Rab34/Rab36 subfamily. Rab34, found primarily in the Golgi, interacts with its effector, Rab-interacting lysosomal protein (RILP). This enables its participation in microtubular dynenin-dynactin-mediated repositioning of lysosomes from the cell periphery to the Golgi. A Rab34 (Rah) isoform that lacks the consensus GTP-binding region has been identified in mice. This isoform is associated with membrane ruffles and promotes macropinosome formation. Rab36 has been mapped to human chromosome 22q11.2, a region that is homozygously deleted in malignant rhabdoid tumors (MRTs). However, experimental assessments do not implicate Rab36 as a tumor suppressor that would enable tumor formation through a loss-of-function mechanism. GTPase activating proteins (GAPs) interact with GTP-bound Rab and accelerate the hydrolysis of GTP to GDP. Guanine nucleotide exchange factors (GEFs) interact with GDP-bound Rabs to promote the formation of the GTP-bound state. Rabs are further regulated by guanine nucleotide dissociation inhibitors (GDIs), which facilitate Rab recycling by masking C-terminal lipid binding and promoting cytosolic localization. Most Rab GTPases contain a lipid modification site at the C-terminus, with sequence motifs CC, CXC, or CCX. Lipid binding is essential for membrane attachment, a key feature of most Rab proteins.