Mutant rab8 Impairs Docking and Fusion of Rhodopsin-bearing Post-Golgi Membranes and Causes Cell Death of Transgenic<i>Xenopus</i>Rods

Moritz, Orson L.; Tam, Beatrice M.; Hurd, Larry L.; Peränen, Johan; Deretic, Dusanka; Papermaster, David S.

doi:10.1091/mbc.12.8.2341

Cited by 221 publications

(226 citation statements)

References 47 publications

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“…The Rab8 small GTPase has been shown to be required for docking and fusion of rhodopsin-containing post-Golgi vesicles at the base of the photoreceptor outer segment and is also required for ciliary localization of other GPCRs (Deretic et al 1995;Moritz et al 2001;Kaplan et al 2010;Mukhopadhyay et al 2010). Similarly, the Arl13 and Arl3 Arf-family small GTPases (Zhang et al 2013) play roles in ciliary transmembrane protein targeting and localization in C. elegans sensory neurons and in mammalian cells (Schrick et al 2006;Larkins et al 2011;Humbert et al 2012;Li et al 2012;Schwarz et al 2012).…”

Section: Resultsmentioning

confidence: 99%

Diverse Cell Type-Specific Mechanisms Localize G Protein-Coupled Receptors to Caenorhabditis elegans Sensory Cilia

Brear

Yoon

Wojtyniak³

et al. 2014

Genetics

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The localization of signaling molecules such as G protein-coupled receptors (GPCRs) to primary cilia is essential for correct signal transduction. Detailed studies over the past decade have begun to elucidate the diverse sequences and trafficking mechanisms that sort and transport GPCRs to the ciliary compartment. However, a systematic analysis of the pathways required for ciliary targeting of multiple GPCRs in different cell types in vivo has not been reported. Here we describe the sequences and proteins required to localize GPCRs to the cilia of the AWB and ASK sensory neuron types in Caenorhabditis elegans. We find that GPCRs expressed in AWB or ASK utilize conserved and novel sequences for ciliary localization, and that the requirement for a ciliary targeting sequence in a given GPCR is different in different neuron types. Consistent with the presence of multiple ciliary targeting sequences, we identify diverse proteins required for ciliary localization of individual GPCRs in AWB and ASK. In particular, we show that the TUB-1 Tubby protein is required for ciliary localization of a subset of GPCRs, implying that defects in GPCR localization may be causal to the metabolic phenotypes of tub-1 mutants. Together, our results describe a remarkable complexity of mechanisms that act in a protein-and cellspecific manner to localize GPCRs to cilia, and suggest that this diversity allows for precise regulation of GPCR-mediated signaling as a function of external and internal context. SIGNALING molecules must be precisely localized to specific subcellular domains to optimize detection and transduction of external stimuli. G protein-coupled receptors (GPCRs) comprise a large family of transmembrane signaling proteins that directly bind and transduce a range of cues including photons, odorants, neurotransmitters, and peptides (Pierce et al. 2002;Kato and Touhara 2009;Demaria and Ngai 2010;Sung and Chuang 2010;Chamero et al. 2012;Frooninckx et al. 2012;Montell 2012;Bathgate et al. 2013). Regulation of GPCR function, including regulation of membrane targeting and trafficking to specific subcellular regions, is a major contributor to the tuning of signaling efficacy and fidelity (e.g., Deretic et al. 1995;Ango et al. 2000;Xia et al. 2003;Esseltine et al. 2012;. However, much remains to be understood regarding the mechanisms by which GPCR trafficking and membrane localization are regulated.GPCR-mediated signal transduction in many cellular contexts requires these proteins to be localized to specialized microtubule-based primary cilia. For example, in photoreceptors and olfactory neurons, efficient sensory signal transduction is mediated via localization of rhodopsin and olfactory receptors, together with other signaling molecules, to photoreceptor outer segments and olfactory neuron cilia, respectively (Insinna and Besharse 2008;Berbari et al. 2009;Pifferi et al. 2010;Deretic and Wang 2012). Receptors in the Hedgehog (Hh) morphogen signaling pathway such as the Smoothened and Patched transmembrane proteins, and the G...

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Section: Resultsmentioning

confidence: 99%

Diverse Cell Type-Specific Mechanisms Localize G Protein-Coupled Receptors to Caenorhabditis elegans Sensory Cilia

Brear

Yoon

Wojtyniak³

et al. 2014

Genetics

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“…Differentiation between these possibilities will have to await further analysis. It is thus not inconceivable that Rab8 may accompany a variety of cargoes out of the TGN, even to differing targets (Deretic et al, 1995;Moritz et al, 2001). For example, in addition to basolateral traffic, Rab8 has been implicated in TGN-to-primary cilium traffic (Nachury et al, 2007).…”

Section: Resultsmentioning

confidence: 99%

“…More than 60 known Rabs collectively regulate the flow of nearly all membrane traffic within the cell (Pfeffer, 1994;Gurkan et al, 2005;Jordens et al, 2005). Of these, mammalian Rab8 has been associated with the flow of newly synthesized proteins to the basolateral surface in polarized epithelial cells (Huber et al, 1993b;Moritz et al, 2001). In yeast, the Rab8 homolog, sec4, is also required for the targeting of membrane traffic to the plasma membrane (Guo et al, 1999).…”

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confidence: 99%

Rab8 Regulates Basolateral Secretory, But Not Recycling, Traffic at the Recycling Endosome

Henry

Sheff

2008

MBoC

110

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Rab8 is a monomeric GTPase that regulates the delivery of newly synthesized proteins to the basolateral surface in polarized epithelial cells. Recent publications have demonstrated that basolateral proteins interacting with the 1-B clathrin adapter subunit pass through the recycling endosome (RE) en route from the TGN to the plasma membrane. Because Rab8 interacts with these basolateral proteins, these findings raise the question of whether Rab8 acts before, at, or after the RE. We find that Rab8 overexpression during the formation of polarity in MDCK cells, disrupts polarization of the cell, explaining how Rab8 mutants can disrupt basolateral endocytic and secretory traffic. However, once cells are polarized, Rab8 mutants cause mis-sorting of newly synthesized basolateral proteins such as VSV-G to the apical surface, but do not cause mis-sorting of membrane proteins already at the cell surface or in the endocytic recycling pathway. Enzymatic ablation of the RE also prevents traffic from the TGN from reaching the RE and similarly results in mis-sorting of newly synthesized VSV-G. We conclude that Rab8 regulates biosynthetic traffic through REs to the plasma membrane, but not trafficking of endocytic cargo through the RE. The data are consistent with a model in which Rab8 functions in regulating the delivery of TGN-derived cargo to REs. INTRODUCTIONThe Rab proteins are small monomeric GTPases of the Ras family. More than 60 known Rabs collectively regulate the flow of nearly all membrane traffic within the cell (Pfeffer, 1994;Gurkan et al., 2005;Jordens et al., 2005). Of these, mammalian Rab8 has been associated with the flow of newly synthesized proteins to the basolateral surface in polarized epithelial cells (Huber et al., 1993b;Moritz et al., 2001). In yeast, the Rab8 homolog, sec4, is also required for the targeting of membrane traffic to the plasma membrane (Guo et al., 1999). It has been suggested that Rab8 may be active in delivery of secretory cargo from the TGN to the plasma membrane. (Chen et al., 1993;Huber et al., 1993b). Studies of vesicular stomatitis virus protein G (VSV-G) delivery from the trans-Golgi network (TGN) have suggested that this process is regulated by Rab8, as dominant-negative (DN) mutants of Rab8 interfere with the delivery of basolateral cargo (Huber et al., 1993b). Rab8 is not localized to the TGN; rather it is localized at or near the recycling endosome (RE) in both polarized and nonpolarized cells (Hattula et al., 2006; Roland et al., 2007). The function of Rab8 at the RE is likely to regulate recycling of membrane traffic, although its role in polarized sorting is not clear. Rab8 is not required for the delivery of all basolateral proteins, but appears to be obligatory in the case of those that bear a tyrosine-dependent basolateral-sorting determinant capable of interacting with the clathrin adapter 1-B (Ang et al., 2003). The basolateral TGN-to-plasma membrane trafficking pathway is not as direct as once thought. Recent reports demonstrate clearly that 1-B-dependent basolater...

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“…First, expression of activated Rab8 or Rabin8 promotes reorganization of actin and cell shape (Armstrong et al, 1996;Peränen et al, 1996;Hattula and Peränen, 2000;Chen et al, 2001; this report). Furthermore, mutant Rab8 causes cell death of transgenic Xenopus rods (Moritz et al, 2001) and depletion of Rab8 from primary neurons inhibits neurite outgrowth (Huber et al, 1995). Second, Rab8 interacts with FIP-2 (optineurin) that also modulates cell morphogenesis and links Rab8 to the huntingtin protein (Li et al, 1998;Hattula and Peränen, 2000).…”

Section: Discussionmentioning

confidence: 99%

A Rab8-specific GDP/GTP Exchange Factor Is Involved in Actin Remodeling and Polarized Membrane Transport

Hattula

Furuhjelm

Arffman

et al. 2002

MBoC

Self Cite

191

220

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The mechanisms mediating polarized delivery of vesicles to cell surface domains are poorly understood in animal cells. We have previously shown that expression of Rab8 promotes the formation of new cell surface domains through reorganization of actin and microtubules. To unravel the function of Rab8, we used the yeast two-hybrid system to search for potential Rab8-specific activators. We identified a coil-coiled protein (Rabin8), homologous to the rat Rabin3 that stimulated nucleotide exchange on Rab8 but not on Rab3A and Rab5. Furthermore, we show that rat Rabin3 has exchange activity on Rab8 but not on Rab3A, supporting the view that rat Rabin3 is the rat equivalent of human Rabin8. Rabin8 localized to the cortical actin and expression of Rabin8 resulted in remodeling of actin and the formation of polarized cell surface domains. Activation of PKC by phorbol esters enhanced translocation of both Rabin8 and Rab8-specific vesicles to the outer edge of lamellipodial structures. Moreover, coexpression of Rabin8 with dominant negative Rab8 (T22N) redistributes Rabin8 from cortical actin to Rab8-specific vesicles and promotes their polarized transport to cell protrusions. The C-terminal region of Rabin8 plays an essential role in this transport. We propose that Rabin8 is a Rab8-specific activator that is connected to processes that mediate polarized membrane traffic to dynamic cell surface structures.

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Mutant rab8 Impairs Docking and Fusion of Rhodopsin-bearing Post-Golgi Membranes and Causes Cell Death of TransgenicXenopusRods

Cited by 221 publications

References 47 publications

Diverse Cell Type-Specific Mechanisms Localize G Protein-Coupled Receptors to Caenorhabditis elegans Sensory Cilia

Diverse Cell Type-Specific Mechanisms Localize G Protein-Coupled Receptors to Caenorhabditis elegans Sensory Cilia

Rab8 Regulates Basolateral Secretory, But Not Recycling, Traffic at the Recycling Endosome

A Rab8-specific GDP/GTP Exchange Factor Is Involved in Actin Remodeling and Polarized Membrane Transport

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