Rif is a small (~21 kDa) signaling G protein (more specifically a GTPase), and is a member of the Rho family of GTPases.[1] It is primarily active in the brain and plays a physiological role in the formation of neuronal dendritic spine. This process is regulated by FARP1, a type of activator for RhoA GTPases.[2] Alternatively, Rif can induce the formation of actin stress fibers in epithelial cells. Which is dependent on the activity levels of ROCK proteins since the absence of ROCK activity would mean Rif would be unable to stimulate the growth of stress fibers.[3]

Rif is also seen expressed in diverse amount of human tissues such as in the colon and stomach due to Rho's use of actin dynamics to absorb intestinal epithelial cells.[4] Rif's function in forming filopodia has a relation to the function of platelets. But in mice, Rif is not necessary for platelets to function.[5]


  1. ^ Ridley AJ (October 2006). "Rho GTPases and actin dynamics in membrane protrusions and vesicle trafficking". Trends in Cell Biology. 16 (10): 522–9. doi:10.1016/j.tcb.2006.08.006. PMID 16949823.
  2. ^ Fan L, Yan H, Pellegrin S, Mellor H (March 2015). "The Rif GTPase regulates cytoskeletal signaling from plexinA4 to promote neurite retraction". Neuroscience Letters. 590: 178–83. doi:10.1016/j.neulet.2015.02.010. PMID 25668492. S2CID 23364498.
  3. ^ Fan L, Pellegrin S, Scott A, Mellor H (April 2010). "The small GTPase Rif is an alternative trigger for the formation of actin stress fibers in epithelial cells". Journal of Cell Science. 123 (Pt 8): 1247–52. doi:10.1242/jcs.061754. PMC 2848113. PMID 20233848.
  4. ^ Fan L, Mellor H (February 2012). "The small Rho GTPase Rif and actin cytoskeletal remodelling". Biochemical Society Transactions. 40 (1): 268–72. doi:10.1042/BST20110625. PMID 22260703.
  5. ^ Goggs R, Savage JS, Mellor H, Poole AW (2013-01-24). "The small GTPase Rif is dispensable for platelet filopodia generation in mice". PLOS ONE. 8 (1): e54663. Bibcode:2013PLoSO...854663G. doi:10.1371/journal.pone.0054663. PMC 3554654. PMID 23359340.