CT and MRI Findings of Low-Flow Mediastinal Vascular Malformation: A Case Report.

Mediastinal vascular malformations are rare and their diagnosis can be challenging. Imaging is vital for diagnosing mediastinal vascular malformations and can help avoid unnecessary invasive procedures. Herein, we report the detailed CT and MRI findings of a rare low-flow mediastinal vascular malformation in an asymptomatic 63-year-old male.

NTRK Fusion in a Cohort of BRAF p. V600E Wild-Type Papillary Thyroid Carcinomas.

Owing to the availability of a potent tropomyosin receptor kinase (TRK) inhibitor, it is necessary to develop an effective strategy to identify an enriched population of NTRK fusions in papillary thyroid carcinoma (PTC) in routine diagnostic practice. The reported prevalence of NTRK fusion in a large cohort of PTC is ∼3%. We performed an analysis to refine the characteristic histologic features of PTCs harboring NTRK fusions and further validate the diagnostic utility of pan-TRK immunohistochemistry as a screening tool. In this study, 450 PTCs known to harbor no BRAF p. V600E mutations were screened by pan-TRK immunohistochemistry, and the cases with TRK expression were confirmed by RNA-based next-generation sequencing assay. Eleven NTRK fusion cases were detected (2.4%), and all PTCs were classical subtypes. NTRK1 and NTRK3 were involved in the fusion with 9 different partner genes. Most cases showed similar characteristic histologic findings. Nodular permeative border, multinodular growth with a predominantly follicular pattern, extensive lymphatic invasion, and prominent internodular and intratumoral fibrosis were the characteristic histologic features of NTRK-rearranged PTCs. The ill-defined margins in the ultrasonography findings, which could not be clearly distinguished from the adjacent nontumorous thyroid tissue, were nodular permeative margins in histologic findings. Therefore, preoperative ultrasonographic findings in nodule margins were consistent with the final histologic findings. NTRK1/3 fusion in PTCs showed an overall sensitivity of 100% (95% CI, 71.51%-100%) and specificity of 100% (95% CI, 71.51%-100%) in the 22 cases examined, as confirmed with next-generation sequencing. Our study provides an integrative report of the preoperative ultrasonographic, histologic, immunohistochemical, and molecular features of NTRK-rearranged PTCs. Based on these findings, we propose an algorithmic approach for the stepwise assessment of NTRK fusions in PTCs.

Cancer-Specific Sequences in the Diagnosis and Treatment of NUT Carcinoma.

PURPOSE: NUT carcinoma (NC) is a solid tumor caused by the rearrangement of NUTM1 that usually develops in midline structures, such as the thorax. No standard treatment has been established despite high lethality. Thus, we investigated whether targeting the junction region of NUTM1 fusion breakpoints could serve as a potential treatment option for NC. Materials and Methods: We designed and evaluated a series of small interfering RNAs (siRNAs) targeting the junction region of BRD4-NUTM1 fusion (B4N), the most common form of NUTM1 fusion. Droplet digital polymerase chain reaction using the blood of patients was also tested to evaluate the treatment responses by the junction sequence of the B4N fusion transcripts. RESULTS: As expected, the majority of NC fusion types were B4N (12 of 18, 67%). B4N fusion-specific siRNA treatment on NC cells showed specific inhibitory effects on the B4N fusion transcript and fusion protein without affecting the endogenous expression of the parent genes, resulting in decreased relative cell growth and attenuation of tumor size. In addition, the fusion transcript levels in platelet-rich-plasma samples of the NC patients with systemic metastasis showed a negative correlation with therapeutic effect, suggesting its potential as a measure of treatment responsiveness. CONCLUSION: This study suggests that tumor-specific sequences could be used to treat patients with fusion genes as part of precision medicine for a rare but deadly disease.

Interlaboratory Comparison Study (Ring Test) of Next-Generation Sequencing-Based NTRK Fusion Detection in South Korea.

PURPOSE: Tropomyosin receptor kinase (TRK) inhibitors are approved for the treatment of neurotrophic receptor tyrosine kinase (NTRK) fusion-positive tumors. The detection of NTRK fusion using a validated method is required before therapeutic application. An interlaboratory comparison study of next-generation sequencing (NGS)-based NTRK gene fusion detection with validated clinical samples was conducted at six major hospitals in South Korea. MATERIALS AND METHODS: A total of 18 samples, including a positive standard reference and eight positive and nine negative clinical samples, were validated using the VENTANA pan-TRK (EPR17341) and TruSight Oncology 500 assays. These samples were then tested using four different NGS panels currently being used at the six participating institutions. RESULTS: NTRK fusions were not detected in any of the nine negative clinical samples, demonstrating 100% specificity in all six participating institutions. All assays showed 100% analytical sensitivity to identify the NTRK fusion status in formalin-fixed paraffin-embedded (FFPE) samples, although with variable clinical sensitivity. False-negative results were due to low tumor purity, poor RNA quality, and DNA-based sequencing panel. The RNA-based targeted NGS assay showed an overall high success rate of identifying NTRK fusion status in FFPE samples. CONCLUSION: This study is the first to test the proficiency of NGS-based NTRK detection in South Korea with the largest participating institutions. RNA-based NGS assays to detect NTRK fusions can accurately characterize fusion transcripts if sufficient RNA of adequate quality is available. The comparative performance data will support the implementation of targeted NGS-based sequencing assays for NTRK fusion detection in routine diagnostics.

Discourse performance and related cognitive function in mild cognitive impairment and dementia: A preliminary study.

OBJECTIVES: This study applied the discourse task and related cognitive items of the Brief Test of Cognitive-Communication Disorders (BCCD) to normal, mild cognitive impairment (MCI), and moderate dementia groups and compared the scores of each area. In addition, the cognitive functions affecting the discourse performance were investigated by group. PARTICIPANTS: 117 normal adults, 38 MCI, and 31 patients with moderate dementia (DEM) conducted BCCD, including discourse and cognitive items. DESIGN/SETTING: The discourse item included repeating an explanatory discourse, and the total discourse score was calculated by summing the scores for each of the four areas of coherence, cohesion, proposition, and pause. The cognitive areas of BCCD were attention, visuospatial ability, memory, organization, reasoning, problem-solving, and executive function. This study performed a one-way multivariate analysis of covariance to compare the scores of the three groups and multiple regression analysis determined the cognitive functions influencing the total discourse score. MEASUREMENTS: The discourse scores reporting differences among all groups were the pause and the total discourse scores, with the normal group showing a higher performance than the patient groups in the cohesion score and the DEM group in the propositions score, respectively. In addition, the cognitive functions affecting discourse performance were attention, organization, and problem-solving in the normal group, and organization and problem-solving in the MCI group. CONCLUSIONS: Organizing information into a series of semantic units related to each other is necessary for coherent and efficient utterances, and the ability to correctly recognize the task and establish a strategy to grasp the core content is necessary for pragmatic language.

Unearthing novel fusions as therapeutic targets in solid tumors using targeted RNA sequencing.

Detection of oncogenic fusion genes in cancers, particularly in the diagnosis of uncertain tumors, is crucial for determining effective therapeutic strategies. Although novel fusion genes have been discovered through sequencing, verifying their oncogenic potential remain difficult. Therefore, we evaluated the utility of targeted RNA sequencing in 165 tumor samples by identifying known and unknown fusions. Additionally, by applying additional criteria, we discovered eight novel fusion genes that are expected to process oncogenicity. Among the novel fusion genes, RAF1 fusion genes were detected in two cases. PTPRG-RAF1 fusion led to an increase in cell growth; while dabrafenib, a BRAF inhibitor, reduced the growth of cells expressing RAF1. This study demonstrated the utility of RNA panel sequencing as a theragnostic tool and established criteria for identifying oncogenic fusion genes during post-sequencing analysis.

NTRK Fusions in 1113 Solid Tumors in a Single Institution.

Most NTRK fusions occur at very low frequencies in various common cancers. Recent recommendations on NTRK testing recommend immunohistochemistry (IHC) as the initial test for tumor types with a low frequency of NTRK fusions. This study investigated the accuracy of an IHC assay to detect NTRK fusions and characterize the clinicopathological and molecular features of NTRK-rearranged tumors. This retrospective study was conducted on 1113 solid tumor samples known to harbor no oncogenic driver alterations, including 510 non-small cell lung cancers (NSCLC), 503 colorectal cancers (CRC), and 79 inflammatory myofibroblastic tumors (IMT). Additionally, 21 ALK expression-positive cases were included. TRK expression was evaluated using a pan-Trk IHC assay, and positive cases were validated using NGS. TRK expression was observed in three NSCLCs (0.6%), six CRCs (1.2%), and six IMTs (6%). NTRK fusions were finally detected in two NSCLCs (0.4%), six CRCs (1.2%), and one IMT (1%). In NSCLC and CRC, the majority of NTRK fusions were readily discernible due to diffuse moderate-to-strong cytoplasmic staining on pan-Trk IHC. In IMT, focal weak nuclear staining indicated the presence of NTRK fusion. Therefore, the utility of pan-Trk IHC should be assessed considering that the difference in performance depends on tumor type.

NTRK oncogenic fusions are exclusively associated with the serrated neoplasia pathway in the colorectum and begin to occur in sessile serrated lesions.

Neurotrophic tropomyosin receptor kinase (NTRK) gene fusions are emerging tissue-agnostic drug targets in malignancies including colorectal carcinomas (CRCs), but their detailed landscape in the context of various colorectal carcinogenesis pathways remains to be investigated. In this study, pan-tropomyosin receptor kinase (TRK) protein expression was assessed by immunohistochemistry (IHC) in retrospectively collected colorectal epithelial tumor tissues, including 441 CRCs [133 microsatellite instability-high (MSI-high) and 308 microsatellite stable (MSS)] and 595 premalignant colorectal lesions (330 serrated lesions and 265 conventional adenomas). TRK-positive cases were then subjected to next-generation sequencing and/or fluorescence in situ hybridization to confirm NTRK rearrangements. TRK IHC positivity was not observed in any of the MSS CRCs, conventional adenomas, traditional serrated adenomas, or hyperplastic polyps, whereas TRK positivity was observed in 11 of 58 (19%) MLH1-methylated MSI-high CRCs, 4 of 23 (17%) sessile serrated lesions with dysplasia (SSLDs), and 5 of 132 (4%) sessile serrated lesions (SSLs). The 11 TRK-positive MSI-high CRCs commonly harbored CpG island methylator phenotype-high (CIMP-high), MLH1 methylation, BRAF/KRAS wild-type, and NTRK1 or NTRK3 fusion (TPM3-NTRK1, TPR-NTRK1, LMNA-NTRK1, SFPQ-NTRK1, ETV6-NTRK3, or EML4-NTRK3). Both NTRK1 or NTRK3 rearrangement and BRAF/KRAS wild-type were detected in all nine TRK-positive SSL(D)s, seven of which demonstrated MSS and/or CIMP-low. TRK expression was selectively observed in distorted serrated crypts within SSLs and was occasionally localized at the base of serrated crypts. NTRK fusions were detected only in SSLs of patients aged ≥50 years, whereas BRAF mutation was found in younger age-onset SSLs. In conclusion, NTRK-rearranged colorectal tumors develop exclusively through the serrated neoplasia pathway and can be initiated from non-dysplastic SSLs without BRAF/KRAS mutations prior to full occurrence of MSI-high/CIMP-high. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

TM4SF4 and LRRK2 Are Potential Therapeutic Targets in Lung and Breast Cancers through Outlier Analysis.

PURPOSE: To find biomarkers for disease, there have been constant attempts to investigate the genes that differ from those in the disease groups. However, the values that lie outside the overall pattern of a distribution, the outliers, are frequently excluded in traditional analytical methods as they are considered to be 'some sort of problem.' Such outliers may have a biologic role in the disease group. Thus, this study explored new biomarker using outlier analysis, and verified the suitability of therapeutic potential of two genes (TM4SF4 and LRRK2). MATERIALS AND METHODS: Modified Tukey's fences outlier analysis was carried out to identify new biomarkers using the public gene expression datasets. And we verified the presence of the selected biomarkers in other clinical samples via customized gene expression panels and tissue microarrays. Moreover, a siRNA-based knockdown test was performed to evaluate the impact of the biomarkers on oncogenic phenotypes. RESULTS: TM4SF4 in lung cancer and LRRK2 in breast cancer were chosen as candidates among the genes derived from the analysis. TM4SF4 and LRRK2 were overexpressed in the small number of samples with lung cancer (4.20%) and breast cancer (2.42%), respectively. Knockdown of TM4SF4 and LRRK2 suppressed the growth of lung and breast cancer cell lines. The LRRK2 overexpressing cell lines were more sensitive to LRRK2-IN-1 than the LRRK2 under-expressing cell lines. CONCLUSION: Our modified outlier-based analysis method has proved to rescue biomarkers previously missed or unnoticed by traditional analysis showing TM4SF4 and LRRK2 are novel target candidates for lung and breast cancer, respectively.

Effects of working memory intervention on language production by individuals with dementia.

The purpose of this study was to investigate the effects of working memory intervention on language production by people with mild or moderate Alzheimer's disease (AD). A total of 39 AD patients, 21 with mild AD and 18 with moderate AD and 18 normal controls were given 18 sessions of working memory intervention. After these sessions, the transfer effects and maintenance effects at the 3-month follow-up were assessed. A word-span task and a digit-span task were used to evaluate working memory. Language-production abilities were compared through four tasks: a verbal fluency, a confrontation naming, a word definition, and a picture-description task. Task performances of working memory and language production were the lowest in the baseline stage and the highest in the transfer-effect stage. The three groups had transfer effects in all tasks, while the maintenance effects were limited by groups and tasks. This study proves that working memory intervention for AD patients is effective for language production. In addition, we have paved the way for working memory intervention to improve language production by AD patients in clinical settings by presenting the transfer and maintenance effect for each task of language production.

Erratum to "Diaphragmatic liposarcoma with gall bladder invasion: CT and MRI findings" [Radiology Case Reports 15 (2020) 511-514].

[This corrects the article DOI: 10.1016/j.radcr.2020.01.036.].

Earlier-Phased Cancer Immunity Cycle Strongly Influences Cancer Immunity in Operable Never-Smoker Lung Adenocarcinoma.

Exome and transcriptome analyses of clinically homogeneous early-stage never-smoker female patients with lung adenocarcinoma were performed to understand tumor-T cell interactions and immune escape points. Using our novel gene panels of eight functional categories in the cancer-immunity cycle, three distinct subgroups were identified in this immune checkpoint blockade-refractory cohort by defective gene expression in two major domains, i.e., type I interferon production/signaling pathway and antigen-presenting machinery. Our approach could play a critical role in understanding immune evasion mechanisms, developing a method for effective selection of rare immune checkpoint blockade responders, and finding new treatment strategies.

Diaphragmatic liposarcoma with gall bladder invasion: CT and MRI findings.

Primary liposarcoma originating from the diaphragm is an extremely rare case. Seventy-four-year-old male presented to emergency department with worsening right upper quadrant abdominal pain with dyspnea. Contrast-enhanced computed tomography of the abdomen demonstrated lobulated mass in right hemidiaphragm exhibiting mass effects to adjacent structures compressing gall bladder. Magnetic resonance imaging of the abdomen showed diaphragmatic mass with heterogeneous signal intensities with partial diffusion restriction. Surgical removal was performed and histology confirmed dedifferentiated liposarcoma arising from the diaphragm with gall bladder invasion.

Clinical significance of abnormal chest radiographic findings for acute kidney injury in patients with scrub typhus.

BACKGROUND: Abnormal chest radiographs are frequently encountered in patients with scrub typhus. This study aimed to investigate whether chest radiography on admission is significant as a predictive factor for acute kidney injury (AKI) in patients with scrub typhus. METHODS: From 2010 to 2016, 467 patients were diagnosed with scrub typhus in our hospital. We divided the patients into two groups: normal chest radiograph (NCR) and abnormal chest radiograph (AbNCR), based on chest radiography findings. The incidence, clinical characteristics, and severity of AKI were compared between AKI and non-AKI groups according to the RIFLE classification. RESULTS: Of the 467 patients, 96 (20.6%) constituted the AbNCR group. Compared with NCR patients, AbNCR patients were older (71 ± 11 vs. 62 ± 13 years, P < 0.001) and had higher total leukocyte counts (9.43 × 103/mL vs. 6.98 × 103/mL, P < 0.001). The AbNCR group had significantly longer duration of hospital stay (8.9 ± 5.5 vs. 6.3 ± 2.8 days, P < 0.001) and higher incidence of AKI (46.9% vs. 15.1%, P < 0.001). The common abnormal chest radiographic findings were pulmonary abnormalities, such as pulmonary congestion and pleural effusion. The overall AKI incidence was 21.6%, of which 12.4%, 7.9%, and 1.3% cases were classified as risk, injury, and failure, respectively. In a multivariable logistic regression analysis for association with AKI, old age, presence of chronic kidney disease or hypertension, leukocytosis, hypoalbuminemia, and chest radiographic abnormalities on admission were significant predictors of AKI. CONCLUSION: Chest radiographic abnormalities on admission were independently associated with AKI in patients with scrub typhus.

IRS2 Amplification as a Predictive Biomarker in Response to Ceritinib in Small Cell Lung Cancer.

Small cell lung cancer (SCLC) is a fast-growing and malignant cancer that responds well to chemotherapy; however, the survival rate is less than 15% after 2 years of diagnosis. Therefore, novel therapeutic agents for treating SCLC patients need to be evaluated. This study aims to identify the therapeutic targets based on the comprehensive genomic profiling of SCLC patients. Among the molecular-profiled SCLC samples obtained using targeted sequencing, the array-based comparative genomic hybridization (array CGH) identified focal insulin receptor substrate 2 (IRS2) amplification in the SCLC patients. IRS2 amplification was confirmed in 5% of 73 SCLC patients. To determine whether IRS2 amplification could act as a therapeutic target, we generated a patient-derived xenograft (PDX) model and subsequently screened 43 targeted agents using the PDX-derived cells (PDCs). Ceritinib significantly inhibited the cell growth and impaired the tumor sphere formation in IRS2-expressing PDCs. Its effects were confirmed in various in vitro assays and were further validated in the mouse xenograft models. In this study, we present that IRS2 amplification and/or expression serve as preclinical implications for a novel therapeutic target in SCLC progression. Furthermore, we suggest that insulin-like growth factor-1 (IGF-1) receptor inhibitor-based therapy could be used for treating SCLC with IRS2 amplification.

Comprehensive Effects of Organized Education for Patients with Chronic Obstructive Pulmonary Disease.

Background: Despite the increasing prevalence of chronic obstructive pulmonary disease (COPD) worldwide, knowledge and awareness of COPD remain extremely low. This prospective study aimed to demonstrate the effectiveness of organized educational intervention. Patients and methods: The study participants included patients diagnosed with COPD and receiving inhaler treatment. In this prospective study, the patients made three sequential visits to the hospital (baseline, 1 month, 3 months). On their first and second visits, patients received systematic education about COPD. On their first and third visits, each patient was evaluated using a COPD Assessment Test, COPD Knowledge Questionnaire, Hospital Anxiety and Depression Scale, and Rosenberg Self-Esteem Scale. Results: Fifty-five participants were enrolled in the study. The mean COPD knowledge score before and after education was 12.51±3.19 and 17.89±1.37, respectively, indicating a significant increase in the score post-education (P<0.001). The measure of patients' inhaler technique also significantly improved after education (5.40±1.50 vs 6.83±0.37 P=0.01). The rate of depression and anxiety after education decreased by 10.9% and 12.7%, respectively (P<0.001). In subgroup analysis, we compared the groups whose knowledge score increased by more than 5 points (Group B) and those whose score did not improve (Group A). In Group B, the mean CAT score significantly improved (2.61±5.88 vs -2.41±7.48, P=0.01), and the duration of their COPD diagnosis before enrollment was significantly shorter (2.72±2.43 vs 5.22±5.11 years, P=0.038) compared to those in Group A. Conclusion: An organized educational program resulted in improved disease-specific knowledge. Disease-specific education is an important part of the treatment of COPD that affects the quality of life and emotional status of patients. Early education after COPD diagnosis can be beneficial.

Association with PD-L1 Expression and Clinicopathological Features in 1000 Lung Cancers: A Large Single-Institution Study of Surgically Resected Lung Cancers with a High Prevalence of EGFR Mutation.

Programmed cell death ligand 1 (PD-L1) expression is an important biomarker for predicting response to immunotherapy in clinical practice. Hence, identification and characterization of factors that predict high expression of PD-L1 in patients is critical. Various studies have reported the association of PD-L1 expression with driver genetic status in non-small cell cancer; however, the results have been conflicting and inconclusive. We analyzed the relationship between PD-L1 expression and clinicopathological factors including driver genetic alterations in 1000 resected lung cancers using a clinically validated PD-L1 immunohistochemical assay. PD-L1 expression was significantly higher in squamous cell carcinoma (SCC) compared to adenocarcinomas. PD-L1 expression in adenocarcinoma was associated with higher N-stage, solid histologic pattern, EGFR wild type, and ALK positive, but no significant association with the clinicopathological factors in SCC. EGFR mutant adenocarcinomas with distinctive clinicopathologic features, especially solid histologic pattern and higher stage showed higher PD-L1 expression. To the best of our knowledge, this study is the largest to evaluate the association between PD-L1 expression and clinicopathological and molecular features in lung cancer with a highly prevalent EGFR mutation. Therefore, our results are useful to guide the selection of lung cancer, even EGFR-mutated adenocarcinoma patients with PD-L1 expression, for further immunotherapy.

Molecular changes in solitary fibrous tumor progression.

Solitary fibrous tumors (SFTs) are NAB2-STAT6 fusion-associated neoplasms. There are several subtypes of NAB2-STAT6 fusions, but their clinical significances are still unclear. Moreover, the mechanisms of malignant progression are also poorly understood. In this study, using 91 SFT cases, we examined whether fusion variants are associated with clinicopathological parameters and also investigated the molecular mechanism of malignant transformation using whole-exome sequencing. We detected variant 1b (NAB2ex4-STAT6ex2) in 51/91 (56%) cases and variants 2a/2b (NAB2ex6-STAT6ex16/17) in 17/91 (19%) cases. The NAB2-STAT6 fusion variant types were significantly associated with their primary site (P < 0.001). In addition, a TERT promoter mutation was detected in 7/73 (10%) cases, and it showed a significant association with malignant SFTs (P = 0.003). To identify molecular changes during malignant progression, we selected an index patient to obtain parallel tissue samples from the primary and metastatic tumors. In the metastatic tissue, 10 unique molecular alterations, including those in TP53 and APAF1, were detected. In vitro functional experiments showed that APAF1 depletion increased the tumor potency of cells expressing NAB2-STAT6 fusion protein under treatment with staurosporine. We found that TP53 immunopositivity (P = 0.006) and loss of APAF1 immunoreactivity (P < 0.001) were significantly associated with malignant SFTs. Our study suggests that dysfunction of TP53 and APAF1 leads to impaired apoptotic function, and eventually contributes toward malignant SFT transformation. KEY MESSAGES: We firstly found that the TERT promoter mutation was strongly associated with malignant SFTs (P = 0.003) and the representative 1b (NAB2ex4-STAT6ex2) or 2a (NAB2ex6-STAT6ex16) fusion variants similarly contribute to tumorigenicity. We also found that TP53 immunopositivity (P = 0.006) and loss of APAF1 immunoreactivity (P < 0.001) were significantly associated with malignant SFTs. Our study suggests that dysfunction of TP53 and APAF1 leads to impaired apoptotic function, and eventually contributes toward malignant SFT transformation.

Assessing of the audiovisual patient educational materials on diabetes care with PEMAT.

OBJECTIVE: The purpose of this study was to evaluate the understandability and actionability of audiovisual educational materials on diabetes in Korea using the Patient Education Materials Evaluation Tool (PEMAT), as well as determine the usefulness of these materials. METHODS: A total of 85 audiovisual materials were collected from Korean websites of territory general hospitals, national health institutions, research associations, and major search engines relating to diabetes that were created between 2006 and 2015. Of these, 34 materials that met the inclusion and exclusion criteria were analyzed. Five trained researchers evaluated the materials independently. RESULTS: More than half of the materials (58.8%) had been created by nongovernment organizations. Slightly more than half (n = 19) of the audiovisual materials were streaming-style animation. The average PEMAT score (58.5%) for these materials was moderate. Compared to "understandability" ratings (49.5%), "actionability" ratings were low (31.4%); indeed, fourteen materials had an actionability of 0%. The average usefulness score of the materials was 4.3 points out of a possible 7. There were few suitable audiovisual materials for patient education on diabetes. CONCLUSIONS: These findings will be useful for developing new audiovisual educational materials for diabetes patients with high understandability, actionability, and usefulness.

Accumulation of PtdIns(4)P at the Golgi mediated by reversible oxidation of the PtdIns(4)P phosphatase Sac1 by H2O2.

Phosphatidylinositol 4-phosphate [PtdIns(4)P] plays a key role in the biogenesis of transport vesicles at the Golgi complex by recruiting coat proteins and their accessory factors. The PtdIns(4)P content of the Golgi is determined by the concerted action of PtdIns 4-kinase (PI4K) and PtdIns(4)P phosphatase enzymes. Sac1 (suppressor of actin 1) is the major PtdIns(4)P phosphatase and is localized to the Golgi and endoplasmic reticulum. The targeting of both PI4Ks and Sac1 to the Golgi membrane is extensively regulated, as is the catalytic activity of PI4Ks at the Golgi. However, regulation of the catalytic activity of Sac1 has been largely unexplored. Here we show that Sac1undergoes reversible inactivation in mammalian cells when its catalytic Cys389 residue is oxidized by exogenous H2O2 to form an intramolecular disulfide with Cys392. The oxidative inactivation of Sac1 results in the accumulation of PtdIns(4)P at the Golgi, with this effect also being supported by the H2O2-induced activation of p38 mitogen-activated protein kinase (MAPK), which was previously shown to promote the translocation of Sac1 from the Golgi to the endoplasmic reticulum. The increase in Golgi PtdIns(4)P due to Sac1 inactivation, however, is faster than that due to Sac1 translocation. Exposure of cells to H2O2 also increased membrane protein trafficking from the Golgi to the plasma membrane as well as protein secretion.