<i>Rabx-5</i> mutations alter the RAB-5 organization in GABAergic motor neurons.

<p>A) A forward genetic screen was conducted by observing GABAergic motor neurons for changes in localization or intensity of P_unc-25YFP::RAB-5. Initial screening isolated mutants in which YFP::RAB-5 was decreased in the cell soma. Further inspection determined if YFP::RAB-5 was increased at the synapse. B) Gene, transcript, and protein structure of <i>rabx-5</i>. The RABX-5 protein consists of a zinc finger motif (ZF) and a motif interacting with ubiquitin (U) that together regulate association with ubiquitinated endosomal cargo; a membrane binding motif and helical bundle required for association with the endosomal membrane; a Vps9 domain that along with the helical bundle promotes guanine exchange activity; and a coiled-coil region that binds rabaptin-5 and contains a motif for autoinhibition of guanine exchange activity. The <i>rabx-5(qa7800)</i> mutation leads to a truncation at the helical bundle. The <i>rabx-5(tm1512)</i> mutation deletes the start site and the exons encoding the zinc finger motif and the motif interacting with ubiquitn. C) P_unc-25YFP::RAB-5 protein localization in the soma (left column) and dorsal cord (right column) of GABAergic motor neurons in wild type and mutant animals. D) P_unc-25YFP::RAB-5 fluorescence intensity was decreased in the soma of mutant animals and increased in the synaptic and intersynaptic regions. This phenotype is recovered with expression of P_unc-25CFP::RABX-5. Each point represents a single soma, synaptic puncta, or intersynaptic axonal region, respectively. Bar represents the mean. **p<0.01, ***p<0.001. E) P_unc-25CFP::RABX-5 expression recovers the <i>rabx-5(qa7800)</i> YFP::RAB-5 phenotype.