Rab11 is required during Drosophila eye development

In an effort to identify the role of Rab11, a small GTP binding protein, during Drosophila differentiation, phenotypic manifestations associated with different alleles of Rab11 were studied. The phenotypes ranged from eye-defects, bristle abnormalities and sterility to lethality during various developmental stages. In this paper, our focus is targeted on eye defects caused by Rab11 mutations. A novel P-element insertion in the Rab11 locus, Rab11mo, displayed characteristic retinal anomalies, which could be reverted by P-element excision and expression of Rab11+ transgenes. During larval development, Rab11 is widely synthesized in photoreceptor cells and localizes to the rhabdomeres and lamina neuropil in adult eyes. Photoreceptors and associated bristles failed to be formed in homozygous clones generated in Rab11EP(3)3017 eyes. Decreased levels of Rab11 protein and increased cell death in Rab11mo third-instar larval eye-antennal discs suggest that the retinal defects originate during larval development. Our data indicate a requirement for Rab11 in ommatidial differentiation during Drosophila eye development.     

Tomato Rab11a characterization evidenced a difference between SYP121-dependent and SYP122-dependent exocytosis

The regulatory functions of Rab proteins in membrane trafficking lie in their ability to perform as molecular switches that oscillate between a GTP- and a GDP-bound conformation. The role of tomato LeRab11a in secretion was analyzed in tobacco protoplasts. Green fluorescent protein (GFP)/red fluorescent protein (RFP)-tagged LeRab11a was localized at the trans-Golgi network (TGN) in vivo. Two serines in the GTP-binding site of the protein were mutagenized, giving rise to the three mutants Rab11S22N, Rab11S27N and Rab11S22/27N. The double mutation reduced secretion of a marker protein, secRGUS (secreted rat beta-glucuronidase), by half, whereas each of the single mutations alone had a much smaller effect, showing that both serines have to be mutated to obtain a dominant negative effect on LeRab11a function. The dominant negative mutant was used to determine whether Rab11 is involved in the pathway(s) regulated by the plasma membrane syntaxins SYP121 and SYP122. Co-expression of either of these GFP-tagged syntaxins with the dominant negative Rab11S22/27N mutant led to the appearance of endosomes, but co-expression of GFP-tagged SYP122 also labeled the endoplasmic reticulum and dotted structures. However, co-expression of Rab11S22/27N with SYP121 dominant negative mutants decreased secretion of secRGUS further compared with the expression of Rab11S22/27N alone, whereas co-expression of Rab11S22/27N with SYP122 had no synergistic effect. With the same essay, the difference between SYP121- and SYP122-dependent secretion was then evidenced. The results suggest that Rab11 regulates anterograde transport from the TGN to the plasma membrane and strongly implicate SYP122, rather than SYP121. The differential effect of LeRab11a supports the possibility that SYP121 and SYP122 drive independent secretory events.     

Rab11-FIP2 regulates differentiable steps in transcytosis

Transcytosis through the apical recycling system of polarized cells is regulated by Rab11a and a series of Rab11a-interacting proteins. We have identified a point mutant in Rab11 family interacting protein 2 (Rab11-FIP2) that alters the function of Rab11a-containing trafficking systems. Rab11-FIP2(S229A/R413G) or Rab11-FIP2(R413G) cause the formation of a tubular cisternal structure containing Rab11a and decrease the rate of polymeric IgA transcytosis. The R413G mutation does not alter Rab11-FIP interactions with any known binding partners. Overexpression of Rab11-FIP2(S229A/R413G) alters the localization of a subpopulation of the apical membrane protein GP135. In contrast, Rab11-FIP2(129-512) alters the localization of early endosome protein EEA1. The distributions of both Rab11-FIP2(S229A/R413G) and Rab11-FIP2(129-512) were not dependent on the integrity of the microtubule cytoskeleton. The results indicate that Rab11-FIP2 regulates trafficking at multiple points within the apical recycling system of polarized cells. Rab11a; immunoglobulin A; trafficking; apical recycling; GP135; early endosome; EEA1; Eps15 homology domain     

Rab11b is essential for recycling of transferrin to the plasma membrane

Members of the Rab family of small GTPases play important roles in membrane trafficking along the exocytic and endocytic pathways. The Rab11 subfamily consists of two highly conserved members, Rab11a and Rab11b. Rab11a has been localized both to the pericentriolar recycling endosome and to the trans-Golgi network and functions in recycling of transferrin. However, the localization and function of Rab11b are completely unknown. In this study green fluorescent protein (GFP)-tagged Rab11b was used to determine its subcellular localization. GFP-Rab11b colocalized with internalized transferrin, and using different mutants of Rab11b, the role of this protein in transferrin uptake and recycling was examined. Two of these mutants, Rab11b-Q/L (constitutively active) and Rab11b-S/N (constitutively inactive), strongly inhibited the recycling of transferrin. Interestingly, both of them had no effect on transferrin uptake. In contrast, the C-terminally altered mutant Rab11b-DeltaC, which cannot be prenylated and therefore cannot interact with membranes, did not interfere with wild-type Rab11b function. From these data we concluded that functional Rab11b is essential for the transport of internalized transferrin from the recycling compartment to the plasma membrane.     

A Functional Interplay between the Small GTPase Rab11a and Mitochondria-shaping Proteins Regulates Mitochondrial Positioning and Polarization of the Actin Cytoskeleton Downstream of Src Family Kinases

It is believed that mitochondrial dynamics is coordinated with endosomal traffic rates during cytoskeletal remodeling, but the mechanisms involved are largely unknown. The adenovirus early region 4 ORF4 protein (E4orf4) subverts signaling by Src family kinases (SFK) to perturb cellular morphology, membrane traffic, and organellar dynamics and to trigger cell death. Using E4orf4 as a model, we uncovered a functional connection between mitochondria-shaping proteins and the small GTPase Rab11a, a key regulator of polarized transport via recycling endosomes. We found that E4orf4 induced dramatic changes in the morphology of mitochondria along with their mobilization at the vicinity of a polarized actin network typifying E4orf4 action, in a manner controlled by SFK and Rab11a. Mitochondrial remodeling was associated with increased proximity between Rab11a and mitochondrial membranes, changes in fusion-fission dynamics, and mitochondrial relocalization of the fission factor dynamin-related protein 1 (Drp1), which was regulated by the Rab11a effector protein FIP1/RCP. Knockdown of FIP1/RCP or inhibition of Drp1 markedly impaired mitochondrial remodeling and actin assembly, involving Rab11a-mediated mitochondrial dynamics in E4orf4-induced signaling. A similar mobilization of mitochondria near actin-rich structures was mediated by Rab11 and Drp1 in viral Src-transformed cells and contributed to the biogenesis of podosome rosettes. These findings suggest a role for Rab11a in the trafficking of Drp1 to mitochondria upon SFK activation and unravel a novel functional interplay between Rab11a and mitochondria during reshaping of the cell cytoskeleton, which would facilitate mitochondria redistribution near energy-requiring actin-rich structures.     

Circadian rhythms of feeding and drinking behavior of rats aged from 3 to 21 months

Circadian rhythms and patterns of feeding and drinking behavior of 8 male and 8 female Long-Evans rats were followed from 3 months of age (mo) to 21 mo at 3 month intervals. Meal number, draft number and feeding events/min/meal of female rats were greater than those of male rats of the same age, while intermeal intervals, interdraft intervals and licking events/min/draft of male rats were greater than those of female rats. Sex differences of meal number, intermeal intervals and feeding events/min/meal as a group disappeared by 21 mo. Light/dark differences of meal number of both sexes, intermeal intervals of females and licking events/min/draft of males as a group also disappeared by 21 mo and difference of feeding events/min/meal disappeared by 15 and 18 mo in males and females, respectively. Occurrence of age-related change varied from 6 to 21 mo depending upon the parameter of the behavior and period (light or dark). Meal number and feeding events/min/meal showed the most clear-cut age-related changes and the decline occurred earlier and was more remarkable in males than in females. The age-related decline of patterns and the power spectrum of drinking behavior was less prominent than that of feeding behavior. These results indicate that feeding behavior is more affected by the aging process than is the drinking behavior of rats, and that male rats show more prominent aging changes than females.(ABSTRACT TRUNCATED AT 250 WORDS)     

Rab14/MACF2 complex regulates endosomal targeting during cytokinesis

Abscission is a complex cellular process that is required for mitotic division. It is well established that coordinated and localized changes in actin and microtubule dynamics are vital for cytokinetic ring formation, as well as establishment of the abscission site. Actin cytoskeleton reorganization during abscission would not be possible without the interplay between Rab11- and Rab35-containing endosomes and their effector proteins, whose roles in regulating endocytic pathways at the cleavage furrow have now been studied extensively. Here, we identified Rab14 as a novel regulator of cytokinesis. We demonstrate that depletion of Rab14 causes either cytokinesis failure or significantly prolongs division time. We show that Rab14 contributes to the efficiency of recruiting Rab11-endosomes to the thin intracellular bridge (ICB) microtubules and that Rab14 knockout leads to inhibition of actin clearance at the abscission site. Finally, we demonstrate that Rab14 binds to microtubule minus-end interacting MACF2/CAMSAP3 complex and that this binding affects targeting of endosomes to the ICB microtubules. Collectively, our data identified Rab14 and MACF2/CAMSAP3 as proteins that regulate actin depolymerization and endosome targeting during cytokinesis.     

Genetic analysis of the Caenorhabditis elegans GLH family of P-granule proteins

The Vasa DEAD-box helicases are widespread markers of germ cells across species, and in some organisms have been shown to be essential for germ-cell formation and development. In contrast to the single Vasa gene in most systems analyzed, Caenorhabditis elegans has four Vasa family members, the germline helicases GLH-1, GLH-2, GLH-3, and GLH-4. Our analysis of deletion alleles of each glh gene demonstrates that GLH-1 is the key member of the family: loss of GLH-1 function causes sterility that is mainly maternal effect, is manifested predominantly at elevated temperature, and is due to reduced germ-cell proliferation and impaired formation of both sperm and oocytes. The other GLHs are not essential. However, GLH-4 serves redundant roles with GLH-1: loss of both genes' function causes glh-1-like sterility at all temperatures. Molecular epistasis analysis demonstrates that GLH-1 and GLH-4 are required for proper association of the PGL family of proteins with P granules, suggesting a pathway of P-granule assembly in which the GLHs are upstream of the PGL proteins and the mRNA cap-binding protein IFE-1. While loss of some P-granule components causes worms to be defective in RNA interference, loss of GLH-1 and GLH-4 does not compromise RNAi. Thus, RNAi likely does not require intact P granules but instead relies on particular P-granule factors. We discuss the evolution of the Vasa/GLH genes and current views of their functions and the assembly and roles of germ granules among species.     

Rab11‐FIP2 Interaction with MYO5B Regulates Movement of Rab11a‐Containing Recycling Vesicles

A tripartite association of Rab11a with both Rab11‐FIP2 and MYO5B regulates recycling endosome trafficking. We sought to define the intermolecular interactions required between Rab11‐FIP2 and MYO5B. Using a random mutagenesis strategy, we identified point mutations at S229P or G233E in Rab11‐FIP2 that caused loss of interaction with MYO5B in yeast two‐hybrid assays as well as loss of interaction of Rab11‐FIP2(129‐356) with MYO5B tail when expressed in HeLa cells. Single mutations or the double S229P/G233E mutation failed to alter the association of full‐length Rab11‐FIP2 with MYO5B tail in HeLa cells. While EGFP‐Rab11‐FIP2 wild type colocalized with endogenous MYO5B staining in MDCK cells, EGFP‐Rab11‐FIP2(S229P/G233E) showed a significant decrease in localization with endogenous MYO5B. Analysis of Rab11a‐containing vesicle movement in live HeLa cells demonstrated that when the MYO5B/Rab11‐FIP2 association is perturbed by mutation or by Rab11‐FIP2 knockdown, vesicle movement is increased in both speed and track length, consistent with an impairment of MYO5B tethering at the cytoskeleton. These results support a critical role for the interaction of MYO5B with Rab11‐FIP2 in stabilizing the functional complex with Rab11a, which regulates dynamic movements of membrane recycling vesicles.      

Rab11 polarization of the Drosophila oocyte: a novel link between membrane trafficking, microtubule organization, and oskar mRNA localization and translation.

The Drosophila embryonic body plan is specified by asymmetries that arise in the oocyte during oogenesis. These asymmetries are apparent in the subcellular distribution of key mRNAs and proteins and in the organization of the microtubule cytoskeleton. We present evidence that the Drosophila oocyte also contains important asymmetries in its membrane trafficking pathways. Specifically, we show that alpha-adaptin and Rab11, which function critically in the endocytic pathways of all previously examined animal cells, are localized to neighboring compartments at the posterior pole of stage 8-10 oocytes. Rab11 and alpha-adaptin localization occurs in the absence of a polarized microtubule cytoskeleton, i.e. in grk null mutants, but is later reinforced and/or refined by Osk, the localization of which is microtubule dependent. Analyses of germline clones of a rab11 partial loss-of-function mutation reveal a requirement for Rab11 in endocytic recycling and in the organization of posterior membrane compartments. Such analyses also reveal a requirement for Rab11 in the organization of microtubule plus ends and osk mRNA localization and translation. We propose that microtubule plus ends and, possibly, translation factors for osk mRNA are anchored to posterior membrane compartments that are defined by Rab11-mediated trafficking and reinforced by Rab11-Osk interactions.     

A Highlights from MBoC Selection: A Rab11a-Rab8a-Myo5B network promotes stretch-regulated exocytosis in bladder umbrella cells

Multiple Rabs are associated with secretory granules/vesicles, but how these GTPases are coordinated to promote regulated exocytosis is not well understood. In bladder umbrella cells a subapical pool of discoidal/fusiform-shaped vesicles (DFVs) undergoes Rab11a-dependent regulated exocytosis in response to bladder filling. We show that Rab11a-associated vesicles are enmeshed in an apical cytokeratin meshwork and that Rab11a likely acts upstream of Rab8a to promote exocytosis. Surprisingly, expression of Rabin8, a previously described Rab11a effector and guanine nucleotide exchange factor for Rab8, stimulates stretch-induced exocytosis in a manner that is independent of its catalytic activity. Additional studies demonstrate that the unconventional motor protein myosin5B motor (Myo5B) works in association with the Rab8a–Rab11a module to promote exocytosis, possibly by ensuring transit of DFVs through a subapical, cortical actin cytoskeleton before fusion. Our results indicate that Rab11a, Rab8a, and Myo5B function as part of a network to promote stretch-induced exocytosis, and we predict that similarly organized Rab networks will be common to other regulated secretory pathways.     

Arfophilins are dual Arf/Rab 11 binding proteins that regulate recycling endosome distribution and are related to Drosophila nuclear fallout

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.     

The p85alpha subunit of phosphatidylinositol 3'-kinase binds to and stimulates the GTPase activity of Rab proteins

Rab5 and Rab4 are small monomeric GTPases localized on early endosomes and function in vesicle fusion events. These Rab proteins regulate the endocytosis and recycling or degradation of activated receptor tyrosine kinases such as the platelet-derived growth factor receptor (PDGFR). The p85alpha subunit of phosphatidylinositol 3'-kinase contains a BH domain with sequence homology to GTPase activating proteins (GAPs), but has not previously been shown to possess GAP activity. In this report, we demonstrate that p85alpha has GAP activity toward Rab5, Rab4, Cdc42, Rac1 and to a lesser extent Rab6, with little GAP activity toward Rab11. Purified recombinant Rab5 and p85alpha can bind directly to each other and not surprisingly, the p85alpha-encoded GAP activity is present in the BH domain. Because p85alpha stays bound to the PDGFR during receptor endocytosis, p85alpha will also be localized to the same early endosomal compartment as Rab5 and Rab4. Taken together, the physical co-localization and the ability of p85alpha to preferentially stimulate the down-regulation of Rab5 and Rab4 GTPases suggests that p85alpha regulates how long Rab5 and Rab4 remain in their GTP-bound active state. Cells expressing BH domain mutants of p85 show a reduced rate of PDGFR degradation as compared with wild type p85 expressing cells. These cells also show sustained activation of the mitogen-activated protein kinase and Akt pathways. Thus, the p85alpha protein may play a role in the down-regulation of activated receptors through its temporal control of the GTPase cycles of Rab5 and Rab4.     

Photoactivation Approaches Reveal a Role for Rab11 in FGFR4 Recycling and Signalling

Fibroblast growth factor receptor 4 (FGFR4) plays important roles during development and in the adult to maintain tissue homeostasis. Moreover, overexpression of FGFR4 or activating mutations in FGFR4 has been identified as tumour‐promoting events in several forms of cancer. Endocytosis is important for regulation of signalling receptors and we have previously shown that FGFR4 is mainly localized to transferrin‐positive structures after ligand‐induced endocytosis. Here, using a cell line with a defined pericentriolar endocytic recycling compartment, we show that FGFR4 accumulates in this compartment after endocytosis. Furthermore, using classical recycling assays and a new, photoactivatable FGFR4‐PA‐GFP fusion protein combined with live‐cell imaging, we demonstrate that recycling of FGFR4 is dependent on Rab11. Upon Rab11b depletion, FGFR4 is trapped in the pericentriolar recycling compartment and the total levels of FGFR4 in cells are increased. Moreover, fibroblast growth factor 1 (FGF1)‐induced autophosphorylation of FGFR4 as well as phosphorylation of phospholipase C (PLC)‐γ is prolonged in cells depleted of Rab11. Interestingly, the activation of mitogen‐activated protein kinase and AKT pathways were not prolonged but rather reduced in Rab11‐depleted cells, indicating that recycling of FGFR4 is important for the nature of its signalling output. Thus, Rab11‐dependent recycling of FGFR4 maintains proper levels of FGFR4 in cells and regulates FGF1‐induced FGFR4 signalling.      

Rac1‐Rab11‐FIP3 regulatory hub coordinates vesicle traffic with actin remodeling and T‐cell activation

The immunological synapse generation and function is the result of a T‐cell polarization process that depends on the orchestrated action of the actin and microtubule cytoskeleton and of intracellular vesicle traffic. However, how these events are coordinated is ill defined. Since Rab and Rho families of GTPases control intracellular vesicle traffic and cytoskeleton reorganization, respectively, we investigated their possible interplay. We show here that a significant fraction of Rac1 is associated with Rab11‐positive recycling endosomes. Moreover, the Rab11 effector FIP3 controls Rac1 intracellular localization and Rac1 targeting to the immunological synapse. FIP3 regulates, in a Rac1‐dependent manner, key morphological events, like T‐cell spreading and synapse symmetry. Finally, Rab11‐/FIP3‐mediated regulation is necessary for T‐cell activation leading to cytokine production. Therefore, Rac1 endosomal traffic is key to regulate T‐cell activation.     

Rab40–Cullin5 complex regulates EPLIN and actin cytoskeleton dynamics during cell migration

Rab40b is a SOCS box–containing protein that regulates the secretion of MMPs to facilitate extracellular matrix remodeling during cell migration. Here, we show that Rab40b interacts with Cullin5 via the Rab40b SOCS domain. We demonstrate that loss of Rab40b–Cullin5 binding decreases cell motility and invasive potential and show that defective cell migration and invasion stem from alteration to the actin cytoskeleton, leading to decreased invadopodia formation, decreased actin dynamics at the leading edge, and an increase in stress fibers. We also show that these stress fibers anchor at less dynamic, more stable focal adhesions. Mechanistically, changes in the cytoskeleton and focal adhesion dynamics are mediated in part by EPLIN, which we demonstrate to be a binding partner of Rab40b and a target for Rab40b–Cullin5-dependent localized ubiquitylation and degradation. Thus, we propose a model where Rab40b–Cullin5-dependent ubiquitylation regulates EPLIN localization to promote cell migration and invasion by altering focal adhesion and cytoskeletal dynamics.     

The novel Rab11-FIP/Rip/RCP family of proteins displays extensive homo- and hetero-interacting abilities

The Rab11-FIP/Rip/RCP proteins are a recently described novel protein family, whose members interact with Rab GTPases that function in endosomal recycling. To date, five such proteins have been described in humans, all of which interact with Rab11, and one (RCP) also interacts with Rab4. Here, we characterise several of these proteins with respect to their ability to interact with Rab4, as well as their ability to self-interact, and to interact with each other. We now demonstrate that two of the family members-pp75/Rip11 and Rab11-FIP3 do not bind Rab4 and show that several members of the family can self-interact and interact with each other. These interactions primarily involve their C-terminal end which includes the Rab binding domain (RBD) that is contained within a predicted coiled-coil, or ERM motif. We identify a new (sixth) member of the protein family, which we propose to name Rab11-FIP4, and report the family evolutionary complexity and chromosomal distribution. Furthermore, we propose that the ability of these proteins to bind each other will be important in effecting membrane trafficking events by forming protein 'platforms,' regulated by Rab11 and/or Rab4 activity.     

Unusual sex roles in a highly promiscuous parrot: the Greater Vasa Parrot Caracopsis vasa

We describe the unusual mating system of the Greater Vasa Parrot Caracopsis vasa . The dull black plumage of males and females is similar but females are significantly larger than males. Females are promiscuous and copulated with at least five different males. Copulations were either short (1–3 s) or very long (mean 35.9 min), and long copulations involved a copulatory tie facilitated by the male's enlarged cloacal protrusion. Multilocus DNA fingerprinting of 17 broods showed that all were of mixed paternity, and that some broods had three fathers. Males never visited nests directly, but during the incubation and chick-rearing periods females came off the nest and were fed regurgitated fruit by multiple males. Four had band-sharing coefficients that suggested they were unrelated. Males copulated with and provided food for several widely separated females simultaneously. During the chick-rearing period females defended a territory around the nest from conspecific females, developed conspicuous orange skin on the head (through feather loss), and uttered loud, complex vocalizations that we refer to as 'song' from prominent perches near the nest. Males showed none of these traits. Females with high song rates attracted more males and as a result received more food than other females. Play-back experiments in which female song rates were either increased or decreased, attracted more or fewer males respectively. We propose that female song, conspicuous head colour and territoriality have all evolved as a result of competition between females for the food provided by males. The selective pressures favouring this highly unusual breeding system in the Greater Vasa Parrot are unclear but some sort of ecological constraint, such as food availability, may be important.     

GRAB is a binding partner for the Rab11a and Rab11b GTPases

Co-ordination of Rab GTPase function has emerged as a crucial mechanism in the control of intracellular trafficking processes in eukaryotic cells. Here, we show that GRAB/Rab3IL1 [guanine nucleotide exchange factor for Rab3A; RAB3A interacting protein (rabin3)-like 1], a protein that has previously be shown to act as a GEF (guanine nucleotide exchange factor) for Rab3a, Rab8a and Rab8b, is also a binding partner for Rab11a and Rab11b, but not the closely related Rab25 GTPase. We demonstrate that exogenous expression of Rab11a and Rab11b shift GRAB’s distribution from the cytoplasm onto membranes. We find that the Rab11a/Rab11b-binding region of GRAB lies within its carboxy-terminus, a region distinct from its GEF domain and Rab3a-binding region. Finally, we describe a GRAB deletion mutant (GRAB_Δ223–228) that is deficient in Rab11-binding ability. These data identify GRAB as a dual Rab-binding protein that could potentially link Rab3 and Rab11 and/or Rab8 and Rab11-mediated intracellular trafficking processes.     

Rab11-FIP3 is critical for the structural integrity of the endosomal recycling compartment

Rab11-FIP3 is an endosomal recycling compartment (ERC) protein that is implicated in the process of membrane delivery from the ERC to sites of membrane insertion during cell division. Here we report that Rab11-FIP3 is critical for the structural integrity of the ERC during interphase. We demonstrate that knockdown of Rab11-FIP3 and expression of a mutant of Rab11-FIP3 that is Rab11-binding deficient cause loss of all ERC-marker protein staining from the pericentrosomal region of A431 cells. Furthermore, we find that fluorophore-labelled transferrin cannot access the pericentrosomal region of cells in which Rab11-FIP3 function has been perturbed. We find that this Rab11-FIP3 function appears to be specific because expression of the equivalent Rab11-binding deficient mutant of Rab-coupling protein does not perturb ERC morphology. In addition, we find that other organelles such as sorting and late endosomes are unaffected by loss of Rab11-FIP3 function. Finally, we demonstrate the presence of an extensive coiled-coil region between residues 463 and 692 of Rab11-FIP3, which exists as a dimer in solution and is critical to support its function on the ERC. Together, these data indicate that Rab11-FIP3 is necessary for the structural integrity of the pericentrosomal ERC.