%0 Journal Article
%T Mutant Rab24 GTPase is targeted to nuclear inclusions
%A William A Maltese
%A Gwendolyn Soule
%A William Gunning
%A Edward Calomeni
%A Brandy Alexander
%J BMC Cell Biology
%D 2002
%I BioMed Central
%R 10.1186/1471-2121-3-25
%X The functions of other Rab proteins have been defined through the use of dominant-negative mutants with amino acid substitutions in the conserved N(T)KxD nucleotide binding motif. Surprisingly, when such Rab24 constructs were expressed in cultured cells, they accumulated in nuclear inclusions which disrupted the integrity of the nuclear envelope. The inclusions reacted positively with antibodies against ubiquitin and Hsp70, similar to protein aggregates observed in polyglutamine disorders. They also appeared to sequester importin-¦Â and GFP-coupled glucocorticoid receptor. Other Rab GTPases with similar mutations in the N(T)KxD motif were never found in inclusions, suggesting that the unusual localization of Rab24 is not related solely to misfolding of its nucleotide-free form. Studies with Rab24/Rab1B chimeras indicated that targeting of the mutant protein to inclusions requires the unique C-terminal domain of Rab24.These studies demonstrate that mutations in Rab24 can trigger a cytopathic cellular response involving accumulation of nuclear inclusions. If the N(T)KxD mutants of Rab24 function as dominant suppressors, these studies may point to a unique role for Rab24 in degradation of misfolded cellular proteins or trafficking of proteins to the nuclear envelope. However, we cannot yet eliminate the possibility that these phenomena are related to unusual non-physiological protein interactions with the mutant form of Rab24.Rab proteins comprise a large family of Ras-related GTPases that function in the anterograde and retrograde trafficking of proteins in mammalian cells [1-3]. Different Rab proteins reside in specific subcellular membranes or organelles, where they mediate vesicular transport between discrete donor and acceptor compartments in the endocytic or exocytic pathways [4,5]. Detailed studies of a few Rab proteins (e.g.; Rab1, Rab5 and Rab9) have led to a general model wherein Rab proteins are presumed to cycle on and off donor and acceptor membranes in con
%U http://www.biomedcentral.com/1471-2121/3/25