Arfophilins Are Dual Arf/Rab 11 Binding Proteins That Regulate Recycling Endosome Distribution and Are Related toDrosophilaNuclear Fallout

Abstract

Arfophilin is an ADP ribosylation factor (Arf) binding protein of unknown function. It is identical to the Rab11 binding protein eferin/Rab11-FIP3, and we show it binds both Arf5 and Rab11. We describe a related protein, arfophilin-2, that interacts with Arf5 in a nucleotide-dependent manner, but not Arf1, 4, or 6 and also binds Rab11. Arfophilin-2 localized to a perinuclear compartment, the centrosomal area, and focal adhesions. The localization of arfophilin-2 to the perinuclear compartment was selectively blocked by overexpression of Arf5-T31N. In contrast, a green fluorescent protein-arfophilin-2 chimera or arfophilin-2 deletions were localized around the centrosome in a region that was also enriched for transferrin receptors and Rab11 but not early endosome markers, suggesting that the distribution of the endosomal recycling compartment was altered. The arfophilins belong to a conserved family that includes Drosophila melanogaster nuclear fallout, a centrosomal protein required for cellularization. Expression of green fluorescent protein-nuclear fallout in HeLa cells resulted in a similar phenotype, indicative of functional homology and thus implicating the arfophilins in mitosis/cytokinesis. We suggest that the novel dual GTPase-binding capacity of the arfophilins could serve as an interface of signals from Rab and Arf GTPases to regulate membrane traffic and integrate distinct signals in the late endosomal recycling compartment.

Arf GTPase-activating Protein ASAP1 Interacts with Rab11 Effector FIP3 and Regulates Pericentrosomal Localization of Transferrin Receptor–positive Recycling Endosome

“…FIP3 preferentially binds to Arf6 and Arf5 (Shin et al, 2001;Hickson et al, 2003;Fielding et al, 2005). We found FIP3 interaction stimulates ASAP1 GAP activity against Arf1, but not against Arf6.…”

RalA-exocyst-dependent Recycling Endosome Trafficking Is Required for the Completion of Cytokinesis

“…2d) similar to certain RE proteins involved in vesicle trafficking during cytokinesis (19,20). Costaining of cells with ␣-tubulin revealed that RalA localized predominantly to the plasma membrane in mitosis, during which endosome recycling stops.…”

Molecular Characterization of Rab11 Interactions with Members of the Family of Rab11-interacting Proteins

“…Consistent with this idea, different FIPs are reported to interact with distinct sets of proteins that are known to regulate various endocytic pathways. For instance, FIP2 interacts with myosin Vb, whereas FIP3 and FIP4 bind to ADP-ribosylation factor GTPases, thereby generating putative Rab11⅐FIP2⅐myosin Vb or Rab11⅐FIP3⅐ADP-ribosylation factor complexes to regulate different transport steps and/or pathways (17,27).…”

“…Recently, several Rab11 effector proteins, Rip11, FIP2, 1 Rab-coupling protein (RCP), FIP3/eferin, and FIP4, were identified using biochemical and yeast two-hybrid methods (12)(13)(14)(15). In addition to Rab11 binding, FIP3 and FIP4 also interact with ADP-ribosylation factor GTPases, thereby coupling these small GTPase families, allowing for potential cross-talk between two signaling pathways (17). All FIPs have a conserved C-terminal motif that is known as the Rab11/25-binding domain (RBD) (18).…”