Rab1B

Rab1B is a member of the Rab family of small GTPases that regulate vesicular trafficking within the early secretory pathway. In particular, Rab1B participates in ER-to-Golgi transport and helps maintain Golgi structure by coordinating vesicle budding, targeting, and tethering.

The human RAB1B gene encodes the Rab1B protein, which is highly conserved with its paralog Rab1A. Rab1B is widely expressed and localizes primarily to membranes associated with the endoplasmic reticulum–Golgi intermediate compartment and the Golgi apparatus.

As a molecular switch, Rab1B cycles between a GDP-bound inactive form and a GTP-bound active form. Activation is promoted by guanine nucleotide exchange factors such as GBF1, while GTPase-activating proteins accelerate inactivation. Active Rab1B engages downstream effector proteins, including tethering factors such as p115 and Golgin-84/GM130, to mediate docking of COPII vesicles to the Golgi and regulate trafficking steps.

Rab1B function is conserved from yeast to humans, aligning with the role of Ypt1p in coordinating early secretory traffic. Disruption of Rab1B activity can impact ER-Golgi transport, Golgi structure, and cellular secretion, with potential consequences for ER stress and secretory capacity.

In human disease research, Rab1B has been examined for its involvement in cancer cell behavior and secretory pathway dysfunction, though its precise contributions require further investigation.