Amyloid formation and depolymerization of tumor suppressor p16INK4a are regulated by a thiol-dependent redox mechanism.

The conversion of a soluble protein into polymeric amyloid structures is a process that is poorly understood. Here, we describe a fully redox-regulated amyloid system in which cysteine oxidation of the tumor suppressor protein p16INK4a leads to rapid amyloid formation. We identify a partially-structured disulfide-bonded dimeric intermediate species that subsequently assembles into fibrils. The stable amyloid structures disassemble when the disulfide bond is reduced. p16INK4a is frequently mutated in cancers and is considered highly vulnerable to single-point mutations. We find that multiple cancer-related mutations show increased amyloid formation propensity whereas mutations stabilizing the fold prevent transition into amyloid. The complex transition into amyloids and their structural stability is therefore strictly governed by redox reactions and a single regulatory disulfide bond.

Characterizing the amyloid core region of the tumor suppressor protein p16INK4a using a limited proteolysis and peptide-based approach.

The human tumor suppressor p16INK4a is a small monomeric protein that can form amyloid structures. Formation of p16INK4a amyloid fibrils is induced by oxidation which creates an intermolecular disulfide bond. The conversion into amyloid is associated with a change from an all α-helical structure into ß-sheet fibrils. Currently, structural insights into p16INK4a amyloid fibrils are lacking. Here, we investigate the amyloid-forming regions of this tumor suppressor using isotope-labeling limited-digestion mass spectrometry analysis. We discover two key regions that likely form the structured core of the amyloid. Further investigations using thioflavin-T fluorescence assays, electron microscopy and solution nuclear magnetic resonance spectroscopy of shorter peptide regions confirm the self-assembly of the identified sequences that include methionine and leucine repeat regions. This work describes a simple approach for studying protein motifs involved in the conversion of monomeric species into aggregated fibril structures. It provides first insights into the polypeptide sequence underlying the core structure of amyloid p16INK4a formed after a unique oxidation-driven structural transition.

Using Non-Invasive Respiratory Monitoring for COVID-19 Pulmonary Embolism Diagnosis.

With the high incidence rate of pulmonary embolism (PE) and pneumonia reported in hospitalized patients with COVID-19, the ability to determine the dominant etiology for severe respiratory distress quickly and accurately is crucial to a patient's well-being. Traditionally, D-dimer blood tests and diagnostic imaging studies would be utilized to determine the presence of a PE or a venous thromboembolism. However, COVID-19 places patients in a prothrombotic state and performing diagnostic imaging studies on all patients with COVID-19 would be impractical, making the need for a simple and reliable method to determine the likelihood of PE or venous thromboembolism a priority for emergency departments. The authors believe the use of non-invasive respiratory monitoring technology to assess lung function in hospitalized patients with COVID-19 can aid in discerning the dominant hypoxia etiology and tailoring of their treatment. Here, the authors outline a case and method of using non-invasive respiratory monitoring of lung function in the successful diagnosis of a PE in a 62-year-old patient with COVID-19.

Implementation science for the adductor canal block: A new and adaptable methodology process.

BACKGROUND: Following the successful Perioperative Surgical Home (PSH) practice for total knee arthroplasty (TKA) at our institution, the need for continuous improvement was realized, including the deimplementation of antiquated PSH elements and introduction of new practices. AIM: To investigate the transition from femoral nerve blocks (FNB) to adductor canal nerve blocks (ACB) during TKA. METHODS: Our 13-month study from June 2016 to 2017 was divided into four periods: a three-month baseline (103 patients), a one-month pilot (47 patients), a three-month implementation and hardwiring period (100 patients), and a six-month evaluation period (185 patients). In total, 435 subjects were reviewed. Data within 30 postoperative days were extracted from electronic medical records, such as physical therapy results and administration of oral morphine equivalents (OME). RESULTS: Our institution reduced FNB application (64% to 3%) and increased ACB utilization (36% to 97%) at 10 mo. Patients in the ACB group were found to have increased ambulation on the day of surgery (4.1 vs 2.0 m) and lower incidence of falls (0 vs 1%) and buckling (5% vs 27%) compared with FNB patients (P < 0.05). While ACB patients (13.9) reported lower OME than FNB patients (15.9), the difference (P = 0.087) did not fall below our designated statistical threshold of P value < 0.05. CONCLUSION: By demonstrating closure of the "knowledge to action gap" within 6 mo, our institution's findings demonstrate evidence in the value of implementation science. Physician education, technical support, and performance monitoring were deemed key facilitators of our program's success. Expanded patient populations and additional orthopedic procedures are recommended for future study.