Rac is a subfamily of the Rho family of GTPases,[1] small (~21 kDa) signaling G proteins (more specifically a GTPase). Just as other G proteins, Rac acts as a molecular switch, remaining inactive while bound to GDP and activated once GEFs remove GDP, permitting GTP to bind. When bound to GTP, Rac is activated. In its activated state, Rac participates in the regulation of cell movement, through its involvement in structural changes to the actin Cytoskeleton.[2] By changing the cytoskeletal dynamics within the cell, Rac-GTPases are able to facilitate the recruitment of neutrophils to the infected tissues, and to regulate degranulation of azurophil and integrin-dependent phagocytosis.[3]

Activated Rac also regulates the effector functions of the target proteins involved in downstream signaling. As an essential subunit of NOX2 (NADPH oxidase enzyme complex), Rac is required for ROS (reactive oxygen species) production involved in the formation of NETs (neutrophil extracellular traps, thus, facilitating the pathogen and debris clearance by neutrophils, and the reduction of inflammation.[3]

The abnormal activities of Rac including its hyperactivation, resistance to degradation, and abnormal localization of its signaling protein components were found to facilitate the development of cancerous cells and resist to anticancer treatment.[4]

Recent experiments on Drosophila suggested that Rac could be involved in mediating the process of forgetting. Hyperactivation of Rac increases the memory decay whereas its inhibition prevents interference-induced forgetting and slows down a passive memory decay.[5][6]

Classification

The Rho family of GTPases includes Rac, Rho, and Cdc42 small G-protein groups. Rac comprises Rac1, Rac2, Rac3, and RhoG subgroups.

The extensive cross-talk within these groups of GTPase provides a significant impact on the biological responses of the cell, influencing the activity of the cell cycle machinery. Ras cooperates with Cdc42 to regulate Elk1 phosphorylation and transcriptional activity of SRF. Ras also cooperates with Rho and Ras to activate other downstream signaling pathways. [7]

References

  1. ^ Ridley AJ (October 2006). "Rho GTPases and actin dynamics in membrane protrusions and vesicle trafficking". Trends in Cell Biology. 16 (10): 522–529. doi:10.1016/j.tcb.2006.08.006. PMID 16949823.
  2. ^ "Rac", Encyclopedia of Cancer, Springer Berlin Heidelberg, 2011, p. 3133, doi:10.1007/978-3-642-16483-5_4891, ISBN 9783642164828
  3. ^ a b Pantarelli C, Welch HC (November 2018). "Rac-GTPases and Rac-GEFs in neutrophil adhesion, migration and recruitment". European Journal of Clinical Investigation. 48 Suppl 2: e12939. doi:10.1111/eci.12939. PMID 29682742.
  4. ^ Sun D, Xu D, Zhang B (December 2006). "Rac signaling in tumorigenesis and as target for anticancer drug development". Drug Resistance Updates. 9 (6): 274–287. doi:10.1016/j.drup.2006.12.001. PMID 17234445.
  5. ^ Shuai Y, Lu B, Hu Y, Wang L, Sun K, Zhong Y (February 2010). "Forgetting is regulated through Rac activity in Drosophila". Cell. 140 (4): 579–589. doi:10.1016/j.cell.2009.12.044. PMID 20178749.
  6. ^ http://scitechstory.com/2010/02/19/brain-memory-is-actively-cleared/
  7. ^ Bar-Sagi, Dafna; Hall, Alan (2010). "Ras and Rho GTPases". Cell. 103 (2): 227–238. doi:10.1016/S0092-8674(00)00115-X.