RESUMEN
Herpes simplex virus (HSV)-encoded glycoprotein B (gB) is the most abundant protein in the viral envelope and promotes fusion of the virus with the cellular membrane. In the present study, we found that gB impacts on the major histocompatibility complex (MHC)-II pathway of antigen presentation by fostering homotypic fusion of early endosomes and trapping MHC-II molecules in these altered endosomes. By using an overexpression approach, we demonstrated that transient expression of gB induces giant vesicles of early endosomal origin, which contained Rab5, early endosomal antigen 1 (EEA1), and large amounts of MHC-II molecules [human leukocyte antigen (HLA)-DR, and HLA-DM], but no CD63. In HSV-1-infected and stably transfected cell lines that expressed lower amounts of gB, giant endosomes were not observed, but strongly increased amounts of HLA-DR and HLA-DM were found in EEA1+ early endosomes. We used these giant vesicles as a model system and revealed that gB interacts with Rab5 and EEA1, and that gB-induced homotypic fusion of early endosomes to giant endosomes requires phosphatidylinositol 3-phosphate, the activity of soluble N-ethylmaleimide-sensitive factor attachment protein receptors, and the cytosolic gB sequence 889YTQVPN894 We conclude that gB expression alters trafficking of molecules of the HLA-II processing pathway, which leads to increased retention of MHC-II molecules in early endosomal compartments, thereby intercepting antigen presentation.-Niazy, N., Temme, S., Bocuk, D., Giesen, C., König, A., Temme, N., Ziegfeld, A., Gregers, T. F., Bakke, O., Lang, T., Eis-Hübinger, A. M., Koch, N. Misdirection of endosomal trafficking mediated by herpes simplex virus-encoded glycoprotein B.
Asunto(s)
Endosomas/metabolismo , Proteínas del Envoltorio Viral/metabolismo , Secuencias de Aminoácidos , Animales , Células COS , Chlorocebus aethiops , Endosomas/virología , Antígenos HLA-D/metabolismo , Antígenos HLA-DR/metabolismo , Células HeLa , Humanos , Fosfatos de Fosfatidilinositol/metabolismo , Transporte de Proteínas , Tetraspanina 30/metabolismo , Proteínas de Transporte Vesicular/metabolismo , Proteínas del Envoltorio Viral/química , Proteínas del Envoltorio Viral/genética , Proteínas de Unión al GTP rab5/metabolismoRESUMEN
Since the identification of the Lowe's oculocerebrorenal syndrome gene, more than 100 distinct OCRL mutations have been observed. Germline mosaicism has rarely been detected in Lowe families; however, the presence of mosaic mutations, in particular triple mosaicism, may often remain undiagnosed. In the course of OCRL analysis in a Polish family, the index case showed a hemizygous nucleotide transition (c.1736A>G, p.His507Arg). Gene analysis in the patient's mother not only provided evidence that she is a carrier of the mutant allele transmitted to her son but also showed an additional c.1736A>T (p.His507Leu) transversion affecting the same base position. DNA from a mouthwash sample from the mother showed a similar fluorescence intensity pattern at the affected nucleotide. These data, together with the findings that maternal grandparents solely showed wildtype sequence, implied a de novo mosaicism in the mother. Triple X syndrome was ruled out by karyotype analysis and a partial or complete gene duplication could be excluded. Allele-specific amplification confirmed the results of three alleles being present in the mother. The amount of wildtype allele detected in qPCR implied the presence of cells solely harboring c.1736A and single-cell PCR experiments confirmed the presence of non-mutant cells in the mother's blood. These data suggest that the mutations observed are the result of two de novo events in early embryogenesis of the mother. To the best of our knowledge, this is the first observation of triple mosaicism at a single nucleotide.