RALB

RalB is a member of the Ral family of small GTPases in the Ras superfamily. It is encoded by the RALB gene in humans and is closely related to RALA. It functions as a molecular switch cycling between GDP-bound inactive and GTP-bound active states.

Activation is driven by specific guanine nucleotide exchange factors (GEFs) such as RALGPS1/2 and RALGDS that promote GDP to GTP exchange. Inactivation is mediated by GTPase-activating proteins like RALGAP1. Like other Ras-like GTPases, RalB is post-translationally modified at the C-terminus (prenylation) enabling membrane association and effector interactions.

Active RalB engages with effector proteins including components of the exocyst complex, notably Sec5 and Exo84, to regulate vesicle trafficking and exocytosis. It also binds RLIP76 (RALBP1) and other effectors to influence actin cytoskeleton dynamics, endocytosis, and membrane trafficking, impacting cell migration and morphogenesis.

In humans, RalB participates in Ras-driven signaling pathways and has been implicated in cancer-related processes such as tumor cell survival, invasion, and metastasis in various cancers. Its activity can contribute to oncogenic phenotypes in models of pancreatic and other cancers, though its exact role can be context-dependent.

RalB operates alongside RalA as part of the broader Ras signaling network, coordinating vesicle trafficking and cytoskeletal organization.