Paul A. Crossey, Claire C. Pillai, John P. Miell
Manabu Shirai, Tomoaki Osugi, Hideyuki Koga, Yoshikazu Kaji, Eiki Takimoto, Issei Komuro, Junichi Hara, Takeshi Miwa, Keiko Yamauchi-Takihara, Yoshihiro Takihara
Simona Nanni, Michela Narducci, Linda Della Pietra, Fabiola Moretti, Annalisa Grasselli, Piero De Carli, Ada Sacchi, Alfredo Pontecorvi, Antonella Farsetti
Duarte C. Barral, José S. Ramalho, Ross Anders, Alistair N. Hume, Holly J. Knapton, Tanya Tolmachova, Lucy M. Collinson, David Goulding, Kalwant S. Authi, Miguel C. Seabra
Charles R. Roe, Lawrence Sweetman, Diane S. Roe, France David, Henri Brunengraber
Junichi Sadoshima, Olivier Montagne, Qian Wang, Guiping Yang, Jill Warden, Jing Liu, Gen Takagi, Vijaya Karoor, Chull Hong, Gary L. Johnson, Dorothy E. Vatner, Stephen F. Vatner
Clive R. Pullinger, Celeste Eng, Gerald Salen, Sarah Shefer, Ashok K. Batta, Sandra K. Erickson, Andrea Verhagen, Christopher R. Rivera, Sean J. Mulvihill, Mary J. Malloy, John P. Kane
We recently showed that human skin fibroblasts internalize fluorescent analogues of the glycosphingolipids lactosylceramide and globoside almost exclusively by a clathrin-independent mechanism involving caveolae. In contrast, a sphingomyelin analogue is internalized approximately equally via clathrin-dependent and caveolar routes. Here, we further characterized the caveolar pathway for glycosphingolipids, showing that Golgi targeting of sphingolipids internalized via caveolae required microtubules and phosphoinositol 3-kinases and was inhibited in cells expressing dominant-negative Rab7 and Rab9 constructs. In addition, overexpression of wild-type Rab7 or Rab9 (but not Rab11) in Niemann-Pick type C (NP-C) lipid storage disease fibroblasts resulted in correction of lipid trafficking defects, including restoration of Golgi targeting of fluorescent lactosylceramide and endogenous GM1 ganglioside, and a dramatic reduction in intracellular cholesterol stores. Our results demonstrate a role for Rab7 and Rab9 in the Golgi targeting of glycosphingolipids and suggest a new therapeutic approach for restoring normal lipid trafficking in NP-C cells.
Amit Choudhury, Michel Dominguez, Vishwajeet Puri, Deepak K. Sharma, Keishi Narita, Christine L. Wheatley, David L. Marks, Richard E. Pagano
Tissue-type plasminogen activator (tPA) is a highly specific serine proteinase expressed in the CNS during events that require neuronal plasticity. In this study we demonstrate that endogenous tPA mediates the progression of kainic acid–induced (KA-induced) seizures by promoting the synchronization of neuronal activity required for seizure spreading, and that, unlike KA-induced cell death, this activity is plasminogen-independent. Specifically, seizure induction by KA injection into the amygdala induces tPA activity and cell death in both hippocampi, and unilateral treatment of rats with neuroserpin, a natural inhibitor of tPA in the brain, enhances neuronal survival in both hippocampi. Inhibition of tPA within the hippocampus by neuroserpin treatment does not prevent seizure onset but instead markedly delays the progression of seizure activity in both rats and wild-type mice. In tPA-deficient mice, seizure progression is significantly delayed, and neuroserpin treatment does not further delay seizure spreading. In contrast, plasminogen-deficient mice show a pattern of seizure spreading and a response to neuroserpin that is similar to that of wild-type animals. These findings indicate that tPA acts on a substrate other than plasminogen and that the effects of neuroserpin on seizure progression and neuronal cell survival are mediated through the inhibition of tPA.
Manuel Yepes, Maria Sandkvist, Timothy A. Coleman, Elizabeth Moore, Jiang-Young Wu, David Mitola, Thomas H. Bugge, Daniel A. Lawrence
We describe a 3-year-old boy with biotin dependency not caused by biotinidase, holocarboxylase synthetase, or nutritional biotin deficiency. We sought to define the mechanism of his biotin dependency. The child became acutely encephalopathic at age 18 months. Urinary organic acids indicated deficiency of several biotin-dependent carboxylases. Symptoms improved rapidly following biotin supplementation. Serum biotinidase activity and Biotinidase gene sequence were normal. Activities of biotin-dependent carboxylases in PBMCs and cultured skin fibroblasts were normal, excluding biotin holocarboxylase synthetase deficiency. Despite extracellular biotin sufficiency, biotin withdrawal caused recurrent abnormal organic aciduria, indicating intracellular biotin deficiency. Biotin uptake rates into fresh PBMCs from the child and into his PBMCs transformed with Epstein Barr virus were about 10% of normal fresh and transformed control cells, respectively. For fresh and transformed PBMCs from his parents, biotin uptake rates were consistent with heterozygosity for an autosomal recessive genetic defect. Increased biotin breakdown was ruled out, as were artifacts of biotin supplementation and generalized defects in membrane permeability for biotin. These results provide evidence for a novel genetic defect in biotin transport. This child is the first known with this defect, which should now be included in the identified causes of biotin dependency.
Rebecca Mardach, Janos Zempleni, Barry Wolf, Martin J. Cannon, Michael L. Jennings, Sally Cress, Jane Boylan, Susan Roth, Stephen Cederbaum, Donald M. Mock