Rab GTPases, which are involved in intracellular trafficking pathways, have recently been reported to be ubiquitinated. However, the functions of ubiquitinated Rab proteins remain unexplored. Here we show that Rab5 is monoubiquitinated on K116, K140, and K165. Upon cotransfection with ubiquitin, Rab5 exhibited abnormalities in endosomal localization and EGFinduced EGF receptor degradation. Rab5 K140R and K165R mutants restored these abnormalities, whereas K116R did not. We derived structural models of individual monoubiquitinated Rab5 proteins (mUbRab5s) by solution scattering and observed different conformational flexibilities in a site-specific manner. Structural analysis combined with biochemical data revealed that interactions with downstream effectors were impeded in mUbRab5K140, whereas GDP release and GTP loading activities were altered in mUbRab5K165. By contrast, mUbRab5K116 apparently had no effect. We propose a regulatory mechanism of Rab5 where monoubiquitination downregulates effector recruitment and GDP/GTP conversion in a site-specific manner.
Bibliographical noteFunding Information:
We thank the staff members at beamline 4C of Pohang Accelerator Laboratory for technical assistance in SAXS data collection. This work was supported by the Basic Science Research Program (NRF-2015R1A2A1A15055951), the Science Research Center Program (SRC-2017R1A5A1014560), and the Pioneer Research Center Program (2012–0009597) through National Research Foundation of Korea (NRF) grants funded by the Korea Ministry of Science and ICT and by the Woo Jang Chun program (PJ009106) through the Rural Development Agency.
© Shin et al.
All Science Journal Classification (ASJC) codes
- Immunology and Microbiology(all)
- Biochemistry, Genetics and Molecular Biology(all)