LRRK1 functions as a scaffold for PTP1B-mediated EGFR sorting into ILVs at the ER-endosome contact site.

Proper control of epidermal growth factor receptor (EGFR) signaling is important for maintaining cellular homeostasis. Given that EGFR signaling occurs at the plasma membrane and endosomes following internalization, endosomal trafficking of EGFR spatiotemporally regulates EGFR signaling. In this process, leucine-rich repeat kinase 1 (LRRK1) has multiple roles in kinase activity-dependent transport of EGFR-containing endosomes and kinase-independent sorting of EGFR into the intraluminal vesicles (ILVs) of multivesicular bodies. Active, phosphorylated EGFR inactivates the LRRK1 kinase activity by phosphorylating Y944. In this study, we demonstrate that LRRK1 facilitates EGFR dephosphorylation by PTP1B (also known as PTPN1), an endoplasmic reticulum (ER)-localized protein tyrosine phosphatase, at the ER-endosome contact site, after which EGFR is sorted into the ILVs of endosomes. LRRK1 is required for the PTP1B-EGFR interaction in response to EGF stimulation, resulting in the downregulation of EGFR signaling. Furthermore, PTP1B activates LRRK1 by dephosphorylating pY944 on the contact site, which promotes the transport of EGFR-containing endosomes to the perinuclear region. These findings provide evidence that the ER-endosome contact site functions as a hub for LRRK1-dependent signaling that regulates EGFR trafficking.

Msp1 Clears Mistargeted Proteins by Facilitating Their Transfer from Mitochondria to the ER.

Normal mitochondrial functions rely on optimized composition of their resident proteins, and proteins mistargeted to mitochondria need to be efficiently removed. Msp1, an AAA-ATPase in the mitochondrial outer membrane (OM), facilitates degradation of tail-anchored (TA) proteins mistargeted to the OM, yet how Msp1 cooperates with other factors to conduct this process was unclear. Here, we show that Msp1 recognizes substrate TA proteins and facilitates their transfer to the endoplasmic reticulum (ER). Doa10 in the ER membrane then ubiquitinates them with Ubc6 and Ubc7. Ubiquitinated substrates are extracted from the ER membrane by another AAA-ATPase in the cytosol, Cdc48, with Ufd1 and Npl4 for proteasomal degradation in the cytosol. Thus, Msp1 functions as an extractase that mediates clearance of mistargeted TA proteins by facilitating their transfer to the ER for protein quality control.

Discovery and Optimization of Inhibitors of the Parkinson's Disease Associated Protein DJ-1.

DJ-1 is a Parkinson's disease associated protein endowed with enzymatic, redox sensing, regulatory, chaperoning, and neuroprotective activities. Although DJ-1 has been vigorously studied for the past decade and a half, its exact role in the progression of the disease remains uncertain. In addition, little is known about the spatiotemporal regulation of DJ-1, or the biochemical basis explaining its numerous biological functions. Progress has been hampered by the lack of inhibitors with precisely known mechanisms of action. Herein, we have employed biophysical methodologies and X-ray crystallography to identify and to optimize a family of compounds inactivating the critical Cys106 residue of human DJ-1. We demonstrate these compounds are potent inhibitors of various activities of DJ-1 in vitro and in cell-based assays. This study reports a new family of DJ-1 inhibitors with a defined mechanism of action, and contributes toward the understanding of the biological function of DJ-1.

Quality control of nonstop membrane proteins at the ER membrane and in the cytosol.

Since messenger RNAs without a stop codon (nonstop mRNAs) for organelle-targeted proteins and their translation products (nonstop proteins) generate clogged translocon channels as well as stalled ribosomes, cells have mechanisms to degrade nonstop mRNAs and nonstop proteins and to clear the translocons (e.g. the Sec61 complex) by release of nonstop proteins into the organellar lumen. Here we followed the fate of nonstop endoplasmic reticulum (ER) membrane proteins with different membrane topologies in yeast to evaluate the importance of the Ltn1-dependent cytosolic degradation and the Dom34-dependent release of the nonstop membrane proteins. Ltn1-dependent degradation differed for membrane proteins with different topologies and its failure did not affect ER protein import or cell growth. On the other hand, failure in the Dom34-dependent release of the nascent polypeptide from the ribosome led to the block of the Sec61 channel and resultant inhibition of other protein import into the ER caused cell growth defects. Therefore, the nascent chain release from the translation apparatus is more instrumental in clearance of the clogged ER translocon channel and thus maintenance of normal cellular functions.

Ubiquitin is phosphorylated by PINK1 to activate parkin.

PINK1 (PTEN induced putative kinase 1) and PARKIN (also known as PARK2) have been identified as the causal genes responsible for hereditary recessive early-onset Parkinsonism. PINK1 is a Ser/Thr kinase that specifically accumulates on depolarized mitochondria, whereas parkin is an E3 ubiquitin ligase that catalyses ubiquitin transfer to mitochondrial substrates. PINK1 acts as an upstream factor for parkin and is essential both for the activation of latent E3 parkin activity and for recruiting parkin onto depolarized mitochondria. Recently, mechanistic insights into mitochondrial quality control mediated by PINK1 and parkin have been revealed, and PINK1-dependent phosphorylation of parkin has been reported. However, the requirement of PINK1 for parkin activation was not bypassed by phosphomimetic parkin mutation, and how PINK1 accelerates the E3 activity of parkin on damaged mitochondria is still obscure. Here we report that ubiquitin is the genuine substrate of PINK1. PINK1 phosphorylated ubiquitin at Ser 65 both in vitro and in cells, and a Ser 65 phosphopeptide derived from endogenous ubiquitin was only detected in cells in the presence of PINK1 and following a decrease in mitochondrial membrane potential. Unexpectedly, phosphomimetic ubiquitin bypassed PINK1-dependent activation of a phosphomimetic parkin mutant in cells. Furthermore, phosphomimetic ubiquitin accelerates discharge of the thioester conjugate formed by UBCH7 (also known as UBE2L3) and ubiquitin (UBCH7∼ubiquitin) in the presence of parkin in vitro, indicating that it acts allosterically. The phosphorylation-dependent interaction between ubiquitin and parkin suggests that phosphorylated ubiquitin unlocks autoinhibition of the catalytic cysteine. Our results show that PINK1-dependent phosphorylation of both parkin and ubiquitin is sufficient for full activation of parkin E3 activity. These findings demonstrate that phosphorylated ubiquitin is a parkin activator.

Intramolecular disulfide bond of Tim22 protein maintains integrity of the TIM22 complex in the mitochondrial inner membrane.

Mitochondrial proteins require protein machineries called translocators in the outer and inner membranes for import into and sorting to their destination submitochondrial compartments. Among them, the TIM22 complex mediates insertion of polytopic membrane proteins into the inner membrane, and Tim22 constitutes its central insertion channel. Here we report that the conserved Cys residues of Tim22 form an intramolecular disulfide bond. By comparison of Tim22 Cys → Ser mutants with wild-type Tim22, we show that the disulfide bond of Tim22 stabilizes Tim22 especially at elevated temperature through interactions with Tim18, which are also important for the stability of the TIM22 complex. We also show that lack of the disulfide bond in Tim22 impairs the assembly of TIM22 pathway substrate proteins into the inner membrane especially when the TIM22 complex handles excess amounts of substrate proteins. Our findings provide a new insight into the mechanism of the maintenance of the structural and functional integrity of the TIM22 complex.

Value of shear wave velocity measurements for the risk assessment of hepatocellular carcinoma development in patients with nonalcoholic fatty liver disease : HCC risk assessment by VTTQ.

PURPOSE: To evaluate the value of measuring shear wave velocity evoked by acoustic radiation force impulse (VTTQ) for the risk assessment of hepatocellular carcinoma (HCC) development in patients with nonalcoholic fatty liver disease (NAFLD). METHODS: VTTQ was measured three times in each of the four liver segments in 163 NAFLD patients, including 14 HCC cases; the results were statistically evaluated. RESULTS: The VTTQ was 3.04 ± 0.17 m/s (median ± median absolute deviation) and 1.27 ± 0.25 m/s in patients with and without HCC, respectively, and was significantly higher in HCC cases (p < 0.001). When the patients were classified as F0-F4 based on VTTQ cutoff values, VTTQ was significantly higher in the left lobe than in the right lobe for F0 (p < 0.0001) and for F1 and F2 combined (p < 0.0001), but not significantly higher for F3 and F4 combined (p = 0.070). The robust coefficient of variation was significantly higher in the left than in the right (p = 0.018) and significantly increased as VTTQ increased (p = 0.0002). Multivariate analysis showed that total bilirubin concentration {p = 0.014, 38.9 (2.08-727) [odds ratio (95 % confidence interval)]} and VTTQ [p = 0.006, 113 (3.91-3245)] were the only independent explanatory factors for HCC presence among the seven variables identified by univariate analysis. The area under the receiver-operating characteristic curve in the differentiation of HCC from non-HCC was 0.943 for VTTQ and was comparable to that for other noninvasive markers such as Fib-4 (0.964) or higher than that in BARD (0.838). CONCLUSIONS: These results suggest that fibrosis occurs heterogeneously throughout the liver and that VTTQ measurements are useful in HCC risk evaluation in a NAFLD cohort.

Relationship between coronary artery disease and retinopathy in patients with type 2 diabetes mellitus.

OBJECTIVE: To examine risk factors for coronary artery disease (CAD) and retinopathy in patients with type 2 diabetes mellitus (DM) and assess the relationship between CAD and retinopathy. METHODS: A total of 1,003 outpatients with type 2 DM (578 men and 425 women) were classified into two groups according to the presence (based on ischemic findings on a resting electrocardiogram or a history of angina or myocardial infarction) or absence of CAD and four retinopathy stages based on the International Clinical Classification of Diabetic Retinopathy. RESULTS: Stepwise multiple regression analyses showed that independent risk factors for CAD were age, the triglyceride (TG) level and smoking, while those for retinopathy included age, age of DM diagnosis, the HbA1c level and a female gender. The prevalence of CAD increased in association with the progression of retinopathy (p<0.01). CONCLUSION: Since it is difficult to distinguish macrovascular and microvascular diseases, diabetic vascular disorders require comprehensive approaches to assessment and treatment.

A safe and effective dose of cisplatin in hepatic arterial infusion chemotherapy for hepatocellular carcinoma.

Cisplatin (CDDP) is an anticancer agent that is commonly used in hepatic arterial infusion (HAI) chemotherapy for hepatocellular carcinoma (HCC). This study aimed to clarify the safe and effective dose of CDDP in HAI for HCC. The hypervascular area was measured in 42 HCCs before and after HAI with CDDP. Serum platinum concentration was quantified in the peripheral and/or middle hepatic veins by atomic absorption spectrometry. The relation between the HCC response and CDDP dose was statistically analyzed. The multiple HCC nodules in an individual case generally demonstrated the same response to CDDP. The free-platinum concentration stayed relatively constant in the hepatic vein during HAI followed by a rapid decline, while total-platinum gradually increased then slowly disappeared over several days. After CDDP-HAI, 15 HCCs shrunk and 27 HCCs grew. The reduction rate in the shrunken nodules was tended to be correlated with CDDP dose after standardization with the target liver volume. On the other hand, the growth rate of the enlarged HCCs was significantly correlated with CDDP dose after normalization with creatinine clearance. These data support a recommendation of CDDP-HAI infusion where the amount of CDDP (mg) administered is less than patient creatinine clearance (mL/min/1.73 m(2)) upon an assumption of HCC doubling time of 90 days, and the targeted liver is smaller than 200 times the CDDP dose (mg). A further analysis is required to define appropriate injection speeds.

Active treatments are a rational approach for hepatocellular carcinoma in elderly patients.

AIM: To determine whether an active intervention is beneficial for the survival of elderly patients with hepatocellular carcinoma (HCC). METHODS: The survival of 740 patients who received various treatments for HCC between 1983 and 2011 was compared among different age groups using Cox regression analysis. Therapeutic options were principally selected according to the clinical practice guidelines for HCC from the Japanese Society of Hepatology. The treatment most likely to achieve regional control capability was chosen, as far as possible, in the following order: resection, radiofrequency ablation, percutaneous ethanol injection, transcatheter arterial chemoembolization, transarterial oily chemoembolization, hepatic arterial infusion chemotherapy, systemic chemotherapy including molecular targeting, or best supportive care. Each treatment was used alone, or in combination, with a clinical goal of striking the best balance between functional hepatic reserve and the volume of the targeted area, irrespective of their age. The percent survival to life expectancy was calculated based on a Japanese national population survey. RESULTS: The median ages of the subjects during each 5-year period from 1986 were 61, 64, 67, 68 and 71 years and increased significantly with time (P < 0.0001). The Child-Pugh score was comparable among younger (59 years of age or younger), middle-aged (60-79 years of age), and older (80 years of age or older) groups (P = 0.34), whereas the tumor-node-metastasis stage tended to be more advanced in the younger group (P = 0.060). Advanced disease was significantly more frequent in the younger group compared with the middle-aged group (P = 0.010), whereas there was no difference between the middle-aged and elderly groups (P = 0.75). The median survival times were 2593, 2011, 1643, 1278 and 1195 d for 49 years of age or younger, 50-59 years of age, 60-69 years of age, 70-79 years of age, or 80 years of age or older age groups, respectively, whereas the median percent survival to life expectancy were 13.9%, 21.9%, 24.7%, 25.7% and 37.6% for each group, respectively. The impact of age on actual survival time was significant (P = 0.020) with a hazard ratio of 1.021, suggesting that a 10-year-older patient has a 1.23-fold higher risk for death, and the overall survival was the worst in the oldest group. On the other hand, when the survival benefit was evaluated on the basis of percent survival to life expectancy, age was again found to be a significant explanatory factor (P = 0.022); however, the oldest group showed the best survival among the five different age groups. The youngest group revealed the worst outcomes in this analysis, and the hazard ratio of the oldest against the youngest was 0.35 for death. The survival trends did not differ substantially between the survival time and percent survival to life expectancy, when survival was compared overall or among various therapeutic interventions. CONCLUSION: These results suggest that a therapeutic approach for HCC should not be restricted due to patient age.

Effects of Fcj1-Mos1 and mitochondrial division on aggregation of mitochondrial DNA nucleoids and organelle morphology.

Mitochondrial DNA (mtDNA) is packaged into DNA-protein complexes called nucleoids, which are distributed as many small foci in mitochondria. Nucleoids are crucial for the biogenesis and function of mtDNA. Here, using a yeast genetic screen for components that control nucleoid distribution and size, we identify Fcj1 and Mos1, two evolutionarily conserved mitochondrial proteins that maintain the connection between the cristae and boundary membranes. These two proteins are also important for establishing tubular morphology of mitochondria, as mitochondria lacking Fcj1 and Mos1 form lamellar sheets. We find that nucleoids aggregate, increase in size, and decrease in number in fcj1 and mos1 cells. In addition, Fcj1 form punctate structures and localized adjacent to nucleoids. Moreover, connecting mitochondria by deleting the DNM1 gene required for organelle division enhances aggregation of mtDNA nucleoids in fcj1 and mos1 cells, whereas single deletion of DNM1 does not affect nucleoids. Conversely, deleting F1Fo-ATP synthase dimerization factors generates concentric ring-like cristae, restores tubular mitochondrial morphology, and suppresses nucleoid aggregation in these mutants. Our findings suggest an unexpected role of Fcj1-Mos1 and organelle division in maintaining the distribution and size of mtDNA nucleoids.

Value of highly sensitive fucosylated fraction of alpha-fetoprotein for prediction of hepatocellular carcinoma recurrence after curative treatment.

BACKGROUND: The fucosylated fraction of alpha-fetoprotein (AFP-L3) has been used as a diagnostic marker for hepatocellular carcinoma (HCC). Recently, a highly sensitive immunoassay using an on-chip electrokinetic reaction and separation by affinity electrophoresis (micro-total analysis system; µTAS) has been developed. AIM: The aim of this study was to investigate the relationship between changes in the serum AFP-L3 level measured by µTAS assay and recurrence of HCC after curative treatment. METHODS: A total of 414 HCC patients who met the Milan criteria and underwent hepatectomy or radiofrequency ablation were investigated prospectively for the relationship between HCC recurrence and values of tumor markers. RESULTS: There were significant differences in recurrence-free survival between groups with and without AFP-L3 elevation measured before and after treatment (p = 0.024 and p = 0.001 for before and after treatment, respectively). Multivariate analysis revealed that AFP-L3 status (p = 0.002) measured 1 month after treatment was a significant independent predictor of HCC recurrence after curative treatment. CONCLUSIONS: Elevation of the serum AFP-L3 level before treatment is a predictor of HCC recurrence, and sustained elevation of the AFP-L3 level after treatment is an indicator of HCC recurrence. Repeated measurement of µTAS AFP-L3 should be performed for surveillance of HCC recurrence after curative treatment.

Phase I study of miriplatin combined with transarterial chemotherapy using CDDP powder in patients with hepatocellular carcinoma.

BACKGROUND: There is no standard therapeutic procedure for the hepatocellular carcinoma (HCC) in patients with poor hepatic reserve function. With the approval of newly developed chemotherapeutic agent of miriplatin, we have firstly conducted the phase I study of CDDP powder (DDP-H) and miriplatin combination therapy and reported its safety and efficacy for treating unresectable HCC in such cases. To determine the maximum tolerated dose (MTD) and dose-limiting toxicity (DLT) for the combination of transarterial oily chemoembolization (TOCE) and transarterial chemotherapy (TAC) using miriplatin and DDP-H for treating unresectable hepatocellular carcinoma (HCC). METHODS: Transarterial chemotherapy using DDP-H was performed through the proper hepatic artery targeting the HCC nodules by increasing the dose of DDP-H (35-65 mg/m(2)) followed by targeting the HCC nodules by transarterial oily chemoembolization with miriplatin. RESULTS: A total of nine patients were enrolled in this study and no DLT was observed with any dose of DDP-H in all cases in whom 80 mg (median, 18-120) miriplatin was administered. An anti-tumour efficacy rating for partial response was obtained in one patient, while a total of four patients (among eight evaluated) showed stable disease response, leading to 62.5% of disease control rate. The pharmacokinetic results showed no further increase in plasma platinum concentration following miriplatin administration. CONCLUSION: Our results suggest that a combination of DDP-H and miriplatin can be safely administered up to their respective MTD for treating HCC. TRIAL REGISTRATION: This study was registered with the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR000003541).

Identification of cellular genes showing differential expression associated with hepatitis B virus infection.

AIM: To investigate the impact of hepatitis B virus (HBV) infection on cellular gene expression, by conducting both in vitro and in vivo studies. METHODS: Knockdown of HBV was targeted by stable expression of short hairpin RNA (shRNA) in huH-1 cells. Cellular gene expression was compared using a human 30K cDNA microarray in the cells and quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR) (qRT-PCR) in the cells, hepatocellular carcinoma (HCC) and surrounding non-cancerous liver tissues (SL). RESULTS: The expressions of HBsAg and HBx protein were markedly suppressed in the cells and in HBx transgenic mouse liver, respectively, after introduction of shRNA. Of the 30K genes studied, 135 and 103 genes were identified as being down- and up-regulated, respectively, by at least twofold in the knockdown cells. Functional annotation revealed that 85 and 62 genes were classified into four up-regulated and five down-regulated functional categories, respectively. When gene expression levels were compared between HCC and SL, eight candidate genes that were confirmed to be up- or down-regulated in the knockdown cells by both microarray and qRT-PCR analyses were not expressed as expected from HBV reduction in HCC, but had similar expression patterns in HBV- and hepatitis C virus-associated cases. In contrast, among the eight genes, only APM2 was constantly repressed in HBV non-associated tissues irrespective of HCC or SL. CONCLUSION: The signature of cellular gene expression should provide new information regarding the pathophysiological mechanisms of persistent hepatitis and hepatocarcinogenesis that are associated with HBV infection.

Hepatocellular carcinoma with progenitor cell features distinguishable by the hepatic stem/progenitor cell marker NCAM.

We analyzed hepatocellular carcinoma (HCC) with progenitor cell features using hepatic stem/progenitor cell marker neural cell adhesion molecule (NCAM). Approximately 8.3% of the operated HCC cases expressed NCAM, and 22.3% of the HCC patients had soluble NCAM levels >1000ng/ml (the "highly soluble" NCAM group). Soluble NCAM status was a significant independent factor predictive of long-term survival in patients with HCC, and high levels of soluble NCAM were significantly related to intrahepatic metastasis. The 140-kDa NCAM isoform was specifically detected in the "highly soluble" NCAM group of HCC patients andits related signals are potential drug targets for NCAM+ HCC.

The dynamin-related GTPase Opa1 is required for glucose-stimulated ATP production in pancreatic beta cells.

Previous studies using in vitro cell culture systems have shown the role of the dynamin-related GTPase Opa1 in apoptosis prevention and mitochondrial DNA (mtDNA) maintenance. However, it remains to be tested whether these functions of Opa1 are physiologically important in vivo in mammals. Here, using the Cre-loxP system, we deleted mouse Opa1 in pancreatic beta cells, in which glucose-stimulated ATP production in mitochondria plays a key role in insulin secretion. Beta cells lacking Opa1 maintained normal copy numbers of mtDNA; however, the amount and activity of electron transport chain complex IV were significantly decreased, leading to impaired glucose-stimulated ATP production and insulin secretion. In addition, in Opa1-null beta cells, cell proliferation was impaired, whereas apoptosis was not promoted. Consequently, mice lacking Opa1 in beta cells develop hyperglycemia. The data suggest that the function of Opa1 in the maintenance of the electron transport chain is physiologically relevant in beta cells.

Multicentric occurrence of hepatocellular carcinoma with nonalcoholic steatohepatitis.

AIM: To reveal the manner of hepatocellular carcinoma (HCC) development in patients with nonalcoholic steatohepatitis (NASH) focusing on multicentric occurrence (MO) of HCC. METHODS: We compared clinicopathological characteristics between patients with and without MO of HCC arising from NASH background. The clinical features were implicated with reference to the literature available. RESULTS: MO of HCC was identified with histological proof in 4 out of 12 patients with NASH-related HCC (2 males and 2 females). One patient had synchronous MO; an advanced HCC, two well-differentiated HCCs and a dysplastic nodule, followed by the development of metachronous MO of HCC. The other three patients had multiple advanced HCCs accompanied by a well-differentiated HCC or a dysplastic nodule. Of these three patients, one had synchronous MO, one had metachronous MO and the other had both synchronous and metachronous MO. There were no obvious differences between the patients with or without MO in terms of liver function tests, tumor markers and anatomical extent of HCC. On the other hand, all four patients with MO of HCC were older than 70 years old and had the comorbidities of obesity, type 2 diabetes mellitus (T2DM), hypertension and cirrhosis. Although these conditions were not limited to MO of HCC, all the conditions were met in only one of eight patients without MO of HCC. Thus, concurrence of these conditions may be a predisposing situation to synchronous MO of HCC. In particular, old age, T2DM and cirrhosis were suggested to be prerequisite for MO because these factors were depicted in common among two other cases with MO of HCC under NASH in the literature. CONCLUSION: The putative predisposing factors and necessary preconditions for synchronous MO of HCC in NASH were suggested in this study. Further investigations are required to clarify the accurate prevalence and predictors of MO to establish better strategies for treatment and prevention leading to the prognostic improvement in NASH.

Mdm35p imports Ups proteins into the mitochondrial intermembrane space by functional complex formation.

Ups1p, Ups2p, and Ups3p are three homologous proteins that control phospholipid metabolism in the mitochondrial intermembrane space (IMS). The Ups proteins are atypical IMS proteins in that they lack the two major IMS-targeting signals, bipartite presequences and cysteine motifs. Here, we show that Ups protein import is mediated by another IMS protein, Mdm35p. In vitro import assays show that import of Ups proteins requires Mdm35p. Loss of Mdm35p led to a decrease in steady state levels of Ups proteins in mitochondria. In addition, mdm35Delta cells displayed a similar phenotype to ups1Deltaups2Deltaups3Delta cells. Interestingly, unlike typical import machineries, Mdm35p associated stably with Ups proteins at a steady state after import. Demonstrating that Mdm35p is a functional component of Ups-Mdm35p complexes, restoration of Ups protein levels in mdm35Delta mitochondria failed to restore phospholipid metabolism. These findings provide a novel mechanism in which the formation of functional protein complexes drives mitochondrial protein import.