Rab GTPases act as molecular switches, being activated by the binding of GTP and deactivated by GDP . The effector proteins (motor proteins, tethers, sorting linkers, regulators, kinases, phosphatases, and other effector types) interact with Rab GTPase-bound forms . In addition to GDP dissociation inhibitor (GDI), the Rab escort protein (REP) also interacts with the bound form of GDP. Rab GTPase undergoes a conformational change from GDP-to GTP-bound forms catalyzed by the GDP/GTP guanine nucleotide exchange factor (GEF). Prenylating Rab GTPase renders it inactive (GDP-bound) and prevents it from being attached to the membrane. This is achieved by covering up the isoprene anchor with GDI. The GDI-Rab complex is dissociated and targeted to a specific cellular compartment by the GDI displacement factor (GDF), which then inserts the isoprene anchor into the membrane. The bound GDP is exchanged to GTP by the guanine nucleotide exchange factor (GEF) , activatin Rab GTPase and establish membrane-bound state . Membrane trafficking is one of the many functions that active, membrane-bound Rab GTPases are capable of carrying out through their interactions with effector proteins. Rab GTPases can be converted from GTP-bound to GDP-bound forms via GTP hydrolysis by GTPase activating proteins (GAPs) . Upon binding to Rab GTPase in its GTP-conjugated state, GAP quickly catalyzes the hydrolysis of GTP to GDP, rendering Rab GTPase inactive. When the hydrophilic geranylgeranyl groups of GDP-Rab proteins are encapsulated by GDI, the proteins become soluble . Because of its solubility after forming a complex with GDP-Rab GTPase in the cytoplasm, GDI can be exported from the membrane . Masking C-terminal lipid binding and facilitating cytoplasmic localization are two ways in which GDI improves the Rab GTPase cycle .