PMID:16236155

Citation	Latijnhouwers, M, Hawes, C, Carvalho, C, Oparka, K, Gillingham, AK and Boevink, P (2005) An Arabidopsis GRIP domain protein locates to the trans-Golgi and binds the small GTPase ARL1. Plant J. 44:459-70
Abstract	GRIP domain proteins are a class of golgins that have been described in yeast and animals. They locate to the trans-Golgi network and are thought to play a role in endosome-to-Golgi trafficking. The Arabidopsis GRIP domain protein, AtGRIP, fused to the green fluorescent protein (GFP), locates to Golgi stacks but does not exactly co-locate with the Golgi marker sialyl transferase (ST)-mRFP, nor with the t-SNAREs Memb11, SYP31 and BS14a. We conclude that the location of AtGRIP is further to the trans side of the stack than STtmd-mRFP. The 185-aa C-terminus of AtGRIP containing the GRIP domain targeted GFP to the Golgi, although a proportion of the fusion protein was still found in the cytosol. Mutation of a conserved tyrosine (Y717) to alanine in the GRIP domain disrupted Golgi localization. ARL1 is a small GTPase required for Golgi targeting of GRIP domain proteins in other systems. An Arabidopsis ARL1 homologue was isolated and shown to target to Golgi stacks. The GDP-restricted mutant of ARL1, AtARL1-T31N, was observed to locate partially to the cytosol, whereas the GTP-restricted mutant AtARL1-Q71L labelled the Golgi and a population of small structures. Increasing the levels of AtARL1 in epidermal cells increased the proportion of GRIP-GFP fusion protein on Golgi stacks. We show, moreover, that AtARL1 interacted with the GRIP domain in a GTP-dependent manner in vitro in affinity chromatography and in the yeast two-hybrid system. This indicates that AtGRIP and AtARL1 interact directly. We conclude that the pathway involving ARL1 and GRIP domain golgins is conserved in plants.
Links	PubMed Online version:10.1111/j.1365-313X.2005.02542.x
Keywords	Amino Acid Sequence; Amino Acid Substitution; Arabidopsis/genetics; Arabidopsis/metabolism; Arabidopsis Proteins/chemistry; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; Gene Expression Regulation, Plant; Membrane Proteins/chemistry; Membrane Proteins/metabolism; Molecular Sequence Data; Monomeric GTP-Binding Proteins/genetics; Monomeric GTP-Binding Proteins/metabolism; Mutation; Plants, Genetically Modified; Protein Binding; Protein Structure, Tertiary; Protein Transport; Sequence Homology, Amino Acid; Tobacco/genetics; trans-Golgi Network/metabolism
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