Melanophilin directly links Rab27a and myosin Va through its distinct coiled‐coil regions

Nagashima, Kazuaki; Torii, Seiji; Yi, Zhaohong; Igarashi, Michihiro; Okamoto, Koichi; Takeuchi, Toshiyuki; Izumi, Tetsuro

doi:10.1016/s0014-5793(02)02634-0

Cited by 146 publications

(144 citation statements)

References 26 publications

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“…Thus, Rab27a may provide a regulatable molecular link that tethers melanosomes to the cortical actin network close to the plasma membrane (24,(46)(47)(48)(49). Although we have not been able to detect granuphilin by Western blotting in mouse urothelial lysates (unpublished data), it seems likely that umbrella cells contain granuphilin-related proteins or other Rab27b effectors that mediate similar cytoskeleton-anchoring functions for fusiform vesicles.…”

Section: Discussionmentioning

confidence: 88%

“…In melanocytes, Rab27a colocalized with melanosomes and was shown to associate via the granuphilin-related bridging molecule, melanophilin, with myosin Va, with which it also colocalized immunocytochemically (30,(46)(47)(48)(49). Thus, Rab27a may provide a regulatable molecular link that tethers melanosomes to the cortical actin network close to the plasma membrane (24,(46)(47)(48)(49).…”

Section: Discussionmentioning

confidence: 96%

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Rab27b is associated with fusiform vesicles and may be involved in targeting uroplakins to urothelial apical membranes

Chen

Guo

Deng

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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The terminally differentiated umbrella cells of bladder epithelium contain unique cytoplasmic organelles, the fusiform vesicles, which deliver preassembled crystalline arrays of uroplakin proteins to the apical cell surface of urothelial umbrella cells. We have investigated the possible role of Rab proteins in this delivery process, and found Rab27b to be expressed at an extraordinary high level (0.1% of total protein) in urothelium, whereas Rab27b levels were greatly reduced (to <5% of normal urothelium) in cultured urothelial cells, which synthesized only small amounts of uroplakins and failed to form fusiform vesicles. Immuno-electron microscopy showed that Rab27b was associated with the cytoplasmic face of the fusiform vesicles, but not with that of the apical plasma membrane. The association of Rab27b with fusiform vesicles and its differentiation-dependent expression suggest that this Rab protein plays a role in regulating the delivery of fusiform vesicles to the apical plasma membrane of umbrella cells.

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Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 96%

Rab27b is associated with fusiform vesicles and may be involved in targeting uroplakins to urothelial apical membranes

Chen

Guo

Deng

et al. 2003

Proc. Natl. Acad. Sci. U.S.A.

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“…MyoVa binds to Mlph's middle domain with its globular tail domain and the melanocyte-specific alternatively spliced exon F (MyoVa-BD) (15,65,66). The C terminus of Mlph harbors an ABD (23,24).…”

Section: Phosphorylation Of Pka Consensus Sites In Mlph's Abd Regulatesmentioning

confidence: 99%

“…The melanosome-bound small GTPase Rab27a associates in a GTPdependent manner with the adaptor protein Mlph. Mlph in turn links MyoVa to the melanosome to form a tripartite transport complex in vivo (11)(12)(13)(14)(15)(16)(17)(18). Importantly, a functional tripartite transport complex could be reconstituted from the Rab27a, Mlph, and MyoVa in vitro (19).…”

mentioning

confidence: 99%

Myosin Va’s adaptor protein melanophilin enforces track selection on the microtubule and actin networks in vitro

Oberhofer

Spieler

Rosenfeld

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Pigment organelles, or melanosomes, are transported by kinesin, dynein, and myosin motors. As such, melanosome transport is an excellent model system to study the functional relationship between the microtubule-and actin-based transport systems. In mammalian melanocytes, it is well known that the Rab27a/melanophilin/myosin Va complex mediates actin-based transport in vivo. However, pathways that regulate the overall directionality of melanosomes on the actin/microtubule networks have not yet been delineated. Here, we investigated the role of PKA-dependent phosphorylation on the activity of the actin-based Rab27a/melanophilin/myosin Va transport complex in vitro. We found that melanophilin, specifically its C-terminal actin-binding domain (ABD), is a target of PKA. Notably, in vitro phosphorylation of the ABD closely recapitulated the previously described in vivo phosphorylation pattern. Unexpectedly, we found that phosphorylation of the ABD affected neither the interaction of the complex with actin nor its movement along actin tracks. Surprisingly, the phosphorylation state of melanophilin was instead important for reversible association with microtubules in vitro. Dephosphorylated melanophilin preferred binding to microtubules even in the presence of actin, whereas phosphorylated melanophilin associated with actin. Indeed, when actin and microtubules were present simultaneously, melanophilin's phosphorylation state enforced track selection of the Rab27a/melanophilin/ myosin Va transport complex. Collectively, our results unmasked the regulatory dominance of the melanophilin adaptor protein over its associated motor and offer an unexpected mechanism by which filaments of the cytoskeletal network compete for the moving organelles to accomplish directional transport on the cytoskeleton in vivo.melanophilin | myosin Va | intracellular transport | transport regulation

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“…Pancreatic islets were isolated by pancreatic duct injection of collagenase solution as described previously . Immunoblotting, immunoprecipitation, and in vitro binding assay with GST fusion proteins were performed as described previously (Nagashima et al, 2002).…”

Section: Antibodies Immunostaining Immunoblotting and Immunoprecipmentioning

confidence: 99%

Exophilin4/Slp2-a Targets Glucagon Granules to the Plasma Membrane through Unique Ca²⁺-inhibitory Phospholipid-binding Activity of the C2A Domain

Kasai

Nagashima

et al. 2007

MBoC

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Rab27a and Rab27b have recently been recognized to play versatile roles in regulating the exocytosis of secretory granules and lysosome-related organelles by using multiple effector proteins. However, the precise roles of these effector proteins in particular cell types largely remain uncharacterized, except for those in pancreatic ␤ cells and in melanocytes. Here, we showed that one of the Rab27a/b effectors, exophilin4/Slp2-a, is specifically expressed in pancreatic ␣ cells, in contrast to another effector, granuphilin, in ␤ cells. Like granuphilin toward insulin granules, exophilin4 promotes the targeting of glucagon granules to the plasma membrane. Although the interaction of granuphilin with syntaxin-1a is critical for the targeting activity, exophilin4 does this primarily through the affinity of its C2A domain toward the plasma membrane phospholipids phosphatidylserine and phosphatidylinositol-4,5-bisphosphate. Notably, the binding activity to phosphatidylserine is inhibited by a physiological range of the Ca 2؉ concentration attained after secretagogue stimulation, which presents a striking contrast to the Ca 2؉ -stimulatory activity of the C2A domain of synaptotagmin I. Analyses of the mutant suggested that this novel Ca 2؉ -inhibitory phospholipid-binding activity not only mediates docking but also modulates the subsequent fusion of the secretory granules.

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Melanophilin directly links Rab27a and myosin Va through its distinct coiled‐coil regions

Cited by 146 publications

References 26 publications

Rab27b is associated with fusiform vesicles and may be involved in targeting uroplakins to urothelial apical membranes

Rab27b is associated with fusiform vesicles and may be involved in targeting uroplakins to urothelial apical membranes

Myosin Va’s adaptor protein melanophilin enforces track selection on the microtubule and actin networks in vitro

Exophilin4/Slp2-a Targets Glucagon Granules to the Plasma Membrane through Unique Ca²⁺-inhibitory Phospholipid-binding Activity of the C2A Domain

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Melanophilin directly links Rab27a and myosin Va through its distinct coiled‐coil regions

Cited by 146 publications

References 26 publications

Rab27b is associated with fusiform vesicles and may be involved in targeting uroplakins to urothelial apical membranes

Rab27b is associated with fusiform vesicles and may be involved in targeting uroplakins to urothelial apical membranes

Myosin Va’s adaptor protein melanophilin enforces track selection on the microtubule and actin networks in vitro

Exophilin4/Slp2-a Targets Glucagon Granules to the Plasma Membrane through Unique Ca2+-inhibitory Phospholipid-binding Activity of the C2A Domain

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Product

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Exophilin4/Slp2-a Targets Glucagon Granules to the Plasma Membrane through Unique Ca²⁺-inhibitory Phospholipid-binding Activity of the C2A Domain