Abstract
RAB GTPases, including RAB5, are known to act as molecular switches through cycling between GTP-bound and GDP-bound states. The GTP-bound state is considered as an active form, with which effector molecules specifically interact to induce downstream reaction. In mammalian cells, many RAB5 effectors are known to trigger various downstream phenomena. RAB5 is conserved in a broad range of eukaryotic organisms including plants. In addition to the conventional-type RAB5 homologs, land plants possess plant-unique RAB5 homologs (ARA6 in Arabidopsis thaliana) (Ueda et al., 2001). Our previous studies indicated that ARA6 and conventional-type RAB5 regulate different membrane trafficking pathways, which could be integrated by RAB5 effector molecules. However, plant RAB5 effectors have not identified thus far. To elucidate the molecular basis of RAB5-regulated trafficking pathways, we attempted to isolate effector molecules of ARA6. By yeast two-hybrid screening, we have identified seven effector candidates. In this meeting, cell biological and physiological significance of these effectors will be presented.
