Structural basis of Irgb6 inactivation by Toxoplasma gondii through the phosphorylation of switch I.

Irgb6 is a priming immune-related GTPase (IRG) that counteracts Toxoplasma gondii. It is known to be recruited to the low virulent type II T. gondii parasitophorous vacuole (PV), initiating cell-autonomous immunity. However, the molecular mechanism by which immunity-related GTPases become inactivated after the parasite infection remains obscure. Here, we found that Thr95 of Irgb6 is prominently phosphorylated in response to low virulent type II T. gondii infection. We observed that a phosphomimetic T95D mutation in Irgb6 impaired its localization to the PV and exhibited reduced GTPase activity in vitro. Structural analysis unveiled an atypical conformation of nucleotide-free Irgb6-T95D, resulting from a conformational change in the G-domain that allosterically modified the PV membrane-binding interface. In silico docking corroborated the disruption of the physiological membrane binding site. These findings provide novel insights into a T. gondii-induced allosteric inactivation mechanism of Irgb6.

TEAD1 trapping by the Q353R-Lamin A/C causes dilated cardiomyopathy.

Mutations in the LMNA gene encoding Lamin A and C (Lamin A/C), major components of the nuclear lamina, cause laminopathies including dilated cardiomyopathy (DCM), but the underlying molecular mechanisms have not been fully elucidated. Here, by leveraging single-cell RNA sequencing (RNA-seq), assay for transposase-accessible chromatin using sequencing (ATAC-seq), protein array, and electron microscopy analysis, we show that insufficient structural maturation of cardiomyocytes owing to trapping of transcription factor TEA domain transcription factor 1 (TEAD1) by mutant Lamin A/C at the nuclear membrane underlies the pathogenesis of Q353R-LMNA-related DCM. Inhibition of the Hippo pathway rescued the dysregulation of cardiac developmental genes by TEAD1 in LMNA mutant cardiomyocytes. Single-cell RNA-seq of cardiac tissues from patients with DCM with the LMNA mutation confirmed the dysregulated expression of TEAD1 target genes. Our results propose an intervention for transcriptional dysregulation as a potential treatment of LMNA-related DCM.

Structural model of microtubule dynamics inhibition by kinesin-4 from the crystal structure of KLP-12 -tubulin complex.

Kinesin superfamily proteins are microtubule-based molecular motors driven by the energy of ATP hydrolysis. Among them, the kinesin-4 family is a unique motor that inhibits microtubule dynamics. Although mutations of kinesin-4 cause several diseases, its molecular mechanism is unclear because of the difficulty of visualizing the high-resolution structure of kinesin-4 working at the microtubule plus-end. Here, we report that KLP-12, a C. elegans kinesin-4 ortholog of KIF21A and KIF21B, is essential for proper length control of C. elegans axons, and its motor domain represses microtubule polymerization in vitro. The crystal structure of the KLP-12 motor domain complexed with tubulin, which represents the high-resolution structural snapshot of the inhibition state of microtubule-end dynamics, revealed the bending effect of KLP-12 for tubulin. Comparison with the KIF5B-tubulin and KIF2C-tubulin complexes, which represent the elongation and shrinking forms of microtubule ends, respectively, showed the curvature of tubulin introduced by KLP-12 is in between them. Taken together, KLP-12 controls the proper length of axons by modulating the curvature of the microtubule ends to inhibit the microtubule dynamics.

From meter-long structures that allow nerve cells to stretch across a body to miniscule 'hairs' required for lung cells to clear mucus, many life processes rely on cells sporting projections which have the right size for their role. Networks of hollow filaments known as microtubules shape these structures and ensure that they have the appropriate dimensions. Controlling the length of microtubules is therefore essential for organisms, yet how this process takes place is still not fully elucidated. Previous research has shown that microtubules continue to grow when their end is straight but stop when it is curved. A family of molecular motors known as kinesin-4 participate in this process, but the exact mechanisms at play remain unclear. To investigate, Tuguchi, Nakano, Imasaki et al. focused on the KLP-12 protein, a kinesin-4 equivalent which helps to controls the length of microtubules in the tiny worm Caenorhabditis elegans. They performed genetic manipulations and imaged the interactions between KLP-12 and the growing end of a microtubule using X-ray crystallography. This revealed that KLP-12 controls the length of neurons by inhibiting microtubule growth. It does so by modulating the curvature of the growing end of the filament to suppress its extension. A 'snapshot' of KLP-12 binding to a microtubule at the resolution of the atom revealed exactly how the protein helps to bend the end of the filament to prevent it from growing further. These results will help to understand how nerve cells are shaped. This may also provide insights into the molecular mechanisms for various neurodegenerative disorders caused by problems with the human equivalents of KLP-12, potentially leading to new therapies.

Malignant pleural mesothelioma in a patient with pneumothorax: A cumbersome subtype both clinically and pathologically.

Here, we report a case of malignant pleural mesothelioma (MPM) that was very difficult to diagnose. A 62-year-old woman with a surgical history of recurrent bilateral pneumothorax was admitted to our hospital with severe dysphagia. Computed tomography (CT) detected stenosis in the lower esophagus. Immunohistochemical examination of a biopsy sample from the stenotic region was suggestive of MPM. Chemotherapy was initiated, but the patient soon weakened and died. Autopsy revealed atypical cells, identical to those seen in the biopsy sample which had spread into the stenotic esophagus and entire thoracic cavity. Although neither pleural thickening/nodules nor asbestos bodies were observed, we finally diagnosed the tumor as a biphasic-type MPM. We re-examined previous surgical specimens of pneumothorax and acknowledged foci of bland mesothelial cell proliferation which had the same pathological findings as tumor cells at autopsy. The lack of asbestos exposure and pleural thickening, an initial manifestation of pneumothorax, and faint cytological atypia prevented an early diagnosis. In cases of recurrent pneumothorax in elderly patients, MPM should be included in the differential diagnosis.

Significant role of Psf3 expression in non-small-cell lung cancer.

The GINS complex associates with cell division cycle (Cdc) protein 45 and mini-chromosome maintenance (Mcm) proteins 2-7 to form the Cdc45-Mcm-GINS (CMG) complex, which is essential for DNA duplication. One member of the GINS complex is Psf3. We previously found that increased Psf3 expression was strongly associated with poor survival in lung adenocarcinoma. Here, we investigated the role of Psf3 expression in non-small-cell lung cancer (NSCLC). We verified Psf3 expression in human NSCLC tissues (180 patients) and cell lines. Immunohistochemical analysis revealed that the overexpression of Psf3 was significantly associated with vessel invasion (P = 0.016), lymphatic invasion (P = 0.002), and pleural invasion (P = 0.036). The overall survival rate in patients with Psf3 overexpression was significantly lower than that in patients without Psf3 overexpression (P = 0.006). Multivariate survival analysis revealed Psf3 expression to be an independent risk factor for an unfavorable outcome (P = 0.049). A proximal ligation assay showed interactions between Psf3 and other CMG components (such as Mcm2 and Cdc45) in both NSCLC specimens and cell lines, indicating that Psf3 acted as the CMG complex, which could lead to excessive proliferation. Knockdown of Psf3 inhibited the proliferation of both cell lines by delaying the S phase, which revealed that Psf3 played an important role in cancer proliferation. Thus, Psf3 acted as the CMG complex, promoting excessive proliferation. These results suggest that Psf3 inhibition might be a therapeutic target for NSCLC with Psf3 overexpression.

Operative outcomes of thoracoscopic lobectomy for non-small-cell lung cancer.

AIM: We examined the advantages of thoracoscopy over thoracotomy in terms of perioperative outcomes and toleration of adjuvant chemotherapy. METHODS: Between April 2010 and March 2013, 657 patients with non-small-cell lung cancer who underwent lobectomy were classified into thoracoscopy (308 patients) and thoracotomy (349 patients) groups and compared. RESULTS: The thoracoscopy group had less blood loss compared to the thoracotomy group (p < 0.001). When limiting the analysis to pathological stage I patients, the results were similar (p < 0.001). In addition, the difference in blood loss between the 2 groups was greater in patients with severe pleural adhesions. The postoperative morbidity of the thoracoscopy group was significantly less than that of the thoracotomy group (13.3% vs. 21.2%, p < 0.001), and this result was similar when analyzing the pathological stage I patients (12.6% vs. 20.6%, p = 0.001). A higher percentage of the thoracoscopy group received both the full planned course and dose of adjuvant chemotherapy compared to the thoracotomy group (84.2% vs. 65.8%, p = 0.032). CONCLUSIONS: These results indicate that totally thoracoscopic lobectomy is the more beneficial surgical approach with regard to the incidence of postoperative complications and toleration of adjuvant chemotherapy.

[Perforation of the Mediastinal Mature Teratoma;Report of a Case].

The mediastinal mature teratoma is uncommon in adult and sometimes ruptures. We present a case of perforation of mediastinal mature teratoma. A 22-year-old man, who had been scheduled for surgery to resect anterior mediastinal teratoma, was referred to our hospital due to sudden chest pain. The enhanced computed tomography findings suggested a perforation of the teratoma and the emergency surgery was performed. Extirpation of the tumor with partial resection of right upper lung, pericardium, and superior vena cava was performed. The histological diagnosis was mature teratoma and the defect of the mediastinal pleura was found to be the site of perforation. The patient was well and discharged from the hospital without complications.