The Slp4-a Linker Domain Controls Exocytosis through Interaction with Munc18-1·Syntaxin-1a Complex

Tsuboi, Takashi; Fukuda, Mitsunori

doi:10.1091/mbc.e05-11-1047

Cited by 75 publications

(114 citation statements)

References 57 publications

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“…Fukuda proposed the assumed functions (38) based on studies using nonosteoblastic cells. (19,27,53,54) Referring to Fukuda's proposal, the function of each effector molecule in the stimulation-dependent RANKL release in osteoblastic cells can be hypothesized as follows: Slp5 regulates recruitment, which is the step before the docking of the RANKL-containing lysosomal vesicles to the plasma membrane; Slp4-a is involved in docking of the lysosomal vesicles to the plasma membrane; and Munc13-4 plays a role in vesicle fusion (Fig. 7).…”

Section: Discussionmentioning

confidence: 99%

Rab27a and Rab27b are involved in stimulation-dependent RANKL release from secretory lysosomes in osteoblastic cells

Kariya

Honma

Hanamura

et al. 2010

Journal of Bone and Mineral Research

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The quantity of the receptor activator of NF-kB ligand (RANKL) expressed at the cell surface of osteoblastic cells is an important factor regulating osteoclast activation. Previously, RANKL was found to be localized to secretory lysosomes in osteoblastic cells and to translocate to the cell surface in response to stimulation with RANK-Fc-conjugated beads. However, the in vivo significance of stimulation-dependent RANKL release has not been elucidated. In this study we show that small GTPases Rab27a and Rab27b are involved in the stimulation-dependent RANKL release pathway in osteoblastic cells. Suppression of either Rab27a or Rab27b resulted in a marked reduction in RANKL release after stimulation. Slp4-a, Slp5, and Munc13-4 acted as effector molecules that coordinated Rab27a/b activity in this pathway. Suppression of Rab27a/b or these effector molecules did not inhibit accumulation of RANKL in lysosomal vesicles around the stimulated sites but did inhibit the fusion of these vesicles to the plasma membrane. In osteoblastic cells, suppression of the effector molecules resulted in reduced osteoclastogenic ability. Furthermore, Jinx mice, which lack a functional Munc13-4 gene, exhibited a phenotype characterized by increased bone volume near the tibial metaphysis caused by low bone resorptive activity. In conclusion, stimulation-dependent RANKL release is mediated by Rab27a/b and their effector molecules, and this mechanism may be important for osteoclast activation in vivo. ß

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Section: Discussionmentioning

confidence: 99%

Rab27a and Rab27b are involved in stimulation-dependent RANKL release from secretory lysosomes in osteoblastic cells

Kariya

Honma

Hanamura

et al. 2010

Journal of Bone and Mineral Research

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“…Purified PCR products were directly inserted into the pGEM-T Easy vector. The cDNA inserts were sequenced by an automated sequencer and then subcloned into the pEF-T7 vector or pmRFP-C1 vector as described previously (15)(16)(17).…”

Section: Methodsmentioning

confidence: 99%

Large Scale Screening for Novel Rab Effectors Reveals Unexpected Broad Rab Binding Specificity

Fukuda

Kanno

Ishibashi

et al. 2008

Molecular & Cellular Proteomics

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Small GTPase Rab is generally thought to control intracellular membrane trafficking through interaction with specific effector molecules. Because of the large number of Rab isoforms in mammals, however, the effectors of most of the mammalian Rabs have never been identified, and the Rab binding specificity of the Rab effectors previously reported has never been thoroughly investigated. In this study we systematically screened for novel Rab effectors by a yeast two-hybrid assay with 28 different mouse or human Rabs (Rab1-30) as bait and identified 27 Rab-binding proteins, including 19 novel ones. We further investigated their Rab binding specificity by a yeast twohybrid assay with a panel of 60 different GTP-locked mouse or human Rabs. Unexpectedly most (17 of 27) of the Rab-binding proteins we identified exhibited broad Rab binding specificity and bound multiple Rab isoforms. As an example, inositol-polyphosphate 5-phosphatase OCRL (oculocerebrorenal syndrome of Lowe) bound the greatest number of Rabs (i.e. 16 distinct Rabs). Others, however, specifically recognized only a single Rab isoform or only two closely related Rab isoforms. The interaction of eight of the novel Rab-binding proteins identified (e.g. INPP5E and Cog4) with a specific Rab isoform was confirmed by co-immunoprecipitation assay and/or colocalization analysis in mammalian cell cultures, and the novel Rab2B-binding domain of Golgi-associated Rab2B interactor (GARI) and GARI-like proteins was identified by deletion and homology search analyses. The findings suggest that most Rab effectors (or Rab-binding proteins) regulate intracellular membrane trafficking through interaction with several Rab isoforms rather than through a single Rab isoform.

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“…Secretion occurs from these granules. Although restricted, the small jittering motions are regulated by Ca 2ϩ and ATP (14) and by various proteins (15)(16)(17)(18). Granules undergo exocytosis during nicotinic agonist stimulation without apparent biased movement closer toward the glass interface (14).…”

mentioning

confidence: 99%

Increased motion and travel, rather than stable docking, characterize the last moments before secretory granule fusion

Degtyar¹,

Allersma²,

Axelrod

et al. 2007

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

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The state of secretory granules immediately before fusion with the plasma membrane is unknown, although the granules are generally assumed to be stably bound (docked). We had previously developed methods using total internal reflection fluorescence microscopy and image analysis to determine the position of chromaffin granules immediately adjacent to the plasma membrane with high precision, often to within Ϸ10 nm, or <5% of the granule diameter (300 nm). These distances are of the dimensions of large proteins and are comparable with the unitary step sizes of molecular motors. Here we demonstrate with quantitative measures of granule travel in the plane parallel to the plasma membrane that secretory granules change position within several hundred milliseconds of nicotinic agonist-induced fusion. Furthermore, just before fusion, granules frequently move to areas that they have rarely visited. The movement of granules to new areas is most evident for granules that fuse later during the stimulus. The movement may increase the probability of productive interactions of the granule with the plasma membrane or may reflect the pull of molecular interactions between the granule and the plasma membrane that are part of the fusion process. Thus, instead of being stably docked before exocytosis, granules undergo molecularscale motions and travel immediately preceding the fusion event.chromaffin cells ͉ exocytosis ͉ granule motion ͉ total internal reflection fluorescence microscopy

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The Slp4-a Linker Domain Controls Exocytosis through Interaction with Munc18-1·Syntaxin-1a Complex

Cited by 75 publications

References 57 publications

Rab27a and Rab27b are involved in stimulation-dependent RANKL release from secretory lysosomes in osteoblastic cells

Rab27a and Rab27b are involved in stimulation-dependent RANKL release from secretory lysosomes in osteoblastic cells

Large Scale Screening for Novel Rab Effectors Reveals Unexpected Broad Rab Binding Specificity

Increased motion and travel, rather than stable docking, characterize the last moments before secretory granule fusion

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