Five Amino Acid Residues Responsible for the High Stability of Hydrogenobacter thermophilus Cytochrome c552

Five amino acid residues responsible for extreme stability have been identified in cytochrome c552 (HT c552) from a thermophilic bacterium, Hydrogenobacter thermophilus. The five residues, which are spatially distributed in three regions of HT c552, were replaced with the corresponding residues in the homologous but less stable cytochrome c551 (PA c551) from Pseudomonas aeruginosa. The quintuple HT c552 variant (A7F/M13V/Y34F/Y43E/I78V) showed the same stability against guanidine hydrochloride denaturation as that of PA c551, suggesting that the five residues in HT c552 necessarily and sufficiently contribute to the overall stability. In the three HT c552 variants carrying mutations in each of the three regions, the Y34F/Y43E mutations resulted in the greatest destabilization, by –13.3 kJ mol–1, followed by A7F/M13V (–3.3 kJ mol–1) and then I78V (–1.5 kJ mol–1). The order of destabilization in HT c552 was the same as that of stabilization in PA c551 with reverse mutations such as F34Y/E43Y, F7A/V13M, and V78I (13.4, 10.3, and 0.3 kJ mol–1, respectively). The results of guanidine hydrochloride denaturation were consistent with those of thermal denaturation for the same variants. The present study established a method for reciprocal mutation analysis. The effects of side-chain contacts were experimentally evaluated by swapping the residues between the two homologous proteins that differ in stability. A comparative study of the two proteins was a useful tool for assessing the amino acid contribution to the overall stability.This work was supported in part by grants from Hiroshima University, the Noda Institute for Scientific Research, and the Japanese Ministry of Education, Science and Culture (grants-in-aid for Scientific Research on Priority Areas)

Type XVII collagen interacts with the aPKC-PAR complex and maintains epidermal cell polarity

Type XVII collagen (COL17) is a transmembrane protein expressed in the basal epidermis. COL17 serves as a niche for epidermal stem cells, and although its reduction has been implicated in altering cell polarity and ageing of the epidermis, it is unknown how COL17 affects epidermal cell polarity. Here, we uncovered COL17 as a binding partner of the aPKC-PAR complex, which is a key regulating factor of cell polarity. Immunoprecipitation-immunoblot assay and protein-protein binding assay revealed that COL17 interacts with aPKC and PAR3. COL17 deficiency or epidermis-specific aPKC lambda deletion destabilized PAR3 distribution in the epidermis, while aPKC zeta knockout did not. Asymmetrical cell division was pronounced in COL17-null neonatal paw epidermis. These results show that COL17 is pivotal for maintaining epidermal cell polarity. Our study highlights the previously unrecognized role of COL17 in the basal keratinocytes

A case of complete remission of Hodgkin lymphoma confirmed histopathologically by neck dissection

Abstract Background Hodgkin lymphoma (HL) is diagnosed definitively by biopsy, and treatment is based on stage. Owing to the nature of the disease, post‐treatment efficacy is determined mainly by fluorodeoxyglucose‐positron emission tomography/computed tomography, and the efficacy of treatment is not confirmed by histopathology. We report a case of tongue cancer after treatment for HL, in which a post‐treatment lymph node with complete remission was histopathologically confirmed by neck dissection. Case The patient was a 74‐year‐old man who was referred to our hospital for cancer on the right side of his tongue. He had previously undergone chemotherapy for HL involving the right side of his neck and achieved complete remission. Because he had cT3N2cM0 tongue cancer, glossectomy and bilateral neck dissection were performed. Surprisingly, histopathological examination revealed that there was neither metastatic lymph nodes nor lymphoma cells in his right neck. Moreover, there was no lymphatic structure in his remnant lymph nodes. Conclusion This was a rare case in which complete remission of HL was confirmed by histopathological analysis. The absence of lymph node structure and lymphatic flow led to contralateral neck lymph node metastases of tongue cancer

A case report of angiosarcoma originating from the tongue

Key Clinical Message Angiosarcoma is a rare malignant disease with an extremely poor prognosis, showing rapid progression of the local tumor and/or distant metastases. Although multidisciplinary approach including systemic chemotherapy and radiation therapy is ideal for this disease, surgical resection have a role in disease control and should be performed as soon as possible. Abstract Angiosarcomas originating from the tongue are rare and have extremely malignant features, leading to a poor prognosis. Herein, we report the case of a patient with angiosarcoma arising from the tongue who was successfully treated surgically. A 71‐year‐old man was diagnosed with a mass on the right side of his tongue and visited the Department of Oral and Maxillofacial Surgery at our hospital. The patient was referred to our department for further examination and treatment after a biopsy of the right edge of the tongue. An irregularly raised tumor 50 mm in length was noted on the right lingual border. The preoperative diagnosis was a primary angiosarcoma of the tongue (clinical stage, T3N2bM0, Stage IV). As his tumor had been growing rapidly, he emergently underwent partial right‐sided tongue resection and right neck dissection without reconstructive surgery. The histopathological diagnosis was pT3N0. Postoperatively, the patient showed no signs of recurrence or metastasis during the 1‐year follow‐up. As for angiosarcomas, surgical resection is the only curative treatment, and surgery should be performed as soon as possible after the final diagnosis