Rac (GTPase)

Rac is a small GTPase, belonging to the Rho family of GTPases, which are themselves part of the Ras superfamily. It is a key signaling protein involved in a variety of cellular processes, including cell motility, cell growth, cell adhesion, cytoskeletal organization, and gene expression.

Rac functions as a molecular switch, cycling between an inactive GDP-bound state and an active GTP-bound state. Activation is triggered by guanine nucleotide exchange factors (GEFs), which promote the exchange of GDP for GTP. Once activated, Rac interacts with various downstream effector proteins to initiate signaling cascades that regulate the cellular functions listed above.

Deactivation is mediated by GTPase-activating proteins (GAPs), which stimulate the intrinsic GTPase activity of Rac, leading to the hydrolysis of GTP to GDP and returning the protein to its inactive state. Guanine nucleotide dissociation inhibitors (GDIs) can also bind to Rac, maintaining it in an inactive, cytosolic state.

Different isoforms of Rac exist, including Rac1, Rac2, and Rac3. While they share a high degree of sequence similarity, they exhibit distinct tissue-specific expression patterns and contribute to different cellular functions. Rac1 is ubiquitously expressed and is the most extensively studied isoform.

Dysregulation of Rac signaling has been implicated in various diseases, including cancer, inflammation, and neurodevelopmental disorders. Therefore, Rac is a target of significant research interest.