Regulation of contractile vacuole formation and activity in Dictyostelium.
The contractile vacuole (CV) system is the osmoregulatory organelle required for survival for many free-living cells under hypotonic conditions. We identified a new CV regulator, Disgorgin, a TBC-domain-containing protein, which translocates to the CV membrane at the late stage of CV charging and regulates CV-plasma membrane fusion and discharging. disgorgin(-) cells produce large CVs due to impaired CV-plasma membrane fusion. Disgorgin is a specific GAP for Rab8A-GTP, which also localizes to the CV and whose hydrolysis is required for discharging. We demonstrate that Drainin, a previously identified TBC-domain-containing protein, lies upstream from Disgorgin in this pathway. Unlike Disgorgin, Drainin lacks GAP activity but functions as a Rab11A effector. The BEACH family proteins LvsA and LvsD were identified in a suppressor/enhancer screen of the disgorgin(-) large CV phenotype and demonstrated to have distinct functions in regulating CV formation. Our studies help define the pathways controlling CV function.
Du
Fei
F
Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093-0380, USA.
Edwards
Kimberly
K
Shen
Zhouxin
Z
Sun
Binggang
B
De Lozanne
Arturo
A
Briggs
Steven
S
Firtel
Richard A
RA
D000818:Animals; D003285:Contractile Proteins / Q000235:genetics / Q000502:physiology*; D004023:Dictyostelium / Q000235:genetics / Q000502:physiology*; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000502:physiology*; D007425:Intracellular Membranes / Q000502:physiology*; D021381:Protein Transport; D015800:Protozoan Proteins / Q000235:genetics / Q000502:physiology*; D014617:Vacuoles / Q000502:physiology*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000502:physiology; D000099193:rab11 GTP-Binding Proteins
D003285:Contractile Proteins; D020690:GTPase-Activating Proteins; D015800:Protozoan Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C403705:LvsA protein, Dictyostelium