Synaptotagmin I functions as a calcium regulator of release probability

Fernández‐Chacón, Rafael; Königstorfer, Andreas; Gerber, Stefan; Garcia, J. Victor; Matos, Maria Auxiliadora Costa; Stevens, Charles F.; Brose, Nils; Rizo, Josep; Rosenmund, Christian; Südhof, Thomas C.

doi:10.1038/35065004

Cited by 895 publications

(900 citation statements)

References 48 publications

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“…Third, the short linker between the two C2 domains would limit the orientations that the C2A domain can adopt, enhancing the rapid response to the calcium signal. In this orientation, C2A may respond to calcium entry either through binding electrostatically to the phospholipid membrane (Fernandez-Chacon et al, 2001) or, as has also been suggested, through the inducible, calcium-dependent, binding to SNAREs (Zhang et al, 2002;Bai et al, 2004). This inducible SYT/SNARE interaction exhibits properties very different from those characteristic of the constitutive association.…”

Section: Discussionmentioning

confidence: 94%

“…Genetic knockouts of SYT1 result in dramatic suppression of evoked release in several model organisms (Bellen, 1999;Sudhof and Scheller, 2001). Of the two C2 domains, mutagenesis of C2B has a more severe effect on the SYT-controlled fast synchronous release (Fernandez-Chacon et al, 2001;Mackler et al, 2002;Robinson et al, 2002). In Drosophila melanogaster, a single mutation of tyrosine to asparagine in the C2B domain severely disrupts calcium-triggered exocytosis (Yoshihara and Littleton, 2002).…”

Section: Discussionmentioning

confidence: 99%

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Conserved Prefusion Protein Assembly in Regulated Exocytosis

Rickman

Jiménez

Graham

et al. 2006

MBoC

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The regulated release of hormones and neurotransmitters is a fundamental process throughout the animal kingdom. The short time scale for the calcium triggering of vesicle fusion in regulated secretion suggests that the calcium sensor synaptotagmin and the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) membrane fusion machinery are well ordered before the calcium signal. To gain insight into the organization of the prefusion protein assembly in regulated exocytosis, we undertook a structural/functional study of the vesicular synaptotagmin1 and the plasma membrane SNARE proteins, which copurify from the brain in the absence of calcium. Based on an evolutionary analysis, mutagenesis screens, and a computational protein docking approach, we now provide the first testable description of the supramolecular prefusion assembly. Perturbing the determined synaptotagmin/SNARE-interacting interface in several models of regulated exocytosis altered the secretion of hormones and neurotransmitters. These mutations also disrupted the constitutive synaptotagmin/SNARE link in full agreement with our model. We conclude that the interaction of synaptotagmin with preassembled plasma membrane SNARE proteins, before the action of calcium, can provide a precisely organized "tethering" scaffold that underlies regulated secretion throughout evolution. INTRODUCTIONIn regulated secretion, fusion of docked secretory vesicles with the plasma membrane is triggered by the rapid elevation of the intracellular calcium concentration (Katz and Miledi, 1967). The membrane fusion itself is brought about by the action of the three soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, whereas the vesicular protein synaptotagmin (SYT) acts as the calcium sensor (Sollner et al., 1993;Sudhof and Scheller, 2001;Bonifacino and Glick, 2004). In neuroendocrine cells, the principal SNAREs are syntaxin1 and synaptosome-associated protein of 25 kDa (SNAP-25) on the plasma membrane (so-called target SNAREs or t-SNAREs), and vesicular synaptobrevin, also known as VAMP. Interaction between synaptobrevin and the two t-SNAREs leads to the formation of the ternary SNARE complex, a twisted parallel fourhelical bundle that probably drives membrane fusion (Sutton et al., 1998). With all the major players involved in vesicle fusion identified, it is becoming possible to tackle a central problem of this cellular process-how does calcium trigger vesicle fusion? Arguably, to understand the action of calcium it is essential to know 1) the extent of the assembly of the SNARE fusion proteins and 2) their organization in relation to the calcium sensor, SYT, before calcium-triggered events.It would be reasonable to assume that the SNAREs are at least partially preassembled, and the plasma membrane syntaxin and SNAP-25 are the first obvious candidates for being in such a ready state (An and Almers, 2004;Rickman et al., 2004b). Importantly, synaptobrevin binds syntaxin and SNAP-25 with high-affinity only when the two...

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Conserved Prefusion Protein Assembly in Regulated Exocytosis

Rickman

Jiménez

Graham

et al. 2006

MBoC

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“…It is therefore not surprising that many of the proteins involved in the regulation of neurotransmitter release have also been identified in the pancreatic B-cell and demonstrated to participate in insulin secretion (Lang 1999 Söllner et al 1993), by tethering the granules to the plasma membrane (Sutton et al 1998). Synaptotagmin is the most likely candidate for the Ca 2π -sensor of the exocytotic machinery (Fernandez-Chacon et al 2001), and essential for Ca 2π -dependent neurotransmission (Littleton et al 1993) and exocytosis of insulin-containing granules (Lang et al 1997). It is a protein of 65 kDa that spans the vesicle membrane once and contains a large cytoplasmic domain with two Ca 2π -binding C2 domains (protein kinase C-homology domains), C2A and C2B (Sutton et al 1995).…”

Section: The Exocytotic Machinerymentioning

confidence: 99%

Mechanisms of Exocytosis in Insulin‐Secreting B‐Cells and Glucagon‐Secreting A‐Cells

Barg

2003

Pharmacology & Toxicology

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In pancreatic B-and A-cells, metabolic stimuli regulate biochemical and electrical processes that culminate in Ca 2π -influx and release of insulin or glucagon, respectively. Like in other (neuro)endocrine cells, Ca 2π -influx triggers the rapid exocytosis of hormone-containing secretory granules. Only a small fraction of granules (Ͻ1% in insulin-secreting B-cells) can be released immediately, while the remainder requires translocation to the plasma membrane and further ''priming'' for release by several ATP-and Ca 2π -dependent reactions. Such functional organization may account for systemic features such as the biphasic time course of glucose-stimulated insulin secretion. Since this release pattern is altered in type-2 diabetes mellitus, it is conceivable that disturbances in the exocytotic machinery underlie the disease. Here I will review recent data from our laboratory relevant for the understanding of these processes in insulin-secreting B-cells and glucagon-secreting A-cells and for the identification of novel targets for antidiabetic drug action. Two aspects are discussed in detail: 1) The importance of a tight interaction between L-type Ca 2π -channels and the exocytotic machinery for efficient secretion; and 2) the role of intragranular acidification for the priming of secretory granules and its regulation by a granular 65-kDa sulfonylurea-binding protein.

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“…After the arrival of an action potential at an excitatory synapse, neurotransmitter release displays two components: 160 a fast and synchronous component triggered by the Ca 2 þ -sensor synaptotagmin 1 161,162 and a slow, asynchronous component that is also Ca 2 þ -dependent but not well understood from the molecular point of view. Calakos et al found that neurons from RIM1-alpha KO mice have an B50% reduction in the asynchronous component of release, which implies RIM1-alpha in a postpriming step related to Ca 2 þ -triggered vesicle fusion.…”

Section: Rim1-alphamentioning

confidence: 99%

“…162,122,174 Synaptotagmin 1 R233Q knockin mice bear a punctual mutation in the C2A domain of synaptotagmin 1, which impairs the Ca 2 þ -dependent phospholipid binding to the C2A domain and translates into an B50% decreased of Pr and increased short-term synaptic plasticity in cultured hippocampal neurons. 162 In contrast to the learning deficits in RIM1-alpha KO mice, the synaptotagmin R233Q knockin did not have any alterations in learning and memory. Interestingly, those results would indicate that a generalized decrease in Pr does not translate into a learning deficit.…”

Section: Rim1-alpha Is Critical For Learning and Memorymentioning

confidence: 99%

Active zones for presynaptic plasticity in the brain

García-Junco-Clemente

Linares-Clemente

Fernández‐Chacón

2005

Mol Psychiatry

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Some of the most abundant synapses in the brain such as the synapses formed by the hippocampal mossy fibers, cerebellar parallel fibers and several types of cortical afferents express presynaptic forms of long-term potentiation (LTP), a putative cellular model for spatial, motor and fear learning. Those synapses often display presynaptic mechanisms of LTP induction, which are either NMDA receptor independent of dependent of presynaptic NMDA receptors. Recent investigations on the molecular mechanisms of neurotransmitter release modulation in short-and long-term synaptic plasticity in central synapses give a preponderant role to active zone proteins as Munc-13 and RIM1-alpha, and point toward the maturation process of synaptic vesicles prior to Ca 2 þ -dependent fusion as a key regulatory step of presynaptic plasticity.

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Synaptotagmin I functions as a calcium regulator of release probability

Cited by 895 publications

References 48 publications

Conserved Prefusion Protein Assembly in Regulated Exocytosis

Conserved Prefusion Protein Assembly in Regulated Exocytosis

Mechanisms of Exocytosis in Insulin‐Secreting B‐Cells and Glucagon‐Secreting A‐Cells

Active zones for presynaptic plasticity in the brain

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