Involvement of Rabphilin-3A in cortical granule exocytosis in mouse eggs.

Masumoto, Nobuyuki; Sasaki, Takuya; Tahara, Masahiro; Mammoto, Akiko; Ikebuchi, Yoshihide; Tasaka, Keiichi; Tokunaga, Masahiro; Takai, Yoshimi; Miyake, Akira

doi:10.1083/jcb.135.6.1741

Cited by 47 publications

(30 citation statements)

References 40 publications

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“…Rabphilin-3A can bind not only to Rab3A but also to Rab3B (Weber et al 1996). Rabphilin-3A positively regulates exocytosis in neuroendocrine cells (Chung et al 1995, Komuro et al 1996 and cortical granule exocytosis in eggs (Masumoto et al 1996). However, we found that Rabphilin-3A is not expressed in pituitary cells (not shown).…”

Section: Discussionmentioning

confidence: 59%

Rab3B is essential for GnRH-induced gonadotrophin release from anterior pituitary cells

Tasaka

Masumoto²,

Mizuki³

et al. 1998

Journal of Endocrinology

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Gonadotrophin-releasing hormone (GnRH) induces the release of gonadotrophins via an increase in cytosolic Ca 2+ concentration ([Ca 2+ ]). Rab3B, a member of the small GTP-binding protein Rab family, is known to be involved in Ca 2+ -regulated exocytosis in pituitary cells. However, it is not known whether Rab3B functions in the physiological process regulated by GnRH in gonadotrophs. In this study using antisense oligonucleotide against Rab3B (AS-Rab3B) we determined that Rab3B is involved in GnRH-induced gonadotrophin release. Rab3B immunopositive cells were reduced in 24% of pituitary cells by AS-Rab3B. This treatment did not affect the population of gonadotrophs or the intracellular contents of gonadotrophins. However, AS-Rab3B significantly inhibited the total amount of basal and GnRH-induced gonadotrophin released from pituitary cells. These results show that Rab3B is involved in basal and GnRH-induced gonadotrophins release but not the storage of gonadotrophins. Next, the changes in [Ca 2+ ] and exocytosis in gonadotrophs treated with AS-Rab3B were compared among Rab3B-positive and -negative cells. The change in [Ca 2+ ] was not different in the two groups, but exocytosis was significantly inhibited in Rab3B-negative cells. These results suggest that Rab3B is essential for GnRH-regulated exocytosis downstream of cytosolic Ca 2+ in gonadotrophs.

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Section: Discussionmentioning

confidence: 59%

Rab3B is essential for GnRH-induced gonadotrophin release from anterior pituitary cells

Tasaka

Masumoto²,

Mizuki³

et al. 1998

Journal of Endocrinology

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“…Rabphilin was originally identified as a specific GTP-Rab3A-binding protein on secretory granules (1,2) that is involved in the control of regulated secretion, including neurotransmitter release and hormone secretion (3)(4)(5)(6). Recent evidence, however, has indicated that rabphilin functions independently of Rab3A.…”

Section: ؉mentioning

confidence: 99%

The C2B Domain of Rabphilin Directly Interacts with SNAP-25 and Regulates the Docking Step of Dense Core Vesicle Exocytosis in PC12 Cells

Tsuboi¹,

Fukuda

2005

Journal of Biological Chemistry

141

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Rabphilin is a membrane trafficking protein on secretory vesicles that consists of an N-terminalRabphilin was originally identified as a specific GTP-Rab3A-binding protein on secretory granules (1, 2) that is involved in the control of regulated secretion, including neurotransmitter release and hormone secretion (3-6). Recent evidence, however, has indicated that rabphilin functions independently of Rab3A. First, rabphilin knock-out animals and Rab3 knock-out animals display distinct phenotypes in terms of neurotransmitter release (7,8). Second, rabphilin promotes dense core vesicle exocytosis by endocrine cells independently of Rab3A (9, 10). Third, we very recently found that an N-terminal Rab-binding domain (RBD) 3 of rabphilin also functions as an effector domain for Rab27A in PC12 cells (11)(12)(13)(14). Although the Rab binding properties of rabphilin have been well documented (1,(11)(12)(13)(14)(15)(16), the function of the C-terminal tandem C2 domains of rabphilin, upon ligand binding during regulated secretion remains largely unknown. Biochemical analysis has indicated that the C2 domains of rabphilin interact with phospholipids in a Ca 2ϩ -dependent manner (17-19), but how the Ca 2ϩ /phospholipid binding to the C2 domains of rabphilin triggers regulated secretion also remains unknown.The functional relationship between Rab27A⅐effector complex and SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) proteins, fundamental fusion machinery of vesicle exocytosis (20), have recently been reported. Slp4-a/granuphilin-a, another Rab27A effector that functions in certain endocrine cells (21-23) and parotid acinar cells (24), was reported to directly interact with syntaxin IA and/or Munc18-1 (23, 25, 26). In addition, the results of a genetic analysis of Caenorhabditis elegans rabphilin and SNARE (syntaxin, SNAP-25, or VAMP/synaptobrevin) double mutants have suggested that rabphilin modulates SNARE function (8). Thus, it is highly possible that rabphilin physically associates with SNARE proteins itself and/or SNARE-associated proteins but that possibility has never been investigated. In this study we systematically investigated the interaction between rabphilin and SNAREs and SNARE-associated proteins by coimmunoprecipitation assays and found that the C2B domain of rabphilin directly interacts with isolated SNAP-25, a target SNARE localized on the plasma membrane. Because there has never been a detailed description of the function of the C2B domain of rabphilin in the recruitment, docking, priming, and fusion of secretory vesicles in live cells, we also investigated the function of the C2B domain of rabphilin on the motion of a single dense core vesicle during exocytosis in PC12 cells by total internal reflection fluorescence microscopy (TIRF, also called evanescent wave or evanescence microscopy) (27) using vesicletargeted fluorescent proteins (28 -31). Expression of the rabphilin-⌬C2B mutant lacking SNAP-25 binding activity inhibited vesicle docking and markedly decreased the number...

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“…Rabphilin is a vesicle-associated protein which is recruited by rab3 and dissociates after GTP hydrolysis, and in the presence of GDI [260]. Microinjection of rabphilin or rabphilin fragments was shown to inhibit neurotransmitter release in squid giant axons and cortical granule release from mouse eggs [261,262], but both native and a membrane-anchored form of rabphilin induced insulin secretion from HIT-T15 cells [263]. RIM, on the other hand, localizes to the presynaptic active zones in synapses, but like rabphilin associates only with the GTP-bound form of rab3 [258].…”

Section: Nsf/snap and Lmamentioning

confidence: 99%

SNAREs and SNARE regulators in membrane fusion and exocytosis

Gerst¹

1999

CMLS, Cell. Mol. Life Sci.

207

153

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Eukaryotes have a remarkably well-conserved apparatus for the trafficking of proteins between intracellular compartments and delivery to their target organelles. This apparatus comprises the secretory (or 'protein export') pathway, which is responsible for the proper processing and delivery of proteins and lipids, and is essential for the derivation and maintenance of those organelles. Protein transport between intracellular compartments is mediated by carrier vesicles that bud from one organelle and fuse selectively with another. Therefore, organelle-specific trafficking of vesicles requires specialized proteins that regulate vesicle transport, docking and fusion. These proteins are generically termed SNAREs and comprise evolutionarily conserved families of membrane-associated proteins (i.e. the synaptobrevin/VAMP, syntaxin and SNAP-25 families) which mediate membrane fusion. SNAREs act at all levels of the secretory pathway, but individual family members tend to be compartment-specific and, thus, are thought to contribute to the specificity of docking and fusion events. In this review, we describe the different SNARE families which function in exocytosis, as well as discuss the role of possible negative regulators (e.g. 'SNARE-masters') in mediating events leading to membrane fusion. A model to illustrate the dynamic cycling of SNAREs between fusion-incompetent and fusion-competent states, called the SNARE cycle, is presented.

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Involvement of Rabphilin-3A in cortical granule exocytosis in mouse eggs.

Cited by 47 publications

References 40 publications

Rab3B is essential for GnRH-induced gonadotrophin release from anterior pituitary cells

Rab3B is essential for GnRH-induced gonadotrophin release from anterior pituitary cells

The C2B Domain of Rabphilin Directly Interacts with SNAP-25 and Regulates the Docking Step of Dense Core Vesicle Exocytosis in PC12 Cells

SNAREs and SNARE regulators in membrane fusion and exocytosis

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