivery of palliative care to patients experiencing homelessness. DESIGN: Data were collected prospectively for all patient encounters involving a health navigator from July 2020 to 2021 and reviewed to determine the distribution of the health navigator's role and the ways in which patient care was impacted. SETTING AND PARTICIPANTS: This study was conducted in Toronto, Ontario with the Palliative Education and Care for the Homeless (PEACH) Program. At any one time, the PEACH health navigator served a total of 50 patients. RESULTS: We identified five key areas of the health navigator role including (1) facilitating access (2) coordinating care (3) addressing social determinants of health (4) advocating for patients, and (5) counselling patients and loved ones. The health navigator role was split evenly between activities pertaining to palliative care for structurally vulnerable populations and community-based palliative care for the general population. To achieve high impact outcomes, a considerable investment of time and energy was required of the health navigator, speaking to the importance of adequate and sustainable funding. CONCLUSIONS: These findings underscore the potential for health navigators to add value to community-based palliative care teams, especially those caring for structurally vulnerable populations.

Palliative Education and Care for the Homeless (PEACH): A Model of Outreach Palliative Care for Structurally Vulnerable Populations.

The Palliative Education and Care for the Homeless (PEACH) program comprises a community palliative care team serving some of the most complex clients in the healthcare system. Formal partnerships bring together physician, nursing, psychosocial and homecare, health and housing navigation supports. PEACH has served over 1,000 clients, leading field-defining research, medical education and public advocacy. The PEACH program demonstrates that innovation through deep interorganizational and intersectoral integration can drive value-based impact for the most complex clients, providing instructive lessons for public health system reform well beyond the margins faced by people who are unhoused. This paper describes how PEACH's unique model, critical community partnerships and research have been necessary for it to become a leader in community-based palliative care for structurally vulnerable people.

Heat shock inhibition of CDK5 increases NOXA levels through miR-23a repression.

Hyperthermia is a proteotoxic stress that is lethal when exposure is extreme but also cytoprotective in that sublethal exposure leads to the synthesis of heat shock proteins, including HSP70, which are able to inhibit stress-induced apoptosis. CDK5 is an atypical cyclin-dependent kinase family member that regulates many cellular functions including motility and survival. Here we show that exposure of a human lymphoid cell line to hyperthermia causes CDK5 insolubilization and loss of tyrosine-15 phosphorylation, both of which were prevented in cells overexpressing HSP70. Inhibition of CDK5 activity with roscovitine-sensitized cells to heat induced apoptosis indicating a protective role for CDK5 in inhibiting heat-induced apoptosis. Both roscovitine and heat shock treatment caused increased accumulation of NOXA a pro-apoptotic BH3-only member of the BCL2 family. The increased abundance of NOXA by CDK5 inhibition was not a result of changes in NOXA protein turnover. Instead, CDK5 inhibition increased NOXA mRNA and protein levels by decreasing the expression of miR-23a, whereas overexpressing the CDK5 activator p35 attenuated both of these effects on NOXA and miR-23a expression. Lastly, overexpression of miR-23a prevented apoptosis under conditions in which CDK5 activity was inhibited. These results demonstrate that CDK5 activity provides resistance to heat-induced apoptosis through the expression of miR-23a and subsequent suppression of NOXA synthesis. Additionally, they indicate that hyperthermia induces apoptosis through the insolubilization and inhibition of CDK5 activity.

Enhanced ubiquitination and proteasomal degradation of catalytically deficient human choline acetyltransferase mutants.

Choline acetyltransferase (ChAT) is essential for cholinergic neuron function as it mediates synthesis of the neurotransmitter acetylcholine. ChAT mutations have been linked to the neuromuscular disorder congenital myasthenic syndrome (CMS). One CMS-related ChAT mutation, V18M, reduces enzyme activity and cellular protein levels, and is positioned within a highly conserved proline-rich motif with the sequence 14 PKLPVPP20 . We demonstrate that N-terminal truncation that includes this proline-rich motif, as well as mutation of prolines-17/19 together to alanine (P17A/P19A), dramatically reduces ChAT steady-state protein levels and cellular activity when expressed in cholinergic SN56 neural cells. The in vitro activity of bacterially expressed recombinant P17A/P19A-ChAT is also reduced, although this is not caused by changes in protein secondary structure or thermal stability. Treatment of SN56 cells with the proteasome inhibitor MG132 increases cellular P17A/P19A-ChAT steady-state protein levels, and by immunoprecipitation we found that ChAT is ubiquitinated and that polyubiquitination of P17A/P19A-ChAT is increased compared to wild-type (WT) ChAT. Using a novel fluorescent-biorthogonal pulse-chase protocol in SN56 cells, we determined that the protein half-life of P17A/P19A-ChAT (2.2 h) is substantially reduced compared to WT-ChAT (19.7 h). Lastly, we show that two CMS-related ChAT mutants (V18M and A513T) have enhanced ubiquitination, and that treatment with MG132 can partially restore both the steady-state protein levels as well as cellular activity of some CMS-mutant ChAT. These results identify a novel mechanism for regulation of ChAT through the ubiquitin-proteasome system that is influenced by the conserved N-terminal proline-rich motif of ChAT and may be implicated in CMS pathology. Choline acetyltransferase (ChAT) synthesizes acetylcholine in cholinergic neurons. In this study we find that steady-state protein levels of human 69-kDa ChAT are regulated by the ubiquitin-proteasome system. Mutation of a highly conserved N-terminal proline-rich motif in human 69-kDa ChAT reduces both cellular ChAT protein levels, through enhanced ubiquitination and proteasomal degradation, and enzyme activity. Ubiquitination of catalytically deficient congenital myasthenic syndrome (CMS)-mutant ChAT is increased in cells, and importantly proteasome inhibition partially restores steady-state protein levels as well as cellular activity of some CMS-mutant ChAT proteins.

Exploring the Barriers and Facilitators Experienced by Palliative Health Care Providers Working with Patients Experiencing Homelessness during the COVID-19 Pandemic.

Background: Patients experiencing homelessness not only have higher rates of medical complexity, comorbidity, and mortality, but also face barriers to accessing palliative care services. In structurally vulnerable populations with palliative care needs, these barriers are compounded, creating significant challenges for both patients and providers that have important health equity implications. Objective: The aim is to explore the experiences of palliative care providers working with patients experiencing homelessness during the COVID-19 pandemic and understand the barriers they faced in providing care, as well as facilitators that aided in the success of their teams. Methods: Seven health care providers from two Canadian palliative outreach teams involved in delivering palliative care services to patients experiencing homelessness during the COVID-19 pandemic participated in audio-recorded and transcribed videoconferencing interviews. Analysis was completed using generic descriptive thematic analysis. Results: Five key themes were identified: (1) factors negatively impacting patient health, (2) use of technology, (3) care provider emotions, (4) care provider education and advocacy, and (5) outreach team factors. Conclusion: Identified barriers during the pandemic included worsening of existing patient vulnerabilities, as well as challenges incorporating technology into care. Providers faced increased emotional burden, with a rise in workload, stress, fear, and grief. However, several facilitators allowed teams to provide high-quality care to this vulnerable population, including team support, interprofessional collaboration, and advocacy and education initiatives. The outreach model also proved to be a highly flexible, resilient, and adaptable model for providing care during the COVID-19 pandemic.

SPAAC Pulse-Chase: A Novel Click Chemistry-Based Method to Determine the Half-Life of Cellular Proteins.

Assessing the stability and degradation of proteins is central to the study of cellular biological processes. Here, we describe a novel pulse-chase method to determine the half-life of cellular proteins that overcomes the limitations of other commonly used approaches. This method takes advantage of pulse-labeling of nascent proteins in living cells with the bioorthogonal amino acid L-azidohomoalanine (AHA) that is compatible with click chemistry-based modifications. We validate this method in both mammalian and yeast cells by assessing both over-expressed and endogenous proteins using various fluorescent and chemiluminescent click chemistry-compatible probes. Importantly, while cellular stress responses are induced to a limited extent following live-cell AHA pulse-labeling, we also show that this response does not result in changes in cell viability and growth. Moreover, this method is not compromised by the cytotoxicity evident in other commonly used protein half-life measurement methods and it does not require the use of radioactive amino acids. This new method thus presents a versatile, customizable, and valuable addition to the toolbox available to cell biologists to determine the stability of cellular proteins.

Transitioning From Hospital to Palliative Care at Home: Patient and Caregiver Perceptions of Continuity of Care.

CONTEXT: Continuity of care is important at improving the patient experience and reducing unnecessary hospitalizations when transitioning across care settings, especially at the end of life. OBJECTIVE: To explore patient and caregiver understanding and valuation of "continuity of care" while transitioning from an in-hospital to a home-based palliative care team. METHODS: Longitudinal qualitative design using semistructured interviews conducted with patients and their caregivers before and after transitioning from hospital to palliative care at home. Interviews were audio-recorded and transcribed verbatim. Data were analyzed using thematic analysis within a postpositivist framework. Thirty-nine participants (18 patients, seven caregivers, and seven patient-caregiver dyads) were recruited from two acute care hospitals, wherein they received care from an inpatient palliative care consultation team and transitioned to home-based palliative care. RESULTS: Patients had a mean age of 68 years, 60% were female and 60% had a diagnosis of cancer. Caregivers had a mean age of 62 years and 50% were female. Participants perceived continuity of care to occur in three ways, depending on which stage they were at in their hospital-to-home transition. In hospital, continuity of care was experienced, as consistency of information exchanged between providers. During the transition from hospital to home, continuity of care was experienced as consistency of treatments. When receiving home-based palliative care, continuity of care was experienced as having consistent providers. CONCLUSION: Patients' and their caregivers' valuation of continuity of care was dependent on their stage of the hospital-to-home transition. Optimizing continuity of care requires an integrated network of providers with reliable information transfer and communication.

Providing Data-Driven Equitable Palliative and End-of-Life Care for Structurally Vulnerable Populations: A Pilot Survey of Information Management Strategies.

BACKGROUND: Considerable gains are being made in data-driven efforts to advance quality improvement in health care. However, organizations providing hospice-oriented palliative care for structurally vulnerable persons with terminal illnesses may not have the enabling data infrastructure or framework to derive such benefits. METHODS: We conducted a pilot cross-sectional qualitative study involving a convenience sample of hospice organizations across North America providing palliative care services for structurally vulnerable patients. Through semistructured interviews, we surveyed organizations on the types of data collected, the information systems used, and the challenges they faced. RESULTS: We contacted 13 organizations across North America and interviewed 9. All organizations served structurally vulnerable populations, including the homeless and vulnerably housed, socially isolated, and HIV-positive patients. Common examples of collected data included the number of referrals, the number of admissions, length of stay, and diagnosis. More than half of the organizations (n = 5) used an electronic medical record, although none of the record systems were specifically designed for palliative care. All (n = 9) the organizations used the built-in reporting capacity of their information management systems and more than half (n = 6) augmented this capacity with chart reviews. DISCUSSION: A number of themes emerged from our discussions. Present data collection is heterogeneous, and storage of these data is highly fragmented within and across organizations. Funding appeared to be a key enabler of more robust data collection and use. Future work should address these gaps and examine opportunities for innovative ways of analysis and reporting to improve care for structurally vulnerable populations.

Correction: Hedgehog inhibition mediates radiation sensitivity in mouse xenograft models of human esophageal adenocarcinoma.

[This corrects the article DOI: 10.1371/journal.pone.0194809.].

Hedgehog inhibition mediates radiation sensitivity in mouse xenograft models of human esophageal adenocarcinoma.

BACKGROUND: The Hedgehog (Hh) signaling pathway is active in esophageal adenocarcinoma (EAC). We used a patient-derived murine xenograft (PDX) model of EAC to evaluate tumour response to conventional treatment with radiation/chemoradiation with or without Hh inhibition. Our goal was to determine the potential radioresistance effects of Hh signaling and radiosensitization by Hh inhibitors. METHODS: PDX models were treated with radiation, chemotherapy or combined chemoradiation. Tumour response was measured by growth delay. Hh transcript levels (qRT-PCR) were compared among frozen tumours from treated and control mice. 5E1, a monoclonal SHH antibody, or LDE225, a clinical SMO inhibitor (Novartis®) inhibited Hh signaling. RESULTS: Precision irradiation significantly delayed xenograft tumour growth in all 7 PDX models. Combined chemoradiation further delayed growth relative to either modality alone in three of six PDX models. Following irradiation, two of three PDX models demonstrated sustained up-regulation of Hh transcripts. Combined LDE225 and radiation, and 5E1 alone delayed growth relative to either treatment alone in a Hh-responsive PDX model, but not in a non-responsive model. CONCLUSION: Hh signaling mediates the radiation response in some EAC PDX models, and inhibition of this pathway may augment the efficacy of radiation in tumours that are Hh dependent.

Chaperone-Mediated Regulation of Choline Acetyltransferase Protein Stability and Activity by HSC/HSP70, HSP90, and p97/VCP.

Choline acetyltransferase (ChAT) synthesizes the neurotransmitter acetylcholine in cholinergic neurons, and mutations of this enzyme are linked to the neuromuscular disorder congenital myasthenic syndrome (CMS). One CMS-related mutation, V18M, reduces ChAT enzyme activity and cellular protein levels, and is located within a highly-conserved N-terminal proline-rich motif at residues 14PKLPVPP20. We showed previously that disruption of this proline-rich motif by either proline-to-alanine mutation (P17A/P19A) or mutation of residue Val18 (V18M) enhances ubiquitination and degradation of these mutant ChAT proteins expressed in cholinergic SN56 cells by an unknown mechanism. In this study, using proximity-dependent biotin identification (BioID), co-immunoprecipitation and in situ proximity-ligation assay (PLA), we identified the heat shock proteins (HSPs) HSC/HSP70 and HSP90 as novel ChAT protein-interactors. These molecular chaperones are well-known for promoting the folding and stabilization of cellular proteins. Thus, we found that inhibition of HSPs by treatment of cells with either the HSC/HSP70 inhibitors 2-phenylethynesulfonamide (PES) or VER-155008, or the HSP90 inhibitor 17-AAG reduced cellular ChAT activity and solubility, and enhanced the ubiquitination and proteasome-dependent loss of ChAT protein. Importantly, the effects of HSP inhibition were greater for mutant ChAT proteins (P17A/P19A-ChAT and CMS-related V18M- and A513T-ChAT) compared to wild-type ChAT. HSPs can promote ubiquitination and degradation of terminally misfolded proteins through cooperative interaction with the E3 ubiquitin ligase CHIP/Stub1, and while we show that ChAT interacts with CHIP in situ, siRNA-mediated knock-down of CHIP had no effect on either wild-type or mutant ChAT protein levels. However, inhibition of the endoplasmic reticulum (ER)- and HSP-associated co-chaperone p97/VCP prevented degradation of ubiquitinated ChAT. Together, these results identify novel mechanisms for the functional regulation of wild-type and CMS-related mutant ChAT by pro-stabilizing HSPs and the pro-degradative co-chaperone p97/VCP that may have broader implications for ChAT function during cellular stress and disease.

82-kDa choline acetyltransferase and SATB1 localize to ß-amyloid induced matrix attachment regions.

The M-transcript of human choline acetyltransferase (ChAT) produces an 82-kDa protein (82-kDa ChAT) that concentrates in nuclei of cholinergic neurons. We assessed the effects of acute exposure to oligomeric amyloid-ß1-42 (Aß1-42) on 82-kDa ChAT disposition in SH-SY5Y neural cells, finding that acute exposure to Aß1-42 results in increased association of 82-kDa ChAT with chromatin and formation of 82-kDa ChAT aggregates in nuclei. When measured by chromatin immunoprecipitation with next-generation sequencing (ChIP-seq), we identified that Aß1-42-exposure increases 82-kDa ChAT association with gene promoters and introns. The Aß1-42-induced 82-kDa ChAT aggregates co-localize with special AT-rich binding protein 1 (SATB1), which anchors DNA to scaffolding/matrix attachment regions (S/MARs). SATB1 had a similar genomic association as 82-kDa ChAT, with both proteins associating with synapse and cell stress genes. After Aß1-42 -exposure, both SATB1 and 82-kDa ChAT are enriched at the same S/MAR on the APP gene, with 82-kDa ChAT expression attenuating an increase in an isoform-specific APP mRNA transcript. Finally, 82-kDa ChAT and SATB1 have patterned genomic association at regions enriched with S/MAR binding motifs. These results demonstrate that 82-kDa ChAT and SATB1 play critical roles in the response of neural cells to acute Aß-exposure.