Centre for Digital Transformation of Health - Research Publications
Now showing items 1-7 of 7
Autophosphorylation of serine 608 in the p85 regulatory subunit of wild type or cancer-associated mutants of phosphoinositide 3-kinase does not affect its lipid kinase activity
BACKGROUND: The α-isoform of the Type 1A Phosphoinositide 3-kinases (PI3Kα) has protein kinase activity as well as phosphoinositide lipid kinase activity. The best described substrate for its protein kinase activity is its regulatory subunit, p85α, which becomes phosphorylated on Serine 608. Phosphorylation of Serine 608 has been reported to down-regulate its lipid kinase activity. RESULTS: We have assessed whether oncogenic mutants of PI3Kα, which have up-regulated lipid kinase activity, have altered levels of Serine 608 phosphorylation compared to wild type PI3Kα, and whether differential phosphorylation of Serine 608 contributes to increased activity of oncogenic forms of PI3Kα with point mutations in the helical or the kinase domains. Despite markedly increased lipid kinase activity, protein kinase activity was not altered in oncogenic compared to wild type forms of PI3Kα. By manipulating levels of phosphorylation of Serine 608 in vitro, we found no evidence that the protein kinase activity of PI3Kα affects its phosphoinositide lipid kinase activity in either wild-type or oncogenic mutants of PI3Kα. CONCLUSIONS: Phosphorylation of p85α S608 is not a significant regulator of wild-type or oncogenic PI3Kα lipid kinase activity.
Independent Interactions of Phosphorylated beta-Catenin with E-Cadherin at Cell-Cell Contacts and APC at Cell Protrusions
(PUBLIC LIBRARY SCIENCE, 2010-11-30)
BACKGROUND: The APC tumour suppressor functions in several cellular processes including the regulation of β-catenin in Wnt signalling and in cell adhesion and migration. FINDINGS: In this study, we establish that in epithelial cells N-terminally phosphorylated β-catenin specifically localises to several subcellular sites including cell-cell contacts and the ends of cell protrusions. N-terminally phosphorylated β-catenin associates with E-cadherin at adherens junctions and with APC in cell protrusions. We isolated APC-rich protrusions from stimulated cells and detected β-catenin, GSK3β and CK1α, but not axin. The APC/phospho-β-catenin complex in cell protrusions appears to be distinct from the APC/axin/β-catenin destruction complex. GSK3β phosphorylates the APC-associated population of β-catenin, but not the cell junction population. β-catenin associated with APC is rapidly phosphorylated and dephosphorylated. HGF and wound-induced cell migration promote the localised accumulation of APC and phosphorylated β-catenin at the leading edge of migrating cells. APC siRNA and analysis of colon cancer cell lines show that functional APC is required for localised phospho-β-catenin accumulation in cell protrusions. CONCLUSIONS: We conclude that N-terminal phosphorylation of β-catenin does not necessarily lead to its degradation but instead marks distinct functions, such as cell migration and/or adhesion processes. Localised regulation of APC-phospho-β-catenin complexes may contribute to the tumour suppressor activity of APC.
Assessing the subcellular distribution of oncogenic phosphoinositide 3-kinase using microinjection into live cells
(PORTLAND PRESS LTD, 2014-01-01)
Oncogenic mutations in PIK3CA lead to an increase in intrinsic phosphoinositide kinase activity, but it is thought that increased access of PI3Kα (phosphoinositide 3-kinase α) to its PM (plasma membrane) localized substrate is also required for increased levels of downstream PIP3/Akt [phosphoinositide-3,4,5-trisphosphate/also called PKB (protein kinase B)] signalling. We have studied the subcellular localization of wild-type and the two most common oncogenic mutants of PI3Kα in cells maintained in growth media, and starved or stimulated cells using a novel method in which PI3Kα is pre-formed as a 1:1 p110α:p85α complex in vitro then introduced into live cells by microinjection. Oncogenic E545K and H1047R mutants did not constitutively interact with membrane lipids in vitro or in cells maintained in 10% (v/v) FBS. Following stimulation of RTKs (receptor tyrosine kinases), microinjected PI3Kα was recruited to the PM, but oncogenic forms of PI3Kα were not recruited to the PM to a greater extent and did not reside at the PM longer than the wild-type PI3Kα. Instead, the E545K mutant specifically bound activated Cdc42 in vitro and microinjection of E545K was associated with the formation of cellular protrusions, providing some preliminary evidence that changes in protein-protein interactions may play a role in the oncogenicity of the E545K mutant in addition to the well-known changes in lipid kinase activity.
Immunopurification of adenomatous polyposis coli (APC) proteins.
(Springer Science and Business Media LLC, 2013-10-25)
BACKGROUND: The adenomatous polyposis coli (APC) tumour suppressor gene encodes a 2843 residue (310 kDa) protein. APC is a multifunctional protein involved in the regulation of β-catenin/Wnt signalling, cytoskeletal dynamics and cell adhesion. APC mutations occur in most colorectal cancers and typically result in truncation of the C-terminal half of the protein. RESULTS: In order to investigate the biophysical properties of APC, we have generated a set of monoclonal antibodies which enable purification of recombinant forms of APC. Here we describe the characterisation of these anti-APC monoclonal antibodies (APC-NT) that specifically recognise endogenous APC both in solution and in fixed cells. Full-length APC(1-2843) and cancer-associated, truncated APC proteins, APC(1-1638) and APC(1-1311) were produced in Sf9 insect cells. CONCLUSIONS: Recombinant APC proteins were purified using a two-step affinity approach using our APC-NT antibodies. The purification of APC proteins provides the basis for detailed structure/function analyses of full-length, cancer-truncated and endogenous forms of the protein.
Sex Differences in Dose Escalation and Overdose Death during Chronic Opioid Therapy: A Population-Based Cohort Study.
(Public Library of Science (PLoS), 2015)
BACKGROUND: The use of opioids for noncancer pain is widespread, and more than 16,000 die of opioid-related causes in the United States annually. The patients at greatest risk of death are those receiving high doses of opioids. Whether sex influences the risk of dose escalation or opioid-related mortality is unknown. METHODS AND FINDINGS: We conducted a cohort study using healthcare records of 32,499 individuals aged 15 to 64 who commenced chronic opioid therapy for noncancer pain between April 1, 1997 and December 31, 2010 in Ontario, Canada. Patients were followed from their first opioid prescription until discontinuation of therapy, death from any cause or the end of the study period. Among patients receiving chronic opioid therapy, 589 (1.8%) escalated to high dose therapy and n = 59 (0.2%) died of opioid-related causes while on treatment. After multivariable adjustment, men were more likely than women to escalate to high-dose opioid therapy (adjusted hazard ratio 1.44; 95% confidence interval 1.21 to 1.70) and twice as likely to die of opioid-related causes (adjusted hazard ratio 2.04; 95% confidence interval 1.18 to 3.53). These associations were maintained in a secondary analysis of 285,520 individuals receiving any opioid regardless of the duration of therapy. CONCLUSIONS: Men are at higher risk than women for escalation to high-dose opioid therapy and death from opioid-related causes. Both outcomes were more common than anticipated.
Preoperative opioid use and complications following total joint replacement: a protocol for a systematic review and meta-analysis.
(BMJ Journals, 2020-06-16)
INTRODUCTION: Mounting evidence now indicates that preoperative opioid use is associated with an array of complications following total joint replacement (TJR). However, evidence of these risks remains fragmented. A comprehensive and well-integrated understanding of this body of evidence is necessary to appropriately inform treatment decisions, the allocation of limited healthcare resources, and the direction of future clinical research. The proposed systematic review and meta-analysis aims to identify and synthesise the available evidence of an association between opioid use prior to TJR and postoperative complications, categorised by complication type. METHODS AND ANALYSIS: We will search MEDLINE, EMBASE, CINAHL, PsycINFO, and Web of Science from inception to April 2020. Observational and experimental studies that compare preoperative opioid users who have undergone elective TJR to opioid naïve TJR patients will be included. The primary outcomes will be postoperative complications, which will be categorised as either mortality, morbidity, or joint-related complications. The secondary outcomes will be persistent postoperative opioid use, readmission, and length of stay. Individual study quality will be assessed using the relevant NIH-NHLBI study quality assessment tools. Findings will be reported in narrative and tabular form, and, where possible, odds ratios (dichotomous outcomes) or standardised mean differences (continuous outcomes) will be reported with 95% confidence intervals. Where appropriate, random effect meta-analyses will be conducted for each outcome, and heterogeneity will be quantified using the I2 statistic and Cochran's Q test. This study will be reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analyses Of Observational Studies in Epidemiology (MOOSE) guidelines. ETHICS AND DISSEMINATION: Ethics approval will not be required as no primary or private data are being collected. Findings will be disseminated through peer-reviewed publication and presentation at academic conferences. PROSPERO REGISTRATION NUMBER: CRD42020153047.
Person-Generated Health Data in Simulated Rehabilitation Using Kinect for Stroke: Literature Review.
(JMIR Publications Inc., 2018-05-08)
BACKGROUND: Person- or patient-generated health data (PGHD) are health, wellness, and clinical data that people generate, record, and analyze for themselves. There is potential for PGHD to improve the efficiency and effectiveness of simulated rehabilitation technologies for stroke. Simulated rehabilitation is a type of telerehabilitation that uses computer technologies and interfaces to allow the real-time simulation of rehabilitation activities or a rehabilitation environment. A leading technology for simulated rehabilitation is Microsoft's Kinect, a video-based technology that uses infrared to track a user's body movements. OBJECTIVE: This review attempts to understand to what extent Kinect-based stroke rehabilitation systems (K-SRS) have used PGHD and to what benefit. METHODS: The review is conducted in two parts. In part 1, aspects of relevance for PGHD were searched for in existing systematic reviews on K-SRS. The following databases were searched: IEEE Xplore, Association of Computing Machinery Digital Library, PubMed, Biomed Central, Cochrane Library, and Campbell Collaboration. In part 2, original research papers that presented or used K-SRS were reviewed in terms of (1) types of PGHD, (2) patient access to PGHD, (3) PGHD use, and (4) effects of PGHD use. The search was conducted in the same databases as part 1 except Cochrane and Campbell Collaboration. Reference lists on K-SRS of the reviews found in part 1 were also included in the search for part 2. There was no date restriction. The search was closed in June 2017. The quality of the papers was not assessed, as it was not deemed critical to understanding PGHD access and use in studies that used K-SRS. RESULTS: In part 1, 192 papers were identified, and after assessment only 3 papers were included. Part 1 showed that previous reviews focused on technical effectiveness of K-SRS with some attention on clinical effectiveness. None of those reviews reported on home-based implementation or PGHD use. In part 2, 163 papers were identified and after assessment, 41 papers were included. Part 2 showed that there is a gap in understanding how PGHD use may affect patients using K-SRS and a lack of patient participation in the design of such systems. CONCLUSIONS: This paper calls specifically for further studies of K-SRS-and for studies of technologies that allow patients to generate their own health data in general-to pay more attention to how patients' own use of their data may influence their care processes and outcomes. Future studies that trial the effectiveness of K-SRS outside the clinic should also explore how patients and carers use PGHD in home rehabilitation programs.