Interactions between proteins implicated in exocytosis and voltage–gated calcium channels

Seagar, Michael; Lévêque, Christian; Charvin, Nathalie; Marqueze, B; Martin-Moutôt, Nicole; Boudier, Jean-Louis; Shoji-Kasai, Yoko; Sato, Kazuki; Takahashi, Masami

doi:10.1098/rstb.1999.0380

Cited by 80 publications

(56 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…For example, Syt III may sense an increase in intracellular Ca 2ϩ due to influx of extracellular Ca 2ϩ , whereas Syt VII may be relevant when intracellular Ca 2ϩ elevation is induced by intracellular mobilization through inositol 1,4,5-trisphosphate receptors. It has been demonstrated that synaptotagmin directly interacts with N-type (49 -57) or P/Q-type (19,54,55) Ca 2ϩ channels in neurons and Lc-type Ca 2ϩ channels (20). Inositol 1,4,5-trisphosphate receptors are present in pancreatic ␤-cells; however, it is currently unclear whether they associate with synaptotagmin.…”

Section: Discussionmentioning

confidence: 99%

Synaptotagmin III/VII Isoforms Mediate Ca2+-induced Insulin Secretion in Pancreatic Islet β-Cells

Gao¹,

Reavey‐Cantwell²,

Young

et al. 2000

Journal of Biological Chemistry

104

124

View full text Add to dashboard Cite

Synaptotagmins (Syt) play important roles in Ca2؉ -induced neuroexocytosis. Insulin secretion of the pancreatic ␤-cell is dependent on an increase in intracellular Ca 2؉ ; however, Syt involvement in insulin exocytosis is poorly understood. Reverse transcriptase-polymerase chain reaction studies showed the presence of Syt isoforms III, IV, V, and VII in rat pancreatic islets, whereas Syt isoforms I, II, III, IV, V, VII, and VIII were present in insulin-secreting ␤TC3 cell. Syt III and VII proteins were identified in rat islets and ␤TC3 and RINm5F ␤-cells by immunoblotting. Confocal microscopy showed that Syt III and VII co-localized with insulin-containing secretory granules. Two-fold overexpression of Syt III in RINm5F ␤-cell (Syt III cell) was achieved by stable transfection, which conferred greater Ca 2؉ sensitivity for exocytosis, and resulted in increased insulin secretion. Glyceraldehyde ؉ carbachol-induced insulin secretion in Syt III cells was 2.5-fold higher than control empty vector cells, whereas potassium-induced secretion was 6-fold higher. In permeabilized Syt III cells, Ca 2؉ -induced and mastoparan-induced insulin secretion was also increased. In Syt VII-overexpressing RINm5F ␤-cells, there was amplification of carbachol-induced insulin secretion in intact cells and of Ca 2؉ -induced and mastoparan-induced insulin secretion in permeabilized cells. In conclusion, Syt III/VII are located in insulincontaining secretory granules, and we suggest that Syt III/VII may be the Ca 2؉ sensor or one of the Ca 2؉ sensors for insulin exocytosis of the ␤-cell.Insulin exocytosis from the ␤-cell of the islets of Langerhans is stimulated by various physiological secretagogues that include glucose, amino acids, and receptor-mediated agonists such as acetylcholine, cholecystokinin, and glucagon like-peptide 1 (1-7). A common mechanism of action for these secretagogues is to cause an increase in cytosolic Ca 2ϩ . Elevation of intracellular Ca 2ϩ is due to an influx of extracellular Ca 2ϩ through voltage-dependent L-type Ca 2ϩ channel and/or mobilization of intracellular Ca 2ϩ from the endoplasmic reticulum (8 -17). However, the mechanisms by which Ca 2ϩ induces insulin granule fusion with the plasma membrane of ␤-cell remain unclear (1,16,18,20,21).1 is a family of membrane proteins initially found to be expressed in brain. At the present, 11 members of Syt have been identified (22,23). The Syt molecule has a single transmembrane domain and two Ca 2ϩ regulatory C 2 domains. The C 2 domains mediate Ca 2ϩ -dependent and Ca 2ϩ -independent interactions with target molecules that may regulate membrane fusion and membrane budding reactions (24,25). Literature concerning the expression and functions of Syt in pancreatic ␤-cell is very limited and contradictory. In an earlier study (26), Syt was found in the non-␤-cell of the islet mantle, but not in the ␤-cell, using a non-isoform-specific antibody, and the mRNAs of Syt A and B were absent in mouse pancreatic ␤-cell and RINm5F cells as demonstrated by in situ hybridization...

show abstract

Section: Discussionmentioning

confidence: 99%

Synaptotagmin III/VII Isoforms Mediate Ca2+-induced Insulin Secretion in Pancreatic Islet β-Cells

Gao¹,

Reavey‐Cantwell²,

Young

et al. 2000

Journal of Biological Chemistry

104

124

View full text Add to dashboard Cite

show abstract

“…(iii) The chaperone hsp70 is well known to interact with cysteine string proteins as syntaxin, synaptotagmin and SNAP-25 [37]. Synaptotagmin functionally interacts with Ca v 2.3d containing E-/ R-type voltage-gated Ca 2+ channels recruiting the protein complex to the plasma membrane of Xenopus oocytes which only would be possible according to panel B [34,35].…”

Section: Discussionmentioning

confidence: 99%

The Molecular Chaperone hsp70 Interacts with the Cytosolic II-III Loop of the Cav2.3 E-type Voltagegated Ca2+ Channel

Krieger

Kanthavel

Pereverzev

et al. 2006

Cell Physiol Biochem

View full text Add to dashboard Cite

Multiple types of voltage-activated Ca2+ channels (T, L, N, P, Q, R type) coexist in excitable cells and participate in synaptic differentiation, secretion, transmitter release, and neuronal plasticity. Ca2+ ions entering cells trigger these events through their interaction with the ion channel itself or through Ca2+ binding to target proteins initiating signalling cascades at cytosolic loops of the ion conducting subunit (Cava1). These loops interact with target proteins in a Ca2+-dependent or independent manner. In Cav2.3-containing channels the cytosolic linker between domains II and III confers a novel Ca2+ sensitivity to E-type Ca2+ channels including phorbol ester sensitive signalling via protein kinase C (PKC) in Cav2.3 transfected HEK-293 cells. To understand Ca2+ and phorbol ester mediated activation of Cav2.3 Ca2+ channels, protein interaction partners of the II-III loop were identified. FLAG-tagged II-III - loop of human Cav2.3 was over-expressed in HEK 293 cells, and the molecular chaperone hsp70, which is known to interact with PKC, was identified as a novel functional interaction partner. Immunopurified II-III loop-protein of neuronal and endocrine Cav2.3 splice variants stimulate autophosphorylation of PKCa, leading to the suggestion that hsp70 - binding to the II-III loop - may act as an adaptor for Ca2+ dependent targeting of PKC to E-type Ca2+ channels.

show abstract

“…This interaction might serve as a molecular link between synaptic vesicles and the calcium channels and in addition might modulate channel function (Seagar et al, 1999). To investigate the functional consequences of Syt1 phosphorylation during exocytosis triggered by calcium influx, we applied a voltage protocol that allows us to distinguish a subpopulation of the RRP, which is located close to calcium channels [immediately releasable pool (IRP)] (Horrigan and Bookman, 1994; Voets et al, 1999).…”

Section: Mutation Of Syt1 At Phosphorylation Sites Leaves Secretion Umentioning

confidence: 99%

Different Effects on Fast Exocytosis Induced by Synaptotagmin 1 and 2 Isoforms and Abundance But Not by Phosphorylation

Nagy¹,

Kim²,

Pang³

et al. 2006

J. Neurosci.

110

View full text Add to dashboard Cite

Synaptotagmins comprise a large protein family, of which synaptotagmin 1 (Syt1) is a Ca 2ϩ sensor for fast exocytosis, and its close relative, synaptotagmin 2 (Syt2), is assumed to serve similar functions. Chromaffin cells express Syt1 but not Syt2. We compared secretion from chromaffin cells from Syt1 null mice overexpressing either Syt isoform. High time-resolution capacitance measurement showed that Syt1 null cells lack the exocytotic phase corresponding to the readily-releasable pool (RRP) of vesicles. Comparison with the amperometric signal confirmed that the missing phase of exocytosis consists of catecholamine-containing vesicles. Overexpression of Syt1 rescued the RRP and increased its size above wild-type values, whereas the size of the slowly releasable pool decreased, indicating that the availability of Syt1 regulates the relative size of the two releasable pools. The RRP was also rescued by Syt2 overexpression, but the kinetics of fusion was slightly slower than in cells expressing Syt1. Biochemical experiments showed that Syt2 has a slightly lower Ca 2ϩ affinity for phospholipid binding than Syt1 because of a difference in the C2A domain. These data constitute evidence for the function of Syt1 and Syt2 as alternative, but not identical, calcium-sensors for RRP fusion. By overexpression of Syt1 mutated in the shared PKC/ calcium/calmodulin-dependent kinase phosphorylation site, we show that phorbol esters act independently and upstream of Syt1 to regulate the size of the releasable pools. We conclude that exocytosis from mouse chromaffin cells can be modified by the differential expression of Syt isoforms and by Syt abundance but not by phosphorylation of Syt1.

show abstract

Interactions between proteins implicated in exocytosis and voltage–gated calcium channels

Cited by 80 publications

References 53 publications

Synaptotagmin III/VII Isoforms Mediate Ca2+-induced Insulin Secretion in Pancreatic Islet β-Cells

Synaptotagmin III/VII Isoforms Mediate Ca2+-induced Insulin Secretion in Pancreatic Islet β-Cells

The Molecular Chaperone hsp70 Interacts with the Cytosolic II-III Loop of the Cav2.3 E-type Voltagegated Ca2+ Channel

Different Effects on Fast Exocytosis Induced by Synaptotagmin 1 and 2 Isoforms and Abundance But Not by Phosphorylation

Contact Info

Product

Resources

About