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Dev Biol. 2014 Oct 1;394(1):110-21. doi: 10.1016/j.ydbio.2014.07.019. Epub 2014 Aug 4.

Polarized exocyst-mediated vesicle fusion directs intracellular lumenogenesis within the C. elegans excretory cell.

Author information

1
Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, NY 10016, USA; Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA.
2
Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute of Biomolecular Medicine, NYU School of Medicine, New York, NY 10016, USA; Department of Cell Biology, NYU School of Medicine, New York, NY 10016, USA. Electronic address: Jeremy.Nance@med.nyu.edu.

Abstract

Lumenogenesis of small seamless tubes occurs through intracellular membrane growth and directed vesicle fusion events. Within the Caenorhabditis elegans excretory cell, which forms seamless intracellular tubes (canals) that mediate osmoregulation, lumens grow in length and diameter when vesicles fuse with the expanding lumenal surface. Here, we show that lumenal vesicle fusion depends on the small GTPase RAL-1, which localizes to vesicles and acts through the exocyst vesicle-tethering complex. Loss of either the exocyst or RAL-1 prevents excretory canal lumen extension. Within the excretory canal and other polarized cells, the exocyst co-localizes with the PAR polarity proteins PAR-3, PAR-6 and PKC-3. Using early embryonic cells to determine the functional relationships between the exocyst and PAR proteins, we show that RAL-1 recruits the exocyst to the membrane, while PAR proteins concentrate membrane-localized exocyst proteins to a polarized domain. These findings reveal that RAL-1 and the exocyst direct the polarized vesicle fusion events required for intracellular lumenogenesis of the excretory cell, suggesting mechanistic similarities in the formation of topologically distinct multicellular and intracellular lumens.

KEYWORDS:

Exocyst; Lumenogenesis; Osmoregulation; PAR proteins; Tubulogenesis; Vesicle trafficking

PMID:
25102190
PMCID:
PMC4373406
DOI:
10.1016/j.ydbio.2014.07.019
[Indexed for MEDLINE]
Free PMC Article

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