Use of Nonhuman Sera as a Highly Cost-Effective Internal Standard for Quantitation of Multiple Human Proteins Using Species-Specific Tryptic Peptides: Applicability in Clinical LC-MS Analyses.

Quantitation of proteins using liquid chromatography-tandem mass spectrometry (LC-MS/MS) is complex, with a multiplicity of options ranging from label-free techniques to chemically and metabolically labeling proteins. Increasingly, for clinically relevant analyses, stable isotope-labeled (SIL) internal standards (ISs) represent the "gold standard" for quantitation due to their similar physiochemical properties to the analyte, wide availability, and ability to multiplex to several peptides. However, the purchase of SIL-ISs is a resource-intensive step in terms of cost and time, particularly for screening putative biomarker panels of hundreds of proteins. We demonstrate an alternative strategy utilizing nonhuman sera as the IS for quantitation of multiple human proteins. We demonstrate the effectiveness of this strategy using two high abundance clinically relevant analytes, vitamin D binding protein [Gc globulin] (DBP) and albumin (ALB). We extend this to three putative risk markers for cardiovascular disease: plasma protease C1 inhibitor (SERPING1), annexin A1 (ANXA1), and protein kinase, DNA-activated catalytic subunit (PRKDC). The results show highly specific, reproducible, and linear measurement of the proteins of interest with comparable precision and accuracy to the gold standard SIL-IS technique. This approach may not be applicable to every protein, but for many proteins it can offer a cost-effective solution to LC-MS/MS protein quantitation.

Twelve tips to develop entrustable professional activities.

Entrustable professional activities (EPAs), units of professional practice that require proficient integration of multiple competencies and can be entrusted to a sufficiently competent learner, are increasingly being used to define and inform curricula of health care professionals. The process of developing EPAs can be challenging and requires a deep yet pragmatic understanding of the concepts underlying EPA construction. Based on recent literature and the authors' lessons learned, this article provides the following practical and more or less sequential recommendations for developing EPAs: [1] Assemble a core team; [2] Build up expertise; [3] Establish a shared understanding of the purpose of EPAs; [4] Draft preliminary EPAs; [5] Elaborate EPAs; [6] Adopt a framework of supervision; [7] Perform a structured quality check; [8] Use a Delphi approach for refinement and/or consensus; [9] Pilot test EPAs; [10] Attune EPAs to their feasibility in assessment; [11] Map EPAs to existing curriculum; [12] Build a revision plan.

The logic behind entrustable professional activity frameworks: A scoping review of the literature.

INTRODUCTION: Entrustable professional activities (EPAs), discrete profession-specific tasks requiring integration of multiple competencies, are increasingly used to help define and inform curricula of specialty training programmes. Although guidelines exist to help guide the developmental process, deciding what logic to use to draft a preliminary EPA framework poses a crucial but often difficult first step. The logic of an EPA framework can be defined as the perspective used by its developers to break down the practice of a profession into units of professional work. This study aimed to map dominant logics and their rationales across postgraduate medical education and fellowship programmes. METHODS: A scoping review using systematic searches within five electronic databases (Medline, Embase, Google Scholar, Scopus and Web of Science) was performed. Dominant logics of included papers were identified using inductive coding and iterative analysis. RESULTS: In total, 42 studies were included. Most studies were conducted in the United States (n = 22; 52%), Canada (n = 6; 14%) and the Netherlands (n = 4; 10%). Across the reported range of specialties, family medicine (n = 4; 10%), internal medicine (n = 4; 10%), paediatrics (n = 3; 7%) and psychiatry (n = 3; 7%) were the most common. Three dominant logics could be identified, namely, 'service provision', 'procedures' and/or 'disease or patient categories'. The majority of papers (n = 37; 88%) used two or more logics when developing EPA frameworks (median = 3, range = 1-4). Disease or patient groups and service provision were the most common logics used (39% and 37%, respectively). CONCLUSIONS: Most programmes used a combination of logics when trying to capture the essential tasks of a profession in EPAs. For each of the three dominant logics, the authors arrived at a definition and identified benefits, limitations and examples. These findings may potentially inform best practice guidelines for EPA development.

The recommended description of an entrustable professional activity: AMEE Guide No. 140.

Entrustable professional activities (EPAs) have received much attention in the literature since they were first proposed in 2005. Useful guidelines, workshops, courses, and conferences have supported faculty in developing programs and designing assessment procedures using EPAs and entrustment decision-making. Yet, the need for clarification remains, particularly as more programs make the step from design to implementation.Well-written EPAs provide a natural construct to establish the outcome of training. To be useful, EPAs require more than a suitable title. This AMEE Guide elaborates eight sections of a full EPA description, and provides explanations and justifications for each. These sections are: title; specification and limitations; risks in case of failure; most relevant competency domains; knowledge, skills, attitudes and experiences; information sources to assess progress and support summative entrustment; entrustment/supervision level expected at which stage of training; and time period to expiration if not practiced.Constructing fully elaborated EPAs creates a shared mental model amongst learners and programs, informs competency-based curriculum design, directs ad-hoc and formal entrustment decision-making, and provides standards for certifying bodies and boundaries for scope of practice. The framework intends to support curricular leaders looking to adopt new EPAs, or revise and define established EPAs for competency-based education.

Creating Entrustable Professional Activities to Assess Internal Medicine Residents in Training: A Mixed-Methods Approach.

Background: Competency-based medical education has not advanced residency training as much as many observers expected. Some medical educators now advocate reorienting competency-based approaches to focus on a resident's ability to do authentic clinical work. Objective: To develop descriptions of clinical work for which internal medicine residents must gain proficiency to deliver meaningful patient care (for example, "Admit and manage a medical inpatient with a new acute problem"). Design: A modified Delphi process involving clinical experts followed by a conference of educational experts. Setting: The Royal College of Physicians and Surgeons of Canada. Participants: In phase 1 of the project, members of the Specialty Committee for Internal Medicine participated in a modified Delphi process to identify activities in internal medicine that represent the scope of the specialty. In phase 2 of the project, 5 experts who were scholars and leaders in competency-based medical education reviewed the results. Measurements: Phase 1 identified important activities, revised descriptions to improve accuracy and avoid overlap, and assigned activities to stages of training. Phase 2 compared proposed activity descriptions with published guidelines for their development and application in medical education. Results: The project identified 29 activities that qualify as entrustable professional activities. The project also produced a detailed description of each activity and guidelines for using them to assess residents. Limitation: These activities reflect the practice patterns of the developers and may not fully represent internal medicine practice in Canada. Conclusion: Identification of these activities is expected to facilitate modification of training and assessment programs for medical residents so that programs focus less on isolated skills and more on integrated tasks. Primary Funding Source: Southeastern Ontario Academic Medical Organization Endowed Scholarship and Education Fund and Queen's University Department of Medicine Innovation Fund.

A 13-Steroid Serum Panel Based on LC-MS/MS: Use in Detection of Adrenocortical Carcinoma.

BACKGROUND: Adrenocortical carcinoma (ACC) is a rare malignancy, with an annual incidence of 1 or 2 cases per million. Biochemical diagnosis is challenging because up to two-thirds of the carcinomas are biochemically silent, resulting from de facto enzyme deficiencies in steroid hormone biosynthesis. Urine steroid profiling by GC-MS is an effective diagnostic test for ACC because of its capacity to detect and quantify the increased metabolites of steroid pathway synthetic intermediates. Corresponding serum assays for most steroid pathway intermediates are usually unavailable because of low demand or lack of immunoassay specificity. Serum steroid analysis by LC-MS/MS is increasingly replacing immunoassay, in particular for steroids most subject to cross-reaction. METHODS: We developed an LC-MS/MS method for the measurement of serum androstenedione, corticosterone, cortisol, cortisone, 11-deoxycorticosterone, 11-deoxycortisol, 21-deoxycortisol, dehydroepiandrosterone sulfate, pregnenolone, 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone, and testosterone. Assay value in discriminating ACC from other adrenal lesions (phaeochromocytoma/paraganglioma, cortisol-producing adenoma, and lesions demonstrating no hormonal excess) was then investigated. RESULTS: In ACC cases, between 4 and 7 steroids were increased (median = 6), and in the non-ACC groups, up to 2 steroids were increased. 11-Deoxycortisol was markedly increased in all cases of ACC. All steroids except testosterone in males and corticosterone and cortisone in both sexes were of use in discriminating ACC from non-ACC adrenal lesions. CONCLUSIONS: Serum steroid paneling by LC-MS/MS is useful for diagnosing ACC by combining the measurement of steroid hormones and their precursors in a single analysis.

Access to controlled medicines for anesthesia and surgical care in low-income countries: a narrative review of international drug control systems and policies.

PURPOSE: This article describes the functioning of the international drug control system, its integration into national legislation and policy, and the collective impact on access to medicines. SOURCE: We conducted a review of the three international drug control conventions, peer-reviewed articles, and grey literature known to the authors that describes national and international drug control systems and their impact on access to controlled medicines. This review was supplemented with literature derived from a structured search of MEDLINE® for articles relating to medical uses of ketamine in low- and middle-income countries conducted to strengthen an advocacy campaign. We illustrate the impact of the drug control system on access to medicines through an analysis of current levels of availability of opioids in many countries as well as through a description of the ongoing advocacy work to ensure the availability of ketamine for medical care in low-income countries. PRINCIPAL FINDINGS: The complexity of the international drug control system, along with health providers' lack of knowledge regarding key provisions, presents a barrier to improving access to safe anesthesia care in low- and middle-income countries. Fifteen of the 46 essential medicines of potential relevance to perioperative care are listed under one or more of the schedules of the three international drug control conventions and, subsequently, are required to be under national controls, potentially decreasing their availability for medical use. CONCLUSION: Improving the capacity and quality of anesthesia care in low- and middle-income countries requires attention to improving access to controlled medicines. Anesthesiologists and others involved in global health work should collaborate with policymakers and others to improve national and international drug control legislation to ensure that attempts to thwart illicit drug trafficking and use do not compromise availability of controlled medicines.

An automated, high-throughput method for targeted quantification of intact insulin and its therapeutic analogs in human serum or plasma coupling mass spectrometric immunoassay with high resolution and accurate mass detection (MSIA-HR/AM).

The detection and quantification of insulin and its therapeutic analogs is important for medical, sports doping, and forensic applications. Synthetic variants contain slight sequence variations to affect bioavailability. To reduce sample handling bias, a universal extraction method is required for simultaneous extraction of endogenous and variant insulins with subsequent targeted quantification by LC-MS. A mass spectrometric immunoassay (MSIA), a multiplexed assay for intact insulin and its analogues that couples immunoenrichment with high resolution and accurate mass (HR/AM) spectrometric detection across the clinical range is presented in this report. The assay is sensitive, selective, semi-automated and can potentially be applied to detect new insulin isoforms allowing their further incorporation into second or third generation assays.

LC-MS candidate reference methods for the harmonisation of parathyroid hormone (PTH) measurement: a review of recent developments and future considerations.

The analysis of intact parathyroid hormone (PTH) (PTH1-84) is useful in the diagnosis of hyper- and hypocalcaemia, hyperparathyroidism, and in the prevention of bone mineral disorders in renal patients. The analysis is complicated by the presence of PTH fragments, which may accumulate in renal failure and cross-react in immunoassays, including the most recent third-generation immunoassays. Large variability exists between different commercially available assays. This article reviews the current literature on PTH testing, with emphasis on the use of mass spectrometry-based methods, and considers the important sources of variation which still need to be addressed prior to the development of much needed candidate reference methods for PTH analysis. Recently, mass spectrometric methods have been developed for the quantitation of PTH1-84 using surrogate tryptic peptides, but even these methods are subject to significant interferences due to the presence of newly observed modified PTH species, such as oxidised and phosphorylated PTH variants, which can accumulate in patient samples. Further work, including: 1) the use of high-resolution mass spectrometry; and 2) the analysis of PTH without prior protease digestion, is required before these approaches can be considered as reference methods against which other methods should be harmonised.

Making assessment a team sport: a qualitative study of facilitated group feedback in internal medicine residency.

Purpose: Competency-based medical education relies on feedback from workplace-based assessment (WBA) to direct learning. Unfortunately, WBAs often lack rich narrative feedback and show bias towards Medical Expert aspects of care. Building on research examining interactive assessment approaches, the Queen's University Internal Medicine residency program introduced a facilitated, team-based assessment initiative ("Feedback Fridays") in July 2017, aimed at improving holistic assessment of resident performance on the inpatient medicine teaching units. In this study, we aim to explore how Feedback Fridays contributed to formative assessment of Internal Medicine residents within our current model of competency-based training. Method: A total of 53 residents participated in facilitated, biweekly group assessment sessions during the 2017 and 2018 academic year. Each session was a 30-minute facilitated assessment discussion done with one inpatient team, which included medical students, residents, and their supervising attending. Feedback from the discussion was collected, summarized, and documented in narrative form in electronic WBA forms by the program's assessment officer for the residents. For research purposes, verbatim transcripts of feedback sessions were analyzed thematically. Results: The researchers identified four major themes for feedback: communication, intra- and inter-personal awareness, leadership and teamwork, and learning opportunities. Although feedback related to a broad range of activities, it showed strong emphasis on competencies within the intrinsic CanMEDS roles. Additionally, a clear formative focus in the feedback was another important finding. Conclusions: The introduction of facilitated team-based assessment in the Queen's Internal Medicine program filled an important gap in WBA by providing learners with detailed feedback across all CanMEDS roles and by providing constructive recommendations for identified areas for improvement.

Objectif: La formation médicale fondée sur les compétences s'appuie sur la rétroaction faite lors de l'évaluation des apprentissages par observation directe dans le milieu de travail. Malheureusement, les évaluations dans le milieu de travail omettent souvent de fournir une rétroaction narrative exhaustive et privilégient les aspects des soins relevant de l'expertise médicale. En se basant sur la recherche ayant étudié les approches d'évaluation interactive, le programme de résidence en médecine interne de l'Université Queen's a introduit en juillet 2017 une initiative d'évaluation facilitée et en équipe (« Les vendredis rétroaction ¼), visant à améliorer l'évaluation holistique du rendement des résidents dans les unités d'enseignement clinique en médecine interne. Dans cette étude, nous visons à explorer comment ces « vendredis rétroaction ¼ ont contribué à l'évaluation formative des résidents en médecine interne dans le cadre de notre modèle actuel de formation axée sur les compétences. Méthode: Au total, 53 résidents ont participé à des séances d'évaluation de groupe facilitées et bi-hebdomadaires au cours de l'année universitaire 2017-2018. Chaque séance consistait en une discussion d'évaluation facilitée de 30 minutes menée avec une équipe de l'unité de soins, qui comprenait des étudiants en médecine, des résidents et le médecin superviseur. Les commentaires issus de la discussion ont été recueillis, résumés et documentés sous forme narrative dans des formulaires électroniques d'observation directe dans le milieu de travail par le responsable de l'évaluation du programme de résidence. À des fins de recherche, les transcriptions verbatim des séances de rétroaction ont été analysées de façon thématique. Résultats: Les chercheurs ont identifié quatre thèmes principaux pour les commentaires : la communication, la conscience intra- et interpersonnelle, le leadership et le travail d'équipe, et les occasions d'apprentissage. Bien que la rétroaction concerne un large éventail d'activités, elle met fortement l'accent sur les compétences liées aux rôles intrinsèques de CanMEDS. De plus, le fait que la rétroaction avait un rôle clairement formatif est une autre constatation importante. Conclusions: L'introduction de l'évaluation en équipe facilitée dans le programme de médecine interne à Queen's a comblé une lacune importante dans l'apprentissage par observation directe dans le milieu de travail en fournissant aux apprenants une rétroaction détaillée sur tous les rôles CanMEDS et en formulant des recommandations constructives sur les domaines à améliorer.

The impact of mitotane therapy on serum-free proteins in patients with adrenocortical carcinoma.

Introduction: Adrenocortical carcinoma (ACC) is a rare malignancy of the adrenal cortex. Whilst surgery is the preferred treatment, adjunctive therapy with mitotane may be offered post-surgically to minimise the risk of recurrence or, in the absence of surgery, to attenuate progression. Aim: The objective was to evaluate the effects of mitotane treatment on serum protein concentrations in patients treated for ACC with mitotane therapy and compare this to patients with other adrenal neoplasms and a normal pregnant cohort. Methods: Serum cortisol, thyroid function tests, adrenocorticotrophic hormone (ACTH), cortisol-binding globulin (CBG), thyroxine-binding globulin (TBG), gonadotrophins and androgens were measured on plasma and serum samples. Thirty-five patients with ACC were included, and mitotane levels were noted to be sub-/supra-therapeutic. Data were tested for normality, reported as mean ± s.d., and compared to other two cohorts using paired-sample t-test with a 5% P-value for significance and a 95% CI. Results: Patients on mitotane therapy had a higher mean serum CBG concentration compared to the adrenal neoplasm group (sub-therapeutic: 79.5 (95% CI: 33.6, 125.4 nmol/L), therapeutic: 85.3 (95% CI: 37.1-133.6 nmol/L), supra-therapeutic: 75.7 (95% CI: -19.3, 170.6 nmol/L) and adrenal neoplasm: 25.5 (95% CI: 17.5, 33.5 nmol/L). Negative correlations between serum cortisol and CBG concentration were demonstrated within the supra-therapeutic plasma mitotane and adrenal neoplasm groups. Conclusion: Patients with ACC and therapeutic plasma mitotane concentrations had higher serum CBG concentrations compared to those with adrenal neoplasms or pregnant women, and higher serum cortisol. Whilst there was no direct correlation with cortisol and mitotane level, the negative correlation of cortisol with CBG may suggest that the direct effect of mitotane in increasing cortisol may also reflect that mitotane has a direct adrenolytic effect.

Enhanced fasting and post-prandial plasma bile acid responses after Roux-en-Y gastric bypass surgery.

OBJECTIVE: Exogenous bile acid (BA) administration is associated with beneficial metabolic effects very similar to those seen after Roux-en-Y gastric bypass (RYGB) surgery. Re-routing of bile into a biliopancreatic limb with simultaneous exclusion of food occurs after RYGB, with subsequent increased fasting plasma BAs. The study assessed fasting and post-prandial plasma BA response before and 15 months after RYGB. MATERIAL AND METHODS: The prospective study recruited 63 obese individuals (43 females), aged 43 (36-56) [median (IQR)] years. Blood samples were collected before and every 30 min for 120 min after a standard 400 kcal meal. Fasting and post-prandial plasma BAs, glucagons like peptide-1 (GLP-1), -tyrosine (PYY), fasting C-reactive protein (CRP), glucose and insulin were measured and homeostasis model assessment-insulin resistance (HOMA-IR) was calculated. RESULTS: Following RYGB, body mass index, CRP, fasting glucose and HOMA-IR decreased; 43.7 (39.3-49.2) kg/m(2) to 29.2 (25.1-35.0) kg/m(2), 7.9 (4.1-11.9) mg/L to 0.4 (0.2-1.0) mg/L, 5.5 (5.0-6.0) mmol/L to 4.6 (4.3-4.9) mmol/L and 5.9 (3.5-9.2) to 1.7 (1.1-2.2), respectively, all P < 0.001. Fasting total BAs, GLP-1 and PYY increased after RYGB; 1.69 (0.70-2.56) µmol/L to 2.43 (1.23-3.82) µmol/L (P = 0.02), 6.8 (1.5-15.3) pmol/L to 17.1 (12.6-23.9) pmol/L (P < 0.001) and 4.0 (1.0-7.1) pmol/L to 15.2 (10.0-28.3) pmol/L (P < 0.001), respectively. The area under the curve for post-prandial total BAs, total glycine-conjugated BAs, GLP-1 and PYY were greater after RYGB; 486 (312-732) µmol/L/min versus 1012 (684-1921) µmol/L/min, 315 (221-466) µmol/L/min versus 686 (424-877) µmol/L/min, 3679 (3162-4537) pmol/L/min versus 5347 (4727-5781) pmol/L/min and 1887 (1423-2092) pmol/L/min versus 3296 (2534-3834) pmol/L/min, respectively, all P < 0.0001. CONCLUSION: Weight loss following RYGB is associated with an increase in post-prandial plasma BA response due to larger amounts of glycine-conjugated BAs. This suggests up regulation of BA production and conjugation after RYGB.

Glypican-1 mediates both prion protein lipid raft association and disease isoform formation.

In prion diseases, the cellular form of the prion protein, PrP(C), undergoes a conformational conversion to the infectious isoform, PrP(Sc). PrP(C) associates with lipid rafts through its glycosyl-phosphatidylinositol (GPI) anchor and a region in its N-terminal domain which also binds to heparan sulfate proteoglycans (HSPGs). We show that heparin displaces PrP(C) from rafts and promotes its endocytosis, suggesting that heparin competes with an endogenous raft-resident HSPG for binding to PrP(C). We then utilised a transmembrane-anchored form of PrP (PrP-TM), which is targeted to rafts solely by its N-terminal domain, to show that both heparin and phosphatidylinositol-specific phospholipase C can inhibit its association with detergent-resistant rafts, implying that a GPI-anchored HSPG targets PrP(C) to rafts. Depletion of the major neuronal GPI-anchored HSPG, glypican-1, significantly reduced the raft association of PrP-TM and displaced PrP(C) from rafts, promoting its endocytosis. Glypican-1 and PrP(C) colocalised on the cell surface and both PrP(C) and PrP(Sc) co-immunoprecipitated with glypican-1. Critically, treatment of scrapie-infected N2a cells with glypican-1 siRNA significantly reduced PrP(Sc) formation. In contrast, depletion of glypican-1 did not alter the inhibitory effect of PrP(C) on the beta-secretase cleavage of the Alzheimer's amyloid precursor protein. These data indicate that glypican-1 is a novel cellular cofactor for prion conversion and we propose that it acts as a scaffold facilitating the interaction of PrP(C) and PrP(Sc) in lipid rafts.

Biochemical abnormalities in COVID-19: a comparison of white versus ethnic minority populations in the UK.

AIMS: Public Health England has identified that in COVID-19, death rates among ethnic minorities far exceeds that of the white population. While the increase in ethnic minorities is likely to be multifactorial, to date, no studies have looked to see whether values for routine clinical biochemistry parameters differ between ethnic minority and white individuals. METHODS: Baseline biochemical data for 22 common tests from 311 SARS-CoV-2 positive patients presenting to hospital in April 2020 in whom ethnicity data were available was retrospectively collected and evaluated. Data comparisons between ethnic minority and white groups were made for all patient data and for the subset of patients subsequently admitted to intensive care. RESULTS: When all patient data were considered, the ethnic minority population had statistically significant higher concentrations of C reactive protein (CRP), aspartate aminotransferase and gamma-glutamyl transferase, while troponin T was higher in the white group. A greater proportion of ethnic minority patients were subsequently admitted to intensive care, but when the presenting biochemistry of this subset of patients was compared, no significant differences were observed between ethnic minority and white groups. CONCLUSION: Our data show for the first time that routine biochemistry at hospital presentation in COVID-19 differs between ethnic minority and white groups. Among the markers identified, CRP was significantly higher in the ethnic minority group pointing towards an increased tendency for severe inflammation in this group.

International consensus on initial screening and follow-up of asymptomatic SDHx mutation carriers.

Approximately 20% of patients diagnosed with a phaeochromocytoma or paraganglioma carry a germline mutation in one of the succinate dehydrogenase (SDHx) genes (SDHA, SDHB, SDHC and SDHD), which encode the four subunits of the SDH enzyme. When a pathogenic SDHx mutation is identified in an affected patient, genetic counselling is proposed for first-degree relatives. Optimal initial evaluation and follow-up of people who are asymptomatic but might carry SDHx mutations have not yet been agreed. Thus, we established an international consensus algorithm of clinical, biochemical and imaging screening at diagnosis and during surveillance for both adults and children. An international panel of 29 experts from 12 countries was assembled, and the Delphi method was used to reach a consensus on 41 statements. This Consensus Statement covers a range of topics, including age of first genetic testing, appropriate biochemical and imaging tests for initial tumour screening and follow-up, screening for rare SDHx-related tumours and management of elderly people who have an SDHx mutation. This Consensus Statement focuses on the management of asymptomatic SDHx mutation carriers and provides clinicians with much-needed guidance. The standardization of practice will enable prospective studies in the near future.

Role of ADAMs in the ectodomain shedding and conformational conversion of the prion protein.

The cellular prion protein (PrP(C)) is essential for the pathogenesis and transmission of prion diseases. PrP(C) is bound to the plasma membrane via a glycosylphosphatidylinositol anchor, although a secreted, soluble form has also been identified. Previously we reported that PrP(C) is subject to ectodomain shedding from the membrane by zinc metalloproteinases with a similar inhibition profile to those involved in shedding the amyloid precursor protein. Here we have used gain-of-function (overexpression) and loss-of-function (small interfering RNA knockdown) experiments in cells to identify the ADAMs (a disintegrin and metalloproteinases) involved in the ectodomain shedding of PrP(C). These experiments revealed that ADAM9 and ADAM10, but not ADAM17, are involved in the shedding of PrP(C) and that ADAM9 exerts its effect on PrP(C) shedding via ADAM10. Using dominant negative, catalytically inactive mutants, we show that the catalytic activity of ADAM9 is required for its effect on ADAM10. Mass spectrometric analysis revealed that ADAM10, but not ADAM9, cleaved PrP between Gly(228) and Arg(229), three residues away from the site of glycosylphosphatidylinositol anchor attachment. The shedding of another membrane protein, the amyloid precursor protein beta-secretase BACE1, by ADAM9 is also mediated via ADAM10. Furthermore, we show that pharmacological inhibition of PrP(C) shedding or activation of both PrP(C) and PrP(Sc) shedding by ADAM10 overexpression in scrapie-infected neuroblastoma N2a cells does not alter the formation of proteinase K-resistant PrP(Sc). Collectively, these data indicate that although PrP(C) can be shed through the action of ADAM family members, modulation of PrP(C) or PrP(Sc) ectodomain shedding does not regulate prion conversion.