CdsA, a CDP-diacylglycerol synthase involved in phospholipid and glycolipid MPIase biosynthesis, possesses multiple initiation codons.

CdsA is a CDP-diacylglycerol synthase essential for phospholipid and glycolipid MPIase biosynthesis, and therefore for growth. The initiation codon of CdsA has been assigned as "TTG," while methionine at the 37th codon was reported to be an initiation codon in the original report. Since a vector containing the open reading frame starting with "TTG" under a controllable promoter complemented the cdsA knockout, "TTG" could function as an initiation codon. However, no evidence supporting that this "TTG" is the sole initiation codon has been reported. We determined the initiation codon by examining the ability of mutants around the N-terminal region to complement cdsA mutants. Even if the "TTG" was substituted with a stop codon, the clear complementation was observed. Moreover, the clones with multiple mutations of stop codons complemented the cdsA mutant up to the 37th codon, indicating that cdsA possesses multiple codons that can function as initiation codons. We constructed an experimental system in which the chromosomal expression of cdsA can be analyzed. By means of this system, we found that the cdsA mutant with substitution of "TTG" with a stop codon is fully functional. Thus, we concluded that CdsA contains multiple initiation codons.

MucA is a small peptide encoded by an overlapping sequence with cdsA that upregulates the biosynthesis of glycolipid MPIase in the cold.

MPIase is a glycolipid involved in protein insertion into and preprotein translocation across the cytoplasmic membranes of E. coli. MPIase is upregulated in the cold conditions to overcome the cold-sensitive protein export. CdsA, a CDP-diacylglycerol synthase, catalyzes the first reaction in MPIase biosynthesis. An open reading frame for a peptide of 50 amino acids is encoded immediately after ispU, a neighboring upstream gene of cdsA, and overlaps cdsA to a large extent. Mutational analysis revealed that the expression of this peptide is essential for upregulation of MPIase in the cold. Consistently, expression of this peptide in trans resulted in cold upregulation of MPIase. We therefore named this peptide MucA after its function (MPIase upregulation in the cold). When the partially purified MucA was added to the reaction of the intermediate in MPIase biosynthesis, a significant increase in the product formation was observed, supporting the function of MucA. The possible role of MucA in MPIase biosynthesis is discussed.

Structural Requirements of a Glycolipid MPIase for Membrane Protein Integration.

MPIase is a glycolipid involved in membrane protein integration in the inner membrane of Escherichia coli. To overcome the trace amounts and heterogeneity of natural MPIase, we systematically synthesized MPIase analogs. Structure-activity relationship studies revealed the contribution of distinctive functional groups and the effect of the MPIase glycan length on membrane protein integration activity. In addition, both the synergistic effects of these analogs with the membrane chaperone/insertase YidC, and the chaperone-like activity of the phosphorylated glycan were observed. These results verified the translocon-independent membrane integration mechanism in the inner membrane of E. coli, in which MPIase captures the highly hydrophobic nascent proteins via its characteristic functional groups, prevents protein aggregation, attracts the proteins to the membrane surface, and delivers them to YidC in order to regenerate its own integration activity.

Expression of Cds4/5 of Arabidopsis chloroplasts in E. coli reveals the membrane topology of the C-terminal region of CDP-diacylglycerol synthases.

CDP-diacylglycerol synthases (Cds) are conserved from bacteria to eukaryotes. Bacterial CdsA is involved not only in phospholipid biosynthesis but also in biosynthesis of glycolipid MPIase, an essential glycolipid that catalyzes membrane protein integration. We found that both Cds4 and Cds5 of Arabidopsis chloroplasts complement cdsA knockout by supporting both phospholipid and MPIase biosyntheses. Comparison of the sequences of CdsA and Cds4/5 suggests a difference in membrane topology at the C-termini, since the region assigned as the last transmembrane region of CdsA, which follows the conserved cytoplasmic domain, is missing in Cds4/5. Deletion of the C-terminal region abolished the function, indicating the importance of the region. Both 6 × His tag attachment to CdsA and substitution of the C-terminal 6 residues with 6 × His did not affect the function. These 6 × His tags were sensitive to protease added from the cytosolic side in vitro, indicating that this region is not a transmembrane one but forms a membrane-embedded reentrant loop. Thus, the C-terminal region of Cds homologues forms a reentrant loop, of which structure is important for the Cds function.

[Theory and Practice of Endoscopic Third Ventriculostomy].

Endoscopic third ventriculostomy(ETV)is a basic procedure for the surgical treatment of hydrocephalus. It buffers pulsatile pressure by creating an alternative route for the flow of cerebrospinal fluid and reduces trans-mantle pulsatile stress, thereby increasing compliance of the brain parenchyma. Blunt perforation of the third ventricular floor is done while avoiding injury to the foramen of Monro, the hypothalamus, the pituitary stalk, and some cisternal vessels. A major complication of ETV is arterial bleeding caused by injury to the basilar artery. Surgeons should wait with irrigation and opening the root into the ventricle to control the intra-ventricular pressure until packing the third ventricle with hematoma. Since ETV may close by gliosis or scarring of the inter-peduncular cistern, regular physical examinations and MRI should follow the procedure.

Increased expression of the bacterial glycolipid MPIase is required for efficient protein translocation across membranes in cold conditions.

Protein integration into and translocation across biological membranes are vital events for organismal survival and are fundamentally conserved among many organisms. Membrane protein integrase (MPIase) is a glycolipid that drives membrane protein integration into the cytoplasmic membrane in Escherichia coli MPIase also stimulates protein translocation across the membrane, but how its expression is regulated is incompletely understood. In this study, we found that the expression level of MPIase significantly increases in the cold (<25 °C), whereas that of the SecYEG translocon does not. Using previously created gene-knockout E. coli strains, we also found that either the cdsA or ynbB gene, both encoding rate-limiting enzymes for MPIase biosynthesis, is responsible for the increase in the MPIase expression. Furthermore, using pulse-chase experiments and protein integration assays, we demonstrated that the increase in MPIase levels is important for efficient protein translocation, but not for protein integration. We conclude that MPIase expression is required to stimulate protein translocation in cold conditions and is controlled by cdsA and ynbB gene expression.

The bacterial protein YidC accelerates MPIase-dependent integration of membrane proteins.

Bacterial membrane proteins are integrated into membranes through the concerted activities of a series of integration factors, including membrane protein integrase (MPIase). However, how MPIase activity is complemented by other integration factors during membrane protein integration is incompletely understood. Here, using inverted inner-membrane vesicle and reconstituted (proteo)liposome preparations from Escherichia coli cells, along with membrane protein integration assays and the PURE system to produce membrane proteins, we found that anti-MPIase IgG inhibits the integration of both the Sec-independent substrate 3L-Pf3 coat and the Sec-dependent substrate MtlA into E. coli membrane vesicles. MPIase-depleted membrane vesicles lacked both 3L-Pf3 coat and MtlA integration, indicating that MPIase is involved in the integration of both proteins. We developed a reconstitution system in which disordered spontaneous integration was precluded, which revealed that SecYEG, YidC, or both, are not sufficient for Sec-dependent and -independent integration. Although YidC had no effect on MPIase-dependent integration of Sec-independent substrates in the conventional assay system, YidC significantly accelerated the integration when the substrate amounts were increased in our PURE system-based assay. Similar acceleration by YidC was observed for MtlA integration. YidC mutants with amino acid substitutions in the hydrophilic cavity inside the membrane were defective in the acceleration of the Sec-independent integration. Of note, MPIase was up-regulated upon YidC depletion. These results indicate that YidC accelerates the MPIase-dependent integration of membrane proteins, suggesting that MPIase and YidC function sequentially and cooperatively during the catalytic cycle of membrane protein integration.

Structural basis of Sec-independent membrane protein insertion by YidC.

Newly synthesized membrane proteins must be accurately inserted into the membrane, folded and assembled for proper functioning. The protein YidC inserts its substrates into the membrane, thereby facilitating membrane protein assembly in bacteria; the homologous proteins Oxa1 and Alb3 have the same function in mitochondria and chloroplasts, respectively. In the bacterial cytoplasmic membrane, YidC functions as an independent insertase and a membrane chaperone in cooperation with the translocon SecYEG. Here we present the crystal structure of YidC from Bacillus halodurans, at 2.4 Å resolution. The structure reveals a novel fold, in which five conserved transmembrane helices form a positively charged hydrophilic groove that is open towards both the lipid bilayer and the cytoplasm but closed on the extracellular side. Structure-based in vivo analyses reveal that a conserved arginine residue in the groove is important for the insertion of membrane proteins by YidC. We propose an insertion mechanism for single-spanning membrane proteins, in which the hydrophilic environment generated by the groove recruits the extracellular regions of substrates into the low-dielectric environment of the membrane.

Alteration of Membrane Physicochemical Properties by Two Factors for Membrane Protein Integration.

After a nascent chain of a membrane protein emerges from the ribosomal tunnel, the protein is integrated into the cell membrane. This process is controlled by a series of proteinaceous molecular devices, such as signal recognition particles and Sec translocons. In addition to these proteins, we discovered two endogenous components regulating membrane protein integration in the inner membrane of Escherichia coli. The integration is blocked by diacylglycerol (DAG), whereas the blocking is relieved by a glycolipid named membrane protein integrase (MPIase). Here, we investigated the influence of these integration-blocking and integration-promoting factors on the physicochemical properties of membrane lipids via solid-state NMR and fluorescence measurements. These factors did not have destructive effects on membrane morphology because the membrane maintained its lamellar structure and did not fuse in the presence of DAG and/or MPIase at their effective concentrations. We next focused on membrane flexibility. DAG did not affect the mobility of the membrane surface, whereas the sugar chain in MPIase was highly mobile and enhanced the flexibility of membrane lipid headgroups. Comparison with a synthetic MPIase analog revealed the effects of the long sugar chain on membrane properties. The acyl chain order inside the membrane was increased by DAG, whereas the increase was cancelled by the addition of MPIase. MPIase also loosened the membrane lipid packing. Focusing on the transbilayer movement, MPIase reduced the rapid flip-flop motion of DAG. On the other hand, MPIase could not compensate for the diminished lateral diffusion by DAG. These results suggest that by manipulating the membrane lipids dynamics, DAG inhibits the protein from contacting the inner membrane, whereas the flexible long sugar chain of MPIase increases the opportunity for interaction between the membrane and the protein, leading to membrane integration of the newly formed protein.

YnbB is a CdsA paralogue dedicated to biosynthesis of glycolipid MPIase involved in membrane protein integration.

MPIase is a glycolipid involved in protein integration in E. coli. Recently, we identified CdsA, a CDP-diacylglycerol (CDP-DAG) synthase, as a biosynthetic enzyme for MPIase. YnbB is a CdsA paralogue with a highly homologous C-terminal half. Under CdsA-depleted conditions, YnbB overproduction restored MPIase expression, but not phospholipid biosynthesis. YnbB complemented the growth defect of the cdsA knockout when Tam41p, a mitochondrial CDP-DAG synthase, was co-expressed, suggesting that YnbB possesses sufficient activity for MPIase biosynthesis, but not for phospholipid biosynthesis. Consistently, a chimera consisting of the CdsA N-terminal half and the YnbB C-terminal half (CdsA-N-YnbB-C) complemented the cdsA knockout by itself, but a chimera consisting of the YnbB N-terminal half and the CdsA C-terminal half (YnbB-N-CdsA-C) required co-expression of Tam41p for the complementation. The biosynthetic rate for CDP-DAG in CdsA and CdsA-N-YnbB-C was much faster than that in YnbB and YnbB-N-CdsA-C, indicating that the N-terminal half of CdsA accelerates CDP-DAG biosynthesis to give the fast cell growth. Therefore, the role of YnbB seems to be as a backup for MPIase biosynthesis, suggesting that YnbB is dedicated to MPIase biosynthesis. A mutant with a high pH-sensitive CdsA8 was unable to grow even under permissive conditions when the ynbB gene was deleted, supporting its auxiliary role in the CdsA function.

Membrane insertion of F0 c subunit of F0F1 ATPase depends on glycolipozyme MPIase and is stimulated by YidC.

The F0 c subunit of F0F1 ATPase (F0-c) possesses two membrane-spanning stretches with N- and C-termini exposed to the periplasmic (extracellular) side of the cytoplasmic membrane of E. coli. Although F0-c insertion has been extensively analyzed in vitro by means of protease protection assaying, it is unclear whether such assays allow elucidation of the insertion process faithfully, since the membrane-protected fragment, an index of membrane insertion, is a full-length polypeptide of F0-c, which is the same as the protease-resistant conformation without membrane insertion. We found that the protease-resistant conformation could be discriminated from membrane-insertion by including octyl glucoside on protease digestion. By means of this system, we found that F0-c insertion depends on MPIase, a glycolipozyme involved in membrane insertion, and is stimulated by YidC. In addition, we found that acidic phospholipids PG and CL transform F0-c into a protease-resistant form, while MPIase prevents the acquisition of such a protease-resistant conformation.

Novel translocation intermediate allows re-evaluation of roles of ATP, proton motive force and SecG at the late stage of preprotein translocation.

Presecretory proteins such as pOmpA are translocated across the inner membrane of Escherichia coli by Sec translocase powered by ATP and proton motive force (PMF). Translocation activity has been determined by protease protection assaying in vitro. We identified a new translocation intermediate at a late stage, which was protected by proteinase K (PK), but became PK sensitive upon urea extraction. At a late stage of pOmpA translocation driven by PMF in the presence of a nonhydrolyzable ATP analogue, the PK-protected materials arose, but were pulled back upon urea extraction, indicating that completion of translocation requires ATP hydrolysis. When inverted membrane vesicles prepared from secG-null strain (ΔSecG IMV) were used in the absence of PMF, the translocation intermediate was accumulated. When the ATP concentration was low in the absence of PMF, the translocation intermediate was also accumulated. Imposition of PMF in the presence of a low ATP concentration caused recovery of pOmpA translocation and resistance to urea extraction for SecG+ IMV, but not for ΔSecG IMV. Thus, analysis of the late translocation intermediate showed that two of three constituents, physiological concentration of ATP, PMF and SecG, are required for the catalytic cycle of preprotein translocation, that is, completion and subsequent initiation of translocation.

Glycolipozyme MPIase is essential for topology inversion of SecG during preprotein translocation.

Presecretory proteins are translocated across biological membranes through protein-conducting channels such as Sec61 (eukaryotes) and SecYEG (bacteria). SecA, a translocation ATPase, pushes preproteins out with dynamic structural changes through SecYEG. SecG, a subunit of the SecYEG channel possessing two transmembrane stretches (TMs), undergoes topology inversion coupled with SecA-dependent translocation. Recently, we characterized membrane protein integrase (MPIase), a glycolipozyme involved in not only protein integration into membranes but also preprotein translocation. We report here that SecG inversion occurs only when MPIase associates with SecYEG. We also found that MPIase modulates the dimer orientation of SecYEG. Cysteine-scanning mutagenesis mapped SecG TM 2 to a relatively hydrophilic environment. The dimer formation of SecG, crosslinked at TM 2, was not observed on SecG inversion, indicating that SecYEG undergoes a dynamic structural change during preprotein translocation.

Long-term outcomes in patients with pineal nongerminomatous malignant germ cell tumors treated by radical resection during initial treatment combined with adjuvant therapy.

BACKGROUND: For pineal nongerminomatous malignant germ cell tumors (NGMGCTs), we mainly performed radical tumor resection during initial treatment combined with adjuvant therapy. METHODS: We retrospectively analyzed 17 patients treated for pineal NGMGCTs between 1986 and 2007 at the University of Niigata. RESULTS: Twelve patients underwent total or subtotal resection of their tumor via the occipital transtentorial approach. Five patients underwent partial resection, and four of them later underwent total resection by salvage surgery. After surgery, eight patients were treated with combined radiochemotherapy including whole-brain irradiation, two received radiation monotherapy, one had chemotherapy with local irradiation, and six were treated with chemotherapy alone. The median follow-up period for surviving patients was 179 months. The 10-year overall survival and progression-free survival rates for the radiochemotherapy group were both 75.0 % (two patients had a recurrence and died); the rates for other adjuvant therapies were 77.8 % (two died) and 22.2 % (seven had a recurrence), respectively. Radiochemotherapy was significantly associated with an increased rate of progression-free survival compared with the other adjuvant therapies (p = 0.0396). CONCLUSIONS: For pineal NGMGCTs, initial treatment strategies including gross total resection of the tumor before or after whole-brain irradiation and chemotherapy provided good therapeutic outcomes. Obtaining complete remission of the primary tumor, irrespective of the timing of surgical resection (i.e., before or after adjuvant therapies), or complete response by neoadjuvant radiochemotherapy during an initial treatment appears to be essential for improving therapeutic outcomes of intracranial NGMGCTs.

A novel three-dimensional and high-definition flexible scope.

PURPOSE: Recent high-tech innovations in digital surgical technology have led to advances in three-dimensional (3D) and high-definition (HD) operating scopes. We introduce a novel 3D-HD flexible surgical scope called "3D-Eye-Flex" and evaluate its utility as an alternative to the operating microscope. METHODS: The 3D-Eye-Flex has a 15 mm long 3D-HD scope-head with a 15 mm outer diameter, a focus distance of 18-100 mm and 80° angle of view. Attached to a 615-mm-long flexible bellows, 3D-Eye-Flex can be easily fixed to the operating table. Microsurgical dissection of wet brain tissue and drilling a skull base model were performed under the scope while using the 3D-HD video monitor. RESULTS: This scope system provided excellent illumination and image quality during the procedures. A large depth of field with stereoscopic vision had a greater advantage over using an operating microscope. 3D-Eye-Flex was easy to manipulate and provided an abundance of space above the operative field. Surgeons felt comfortable while working and could easily shift the position of the scope. CONCLUSION: This novel 3D-HD flexible scope is an effective alternative to the operating microscope as a new surgeon's eye and will be suitable for digital image-based surgery with further refinement.

Prediction of histological types of endometrial cancer by endometrial cytology.

AIM: Few studies have examined the accuracy of preoperative endometrial cytology in diagnosing low- and high-risk histology in women with endometrial cancer (EC). This single-institutional retrospective study compared the accuracy of endometrial cytology and biopsy in preoperatively predicting low-risk and high-risk histology of EC. METHODS: Between January 2006 and March 2013, 198 women with EC were examined by endometrial cytology, endometrial biopsy and hysterectomy specimen in National Kyushu Cancer Center. Among these women, 110 had endometrial cytology samples available to compare with endometrial biopsy, and were enrolled in our study (mean age ± standard deviation: 59.57 ± 10.32 years). Single-use plastic endometrial suction curettes were used in 12 of the 110 cases and thin metallic curettes for the rest. RESULTS: For type 2 EC, which includes grade 3 endometrioid adenocarcinoma and non-endometrioid histology, biopsy was 67.6% sensitive (25/37) and 84.9% specific (62/73); whereas cytology was 70.3% sensitive (26/37) and 91.8% specific (67/73). Cytology precisely diagnosed only one of 14 cases of serous carcinoma, but it diagnosed 11 of the 14 cases as type 2 EC, and its accuracy in distinguishing EC types was not inferior to endometrial biopsy (10/14). For EC, 9.1% (10/110) were unevaluable using biopsy, significantly more than the 0% (0/110) by cytology (P = 0.002). CONCLUSION: Although preoperative prediction of serous carcinoma was difficult, endometrial cytology had a higher evaluable rate for EC types. Endometrial cytology may complement endometrial biopsy in preoperative women with EC.

Regression of thymoma associated with a multilocular thymic cyst: report of a case.

A 28-year-old male was diagnosed with acute pericarditis after presenting with acute chest pain, fever and an abnormality in an electrocardiogram. No symptoms suggestive of myasthenia gravis were observed. Although the symptoms were alleviated by antibiotics, computed tomography (CT) showed an anterior mediastinal mass with bilateral pleural effusion. He was, therefore, diagnosed with thymoma and referred to our hospital. Surgery was performed, since the pleural effusion disappeared. The pathological examination revealed the mass to be a type B2 thymoma classified as pathological stage I (Masaoka's classification) with a multilocular thymic cyst.

Renal Failure Without Hemodialysis Is a Risk Factor for Postoperative Complications in Colorectal Cancer Surgery.

Background/Aim: Surgical outcomes of colorectal cancer (CRC) in patients with renal failure (RF) remain to be clarified. The objective of this research was to investigate how RF impacts the surgical outcomes in patients with CRC. Patients and Methods: A retrospective analysis was performed on clinical data from 633 patients who underwent colorectal resection for CRC between January 2017 and December 2021. Outcomes of the patients with and without RF were compared. RF was defined as estimated Glomerular Filtration Rate less than 30. Results: Forty-five (7%) patients with RF were identified. RF was a significant risk factor for postoperative complications after colorectal cancer surgery (odds ratio=2.19, 95% confidence interval=1.08-4.42, p=0.0284). The patients with RF had significantly more comorbidity (p=0.016), and higher American Society of Anesthesiologists physical status (p<0.01). Hemoglobin level (p<0.01) and PNI (p<0.01) were significantly lower in those with RF. Postoperative complications were significantly higher (p=0.016), and the postoperative hospital stay was significantly longer (p<0.01) among patients with RF compared to those without RF. Patients with RF, excluding those undergoing hemodialysis, had significantly more complications compared to those without RF (p=0.004). Conclusion: Careful attention should be paid to perioperative management in RF colorectal cancer patients.

Multiple SecA molecules drive protein translocation across a single translocon with SecG inversion.

SecA is a translocation ATPase that drives protein translocation. D209N SecA, a dominant-negative mutant, binds ATP but is unable to hydrolyze it. This mutant was inactive to proOmpA translocation. However, it generated a translocation intermediate of 18 kDa. Further addition of wild-type SecA caused its translocation into either mature OmpA or another intermediate of 28 kDa that can be translocated into mature by a proton motive force. The addition of excess D209N SecA during translocation caused a topology inversion of SecG. Moreover, an intermediate of SecG inversion was identified when wild-type and D209N SecA were used in the same amounts. These results indicate that multiple SecA molecules drive translocation across a single translocon with SecG inversion. Here, we propose a revised model of proOmpA translocation in which a single catalytic cycle of SecA causes translocation of 10-13 kDa with ATP binding and hydrolysis, and SecG inversion is required when the next SecA cycle begins with additional ATP hydrolysis.