The Cdc48-20S proteasome degrades a class of endogenous proteins in a ubiquitin-independent manner

The 26S proteasome is the major degradation machinery for soluble proteins in eukaryotes. Recent evidence reveals the existence of an alternative ATP-powered protein degradation complex, the Cdc48-20S proteasome complex, and we have identified yeast Sod1, a copper-zinc superoxide dismutase, as an endogenous substrate protein. Here, we identified yeast Ths1, an essential threonyl tRNA synthetase, as another endogenous substrate protein of the Cdc48-20S proteasome. In order to analyze the degradation mechanism in more details, we established an in vitro degradation system reconstituted using purified yeast components. Recombinant Sod1 and Ths1 directly interacted with Cdc48, and were degraded in a Cdc48-20S proteasome-dependent manner. Because the substrate proteins were purified from E. coli cells, no eukaryotic modifications including ubiquitination and phosphorylation exist. Therefore, although the 26S proteasome requires ubiquitination for specific recognition of the substrate proteins, the Cdc48-20S proteasome can degrade a class of substrate proteins without any modifications.

A AAA ATPase Cdc48 with a cofactor Ubx2 facilitates ubiquitylation of a mitochondrial fusion-promoting factor Fzo1 for proteasomal degradation

Dynamic functionality of mitochondria is maintained by continual fusion and fission events. A mitochondrial outer membrane protein Fzo1 plays a pivotal role upon mitochondrial fusion by homo-oligomerization to tether fusing mitochondria. Fzo1 is tightly regulated by ubiquitylations and the ubiquitin-responsible AAA protein Cdc48. Here, we show that a Cdc48 cofactor Ubx2 facilitates Fzo1 turnover. The Cdc48-Ubx2 complex has been shown to facilitate degradation of ubiquitylated proteins stacked at the protein translocation complex in the mitochondrial outer membrane by releasing them from the translocase. By contrast, in the degradation process of Fzo1, the Cdc48-Ubx2 complex appears to facilitate the degradation-signalling ubiquitylation of the substrate itself. In addition, the Cdc48-Ubx2 complex interacts with Ubp2, a deubiquitylase reversing the degradation-signalling ubiquitylation of Fzo1. These results suggest that the Cdc48-Ubx2 complex regulates Fzo1 turnover by modulating ubiquitylation status of the substrate.

Feasibility of resecting the portal vein only when necessary during pancreatoduodenectomy for pancreatic cancer

Background

Whether the portal/superior mesenteric vein (PV) should be resected during pancreatoduodenectomy for pancreatic ductal adenocarcinoma (PDAC) based on preoperative CT or intraoperative findings is controversial.

Methods

This was a retrospective study with data of patients who had undergone pancreatoduodenectomy for PDAC between 2002 and 2016 in a tertiary referral centre. Based on the extent of contact between the PV and tumour on CT, patients were categorized into: group 1, no contact; group 2, contact 180° or less; group 3, contact greater than 180°. Extent of pathological PV invasion (pPV) (no invasion, pv0; invasion to tunica adventitia, pv1; invasion to media, pv2; invasion to intima, pv3) was compared with patient survival. To assess the feasibility of performing PV resection (PVR) based on intraoperative findings, the prognosis of patients in groups 1 and 2 with pv0 and no PVR (PVR(−)pv0) was compared with that of patients who had PVR (PVR(+)pv0), selected using propensity score matching.

Results

Groups 1, 2 and 3 comprised 230, 232 and 38 patients respectively, and PVR was performed in 10·9, 73·3 and 95 per cent of them (P < 0·001). Extent of pPV differed significantly (P < 0·001). The positive predictive value of radiological tumour contact with PV in predicting positive pPV was 42·6 per cent. In 64 patients with PVR(−)pv0 and 64 matched patients with PVR(+)pv0, the R0 resection rate (66 versus 73 per cent respectively; P = 0·337) and survival (median 32·4 versus 32·1 months; P = 0·780) were not significantly different.

Conclusion

PVR is needed only when the tumour is in clear contact with the PV and cannot be detached during surgery.

Contribution of pharmacists with expertise in infectious diseases to appropriate individualized vancomycin dosing

BACKGROUND/AIM

Dose adjustment of vancomycin (VCM) is important in improving clinical outcomes and avoiding adverse effects such as nephrotoxicity. Although pharmacist-managed VCM therapy has been reported to optimize treatment, there are no studies focused on pharmacist expertise to date. In this study, we compared the contribution of pharmacists trained for infectious diseases and general pharmacists to dose adjustment of VCM.

PATIENTS AND METHODS

We retrospectively investigated VCM trough concentration after dose adjustment by both trained (n = 67) and general (without special training for infectious diseases; n = 85) pharmacists. We also compared the incidence of nephrotoxicity during VCM treatment in both groups.

RESULTS

The rate of achieving therapeutic VCM trough concentration (10-20 μg/mL) was higher in the trained group than in the control group (80.6 vs. 54.1%, p < 0.001). No significant differences in incidence of nephrotoxicity were observed between the two groups (p = 0.744). Trained pharmacists could contribute more successfully to the achievement of therapeutic VCM concentration ranges without increasing the risk of nephrotoxicity.

Two Cdc48 cofactors Ubp3 and Ubx2 regulate mitochondrial morphology and protein turnover

Mitochondria continuously undergo coordinated fusion and fission during vegetative growth to keep their homogeneity and to remove damaged components. A cytosolic AAA ATPase, Cdc48, is implicated in the mitochondrial fusion event and turnover of a fusion-responsible GTPase in the mitochondrial outer membrane, Fzo1, suggesting a possible linkage of mitochondrial fusion and Fzo1 turnover. Here, we identified two Cdc48 cofactor proteins, Ubp3 and Ubx2, involving mitochondria regulation. In the absence of UBP3, mitochondrial fragmentation and aggregation were observed. The turnover of Fzo1 was not affected in Δubp3, but instead a deubiquitylase Ubp12 that removes fusion-required polyubiquitin chains from Fzo1 was stabilized. Thus, excess amount of Ubp12 may lead to mitochondrial fragmentation by removal of fusion-competent ubiquitylated Fzo1. In contrast, deletion of UBX2 perturbed disassembly of Fzo1 oligomers and their degradation without alteration of mitochondrial morphology. The UBX2 deletion led to destabilization of Ubp2 that negatively regulates Fzo1 turnover by removing degradation-signalling polyubiquitin chains, suggesting that Ubx2 would directly facilitate Fzo1 degradation. These results indicated that two different Cdc48-cofactor complexes independently regulate mitochondrial fusion and Fzo1 turnover.

Continuous amnioinfusion in women with PPROM at periviable gestational ages

Objective: To elucidate the efficacy of continuous amnioinfusion on perinatal outcome in women with preterm premature rupture of membranes (PPROM) at periviable gestational ages.Methods: A database was reviewed to identify women with singleton pregnancies who were admitted to the Japanese Red Cross Nagoya Daiichi Hospital due to PPROM before 26 + 0-week gestation between July 2009 and July 2017.Results: A total of 81 women met the criteria for inclusion in this study including 70 and 11 women with and without amnioinfusion, respectively. The latency period between PPROM and delivery was significantly longer in women who underwent amnioinfusion compared with women without amnioinfusion (median: 13 versus 4 days, p < .001). In the survival analysis, the number of women who remained undelivered was significantly higher in the amnioinfusion group than in the non-amnioinfusion group for each gestational age after PPROM (p < .001). Cox's proportional hazards analysis with stepwise backward selection showed that both white blood cell counts on admission and amnioinfusion finally remained as variables that affected the time interval between PPROM and delivery [hazard ratio (95% confidence interval): 1.12 (1.06-1.18) and 0.34 (0.12-0.98), respectively].Conclusions: Continuous amnioinfusion in women with PPROM at periviable gestational ages resulted in significant prolongation of pregnancy and may help improve neonatal outcomes.

Extent of lymph node dissection in patients with gallbladder cancer

Background

Definitions of regional lymph nodes for gallbladder cancer differ according to staging system. Hence, the appropriate extent of lymph node dissection has not yet been standardized.

Methods

Pathological stages and disease-specific survival (DSS) of patients who had undergone surgical resection of gallbladder cancer between 1990 and 2016 were reviewed. Patients with nodal metastases limited to the hepatoduodenal ligament or common hepatic artery, extending to the posterosuperior pancreatic head lymph nodes (PSPLNs), or in nodes along the coeliac axis or superior mesenteric vessels were grouped as having Na, Nb and Nc disease respectively. Metastases beyond these regions were defined as distant metastases (M1). Absence of distant metastasis was expressed as M0.

Results

A total of 259 patients were evaluated. There were 74, 31 and nine patients respectively in the Na, Nb and Nc groups. Twenty-five, nine and four patients in the respective groups had M1 disease (P = 0·682). The 5-year DSS rate was comparable between patients with Na M0 and those with Nb M0 disease (36 versus 34 per cent respectively; P = 0·950), whereas the rate in patients with Nc M0 status (0 per cent) was worse than that of patients with Nb M0 (P = 0·017) and comparable to that of patients with M1 disease (14 per cent; P = 0·590). Among 22 patients with Nb M0 disease, the 5-year DSS rate did not differ between those who had undergone pancreatoduodenectomy and those who had had dissection of PSPLNs without pancreatoduodenectomy (50 versus 30 per cent respectively; P = 0·499).

Conclusion

PSPLNs and nodes along the hepatoduodenal ligament and hepatic artery should be considered regional nodes for gallbladder cancer, and should be resected.

Biological and Pathological Implications of an Alternative ATP-Powered Proteasomal Assembly With Cdc48 and the 20S Peptidase

The ATP-powered protein degradation machinery plays essential roles in maintaining protein homeostasis in all organisms. Robust proteolytic activities are typically sequestered within protein complexes to avoid the fatal removal of essential proteins. Because the openings of proteolytic chambers are narrow, substrate proteins must undergo unfolding. AAA superfamily proteins (ATPases associated with diverse cellular activities) are mostly located at these openings and regulate protein degradation appropriately. The 26S proteasome, comprising 20S peptidase and 19S regulatory particles, is the major ATP-powered protein degradation machinery in eukaryotes. The 19S particles are composed of six AAA proteins and 13 regulatory proteins, and bind to both ends of a barrel-shaped proteolytic chamber formed by the 20S peptidase. Several recent studies have reported that another AAA protein, Cdc48, can replace the 19S particles to form an alternative ATP-powered proteasomal complex, i.e., the Cdc48-20S proteasome. This review focuses on our current knowledge of this alternative proteasome and its possible linkage to amyotrophic lateral sclerosis.

Significance of measurement of serum trough level and anti-drug antibody of adalimumab as personalised pharmacokinetics in patients with Crohn's disease: a subanalysis of the DIAMOND trial

BACKGROUND

Significance of monitoring adalimumab trough levels and anti-adalimumab antibodies (AAA) for disease outcome in Crohn's disease (CD) patients remained unclear.

AIM

To evaluate the association of adalimumab trough levels and AAA at week 26 with clinical remission at week 52, the effect of azathiopurine on AAA and factors influencing trough levels in CD patients in the DIAMOND trial.

METHODS

We performed this study using adalimumab trough levels, AAA at week 26 and 6-thioguanine nucleotide (TGN) in red blood cells at week 12. A multiple regression model and receiver operating analysis was performed to identify factors influencing adalimumab trough levels and AAA, and adalimumab thresholds for predicting disease activity.

RESULTS

There was a significant difference of adalimumab trough level at week 26 between patients with disease remission and without at week 52 (7.7 ± 3.3 μg/mL vs 5.4 ± 4.3 μg/mL: P <.001). Adalimumab trough level of 5.0 μg/mL yielded optimal sensitivity and specificity for remission prediction (80.2% and 55.6%, respectively). AAA development at week 26 significantly affected remission at week 52 (P = .021), which was strongly associated with adalimumab trough levels. Female gender and increasing body weight were independently associated with low adalimumab trough levels, and female gender was associated with AAA development. A cut-off 6TGN level of >222.5 p mol/8 ×10⁸ RBCs yielded sensitivity (100%) and specificity (60.6%) for AAA negativity.

CONCLUSION

Adalimumab trough levels and AAA occurrence were significantly associated with clinical remission. Higher 6TGN affected AAA negativity. The combination therapy is beneficial in some relevant aspects for CD patients. (UMIN Registration No. 000005146).

The influence of CYP2C19 polymorphisms on exacerbating effect of rabeprazole in celecoxib-induced small bowel injury

BACKGROUND

Simultaneous use of proton pump inhibitors (PPIs) has been shown to increase the risk of nonsteroidal anti-inflammatory drug (NSAID)-induced small bowel injury.

AIM

To investigate whether polymorphisms of the cytochrome P450 2C19 gene (CYP2C19), encoding a key metabolising enzyme for PPIs, are associated with small bowel injury induced by celecoxib in combination with the PPI rabeprazole.

METHODS

Study participants included 55 healthy Japanese volunteers, who participated in the PPI-NSAID Kyushu University Study using video capsule endoscopy. For 2 weeks, 26 subjects were treated with celecoxib plus rabeprazole (rabeprazole group), and 29 subjects received celecoxib plus placebo (placebo group). All subjects were genotyped for CYP2C19 using real-time fluorescent polymerase chain reaction. Subjects were sub-classified as poor metabolizers or extensive metabolizers. The incidence and number of small bowel injuries were compared between poor metabolizers and extensive metabolizers in each group.

RESULTS

In the rabeprazole group, the incidence of small bowel injuries was significantly higher in poor metabolizers than in extensive metabolizers (85.7% vs 31.6%, P=.026). The number of mucosal injuries in the rabeprazole group was also significantly higher in poor metabolizers compared with extensive metabolizers (median [range] 3 [0-31] vs 0 [0-7], P=.01). In addition, we found a significant interaction between CYP2C19 genotype and concomitant use of rabeprazole in subjects at risk for celecoxib-induced small bowel injury.

CONCLUSIONS

The CYP2C19 genotype might be associated with the risk of small bowel injury when celecoxib is combined with rabeprazole.

Deviation of the typical AAA substrate-threading pore prevents fatal protein degradation in yeast Cdc48

Yeast Cdc48 is a well-conserved, essential chaperone of ATPases associated with diverse cellular activity (AAA) proteins, which recognizes substrate proteins and modulates their conformations to carry out many cellular processes. However, the fundamental mechanisms underlying the diverse pivotal roles of Cdc48 remain unknown. Almost all AAA proteins form a ring-shaped structure with a conserved aromatic amino acid residue that is essential for proper function. The threading mechanism hypothesis suggests that this residue guides the intrusion of substrate proteins into a narrow pore of the AAA ring, thereby becoming unfolded. By contrast, the aromatic residue in one of the two AAA rings of Cdc48 has been eliminated through evolution. Here, we show that artificial retrieval of this aromatic residue in Cdc48 is lethal, and essential features to support the threading mechanism are required to exhibit the lethal phenotype. In particular, genetic and biochemical analyses of the Cdc48 lethal mutant strongly suggested that when in complex with the 20S proteasome, essential proteins are abnormally forced to thread through the Cdc48 pore to become degraded, which was not detected in wild-type Cdc48. Thus, the widely applicable threading model is less effective for wild-type Cdc48; rather, Cdc48 might function predominantly through an as-yet-undetermined mechanism.

Salvage hepatectomy for local recurrence of hepatocellular carcinomas offers survival comparable to that of matched patients who undergo primary hepatectomies

BACKGROUND

The feasibility of salvage hepatectomy for locally recurrent hepatocellular carcinomas (HCCs) is unclear, especially for patients with viable parts of previously multinodular tumors.

METHODS

We reviewed charts of patients who underwent initial hepatectomies between 2000 and 2014 to select those with local recurrences (LR) after non-surgical treatments. Their postoperative outcomes, including morbidity, recurrence-free survival (RFS), and overall survival (OS) were compared with matched patients who underwent initial hepatectomies for primary HCCs (PR). Their local recurrence patterns were divided into recurrent solitary tumors (Subgroup A); and recurrent parts of multinodular tumors (Subgroup B).

RESULTS

Among 664 patients, hepatectomy for LR was performed in 62 patients. Matched 59 patients were selected as PR. Clinicopathologic profiles at initial surgery were comparable between the LR and PR groups. Incidence of major morbidity (LR vs. PR, 7% vs. 5%, P = 1.00), 5-year RFS (21% vs. 37%, P = 0.28), and 5-year OS (69% vs. 69%, P = 0.62) were comparable. In the LR group, Subgroup B showed worse 5-year RFS (A vs. B, 29% vs. 0%, P < 0.01) and 5-year-OS (80% vs. 53%, P = 0.01). Postoperative recurrence occurred in 46 patients, but local and extrahepatic recurrence was seen only in 2 patients and 2 patients, respectively.

CONCLUSION

Salvage hepatectomy for locally recurrent HCCs is feasible, and results in prognosis comparable with hepatectomy for primary HCCs. Although the risk of postoperative recurrence was high in Subgroup B, rare local recurrence suggests the usefulness of salvaging uncontrolled tumor by nonsurgical treatment.

Microtubule severing by katanin p60 AAA+ ATPase requires the C-terminal acidic tails of both α- and β-tubulins and basic amino acid residues in the AAA+ ring pore

The microtubule (MT) network is highly dynamic and undergoes dramatic reorganizations during the cell cycle. Dimers of α- and β-tubulins rapidly polymerize to and depolymerize from the end of MT fibrils in an intrinsic GTP-dependent manner. MT severing by ATP-driven enzymes such as katanin and spastin contributes significantly to microtubule dynamics, and it has been shown that katanin p60, a AAA+ family protein, has ATPase and MT-severing activities. The mechanism of MT severing by katanin p60 is poorly understood, and the residues in katanin p60 and tubulins important for severing activity were therefore explored in this study. MT-severing activity, but not ATPase activity, was inhibited by mutations of the conserved aromatic residue and the flanking basic residues in the pore region of the katanin p60 hexameric ring. When the acidic residue-rich C-terminal unstructured segment of either α- or β-tubulin was removed, polymerized MTs were resistant to katanin p60 treatment. Interactions between katanin p60 and the mutant MTs, on the other hand, were unaffected. Taken together, these findings led us to propose that the interactions between the positively charged residues of katanin p60 and the acidic tails of both tubulins are essential for efficient severing of MTs.

Multicentre analysis of long-term outcome after surgical resection for gastric cancer liver metastases

Background

The efficacy of surgical resection for gastric cancer liver metastases (GCLMs) is currently debated. Hitherto, no large-scale clinical studies have been conducted.

Methods

This retrospective multicentre study analysed a database of consecutive patients with either synchronous or metachronous metastases who underwent surgical R0 resection for GCLM between 1990 and 2010. Clinical data were collected from five cancer centres in Japan. Survival curves were assessed, and clinical parameters were evaluated to identify predictors of prognosis.

Results

A total of 256 patients were enrolled. The mean(s.d.) number of hepatic tumours resected was 2·0(2·4). The surgical mortality rate was 1·6 per cent. Median follow-up was 65 (range 1–261) months. Recurrences were detected in 192 patients (75·0 per cent). The median interval from hepatic resection to recurrence was 7 (range 1–72) months, and the dominant site of recurrence was the liver (72·4 per cent). Actuarial 1-, 3- and 5-year overall and recurrence-free survival rates were 77·3, 41·9 and 31·1 per cent, and 43·6, 32·4 and 30·1 per cent, respectively. Median overall and recurrence-free survival times were 31·1 and 9·4 months respectively. Multivariable analysis identified serosal invasion of the primary gastric cancer (hazard ratio (HR) 1·50; P = 0·012), three or more liver metastases (HR 2·33; P &lt; 0·001) and liver tumour diameter at least 5 cm (HR 1·62; P = 0·005) as independent predictors of poor survival.

Conclusion

Clinically resectable GCLM is rare, but strict and careful patient selection can lead to long-term survival following R0 surgical resection.

Serial block-face scanning electron microscopy for three-dimensional analysis of morphological changes in mitochondria regulated by Cdc48p/p97 ATPase

Cdc48p is a highly conserved cytosolic AAA chaperone that is involved in a wide range of cellular processes. It consists of two ATPase domains (D1 and D2), with regulatory regions at the N- and C-terminals. We have recently shown that Cdc48p regulates mitochondrial morphology, in that a loss of the ATPase activity or positive cooperativity in the D2 domain leads to severe fragmentations and aggregations of mitochondria in the cytoplasm. We have now used serial block-face scanning electron microscopy (SBF-SEM), an advanced three-dimensional (3D) electron microscopic technique to examine the structures and morphological changes of mitochondria in the yeast Saccharomyces cerevisiae. We found that mutants lacking ATPase activity of Cdc48p showed mitochondrial fragmentations and aggregations, without fusion of the outer membrane. This suggests that the ATPase activity of Cdc48p is necessary for fusion of the outer membranes of mitochondria. Our results also show that SBF-SEM has considerable advantages in morphological and quantitative studies on organelles and intracellular structures in entire cells.

Intraoperative enteroscopy detects more lesions but is not predictive of postoperative recurrence in Crohn’s disease

BACKGROUND

The aim of this investigation was to elucidate the clinical value of intraoperative enteroscopy (IOE) for Crohn's disease, and to determine the value of IOE in predicting recurrent disease.

METHODS

In this study 27 patients requiring surgery were examined by both preoperative radiography and IOE. The findings obtained by these procedures in the remnant small intestine were compared. In 19 patients, the clinical course and colonoscopic or radiographic findings after surgery were analyzed.

RESULTS

Intestinal lesions were identified in 23 patients by IOE, and in 19 patients by radiography. Longitudinal ulcers were equivalently detected by IOE (63%) and radiography (56%), whereas small ulcers and inflammatory polyps were less frequently detected by radiography than by IOE (37% vs 74% and 19% vs 33%, respectively). Neither the presence nor the distribution of IOE findings was related to postoperative recurrence.

CONCLUSIONS

Whereas IOE demonstrates small intestinal lesions in detail, the procedure alone cannot predict postoperative recurrence in Crohn's disease.

Sec16 influences transitional ER sites by regulating rather than organizing COPII

During the budding of coat protein complex II (COPII) vesicles from transitional endoplasmic reticulum (tER) sites, Sec16 has been proposed to play two distinct roles: negatively regulating COPII turnover and organizing COPII assembly at tER sites. We tested these ideas using the yeast Pichia pastoris. Redistribution of Sec16 to the cytosol accelerates tER dynamics, supporting a negative regulatory role for Sec16. To evaluate a possible COPII organization role, we dissected the functional regions of Sec16. The central conserved domain, which had been implicated in coordinating COPII assembly, is actually dispensable for normal tER structure. An upstream conserved region (UCR) localizes Sec16 to tER sites. The UCR binds COPII components, and removal of COPII from tER sites also removes Sec16, indicating that COPII recruits Sec16 rather than the other way around. We propose that Sec16 does not in fact organize COPII. Instead, regulation of COPII turnover can account for the influence of Sec16 on tER sites.

Left hepatic trisectionectomy for advanced perihilar cholangiocarcinoma

BACKGROUND

Data on outcomes of left hepatic trisectionectomy (LT) for perihilar cholangiocarcinoma are limited. The aim of this study was to clarify short- and long-term outcomes of LT for perihilar cholangiocarcinoma.

METHODS

Patients with perihilar cholangiocarcinoma who underwent LT between January 2000 and October 2011 were analysed. Surgical variables, mortality, morbidity (Clavien grade I-V), recurrence sites and survival were compared between subjects who underwent LT, right hemihepatectomy or left hemihepatectomy.

RESULTS

A total 214 patients underwent resection for perihilar cholangiocarcinoma, 25 (11·7 per cent) of whom underwent LT, 88 (41·1 per cent) right hemihepatectomy and 94 (43·9 per cent) left hepatectomy. There were no deaths among those who had LT, but 20 patients developed complications. The incidence of grade IIIa complications was significantly higher among patients who underwent LT than in patients who had right or left hemihepatectomy (P = 0·001 and P < 0·001 respectively). Only one patient developed a grade IIIb or IV complication (liver failure) after LT. The overall 5-year survival rate after LT was 39 per cent and median survival was 45 months. There were no significant differences in survival between patients who underwent LT and those who had a right or left hemihepatectomy.

CONCLUSION

LT may provide a good outcome for advanced perihilar cholangiocarcinoma.

The Tom40 assembly process probed using the attachment of different intramitochondrial sorting signals

The β-barrel protein Tom40 functions as a protein-conducting channel in the mitochondrial outer membrane. By attaching mitochondrial presequences for various mitochondrial destinations to Tom40, it is possible to follow its sorting process. The results provide insight into the mechanism for the precise delivery of β-barrel proteins to the outer membrane.

The TOM40 complex is a protein translocator in the mitochondrial outer membrane and consists of several different subunits. Among them, Tom40 is a central subunit that constitutes a protein-conducting channel by forming a β-barrel structure. To probe the nature of the assembly process of Tom40 in the outer membrane, we attached various mitochondrial presequences to Tom40 that possess sorting information for the intermembrane space (IMS), inner membrane, and matrix and would compete with the inherent Tom40 assembly process. We analyzed the mitochondrial import of those fusion proteins in vitro. Tom40 crossed the outer membrane and/or inner membrane even in the presence of various sorting signals. N-terminal anchorage of the attached presequence to the inner membrane did not prevent Tom40 from associating with the TOB/SAM complex, although it impaired its efficient release from the TOB complex in vitro but not in vivo. The IMS or matrix-targeting presequence attached to Tom40 was effective in substituting for the requirement for small Tim proteins in the IMS for the translocation of Tom40 across the outer membrane. These results provide insight into the mechanism responsible for the precise delivery of β-barrel proteins to the outer mitochondrial membrane.

The C-terminal α-helix of SPAS-1, a Caenorhabditis elegans spastin homologue, is crucial for microtubule severing

Spastin belongs to the meiotic subfamily, together with Vps4/SKD1, fidgetin and katanin, of AAA (ATPases associated with diverse cellular activities) proteins, and functions in microtubule severing. Interestingly, all members of this subgroup specifically contain an additional α-helix at the very C-terminal end. To understand the function of the C-terminal α-helix, we characterised its deletion mutants of SPAS-1, a Caenorhabditis elegans spastin homologue, in vitro and in vivo. We found that the C-terminal α-helix plays essential roles in ATP binding, ATP hydrolysing and microtubule severing activities. It is likely that the C-terminal α-helix is required for cellular functions of members of meiotic subgroup of AAA proteins, since the C-terminal α-helix of Vps4 is also important for assembly, ATPase activity and in vivo function mediated by ESCRT-III complexes.

Caenorhabditis elegans fidgetin homolog FIGL-1, a nuclear-localized AAA ATPase, binds to SUMO

Fidgetin is a member of the AAA (ATPases associated with diverse cellular activities) chaperones. It is well-known that the specific function of a given AAA protein primarily depends upon its subcellular localization and interacting partners. FIGL-1, a Caenorhabditis elegans homolog of mammalian fidgetin, is localized in the nucleus. Here, we identified that the N-terminal PKRVK sequence of FIGL-1 functions as a monopartite nuclear localization signal. Nuclear localization of FIGL-1 is required for its function. We also found that FIGL-1 specifically interacted with SMO-1, a C. elegans homolog of small ubiquitin-like modifier (SUMO), using a yeast two-hybrid assay. Furthermore, the direct physical interaction between FIGL-1 and SMO-1 was demonstrated by pull-down assay using purified proteins as well as immunoprecipitation assay using lysates from epitope-tagged SMO-1-expressing worms. Binding of FIGL-1 to SMO-1 is required for its function. The depletion of FIGL-1 and SMO-1 resulted in developmental defects in C. elegans. Taken altogether, our results indicate that FIGL-1 is a nuclear protein and that in concert with SMO-1, FIGL-1 plays an important role in the regulation of C. elegans development.

Cdc48p/p97-mediated regulation of mitochondrial morphology is Vms1p-independent

Cdc48p/p97 is a cytosolic essential AAA chaperone, which regulates multiple cellular reactions in a ubiquitin-dependent manner. We have recently shown that Cdc48p exhibits positively cooperative ATPase activity and loss of the positive cooperativity results in yeast cell death. Here we show that loss of the positive cooperativity of the yeast Cdc48p ATPase activity led to severe mitochondrial aggregation. The actin cytoskeleton and distribution of the ER-mitochondria tethering complex (ERMES) were eliminated from the cause of the mitochondrial aggregation. Instead, a mitochondrial outer membrane protein Fzo1p, which is required for mitochondrial fusion, and components of ERMES, which is involved in mitochondrial morphology, were remarkably stabilized in the Cdc48p mutants. In the last couple of years, it was shown that Vms1p functions as a cofactor of Cdc48p for the function of protein degradation of mitochondrial outer membrane proteins. Nevertheless, we found that Vms1p was not involved in the Cdc48p-dependent mitochondrial aggregation and loss of Vms1p did not significantly affect degradation rates of proteins anchored to the mitochondrial outer membrane. These results suggest that Cdc48p controls mitochondrial morphology by regulating turnover of proteins involved in mitochondrial morphology in a Vms1p-independent manner.

Positive cooperativity of the p97 AAA ATPase is critical for essential functions

p97 is composed of two conserved AAA (ATPases associated with diverse cellular activities) domains, which form a tandem hexameric ring. We characterized the ATP hydrolysis mechanism of CDC-48.1, a p97 homolog of Caenorhabditis elegans. The ATPase activity of the N-terminal AAA domain was very low at physiological temperature, whereas the C-terminal AAA domain showed high ATPase activity in a coordinated fashion with positive cooperativity. The cooperativity and coordination are generated by different mechanisms because a noncooperative mutant still showed the coordination. Interestingly, the growth speed of yeast cells strongly related to the positive cooperativity rather than the ATPase activity itself, suggesting that the positive cooperativity is critical for the essential functions of p97.

Extended right hemihepatectomy for gallbladder carcinoma involving the hepatic hilum

BACKGROUND

Major hemihepatectomy for advanced gallbladder carcinoma remains controversial as it is associated with serious postoperative complications and poor prognosis.

METHODS

All those who underwent extended right hemihepatectomy were identified from a database of patients with gallbladder carcinoma who had surgical resection between 1999 and 2009. The clinicopathological data for these patients were analysed retrospectively.

RESULTS

A total of 126 patients underwent surgical resection, 35 of whom had extended right hemihepatectomy. There were no deaths, but 16 patients had complications. The mean(s.d.) duration of operation and blood loss were 564(206) min and 1472(1268) ml respectively. No blood transfusions were needed in 28 patients. Tumour stage (International Union Against Cancer, sixth edition) was IIA in four, IIB in four, III in 15 and IV in 12 patients. The overall 5-year survival rate was 17 per cent with a median survival of 2·2 years. Three patients survived more than 5 years. The presence of hepatic metastases and gallbladder carcinoma originating from the cystic duct were indicators of poor prognosis.

CONCLUSION

Extended right hemihepatectomy for gallbladder cancer is safe and may contribute to long-term survival in selected patients.

ATP-bound form of the D1 AAA domain inhibits an essential function of Cdc48p/p97

Cdc48p/p97 is a highly conserved essential AAA protein that is required for many cellular processes, and is identified as a causative gene for an autosomal dominant human disorder, inclusion body myopathy associated with Paget's disease of the bone and frontotemporal dementia (IBMPFD). Cdc48p/p97 is composed of an N-terminal domain, followed by two AAA domains (D1 and D2) whose ATPase activities have been characterized extensively. In this study, effects of mutations on the essential functions of yeast Cdc48p/p97 in vivo were systematically analyzed. IBMPFD-related mutations do not affect the essential functions of Cdc48p/p97. Loss of ATPase activity of D2 leads to loss of function of the protein in vivo. In contrast, ATPase activity of D1 per se is not essential, but a mutation locking D1 in an ATP-bound form is exceptionally lethal. Site-directed and random mutagenesis analyses suggest that the ATP-bound form of D1 changes an inter-domain interaction, thereby perturbing an essential function of Cdc48p/p97.

Roles of Tom70 in import of presequence-containing mitochondrial proteins

Mitochondrial protein traffic requires precise recognition of the mitochondrial targeting signals by the import receptors on the mitochondrial surface including a general import receptor Tom20 and a receptor for presequence-less proteins, Tom70. Here we took a proteome-wide approach of mitochondrial protein import in vitro to find a set of presequence-containing precursor proteins for recognition by Tom70. The presequences of the Tom70-dependent precursor proteins were recognized by Tom20, whereas their mature parts exhibited Tom70-dependent import when attached to the presequence of Tom70-independent precursor proteins. The mature parts of the Tom70-dependent precursor proteins have the propensity to aggregate, and the presence of the receptor domain of Tom70 prevents their aggregate formation. Therefore Tom70 plays the role of a docking site for not only cytosolic chaperones but also aggregate-prone substrates to maintain their solubility for efficient transfer to downstream components of the mitochondrial import machineries.

Relationship between folic acid intake and gingival health in non-smoking adults in Japan

OBJECTIVE

To assess the relationship between dietary intake of folate and gingival bleeding in non-smoking adults in Japan.

MATERIALS AND METHODS

Data were obtained from residents who participated in the regional nutrition survey and survey of dental diseases conducted by the administrative office of northernmost prefecture of Japan. Dietitians visited households to collect data on dietary intake. Clinical parameters, including Community Periodontal Index (CPI) and bleeding on probing (BOP), were examined in community centers. Information on smoking habit was obtained from the interview. Then the data from 497 non-smoking adults with 20 teeth or more, aged 18 years or older, were analyzed. The relationship between dietary intake of folic acid and gingival bleeding status was estimated using multivariate analysis.

RESULTS

Pearson's correlation coefficient showed a significant negative correlation between dietary folate level and bleeding on probing. The negative association between folate level and bleeding on probing remained statistically significant in multiple regression analysis (standardized beta = -0.204, P < 0.001). However, no significant association was found between CPI scores and folate intake level.

CONCLUSIONS

The results suggest that dietary intake of folic acid, an important indicator of gingival bleeding in adults, may provide an important clinical target for intervention to promote gingival health.

Step-size analyses of the mitochondrial Hsp70 import motor reveal the Brownian ratchet in operation

Newly synthesized mitochondrial precursor proteins have to become unfolded by the mitochondrial Hsp70 (mtHsp70) import motor to cross the mitochondrial membranes. To assess the mechanism of unfolding of precursor proteins by mtHsp70, we designed a system to measure step sizes of the mtHsp70 import motor, which are distances at which the motor system moves along polypeptide chains during a single turnover of ATP. We made a series of fusion proteins consisting of a mitochondrial presequence containing the first mtHsp70 binding site, a spacer sequence containing an Hsp70 avoidance segment followed by the second mtHsp70 binding site, and different folded mature domains. Analyses of the dependence of the import rates of those fusion proteins on the lengths of Hsp70 avoidance segments allowed us to estimate the step sizes, which differ for different mature domains and different lengths of the spacers. These results suggest that the mtHsp70 import motor functions at least as a molecular Brownian ratchet to unfold mitochondrial precursor proteins.

p97 Homologs from Caenorhabditis elegans, CDC-48.1 and CDC-48.2, suppress the aggregate formation of huntingtin exon1 containing expanded polyQ repeat

Polyglutamine (polyQ)-expanded proteins are associated with cytotoxicity in some neurodegenerative disorders such as Huntington's disease. We have reported that the aggregation of the polyQ-expanded protein is partially suppressed by co-expression of either of two homologs of an AAA chaperone p97, CDC-48.1 or CDC-48.2, in Caenorhabditis elegans, but how p97 regulates the aggregation of polyQ-expanded proteins remains unclear. Here we present direct evidence that CDC-48.1 and CDC-48.2 suppress the aggregation of a huntingtin (Htt) exon1 fragment containing an expanded polyQ repeat in vitro. CDC-48.1 and CDC-48.2 bound the Htt exon1 fragment directly, and suppressed the formation of SDS-insoluble aggregates of Htt fragments containing 53 glutamine residues (HttQ53) independently of nucleotides. CDC-48.1 and CDC-48.2 also modulated the oligomeric states of HttQ53 during the aggregate formation. In the absence of CDC-48.1 and CDC-48.2, HttQ53 formed 70-150 kDa oligomers, whereas 300-500 kDa oligomers as well as 70-150 kDa oligomers accumulated in the presence of CDC-48.1 and CDC-48.2. Taken together, these results suggest that p97 plays a protective role in neurodegenerative disorders by directly suppressing the protein aggregation as a molecular chaperone.

Genomic and functional analyses of MUTYH in Japanese patients with adenomatous polyposis

The present study was undertaken to elucidate germ line mutations of the base excision repair gene, MUTYH, in Japanese patients with adenomatous polyposis. We screened germ line mutations of adenomatous polyposis coli (APC) gene and MUTYH in 66 Japanese patients with adenomatous polyposis. APC was screened by the protein truncation test, while MUTYH was screened by polymerase chain reaction-based single-strand conformation polymorphism and direct sequencing. The nicking assay was applied in order to evaluate the DNA glycosylase activity of the identified MUTYH variant. In this study, Seven MUTYH variants were identified in 16 of 21 APC-negative patients. Q324H mutation was the most frequent mutation, with an allele frequency of 49%. Two patients carried biallelic mutations other than Q324H; a patient had biallelic G272E and A359V mutations, while the other had compound heterozygotes of P18L and G25D mutations. Nicking assay for G272E using the corresponding mouse MUTYH mutant with G257E revealed that G272E is a variant to cause an impaired DNA glycosylase activity. Homozygous MUTYH mutation accounts for approximately 10% of Japanese patients with adenomatous polyposis. G272E may be one of the mutations specific to patients with adenomatous polyposis in East Asia.

Tom20 and Tom22 share the common signal recognition pathway in mitochondrial protein import

Precise targeting of mitochondrial precursor proteins to mitochondria requires receptor functions of Tom20, Tom22, and Tom70 on the mitochondrial surface. Tom20 is a major import receptor that recognizes preferentially mitochondrial presequences, and Tom70 is a specialized receptor that recognizes presequence-less inner membrane proteins. The cytosolic domain of Tom22 appears to function as a receptor in cooperation with Tom20, but how its substrate specificity differs from that of Tom20 remains unclear. To reveal possible differences in substrate specificities between Tom20 and Tom22, if any, we deleted the receptor domain of Tom20 or Tom22 in mitochondria in vitro by introducing cleavage sites for a tobacco etch virus protease between the receptor domains and transmembrane segments of Tom20 and Tom22. Then mitochondria without the receptor domain of Tom20 or Tom22 were analyzed for their abilities to import various mitochondrial precursor proteins targeted to different mitochondrial subcompartments in vitro. The effects of deletion of the receptor domains on the import of different mitochondrial proteins for different import pathways were quite similar between Tom20 and Tom22. Therefore Tom20 and Tom22 are apparently involved in the same step or sequential steps along the same pathway of targeting signal recognition in import.

Risk factors for local recurrence of superficial esophageal cancer after treatment by endoscopic mucosal resection

BACKGROUND AND STUDY AIM

The aim of this study was to elucidate the risk factors for local recurrence after endoscopic mucosal resection (EMR) treatment for superficial esophageal cancer (SEC).

PATIENTS AND METHODS

We performed a retrospective analysis of the clinical course of 62 patients with 64 SECs that were treated by EMR between 1993 and 2004. Follow-up examinations by chromoscopy with iodine solution and biopsy were performed 3 months, 6 months, 12 months, and then annually after EMR. Local recurrence was defined as a histologically confirmed finding of cancer cells at the site of the preceding EMR. The contributions of lesion-related and procedure-related factors to local recurrence were analyzed retrospectively.

RESULTS

Local recurrence was detected in 14/64 SECs 3-36 months after EMR. Of the lesion-related factors we assessed, local recurrence was found to be more frequent in SECs with a larger diameter (P = 0.01), larger circumferential spread (P = 0.04), or deeper invasion (P = 0.04), although the last two factors failed to demonstrate statistical significance after correction for multiple testing. Piecemeal resection did not increase the risk of local recurrence (P = 0.11), but the need for adjunctive coagulation therapy was found to increase the risk of local recurrence (P = 0.06).

CONCLUSIONS

Larger SECs are associated with a higher risk of local recurrence after EMR. In patients with residual lesions, coagulation therapy does not seem to be adequate as additional endoscopic treatment.

The budding yeastPichia pastorishas a novel Sec23p homolog

In Pichia pastoris, coat protein complex II (COPII) vesicles form at discrete transitional ER (tER) sites. Analyzing COPII coat proteins in this yeast will help to reveal the mechanisms of tER organization. Here, we show that like Saccharomyces cerevisiae, P. pastoris contains essential SEC23 and SEC24 genes, as well as the non-essential SEC24 homolog LST1. In addition, P. pastoris contains a novel non-essential SEC23 homolog that we have designated SHL23. The products of all four genes are concentrated at tER sites. Deletion of SHL23 does not disrupt tER morphology. As judged by two-hybrid analysis, Sec23p associates with both Sec24p and Lst1p, whereas Shl23p associates selectively with Lst1p. These results suggest that P. pastoris COPII vesicles contain an Shl23p/Lst1p complex that is absent in S. cerevisiae.