Ras-related protein Rab-5B (RAB5B) belongs to the Rab family of small (monomeric) G proteins. RAB5B is involved in endocytosis and recycling of cell surface molecules. RAB5B interacts with RIN2 and RIN3, which regulate its function, possibly by acting as GEFs. Knockdown of RAB5B abolished group I metabotropic glutamate receptor (mGluR)-mediated neuroprotection.