title: Caenorhabditis elegans Rab escort protein (REP-1) differently regulates each Rab protein function and localization in a tissue-dependent manner.
abstract: Rab proteins play a critical role in intracellular vesicle trafficking and require post-translational modification by adding lipids at the C-terminus for proper functions. This modification is preceded by the formation of a trimeric protein complex with the Rab escort protein (REP) and the Rab geranylgeranyltransferase (RabGGTase). However, the genetic hierarchy among these proteins and the tissue-specificity of each protein function are not yet clearly understood. Here we identified the Caenorhabditis elegans rep-1 gene and found that a rep-1 mutant showed a mild defect in synaptic transmission and defecation behaviors. Genetic analyses using the exocytic Rab mutants rab-3 or rab-27 suggested that rep-1 functions only in the RAB-27 pathway, and not in the RAB-3 pathway, for synaptic transmission at neuromuscular junctions. However, the disruption of REP-1 did not cause defecation defects compared to severe defects in either RAB-27 or RabGGTase disruption, suggesting that REP-1 is not essential for RAB-27 signaling in defection. Some Rab proteins did not physically interact with REP-1, and localization of these Rab proteins was not severely affected by REP-1 disruption. These findings suggest that REP-1 functions are required in specific Rab pathways and in specific tissues, and that some Rab proteins are functionally prenylated without REP-1.
authors.affiliation: Neuroscience Research Institute, AIST, Tsukuba, Ibaraki 305-8566, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Tanaka
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Kameyama
authors.forename: Harumasa
authors.initials: H
authors.lastname: Okamoto
authors.forename: Motomichi
authors.initials: M
authors.lastname: Doi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation; D009154:Mutation; D020691:rab GTP-Binding Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D000075745:rab27 GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D029742:Caenorhabditis elegans Proteins; D000075745:rab27 GTP-Binding Proteins; C534877:aex-6 protein, C elegans; D020691:rab GTP-Binding Proteins; D020692:rab3 GTP-Binding Proteins