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VPS8D, a CORVET subunit, is required to maintain the contractile vacuole complex in Tetrahymena thermophila
  • Chao-Yin Cheng,
  • Josefina Hernández,
  • Aaron P. Turkewitz
Chao-Yin Cheng
University of Chicago Department of Molecular Genetics and Cell Biology
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Josefina Hernández
University of Chicago Department of Molecular Genetics and Cell Biology
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Aaron P. Turkewitz
University of Chicago Department of Molecular Genetics and Cell Biology

Corresponding Author:[email protected]

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Abstract

Contractile vacuole complexes (CVCs) are complex osmoregulatory organelles, with vesicular (bladder) and tubular (spongiome) subcompartments. The mechanisms that underlie their formation and maintenance within the eukaryotic endomembrane network are poorly understood. In the Ciliate Tetrahymena thermophila, six differentiated CORVETs (class C core vacuole/endosome tethering complexes), with Vps8 subunits designated A-F, are likely to direct endosomal trafficking. Vps8Dp localizes to both bladder and spongiome. We show by inducible knockdown that VPS8D is essential to CVC organization and function. VPS8D knockdown increased susceptibility to osmotic shock, tolerated in the wildtype but triggering irreversible lethal swelling in the mutant. The knockdown rapidly triggered contraction of the spongiome and lengthened the period of the bladder contractile cycle. More prolonged knockdown resulted in disassembly of both the spongiome and bladder, and dispersal of proteins associated with those compartments. In stressed cells where the normally singular bladder is replaced by numerous vesicles bearing bladder markers, Vps8Dp concentrated conspicuously at long-lived inter-vesicle contact sites, consistent with tethering activity. Similarly, Vps8Dp in cell-free preparations accumulated at junctions formed after vacuoles came into close contact. Also consistent with roles for Vps8Dp in tethering and/or fusion were the emergence in knockdown cells of multiple vacuole-related structures, replacing the single bladder.
10 Nov 2023Submitted to Traffic
10 Nov 2023Submission Checks Completed
10 Nov 2023Assigned to Editor
10 Nov 2023Review(s) Completed, Editorial Evaluation Pending
10 Nov 2023Reviewer(s) Assigned