Sterol, Protein and Lipid Trafficking in Chinese Hamster Ovary Cells with Niemann-Pick Type C1 Defect

Authors

  • Nina H. Pipalia,

    1. Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA
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    • These authors contributed equally to the work

  • Mingming Hao,

    1. Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA
    2. Current address: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
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    • These authors contributed equally to the work

  • Sushmita Mukherjee,

    Corresponding author
    1. Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA
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  • Frederick R. Maxfield

    Corresponding author
    1. Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA
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Sushmita Mukherjee, smukherj@med.cornell.edu; Frederick R. Maxfield, frmaxfie@med.cornell.edu

Abstract

We studied the trafficking of sterols, lipids and proteins in Niemann-Pick type C (NPC) cells. The NPC is an inherited disorder involving the accumulation of sterol and lipids in modified late-endosome/lysosome-like storage organelles. Most sterol accumulation studies in NPC cells have been carried out using low-density lipoprotein (LDL) as the sterol source, and it has been shown that sterol efflux from late endosomes is impaired in NPC cells. In this study, we used a fluorescent sterol analog, dehydroergosterol, which can be quickly and efficiently delivered to the plasma membrane. Thus, we were able to study the trafficking kinetics of the non-LDL-derived sterol pool, and we found that dehydroergosterol accumulates in the storage organelles over the course of several hours in NPC cells. We also found that dialkylindocarbocyanine lipid-mimetic analogs that recycle efficiently from early endosomes in wild-type cells are targeted to late endosomal organelles in NPC cells, and transferrin receptors recycle slowly and inefficiently in NPC cells. These data are consistent with multiple trafficking defects in both early and late endosomes in NPC cells.

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