RESUMEN
Carney-Stratakis syndrome, an inherited condition predisposing affected individuals to gastrointestinal stromal tumor (GIST) and paraganglioma, is caused by germline mutations in succinate dehydrogenase (SDH) subunits B, C, or D, leading to dysfunction of complex II of the electron transport chain. We evaluated the role of defective cellular respiration in sporadic GIST lacking mutations in KIT or PDGFRA (WT). Thirty-four patients with WT GIST without a personal or family history of paraganglioma were tested for SDH germline mutations. WT GISTs lacking demonstrable SDH genetic inactivation were evaluated for SDHB expression by immunohistochemistry and Western blotting and for complex II activity. For comparison, SDHB expression was also determined in KIT mutant and neurofibromatosis-1-associated GIST, and complex II activity was also measured in SDH-deficient paraganglioma and KIT mutant GIST; 4 of 34 patients (12%) with WT GIST without a personal or family history of paraganglioma had germline mutations in SDHB or SDHC. WT GISTs lacking somatic mutations or deletions in SDH subunits had either complete loss of or substantial reduction in SDHB protein expression, whereas most KIT mutant GISTs had strong SDHB expression. Complex II activity was substantially decreased in WT GISTs. WT GISTs, particularly those in younger patients, have defects in SDH mitochondrial complex II, and in a subset of these patients, GIST seems to arise from germline-inactivating SDH mutations. Testing for germline mutations in SDH is recommended in patients with WT GIST. These findings highlight a potential central role of SDH dysregulation in WT GIST oncogenesis.
Asunto(s)
Respiración de la Célula/fisiología , Tumores del Estroma Gastrointestinal/enzimología , Predisposición Genética a la Enfermedad/genética , Proteínas Proto-Oncogénicas c-kit/genética , Receptor alfa de Factor de Crecimiento Derivado de Plaquetas/genética , Succinato Deshidrogenasa/genética , Adolescente , Western Blotting , Respiración de la Célula/genética , Análisis Mutacional de ADN , Complejo II de Transporte de Electrones/genética , Complejo II de Transporte de Electrones/metabolismo , Mutación de Línea Germinal/genética , Humanos , Inmunohistoquímica , Paraganglioma/enzimología , Polimorfismo de Nucleótido Simple , Subunidades de Proteína/genética , Succinato Deshidrogenasa/metabolismo , SíndromeRESUMEN
We demonstrate a method for generating discretely structured protein nanotubes from the simple ring-shaped building block, homohexameric Hcp1 from Pseudomonas aeruginosa. Our design exploited the observation that the crystal lattice of Hcp1 contains rings stacked in a repeating head-to-tail pattern. High-resolution detail of the ring-ring interface allowed the selection of sites for specific cysteine mutations capable of engaging in disulfide bond formation across rings, thereby generating stable Hcp1 nanotubes. Protein nanotubes containing up to 25 subunits ( approximately 100 nm in length) were self-assembled under simple conditions. Furthermore, we demonstrate that the tube ends and interior can be independently and specifically functionalized to generate nanocapsules.