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Author Notes:

Address correspondence to: Steven W. L'Hernault (Email: bioslh@biology.emory.edu) or Victor Faundez (Email: faundez@cellbio.emory.edu).

We acknowledge Drs. Melanie L. Styers, James J. Lah, Edwin R. Smith, and Ms. Tamara Lindsay for assistance with mammalian cell culture, immunostaining, and immunoblotting techniques.

Nancy L'Hernault provided assistance with electron microscopy.

We thank Dr. Andrew Peden for antibodies and Karen A. Newell-Litwa, Dr. Laura Volpicelli, Dr. H. Stenmark, and Dr. Yuji Kohara for various DNA clones used in this study.

The Caenorhabditis Genetics Center provided several nematode strains and is funded by the National Institutes of Health National Center for Research Resources.

B. F. was supported by the Emory University SURE summer program, which is funded by Howard Hughes Medical Institute award 52003727 to the Center for Science Education, Emory University.

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Research Funding:

This work was also supported by National Institutes of Health grants GM-40697 and GM-082932 (to S.W.L.) and NS-42599 and GM-077569 (to V. F.), funds from Emory College, and an Emory University Research Committee award.

SPE-39 Family Proteins Interact with the HOPS Complex and Function in Lysosomal Delivery

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Journal Title:

Molecular Biology of the Cell

Volume:

Volume 20, Number 4

Publisher:

, Pages 1223-1240

Type of Work:

Article | Final Publisher PDF

Abstract:

Yeast and animal homotypic fusion and vacuole protein sorting (HOPS) complexes contain conserved subunits, but HOPS-mediated traffic in animals might require additional proteins. Here, we demonstrate that SPE-39 homologues, which are found only in animals, are present in RAB5-, RAB7-, and RAB11-positive endosomes where they play a conserved role in lysosomal delivery and probably function via their interaction with the core HOPS complex. Although Caenorhabditis elegans spe-39 mutants were initially identified as having abnormal vesicular biogenesis during spermatogenesis, we show that these mutants also have disrupted processing of endocytosed proteins in oocytes and coelomocytes. C. elegans SPE-39 interacts in vitro with both VPS33A and VPS33B, whereas RNA interference of VPS33B causes spe-39–like spermatogenesis defects. The human SPE-39 orthologue C14orf133 also interacts with VPS33 homologues and both coimmunoprecipitates and cosediments with other HOPS subunits. SPE-39 knockdown in cultured human cells altered the morphology of syntaxin 7-, syntaxin 8-, and syntaxin 13-positive endosomes. These effects occurred concomitantly with delayed mannose 6-phosphate receptor-mediated cathepsin D delivery and degradation of internalized epidermal growth factor receptors. Our findings establish that SPE-39 proteins are a previously unrecognized regulator of lysosomal delivery and that C. elegans spermatogenesis is an experimental system useful for identifying conserved regulators of metazoan lysosomal biogenesis.

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© 2009 by The American Society for Cell Biology

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