Plant and Cell Physiology Advance Access originally published online on October 17, 2005
Plant and Cell Physiology 2005 46(12):2005-2018; doi:10.1093/pcp/pci215
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
OsGAP1 Functions as a Positive Regulator of OsRab11-mediated TGN to PM or Vacuole Trafficking
1 Division of Applied Life Sciences, Graduate School of Gyeongsang National University, Jinju 660-701, Korea
2 Environmental Biotechnology National Core Research Center (EBNCRC), Gyeongsang National University, Jinju 660-701, Korea
* Corresponding author: E-mail, jdbahk{at}gsnu.ac.kr; Fax, +82-55-752-7062.
The Ypt/Rab family of small G-proteins is important in regulating vesicular transport. Rabs hydrolyze GTP very slowly on their own and require GTPase-activating proteins (GAPs). Here we report the identification and characterization of OsGAP1, a Rab-specific rice GAP. OsGAP1 strongly stimulated OsRab8a and OsRab11, which are homologs of the mammalian Rab8 and Rab11 proteins that are essential for Golgi to plasma membrane (PM) and trans-Golgi network (TGN) to PM trafficking, respectively. Substitution of two invariant arginines within the catalytic domain of Oryza sativa GTPase-activating protein 1 (OsGAP1) with alanines significantly inhibited its GAP activity. In vivo targeting experiments revealed that OsGAP1 localizes to the TGN or pre-vacuolar compartment (PVC). A yeast expression system demonstrated that wild-type OsGAP1 facilitates O. sativa dissociation inhibitor 3 (OsGDI3)-catalyzed OsRab11 recycling at an early stage, but the OsGAP1(R385A) and (R450A) mutants do not. Thus, GTP hydrolysis is essential for Rab recycling. Moreover, expression of the OsGAP1 mutants in Arabidopsis protoplasts inhibited the trafficking of some cargo proteins, including the PM-localizing H+-ATPase–green fluorescent protein (GFP) and Ca2+-ATPase8–GFP and the central vacuole-localizing Arabidopsis aleurain-like protein (AALP)–GFP. The OsGAP1 mutants caused these proteins to accumulate at the Golgi apparatus. Surprisingly, OsRab11 overproduction relieved the inhibitory effect of the OsGAP1 mutants on vesicular trafficking. OsRab8a had no such effect. Thus, the OsGAP1 mutants may inhibit TGN to PM or central vacuole trafficking because they induce the sequestration of endogenous Rab11. We propose that OsGAP1 facilitates vesicular trafficking from the TGN to the PM or central vacuole by both stimulating the GTPase activity of OsRab11 and increasing the recycling of inactive OsRab11.
The accession numbers for the proteins described in this article are as follows; AP003443 [GenBank] (OsRab1), XP466431 (OsRab2), CAC19792 [GenBank] (OsRab5), NM_187359 [GenBank] (OsRab6), AY226827 [GenBank] (OsRab7), XM_470131 [GenBank] (OsRab8a), XM_477215 [GenBank] (OsRab8b), XM_466431 [GenBank] (OsRab8c) and AK066548 [GenBank] (OsRab11).
(Received August 22, 2005; Accepted October 7, 2005)
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  I. Hwang Sorting and Anterograde Trafficking at the Golgi Apparatus Plant Physiology, October 1, 2008; 148(2): 673 - 683. [Full Text] [PDF]
|
|
|
|
|
|
E. Nielsen, A. Y. Cheung, and T. Ueda The Regulatory RAB and ARF GTPases for Vesicular Trafficking Plant Physiology, August 1, 2008; 147(4): 1516 - 1526. [Full Text] [PDF]
|
|
|
|
 |
|
 R. U. Rehman, E. Stigliano, G. W. Lycett, L. Sticher, F. Sbano, M. Faraco, G. Dalessandro, and G.-P. Di Sansebastiano Tomato Rab11a Characterization Evidenced a Difference Between SYP121-Dependent and SYP122-Dependent exocytosis Plant Cell Physiol., May 1, 2008; 49(5): 751 - 766. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C.-M. Chow, H. Neto, C. Foucart, and I. Moore Rab-A2 and Rab-A3 GTPases Define a trans-Golgi Endosomal Membrane Domain in Arabidopsis That Contributes Substantially to the Cell Plate PLANT CELL, January 1, 2008; 20(1): 101 - 123. [Abstract] [Full Text] [PDF]
|
|