UNC119B is an ARL3 effector that binds directly to the myristoyl moieties at glycine 2 of NPHP3 and CYS1 (Wright et al, 2011). Myristoylation is required for the ciliary localization of these proteins (Wright et al, 2011; Tao et al, 2006), and both mutation of the glycine 2 myristoylation target in NPHP3 and siRNA knockdown of UNC119B dramatically reduce the ciliary localization of NPHP3 and CYS1 (Tao et al, 2006; Wright et al, 2011; reviewed in Schwarz et al, 2012).
ARL3 is an ARF-like small GTPase that is localized to the cilium in both the GDP- and the GTP-bound form (Zhou et al, 2006; Wright et al, 2011). ARL3 binds UNC119B in a GTP-dependent fashion and is required for the ciliary localization of NPHP3 and CYS1. Upon GTPase activation, ARL3 promotes the transfer of the myristoylated cargo into the ciliary membrane (Wright et al, 2011).
UNC119B promotes the translocation of myristoylated NPHP3 from the ER membrane to the cilium by an unknown mechanism. Ciliary localization depends both on myristoylation and UNC119B, as mutation of the glycine 2 acceptor site or siRNA knockdown of UNC119B drastically reduces the amount of NPHP3 or CYS1 in the cilium (Wright et al, 2011).
Binding of ARL3 to UNC119B induces a conformational change that obstructs UNC119B cargo-binding and promotes the release of the myrisoylated cargo into the ciliary membrane (Wright et al, 2011; Ismail et al, 2012).
RP2 is an ARL3 GAP that is localized to the cilium and plays a role in trafficking proteins from the Golgi to the ciliary membrane (Veltel et al, 2008a; Hurd et al, 2011; Evans et al, 2010; Wright et al, 2011). RP2 forms a ternary complex with UNC119B and ARL3, activating the ARL3 GTPase activity and promoting the release of UNC119B (Veltel et al, 2008b; Wright et al, 2011; Kuhnel et al, 2006; reviewed in Schwarz et al, 2012; Li et al, 2012)
RP2 is an ARL3 GAP that is localized to the cilium and plays a role in trafficking proteins from the Golgi to the ciliary membrane (Veltel et al, 2008a; Hurd et al, 2011; Evans et al, 2010; Wright et al, 2011). RP2 forms a ternary complex with UNC119B and ARL3, activating the ARL3 GTPase activity and promoting the release of UNC119B (Veltel et al, 2008b; Wright et al, 2011; Kuhnel et al, 2006; reviewed in Schwarz et al, 2012; Li et al, 2012)
RP2 is an ARL3 GAP that is localized to the cilium and plays a role in trafficking proteins from the Golgi to the ciliary membrane (Veltel et al, 2008a; Hurd et al, 2011; Evans et al, 2010; Wright et al, 2011). RP2 forms a ternary complex with UNC119B and ARL3, activating the ARL3 GTPase activity and promoting the release of UNC119B (Veltel et al, 2008b; Wright et al, 2011; Kuhnel et al, 2006; reviewed in Schwarz et al, 2012; Li et al, 2012)