A dominant negative form of the AAA ATPase SKD1/VPS4 impairs membrane trafficking out of endosomal/lysosomal compartments: class E vps phenotype in mammalian cells.
SKD1 is a member of the family of ATPases associated with cellular activities whose yeast homologue Vps4p has been implicated in endosomal/vacuolar membrane transports. When a mutant of SKD1 that lacks ATPase activity [SKD1(E235Q)] was overexpressed in mammalian cells, it induced a dominant negative phenotype characterized by aberrant endosomal structures (denoted as E235Q compartments). Expression of SKD1(E235Q) caused an accumulation of basolateral recycling receptors, such as asialoglycoprotein receptor and low-density lipoprotein in polarized hepatocytes and Madin-Darby canine kidney cells, respectively, in E235Q compartments. In addition, SKD1(E235Q) also abrogated, via endosomes, transport to the trans-Golgi network, as indicated by an accumulation of TGN38 in E235Q compartments. Three lines of evidence further demonstrated that SKD1 participates in the membrane transport from early endosomes to late endosomes/lysosomes: (1) a redistribution of a late endosomal and lysosomal membrane protein endolyn in E235Q compartments; (2) an inhibition of epidermal growth factor receptor degradation, due to an accumulation of the receptors in E235Q compartments; and (3) a mis-sorting of and defect in the proteolytic processing of newly synthesized cathepsin D. An intriguing finding was that the expression of SKD1(E235Q) caused the number of lysosomes to decrease (to one-sixth of control numbers) but their size to increase (2.4-fold larger in diameter than control lysosomes). Indeed, an ultrastructural analysis revealed that the expression of SKD1(E235Q) causes an accumulation of hybrid organelles formed by direct fusion between late endosomes and lysosomes. We conclude that SKD1 regulates multiple steps of membrane transport out of early endosomes and the reformation of lysosomes from a hybrid organelle.
Fujita
Hideaki
H
Graduate School of Pharmaceutical Sciences, Kyushu University 3-1-1, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Yamanaka
Motoko
M
Imamura
Kanako
K
Tanaka
Yoshitaka
Y
Nara
Atsuki
A
Yoshimori
Tamotsu
T
Yokota
Sadaki
S
Himeno
Masaru
M
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000172:deficiency* / Q000235:genetics; D000818:Animals; D051929:CD146 Antigen; D002402:Cathepsin D / Q000378:metabolism; D002451:Cell Compartmentation / Q000235:genetics*; D051930:Endolyn; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D066246:ErbB Receptors / Q000378:metabolism; D005057:Eukaryotic Cells / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D008247:Lysosomes / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008562:Membrane Glycoproteins / Q000378:metabolism; D008854:Microscopy, Electron; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D021381:Protein Transport / Q000235:genetics*; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics; D014407:Tumor Cells, Cultured; D025262:Vacuolar Proton-Translocating ATPases; D033921:Vesicular Transport Proteins
D051929:CD146 Antigen; C497901:Cd164 protein, rat; D051930:Endolyn; D056827:Endosomal Sorting Complexes Required for Transport; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D012097:Repressor Proteins; D033921:Vesicular Transport Proteins; D066246:ErbB Receptors; D002402:Cathepsin D; D000251:Adenosine Triphosphatases; D025262:Vacuolar Proton-Translocating ATPases; D000074183:ATPases Associated with Diverse Cellular Activities; C490305:VPS4A protein, human