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bioRxiv · 10.1101/398685

Acetate and hypertonic stress stimulate organelle membrane fission using distinct phosphatidylinositol signals

Patel, D.·Brett, C. L.
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Abstract

Organelle morphology reflects an equilibrium between membrane fusion and fission that determines size, shape and copy number. By studying the yeast vacuole as a model, the conserved molecular mechanisms responsible for organelle fusion have been revealed. However, a detailed understanding of vacuole fission and how these opposing processes respond to the cell cycle, osmoregulation or metabolism to change morphology remain elusive. Thus, herein we describe a new fluorometric assay to measure vacuole fission in vitro. For proof-of-concept, we use this assay to confirm that acetate, a key intermediary metabolite, triggers vacuole fission in vitro and show that it also blocks homotypic vacuole fusion. The basis of this effect is distinct from hypertonic stress, a known trigger of fission and inhibitor of fusion that inactivates the Rab-GTPase Ypt7: Treatment with the phosphatidylinositol-kinase inhibitor wortmannin or the catalytic domain of the Rab-GAP (GTPase Activating Protein) Gyp1 reveal that fission can be triggered by Ypt7 inactivation alone in absence of hypertonic stress, placing it upstream of PI-3,5-P2 synthesis and osmosis required for membrane scission. Whereas acetate seems to block PI-4-kinase to possibly increase the pool of PI on vacuole membranes needed to synthesize sufficient PI-3,5-P2 for fission. Thus, we speculate that both PI-4-P and PI-3-P arms of PI-P signaling drive changes in membrane fission and fusion responsible altering vacuole morphology in response to cellular metabolism or osmoregulation.\n\nGRAPHICAL ABSTRACT\n\nO_FIG O_LINKSMALLFIG WIDTH=190 HEIGHT=200 SRC=\"FIGDIR/small/398685_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (28K):\norg.highwire.dtl.DTLVardef@896c6dorg.highwire.dtl.DTLVardef@2d8100org.highwire.dtl.DTLVardef@1702e45org.highwire.dtl.DTLVardef@1eddbba_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Patel, D., Brett, C. L.. 2018-08-23. Acetate and hypertonic stress stimulate organelle membrane fission using distinct phosphatidylinositol signals. https://doi.org/10.1101/398685

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