RAB3C

Rab3C is a member of the Rab family of small GTPases and one of the Rab3 paralogs in humans. It is encoded by the RAB3C gene and, like other Rab proteins, functions as a molecular switch that cycles between GDP-bound inactive and GTP-bound active states. Activation is driven by guanine nucleotide exchange factors, while GTP hydrolysis is accelerated by GTPase-activating proteins. In its GTP-bound form, Rab3C associates with secretory vesicles and participates in Ca2+-regulated exocytosis.

Rab3C plays a role in the regulation of neurotransmitter and hormone release by linking secretory vesicles to components of the presynaptic release machinery. It interacts with a set of effector proteins, including Rabphilin and Rab3-interacting molecule (RIM) family proteins, which help coordinate vesicle docking, priming, and fusion at the plasma membrane. The activity and localization of Rab3C are modulated by post-translational prenylation at the C-terminus, which anchors the protein to vesicle membranes.

Expression studies show Rab3C in neuronal tissues and endocrine cells, with broader expression reported across various tissues. Its precise distribution and levels can vary with development and physiological state, reflecting a role in regulated secretion across cell types.

In the broader context of vesicle trafficking, Rab3C is studied alongside other Rab3 paralogs to understand conserved and distinct functions in exocytosis. While detailed mechanisms continue to be explored, Rab3C is recognized as a contributor to efficient regulated secretion and synaptic transmission, and research continues to assess its involvement in neurological and endocrine processes.