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Abstract Detail

Organelle Biology

Sliwinski, Marek K. [1], Haas, Thomas [2], Otegui, Marisa [2].

Function of Arabidopsis class E proteins in the endosomal sorting pathway.

Endosomes play a crucial role in both the endocytic and the secretory/biosynthetic pathways of all eukaryotic cells, sorting proteins for recycling or degradation, downregulating receptors, and mediating the transport of proteins to the vacuole. Endosomal trafficking is regulated by a complex molecular machinery consisting of class E proteins. In yeast and mammals, the AAA ATPase Vps4p/SKD1 (Vacuolar protein sorting 4/ Suppressor of K+ transport growth defect 1) is required for endosomal trafficking. We have identified a VPS4/SKD1 homolog in Arabidopsis called AtSKD1 that localizes to the cytoplasm and multivesicular endosomes. In addition, the fluorescent  fusion protein GFP-SKD1 colocalizes on endosomes with fluorescent fusion proteins of well characterized endosomal Rab GTPases and with the endocytic marker FM4-64. The expression of SKD1E232Q, an ATPase-deficient version of SKD1, induces alterations in the endosomal systems of tobacco BY2 cells and ultimately leads to cell death. The inducible expression of SKD1E232Q in Arabidopsis produced enlarged endosomes with a reduced number of internal vesicles. In a yeast two-hybrid screening using Arabidopsis SKD1 as bait, we isolated a putative homologue of mammalian LIP5/SBP1 (LYST-interacting protein 5 /SKD1 binding protein 1). AtLIP5 acts as a positive regulator of SKD1 by increasing 4-5 fold its in vitro ATPase activity. We isolated an Arabidopsis mutant line with a T-DNA insertion in LIP5. RT-PCR of RNA extracts of homozygous lip5 plants with primers flanking the insertion indicates that this is a null mutant. The lip5 plants show no phenotypic alterations in normal growth conditions, suggesting that basal SKD1 ATPase activity is sufficient for plant development and growth.

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1 - University of Wisconsin, Botany, 430 Lincoln Drive, Madison, WI, 53706, USA
2 - University of Wisconsin, Botany


Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P18012
Abstract ID:359

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