RVxP motif is a protein motif involved in localizing proteins into cilia.
Cilia are sensory organelle of cells, whose malfunction can cause diseases such as polycystic kidney disease, [1] nephronophthisis and Bardet-Biedl syndrome. Proteins employed in the cilia are targeted there when they bear specific entry signals, whereas proteins not situated in cilia are removed or prevented from entering the organelles. [2] Entry signals have been found in ciliary/flagellar proteins of the protozoans Leishmania and Trypanosoma . [3]
The RVxP motif was first described for the PKD2 protein [4] and when inserted in the transferrin receptor it can target it to cilia. [5] It probably carries out its signal function through protein interactions [3] although the exact process [6] and where in the cell it takes place are unknown. [7] Three candidate proteins involved in "receiving" this signal are pericentrin at the basal body of cilia, intraflagellar transport proteins such as IFT57 [3] and ARF4 [8] while the BBSome does not appear to interact with the sequence. [9] The kinesins KIF17 is implicated in transporting the CNGB1 protein which has a RVxP motif into human cilia, [4] as is Rab8a in transporting PKD2. [5] Not all ciliary proteins use a RVxP motif for transport, however; [10] VxPx and Ax(S/A)xQ have also been described as cilium-targeting motifs. [6]
Examples of proteins with RVxP motifs associated with cilia:
Other proteins associated with cilia for which the occurrence of a RVxP motif has been discussed are PKD1 and PSEN2. [24]