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 is one way of generating
filopodia (Rif-induced filopodia) through its interaction with mDia2. Specifically, the interaction is between the GTP from Rif and the GTPase binding domain (GBD) of mDia2.[3][5] 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.[6] The co-expression of Rif with
Rac or
Cdc42, other GTPases that also participate in regulating cell structure and morphology, can give rise to new filopodial structures that differ from the filopodia arrangements stimulated by each of these GTPases functioning separately.[7]
References
^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.
PMID16949823.
^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.
PMID25668492.
S2CID23364498.