guanosine-triphosphate and Lung-Diseases

Topics: Adult; B-Lymphocytes; Disease Progression; Gain of Function Mutation; Graft vs Host Disease; GTPase-Activating Proteins; Guanosine Triphosphate; Hematopoietic Stem Cell Transplantation; Heterozygote; Humans; Immunologic Memory; Immunosuppressive Agents; Infant; Lung Diseases; Lung Transplantation; Lymphopenia; Male; Molecular Docking Simulation; Neutrophils; Primary Immunodeficiency Diseases; rac GTP-Binding Proteins; RAC2 GTP-Binding Protein; Recurrence; Respiratory Tract Infections; T-Lymphocyte Subsets; T-Lymphocytes

Rab38 is a low-molecular-weight G-protein highly expressed in melanocytes of the skin and alveolar type II cells in the lung. A point mutation in the postulated GTP/GDP-interacting domain of Rab38 has been identified as the genetic lesion responsible for oculocutaneous albinism (OCA) in chocolate (cht) mice. Another point mutation that prevents translation of Rab38 mRNA is the molecular basis of the Ruby gene mutation causing the phenotype of OCA and prolonged bleeding time in Fawn-Hooded and Tester-Moriyama rats. Cht mice show conspicuously enlarged lamellar bodies in alveolar type II cells and abnormal lung structure. Triton X-114 phase partitioning of cht mouse lung showed that Rab38cht-protein was recovered in the aqueous phase. We produced recombinant Rab38cht-protein using a baculovirus/insect cell-protein expression system. The results demonstrate that Rab38cht-protein is inactive due to reduced membrane binding and enhanced intracellular degradation. Rab38 is a new strong candidate gene for human Hermansky-Pudlak syndrome (HPS) that is characterized by OCA, bleeding diathesis, and lung disease.

Topics: Albinism, Oculocutaneous; Animals; Female; Guanosine Triphosphate; Hermanski-Pudlak Syndrome; Humans; Lung Diseases; Male; Mice; Microscopy, Electron; rab GTP-Binding Proteins; Rats; Recombinant Proteins

Pulmonary pathologies including adult respiratory distress syndrome are characterized by disruption of pulmonary integrity and edema compromising respiratory function. Sphingosine 1-phosphate (S1P) is a lipid mediator synthesized and/or stored in mast cells, platelets, and epithelial cells, with production up-regulated by the proinflammatory cytokines IL-1 and TNF. S1P administration via the airways but not via the vasculature induces lung leakage. Using receptor-null mice, we show that S1P, acting on S1P3 receptor expressed on both type I and type II alveolar epithelial cells but not vascular endothelium, induces pulmonary edema by acute tight junction opening. WT but not S1P3-null mice showed disruption of pulmonary epithelial tight junctions and the appearance of paracellular gaps between epithelial cells by electron microscopy within 1 h of airways exposure to S1P. We further show by fluorescence microscopy that S1P induced rapid loss of ZO-1 reactivity, an essential component of the cytoplasmic plaque associated with tight junctions, as well as of the tetraspannin Claudin-18, an integral membrane organizer of tight junctions. S1P shows synergistic activity with the proinflammatory cytokine TNF, showing both pulmonary edema and mortality at subthreshold S1P doses. Specifically, preexposure of mice to subthreshold doses of TNF, which alone induced no lung edema, exacerbated S1P-induced edema and impaired survival. S1P, acting through S1P3, regulates epithelial integrity and acts additively with TNF in compromising respiratory barrier function. Because S1P3-null mice are resistant to S1P-induced pulmonary leakage, either alone or in the presence of TNF, S1P3 antagonism may be useful in protecting epithelial integrity in pulmonary disease.

Topics: Animals; Cell Membrane; Cell Nucleus; Chromatography, Liquid; Claudins; Cytoplasm; Endothelium, Vascular; Epithelial Cells; Epithelium; Guanosine Triphosphate; Homozygote; Inflammation; Interleukin-1; Ligands; Lung; Lung Diseases; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Microscopy, Electron; Microscopy, Fluorescence; Models, Biological; Permeability; Protein Binding; Receptors, Lysosphingolipid; RNA, Messenger; Tight Junctions; Time Factors; Tumor Necrosis Factor-alpha