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1.
Lancet Neurol ; 22(9): 800-811, 2023 09.
Article in English | MEDLINE | ID: mdl-37596006

ABSTRACT

BACKGROUND: Timely treatment of acute stroke depends on early identification and triage. Improved methods for recognition of stroke in the prehospital setting are needed. We aimed to assess whether use of the National Institutes of Health Stroke Scale (NIHSS) by paramedics in the ambulance could improve communication with the hospital, augment triage, and enhance diagnostic accuracy of acute stroke. METHODS: The Paramedic Norwegian Acute Stroke Prehospital Project (ParaNASPP) was a stepped-wedge, single-blind, cluster-randomised controlled trial. Patients with suspected acute stroke, who were evaluated by paramedics from five ambulance stations in Oslo, Norway, were eligible for inclusion. The five ambulance stations (defined as clusters) all initially managed patients according to a standard stroke protocol (control group), with randomised sequential crossover of each station to the intervention group. The intervention consisted of supervised training on NIHSS scoring, a mobile application to aid scoring, and standardised communication with stroke physicians. Random allocation was done via a simple lottery draw by administrators at Oslo University Hospital, who were independent of the research team. Allocation concealment was not possible due to the nature of the intervention. The primary outcome was the positive predictive value (PPV) for prehospital identification of patients with a final discharge diagnosis of acute stroke, analysed by intention to treat. Prespecified secondary safety outcomes were median prehospital on-scene time and median door-to-needle time. This trial is registered with ClinicalTrials.gov, NCT04137874, and is completed. FINDINGS: Between June 3, 2019, and July 1, 2021, 935 patients were evaluated by paramedics for suspected acute stroke. 134 patients met exclusion criteria or did not consent to participate. The primary analysis included 447 patients in the intervention group and 354 in the control group. There was no difference in PPV for prehospital identification of patients with a final discharge diagnosis of acute stroke between the intervention group (48·1%, 95% CI 43·4-52·8) and control group (45·8%, 40·5-51·1), with an estimated percentage points difference between groups of 2·3 (95% CI -4·6 to 9·3; p=0·51). Median prehospital on-scene time increased by 5 min in the intervention group (29 min [IQR 23-36] vs 24 min [19-31]; p<0·0001), whereas median door-to-needle time was similar between groups (26 min [21-36] vs 27 min [20-36]; p=0·90). No prehospital deaths were reported in either group. INTERPRETATION: The intervention did not improve diagnostic accuracy in patients with suspected stroke. A general increase in prehospital time during the pandemic and the identification of smaller strokes that require more deliberation are possible explanations for the increased on-scene time. The ParaNASPP model is to be implemented in Norway from 2023, and will provide real-life data for further research. FUNDING: Norwegian Air Ambulance Foundation and Oslo University Hospital.


Subject(s)
Administrative Personnel , Mobile Applications , United States , Humans , Single-Blind Method , Pandemics , National Institutes of Health (U.S.)
2.
Scand J Trauma Resusc Emerg Med ; 31(1): 1, 2023 Jan 05.
Article in English | MEDLINE | ID: mdl-36604741

ABSTRACT

INTRODUCTION: Rapid identification and treatment of stroke is crucial for the outcome of the patient. We aimed to determine the performance of glial fibrillary acidic protein (GFAP) independently and in combination with the Prehospital Stroke Score (PreSS) for identification and differentiation of acute stroke within 4.5 h after symptom onset. PATIENTS AND METHODS: Clinical data and serum samples were collected from the Treat-Norwegian Acute Stroke Prehospital Project (Treat-NASPP). Patients with suspected stroke and symptoms lasting ≤ 4.5 h had blood samples collected and were evaluated with the National Institutes of Health Stroke Scale prospectively. In this sub study, NIHSS was retrospectively translated into PreSS and GFAP was measured using the sensitive single molecule array (SIMOA). RESULTS: A total of 299 patients with suspected stroke were recruited from Treat-NASPP and included in this study (44% acute ischemic stroke (AIS), 10% intracranial hemorrhage (ICrH), 7% transient ischemic attack (TIA), and 38% stroke mimics). ICrH was identified with a cross-fold validated area under the receiver-operating characteristic curve (AUC) of 0.73 (95% CI 0.62-0.84). A decision tree with PreSS and GFAP combined, first identified patients with a low probability of stroke. Subsequently, GFAP detected patients with ICrH with a 25.0% sensitivity (95% CI 11.5-43.4) and 100.0% specificity (95% CI 98.6-100.0). Lastly, patients with large-vessel occlusion (LVO) were detected with a 55.6% sensitivity (95% CI 35.3-74.5) and 82.4% specificity (95% CI 77.3-86.7). CONCLUSION: In unselected patients with suspected stroke, GFAP alone identified ICrH. Combined in a decision tree, GFAP and PreSS identified subgroups with high proportions of stroke mimics, ICrH, LVO, and AIS (non-LVO strokes).


Subject(s)
Brain Ischemia , Emergency Medical Services , Ischemic Stroke , Stroke , Humans , Brain Ischemia/diagnosis , Retrospective Studies , Glial Fibrillary Acidic Protein , Prospective Studies , Stroke/therapy , Intracranial Hemorrhages
3.
Tidsskr Nor Laegeforen ; 142(12)2022 09 06.
Article in English, Norwegian | MEDLINE | ID: mdl-36066221

ABSTRACT

Mobile stroke units save time from symptom onset to treatment in cases of acute ischaemic stroke, have a sustainable cost-benefit profile and are now recommended in European guidelines. We should investigate the use of mobile stroke units in the pre-hospital healthcare service in Norway as well.


Subject(s)
Stroke , Thrombolytic Therapy , Humans , Mobile Health Units , Stroke/drug therapy
4.
Stroke ; 53(10): 3173-3181, 2022 10.
Article in English | MEDLINE | ID: mdl-35862205

ABSTRACT

BACKGROUND: Acute ischemic stroke treatment in mobile stroke units (MSUs) reduces time-to-treatment and increases thrombolytic rates, but implementation requires substantial investments. We wanted to explore the cost-effectiveness of MSU care incorporating novel efficacy data from the Norwegian MSU study, Treat-NASPP (the Norwegian Acute Stroke Prehospital Project). METHODS: We developed a Markov model linking improvements in time-to-treatment and thrombolytic rates delivered by treatment in an MSU to functional outcomes for the patients in a lifetime perspective. We estimated incremental costs, health benefits, and cost-effectiveness of MSU care as compared with conventional care. In addition, we estimated a minimal MSU utilization level for the intervention to be cost-effective in the publicly funded health care system in Norway. RESULTS: MSU care was associated with an expected quality-adjusted life-year-gain of 0.065 per patient, compared with standard care. Our analysis suggests that about 260 patients with ischemic stroke need to be treated with MSU annually to result in an incremental cost-effectiveness ratio of about NOK385 000 (US$43 780) per quality-adjusted life-year for MSU compared with standard care. The incremental cost-effectiveness ratio varies between some NOK1 000 000 (US$113 700) per quality-adjusted life-year if an MSU treats 100 patients per year and to about NOK340 000 (US$38 660) per quality-adjusted life-year if 300 patients with acute ischemic stroke are treated. CONCLUSIONS: MSU care in Norwegian settings is potentially cost-effective compared with conventional care, but this depends on a relatively high annual number of treated patients with acute ischemic stroke per vehicle. These results provide important information for MSU implementation in government-funded health care systems.


Subject(s)
Ischemic Stroke , Stroke , Cost-Benefit Analysis , Fibrinolytic Agents/therapeutic use , Humans , Mobile Health Units , Stroke/drug therapy , Thrombolytic Therapy/methods
5.
Stroke ; 53(6): 2050-2057, 2022 06.
Article in English | MEDLINE | ID: mdl-35291821

ABSTRACT

BACKGROUND: National Institutes of Health Stroke Scale (NIHSS) is the most validated clinical scale for stroke recognition, severity grading, and symptom monitoring in acute care and hospital settings. Numerous modified prehospital stroke scales exist, but these scales contain less clinical information and lack compatibility with in-hospital stroke scales. In this real-life study, we aimed to investigate if NIHSS conducted by paramedics in the field is a feasible and accurate prehospital diagnostic tool. METHODS: This prospective cohort study is part of Treat-NASPP (Treat-Norwegian Acute Stroke Prehospital Project) conducted at a single medical center in Østfold, Norway. Sixty-three paramedics were trained and certified in NIHSS, and the prehospital NIHSS scores were compared with the scores obtained by in-hospital stroke physicians. Interrater agreement was assessed using a Bland-Altman plot with 95% limits of agreement. In secondary analysis, Cohen κ was used for the clinical categories NIHSS score of 0 to 5 and ≥6. As a safety measure, prehospital time was compared between paramedics conducting NIHSS and conventional paramedics. RESULTS: We included 274 patients. The mean difference in NIHSS scores between the paramedics and the stroke physicians was 0.92 with limits of agreement from -5.74 to 7.59. Interrater agreement for the 2 clinical categories was moderate with a κ of 0.58. The prehospital NIHSS scoring was performed mean (SD) 42 (14) minutes earlier than the in-hospital scoring. Prehospital time was not significantly increased in the NIHSS-trained paramedic group compared with conventional paramedics (median [interquartile range] on-scene-time 18 [13-25] minutes versus 16 [11-23] minutes, P=0.064 and onset-to-hospital time 86 [65-128] minutes versus 84 [56-140] minutes, P=0.535). CONCLUSIONS: Paramedics can use NIHSS as an accurate and time efficient prehospital stroke severity quantification tool. Introducing NIHSS in the emergency medical services will enable prehospital evaluation of stroke progression and provide a common language for stroke assessment between paramedics and stroke physicians. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique identifier: NCT03158259.


Subject(s)
Emergency Medical Services , Emergency Medical Technicians , Stroke , Humans , National Institutes of Health (U.S.) , Prospective Studies , Stroke/diagnosis , Stroke/therapy , United States
6.
Eur J Neurol ; 28(8): 2488-2496, 2021 08.
Article in English | MEDLINE | ID: mdl-33890385

ABSTRACT

BACKGROUND: Acute stroke treatment in mobile stroke units (MSU) is feasible and reduces time-to-treatment, but the optimal staffing model is unknown. We wanted to explore if integrating thrombolysis of acute ischemic stroke (AIS) in an anesthesiologist-based emergency medical services (EMS) reduces time-to-treatment and is safe. METHODS: A nonrandomized, prospective, controlled intervention study. INCLUSION CRITERIA: age ≥18 years, nonpregnant, stroke symptoms with onset ≤4 h. The MSU staffing is inspired by the Norwegian Helicopter Emergency Medical Services crew with an anesthesiologist, a paramedic-nurse and a paramedic. Controls were included by conventional ambulances in the same catchment area. Primary outcome was onset-to-treatment time. Secondary outcomes were alarm-to-treatment time, thrombolytic rate and functional outcome. Safety outcomes were symptomatic intracranial hemorrhage and mortality. RESULTS: We included 440 patients. MSU median (IQR) onset-to-treatment time was 101 (71-155) minutes versus 118 (90-176) minutes in controls, p = 0.007. MSU median (IQR) alarm-to-treatment time was 53 (44-65) minutes versus 74 (63-95) minutes in controls, p < 0.001. Golden hour treatment was achieved in 15.2% of the MSU patients versus 3.7% in the controls, p = 0.005. The thrombolytic rate was higher in the MSU (81% vs 59%, p = 0.001). MSU patients were more often discharged home (adjusted OR [95% CI]: 2.36 [1.11-5.03]). There were no other significant differences in outcomes. CONCLUSIONS: Integrating thrombolysis of AIS in the anesthesiologist-based EMS reduces time-to-treatment without negatively affecting outcomes. An MSU based on the EMS enables prehospital assessment of acute stroke in addition to other medical and traumatic emergencies and may facilitate future implementation.


Subject(s)
Brain Ischemia , Stroke , Adolescent , Anesthesiologists , Brain Ischemia/drug therapy , Humans , Prospective Studies , Stroke/drug therapy , Thrombolytic Therapy
9.
Neurocrit Care ; 33(1): 39-48, 2020 08.
Article in English | MEDLINE | ID: mdl-32096121

ABSTRACT

BACKGROUND: Biomarkers indicative of intracerebral hemorrhage (ICH) may help triage acute stroke patients in the pre-hospital phase. We hypothesized that serum concentration of glial fibrillary acidic protein (GFAP) in combination with ubiquitin carboxy-terminal hydrolase-L1 (UCH-L1), measured by a rapid bio-assay, could be used to distinguish ICH from ischemic stroke. METHODS: This prospective two-center study recruited patients with a clinical diagnosis of acute stroke both in the pre-hospital phase and at hospital admission (within 4 and 6 h after symptom onset, respectively). Blood samples were analyzed for concentrations of GFAP and UCH-L1 using ELISA techniques. The reference standard was the diagnosis of ICH, ischemic stroke, or stroke mimicking condition achieved after clinical workup including brain imaging. RESULTS: A total of 251 patients were included (mean age [± SD] 72 ± 15 years; 5 ICH, 23 ischemic strokes and 14 stroke mimics in the pre-hospital part; and 59 ICH, 148 ischemic strokes and 2 stroke mimics in the in-hospital part). Mean delay (± SD) from symptom onset to blood withdrawal was 130 ± 79 min for the pre-hospital patients and 136 ± 86 min for the in-hospital patients. Both GFAP and UCH-L1 serum concentrations were higher in patients having ICH as compared to other diagnoses (GFAP: median 330 ng/L [interquartile range 64-7060, range 8-56,100] vs. 27.5 ng/L [14-57.25, 0-781], p < 0.001; UCH-L1: 401 ng/L [265-764, 133-1812] vs. 338 ng/L [213-549.5, 0-2950], p = 0.025). Area-under-the-curve values were 0.866 (95% CI 0.809-0.924, p < 0.001) for GFAP, and 0.590 (0.511-0.670, p = 0.033) for UCH-L1. Regarding overall diagnostic accuracy, UCH-L1 did not add significantly to the performance of GFAP. CONCLUSIONS: GFAP may differentiate ICH from ischemic stroke and stroke mimics. A point-of-care test to distinguish between ischemic and hemorrhagic strokes might facilitate triage to different treatment pathways or locations, or be used to select patients for trials of ultra-early interventions.


Subject(s)
Glial Fibrillary Acidic Protein/blood , Hemorrhagic Stroke/blood , Ischemic Stroke/blood , Ubiquitin Thiolesterase/blood , Aged , Aged, 80 and over , Diagnosis, Differential , Female , Hemorrhagic Stroke/diagnosis , Humans , Ischemic Stroke/diagnosis , Male , Middle Aged , Point-of-Care Testing
13.
JMIR Res Protoc ; 7(2): e53, 2018 Feb 28.
Article in English | MEDLINE | ID: mdl-29490898

ABSTRACT

BACKGROUND: Acute ischemic stroke (AIS) is a medical emergency. The outcome is closely linked to the time elapsing from symptom onset to treatment, and seemingly small delays can mean the difference between full recovery and physical and cognitive dysfunction. Recanalization to allow blood to reenter the affected area is most efficient immediately after symptoms occur, and intravenous thrombolysis must be initiated no later than 4.5 hours after the symptom onset. A liable diagnosis is mandatory to administer the appropriate treatment. Prehospital diagnosis and, in cases where contraindications are ruled out, prehospital initiation of intravenous thrombolysis have been shown to significantly decrease the time from alarm to the treatment. OBJECTIVE: The objective of this paper is to investigate the effectiveness of prehospital thrombolysis as measured by (1) time spent from symptom onset to treatment and (2) the number of patients treated within 4.5 hours. In addition, we want to conduct explorative studies. These will include (1) the use of biomarkers for diagnostic and prognostic use where we will collect blood samples from various time points, including the hyperacute phase and (2) the study of magnetic resonance imaging (MRI) images at day 1 to determine the infarct volume and if the time to thrombolysis has an influence on this. METHODS: This is a prospective controlled intervention study. The intervention will involve a computed tomography (CT) and thrombolysis in a physician-manned ambulance called a mobile stroke unit (MSU). The control will be the conventional pathway where the patient is transported to the hospital for CT, and thrombolysis as per current procedure. RESULTS: Patient inclusion has started and a total of 37 patients are enrolled (control and intervention combined). The estimated time to completed inclusion is 36 months, starting from May 2017. The results of this study will be analyzed and published at the end of the trial. CONCLUSIONS: This trial aims to document the feasibility of saving time for all stroke patients by providing prehospital diagnostics and treatment, as well as transport to appropriate level of care, in a safe environment provided by anesthesiologists trained in prehospital critical care. TRIAL REGISTRATION: ClinicalTrials.gov NCT03158259; https://clinicaltrials.gov/show/NCT03158259 (Archived by WebCite at http://www.webcitation.org/6wxNEUMUD).

14.
J Neuroimaging ; 28(1): 106-111, 2018 01.
Article in English | MEDLINE | ID: mdl-28766306

ABSTRACT

BACKGROUND AND PURPOSE: In acute stroke, thromboembolism or spontaneous hemorrhage abruptly reduces blood flow to a part of the brain. To limit necrosis, rapid radiological identification of the pathological mechanism must be conducted to allow the initiation of targeted treatment. The aim of the Norwegian Acute Stroke Prehospital Project is to determine if anesthesiologists, trained in prehospital critical care, may accurately assess cerebral computed tomography (CT) scans in a mobile stroke unit (MSU). METHODS: In this pilot study, 13 anesthesiologists assessed unselected acute stroke patients with a cerebral CT scan in an MSU. The scans were simultaneously available by teleradiology at the receiving hospital and the on-call radiologist. CT scan interpretation was focused on the radiological diagnosis of acute stroke and contraindications for thrombolysis. The aim of this study was to find inter-rater agreement between the pre- and in-hospital radiological assessments. A neuroradiologist evaluated all CT scans retrospectively. Statistical analysis of inter-rater agreement was analyzed with Cohen's kappa. RESULTS: Fifty-one cerebral CT scans from the MSU were included. Inter-rater agreement between prehospital anesthesiologists and the in-hospital on-call radiologists was excellent in finding radiological selection for thrombolysis (kappa .87). Prehospital CT scans were conducted in median 10 minutes (7 and 14 minutes) in the MSU, and median 39 minutes (31 and 48 minutes) before arrival at the receiving hospital. CONCLUSION: This pilot study shows that anesthesiologists trained in prehospital critical care may effectively assess cerebral CT scans in an MSU, and determine if there are radiological contraindications for thrombolysis.


Subject(s)
Brain/diagnostic imaging , Mobile Health Units , Stroke/diagnostic imaging , Tomography, X-Ray Computed , Critical Care , Humans , Neuroimaging/methods , Pilot Projects , Point-of-Care Systems , Retrospective Studies , Tomography Scanners, X-Ray Computed
15.
PLoS One ; 6(3): e17086, 2011 Mar 24.
Article in English | MEDLINE | ID: mdl-21455500

ABSTRACT

The tumor suppressor activity of Beclin 1 (BECN1), a subunit of class III phosphatidylinositol 3-kinase complex, has been attributed to its regulation of apoptosis and autophagy. Here, we identify FYVE-CENT (ZFYVE26), a phosphatidylinositol 3-phosphate binding protein important for cytokinesis, as a novel interacting protein of Beclin 1. A mutation in FYVE-CENT (R1945Q) associated with breast cancer abolished the interaction between FYVE-CENT and Beclin 1, and reduced the localization of these proteins at the intercellular bridge during cytokinesis. Breast cancer cells containing the FYVE-CENT R1945Q mutation displayed a significant increase in cytokinetic profiles and bi-multinuclear phenotype. Both Beclin 1 and FYVE-CENT were found to be downregulated in advanced breast cancers. These findings suggest a positive feedback loop for recruitment of FYVE-CENT and Beclin 1 to the intercellular bridge during cytokinesis, and reveal a novel potential tumor suppressor mechanism for Beclin 1.


Subject(s)
Apoptosis Regulatory Proteins/metabolism , Breast Neoplasms/metabolism , Carrier Proteins/metabolism , Cytokinesis/physiology , Membrane Proteins/metabolism , Apoptosis Regulatory Proteins/genetics , Beclin-1 , Breast Neoplasms/genetics , Carrier Proteins/genetics , Cell Line, Tumor , Cytokinesis/genetics , Female , HeLa Cells , Humans , Immunoblotting , Immunoprecipitation , Membrane Proteins/genetics , Microscopy, Confocal , Microscopy, Fluorescence , Polyploidy , Protein Binding/genetics , Protein Binding/physiology , RNA Interference , Two-Hybrid System Techniques
16.
Mol Biol Cell ; 17(6): 2513-23, 2006 Jun.
Article in English | MEDLINE | ID: mdl-16554368

ABSTRACT

The endosomal sorting complexes required for transport, ESCRT-I, -II, and -III, are thought to mediate the biogenesis of multivesicular endosomes (MVEs) and endosomal sorting of ubiquitinated membrane proteins. Here, we have compared the importance of the ESCRT-I subunit tumor susceptibility gene 101 (Tsg101) and the ESCRT-III subunit hVps24/CHMP3 for endosomal functions and receptor signaling. Like Tsg101, endogenous hVps24 localized mainly to late endosomes. Depletion of hVps24 by siRNA showed that this ESCRT subunit, like Tsg101, is important for degradation of the epidermal growth factor (EGF) receptor (EGFR) and for transport of the receptor from early endosomes to lysosomes. Surprisingly, however, whereas depletion of Tsg101 caused sustained EGF activation of the mitogen-activated protein kinase pathway, depletion of hVps24 had no such effect. Moreover, depletion of Tsg101 but not of hVps24 caused a major fraction of internalized EGF to accumulate in nonacidified endosomes. Electron microscopy of hVps24-depleted cells showed an accumulation of EGFRs in MVEs that were significantly smaller than those in control cells, probably because of an impaired fusion with lyso-bisphosphatidic acid-positive late endosomes/lysosomes. Together, our results reveal functional differences between ESCRT-I and ESCRT-III in degradative protein trafficking and indicate that degradation of the EGFR is not required for termination of its signaling.


Subject(s)
ErbB Receptors/metabolism , Vesicular Transport Proteins/metabolism , Down-Regulation , Endocytosis , Endosomal Sorting Complexes Required for Transport , Endosomes/metabolism , Endosomes/ultrastructure , ErbB Receptors/genetics , Gene Silencing , HeLa Cells , Humans , Lysosomes/metabolism , Protein Subunits/metabolism , RNA, Small Interfering/genetics
17.
J Cell Sci ; 118(Pt 12): 2625-35, 2005 Jun 15.
Article in English | MEDLINE | ID: mdl-15914539

ABSTRACT

Alix/AIP1 is a proline-rich protein that has been implicated in apoptosis, endocytic membrane trafficking and viral budding. To further elucidate the functions of Alix, we used RNA interference to specifically suppress its expression. Depletion of Alix caused a striking redistribution of early endosomes from a peripheral to a perinuclear location. The redistribution of endosomes did not affect transferrin recycling or degradation of endocytosed epidermal growth factor receptors, although the uptake of transferrin was mildly reduced when Alix was downregulated. Quantitative immunoelectron microscopy showed that multivesicular endosomes of Alix-depleted cells contained normal amounts of CD63, whereas their levels of lysobisphosphatidic acid were reduced. Alix depletion also caused an accumulation of unusual actin structures that contained clathrin and cortactin, a protein that couples membrane dynamics to the cortical actin cytoskeleton. Our results suggest that Alix functions in the actin-dependent intracellular positioning of endosomes, but that it is not essential for endocytic recycling or for trafficking of membrane proteins between early and late endosomes in non-polarised cells.


Subject(s)
Actins/metabolism , Calcium-Binding Proteins/metabolism , Carrier Proteins/metabolism , Cell Cycle Proteins/metabolism , Endosomes/metabolism , Actins/chemistry , Actins/genetics , Antigens, CD/metabolism , Calcium-Binding Proteins/biosynthesis , Calcium-Binding Proteins/deficiency , Calcium-Binding Proteins/genetics , Carrier Proteins/biosynthesis , Carrier Proteins/genetics , Cell Cycle Proteins/biosynthesis , Cell Cycle Proteins/genetics , Cells, Cultured , Clathrin/chemistry , Clathrin/metabolism , Cortactin , Down-Regulation , Endocytosis , Endosomal Sorting Complexes Required for Transport , Endosomes/chemistry , Endosomes/ultrastructure , ErbB Receptors/metabolism , HeLa Cells , Humans , Intracellular Membranes , Lysophospholipids/metabolism , Microfilament Proteins/metabolism , Monoglycerides , Platelet Membrane Glycoproteins/metabolism , Protein Binding , Protein Transport , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Tetraspanin 30 , Transferrin/metabolism , rab GTP-Binding Proteins/metabolism
18.
J Biol Chem ; 280(20): 19600-6, 2005 May 20.
Article in English | MEDLINE | ID: mdl-15755741

ABSTRACT

Ubiquitination serves as a key sorting signal in the lysosomal degradation of endocytosed receptors through the ability of ubiquitinated membrane proteins to be recognized and sorted by ubiquitin-binding proteins along the endocytic route. The ESCRT-II complex in yeast contains one such protein, Vps36, which harbors a ubiquitin-binding NZF domain and is required for vacuolar sorting of ubiquitinated membrane proteins. Surprisingly, the presumptive mammalian ortholog Eap45 lacks the ubiquitin-binding module of Vps36, and it is thus not clear whether mammalian ESCRT-II functions to bind ubiquitinated cargo. In this paper, we provide evidence that Eap45 contains a novel ubiquitin-binding domain, GLUE (GRAM-like ubiquitin-binding in Eap45), which binds ubiquitin with similar affinity and specificity as other ubiquitin-binding domains. The GLUE domain shares similarities in its primary and predicted secondary structures to phosphoinositide-binding GRAM and PH domains. Accordingly, we find that Eap45 binds to a subset of 3-phosphoinositides, suggesting that ubiquitin recognition could be coordinated with phosphoinositide binding. Furthermore, we show that Eap45 colocalizes with ubiquitinated proteins on late endosomes. These results are consistent with a role for Eap45 in endosomal sorting of ubiquitinated cargo.


Subject(s)
DNA-Binding Proteins/chemistry , DNA-Binding Proteins/metabolism , Transcription Factors/chemistry , Transcription Factors/metabolism , Ubiquitin/metabolism , Amino Acid Sequence , Animals , Binding Sites , Carrier Proteins/chemistry , Carrier Proteins/genetics , Carrier Proteins/metabolism , DNA-Binding Proteins/genetics , Endosomal Sorting Complexes Required for Transport , Endosomes/metabolism , HeLa Cells , Humans , In Vitro Techniques , Membrane Transport Proteins/chemistry , Membrane Transport Proteins/genetics , Membrane Transport Proteins/metabolism , Mice , Models, Molecular , Molecular Sequence Data , Multiprotein Complexes , Protein Binding , Protein Structure, Tertiary , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Saccharomyces cerevisiae Proteins/chemistry , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae Proteins/metabolism , Sequence Homology, Amino Acid , Transcription Factors/genetics , Vesicular Transport Proteins
19.
Mol Biol Cell ; 15(9): 4337-46, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15240819

ABSTRACT

The biogenesis of multivesicular bodies and endosomal sorting of membrane cargo are driven forward by the endosomal sorting complexes required for transport, ESCRT-I, -II, and -III. ESCRT-I is characterized in yeast as a complex consisting of Vps23, Vps28, and Vps37. Whereas mammalian homologues of Vps23 and Vps28 (named Tsg101 and hVps28, respectively) have been identified and characterized, a mammalian counterpart of Vps37 has not yet been identified. Here, we show that a regulator of proliferation, hepatocellular carcinoma related protein 1 (HCRP1), interacts with Tsg101, hVps28, and their upstream regulator Hrs. The ability of HCRP1 (which we assign the alternative name hVps37A) to interact with Tsg101 is conferred by its mod(r) domain and is shared with hVps37B and hVps37C, two other mod(r) domain-containing proteins. HCRP1 cofractionates with Tsg101 and hVps28 by size exclusion chromatography and colocalizes with hVps28 on LAMP1-positive endosomes. Whereas depletion of Tsg101 by siRNA reduces cellular levels of both hVps28 and HCRP1, depletion of HCRP1 has no effect on Tsg101 or hVps28. Nevertheless, HCRP1 depletion strongly retards epidermal growth factor (EGF) receptor degradation. Together, these results indicate that HCRP1 is a subunit of mammalian ESCRT-I and that its function is essential for lysosomal sorting of EGF receptors.


Subject(s)
ErbB Receptors/metabolism , Vesicular Transport Proteins/chemistry , Vesicular Transport Proteins/metabolism , Amino Acid Sequence , DNA-Binding Proteins/genetics , DNA-Binding Proteins/metabolism , Down-Regulation , Endosomal Sorting Complexes Required for Transport , Endosomes/metabolism , GTPase-Activating Proteins/metabolism , HeLa Cells , Humans , Lysosomal Membrane Proteins , Lysosomes/metabolism , Membrane Glycoproteins/metabolism , Molecular Sequence Data , Phosphoproteins/metabolism , Protein Subunits , RNA, Small Interfering/genetics , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae Proteins/genetics , Sequence Homology, Amino Acid , Species Specificity , Transcription Factors/genetics , Transcription Factors/metabolism , Two-Hybrid System Techniques , Vesicular Transport Proteins/genetics
20.
EMBO J ; 23(14): 2707-12, 2004 Jul 21.
Article in English | MEDLINE | ID: mdl-15229652

ABSTRACT

Most growth factors control cellular functions by activating specific receptor tyrosine kinases (RTKs). While overactivation of RTK signalling pathways is strongly associated with carcinogenesis, it is becoming increasingly clear that impaired deactivation of RTKs may also be a mechanism in cancer. A major deactivation pathway, receptor downregulation, involves ligand-induced endocytosis of the RTK and subsequent degradation in lysosomes. A complex molecular machinery that uses the small protein ubiquitin as a key regulator assures proper endocytosis and degradation of RTKs. Here we discuss evidence that implicates deregulation of this machinery in cancer.


Subject(s)
Down-Regulation , Neoplasms/metabolism , Receptor Protein-Tyrosine Kinases/metabolism , Animals , DNA-Binding Proteins/metabolism , Endocytosis/physiology , Endosomal Sorting Complexes Required for Transport , Humans , Ligands , Lysosomes/metabolism , Models, Biological , Protein Transport , Signal Transduction , Transcription Factors/metabolism , Ubiquitin/metabolism
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