Rab3 superprimes synaptic vesicles for release: implications for short-term synaptic plasticity

“Paired-pulse facilitation is inversely proportional to the initial release probability (Zucker and Regehr, 2002).”

“Rab3 proteins are abundant GTP-binding proteins of synaptic vesicles (Sudhof, 2004).”

“It seems feasible that moderate and uniform change in synaptic strength can readily be adjusted by homeostatic mechanisms (Panzeri et al., 2001; Turrigiano and Nelson, 2004).”

“Rab3-deficient neurons and Rab3a-containing neurons were indistinguishable in this assay, with both exhibiting a recovery time constant of 6 s, similar to wild-type synapses (Rosenmund and Stevens, 1996) (Fig.”

“In all analyses, cultures from the respective KO mice and their littermate control mice were initially established and later analyzed on the same days to avoid culture artifacts (Fernandez-Chacon et al., 2001).”

“, 1999 ) , and deletion of Rim1 in mice causes a change of other parameters compared with Rab3 - deficient mice ( Schoch et al .”

“, 1999), and deletion of Rim1 in mice causes a change of other parameters compared with Rab3-deficient mice (Schoch et al., 2002; Calakos et al., 2004).”

“Hippocampi from the entire litter were isolated and cultured in a chemically defined media (Neurobasal medium A; Invitrogen, San Diego, CA) supplemented with B27 (Invitrogen) on glial microdot islands (Bekkers and Stevens, 1991; Pyott and Rosenmund, 2002).”

“These means of affecting Ca 2 influx have been shown previously to affect presynaptic release in a similar manner (Mintz et al., 1995).”

“At room temper - ature , synaptic vesicles at hippocampal syn - apses are released with two time courses : a fast synchronous component , accounting for ϳ80% of the charge of an EPSC , and a slow asynchronous component ( Goda and Stevens , 1994 ) .”

“It seems feasible that moderate and uniform change in synaptic strength can readily be adjusted by homeostatic mechanisms (Panzeri et al., 2001; Turrigiano and Nelson, 2004).”

“, 1999 ) , and deletion of Rim1 in mice causes a change of other parameters compared with Rab3 - deficient mice ( Schoch et al .”

“Relative changes in the Ca 2ϩ dependence of EPSC amplitudes were determined by applying an external solution with an initial high release probability (12 mM CaCl 2 , 1 mM MgCl 2 ) and the effect of subsequent reduction of Ca 2ϩ influx on EPSC amplitude was determined by alternating between control solution and solutio…”

“Despite the lack of change of the number of docked vesicles, the absence of synapsin I causes a reduction of the immediately releasable pool (Li et al., 1995; Ryan et al., 1996).”

“Four Rab3 paralogs (Rab3A, Rab3B, Rab3C, and Rab3D) are expressed in the brain (Touchot et al., 1987; Zahraoui et al., 1989; Baldini et al., 1995; Schluter et al., 2002) and are apparently functionally redundant.”

“heterogeneity in the time course of triggered release (Wu and Borst, 1999).”

“Four Rab3 paralogs (Rab3A, Rab3B, Rab3C, and Rab3D) are expressed in the brain (Touchot et al., 1987; Zahraoui et al., 1989; Baldini et al., 1995; Schluter et al., 2002) and are apparently functionally redundant.”

“Indeed, the paired-pulse ratio at a CA1 pyramidal cell synapse is increased in the synapsin I KO mice (Rosahl et al., 1993).”

“In addition, spike train-dependent increases of intraterminal Ca 2ϩ can accelerate vesicle priming (Stevens and Wesseling, 1998).”

“We see an initial reduction in the EPSC amplitude but no change in vesicle pool size in Rab3-deficient neurons (Schluter et al., 2004).”

“Other factors that affect STP include feedback activation of presynaptic receptors (von Gersdorff et al., 1997), presynaptic Ca 2ϩ handling (Edmonds et al., 2000; Rozov et al., 2001; Blatow et al., 2003; Sippy et al., 2003), heterogeneous release probability (Trommershauser et al., 2003), Ca 2ϩ…”

“First, Rab3 may serve to direct vesicles to release sites with intrinsically high release probability, for example next to Ca 2 channels, because close proximity of vesicles to Ca 2 channels increases their release probability (Meinrenken et al., 2002).”

“Using previously published data from other synapses as a yard stick (Silver et al., 1998; Sakaba and Neher, 2001a), we probed whether this shift is based on a modification of one of the two kinetic components of pool recovery by replotting the normalized recovery phase of the EPSC (Fig.”

“When the readily releasable pool of vesicles is depleted by an action potential train, the rate of pool refilling is faster than at resting Ca 2 concentrations (Stevens and Sullivan, 1998; Rhee et al., 2002).”

“…Ca 2ϩ handling (Edmonds et al., 2000; Rozov et al., 2001; Blatow et al., 2003; Sippy et al., 2003), heterogeneous release probability (Trommershauser et al., 2003), Ca 2ϩ -dependent Ca 2ϩ channel inactivation (Xu and Wu, 2005), and postsynaptic receptor desensitization (Otis et al., 1996).”

“, 1998 ; Sakaba and Neher , 2001a ) , we probed whether this shift is based on a modification of one of the two kinetic components of pool recovery by replotting the normalized recovery phase of the EPSC ( Fig .”

“…Ca 2ϩ handling (Edmonds et al., 2000; Rozov et al., 2001; Blatow et al., 2003; Sippy et al., 2003), heterogeneous release probability (Trommershauser et al., 2003), Ca 2ϩ -dependent Ca 2ϩ channel inactivation (Xu and Wu, 2005), and postsynaptic receptor desensitization (Otis et al., 1996).”

“Rab proteins are the largest family of ras-related GTPases (Pereira-Leal et al., 2001).”

“Multiple mechanisms can contribute to changes in STP, including changes in the presynaptic Ca 2ϩ handling (Edmonds et al., 2000; Rozov et al., 2001; Blatow et al., 2003; Sippy et al., 2003).”

“Four Rab3 paralogs (Rab3A, Rab3B, Rab3C, and Rab3D) are expressed in the brain (Touchot et al., 1987; Zahraoui et al., 1989; Baldini et al., 1995; Schluter et al., 2002) and are apparently functionally redundant.”

“, 1999), and deletion of Rim1 in mice causes a change of other parameters compared with Rab3-deficient mice (Schoch et al., 2002; Calakos et al., 2004).”

“Despite the lack of change of the number of docked vesicles, the absence of synapsin I causes a reduction of the immediately releasable pool (Li et al., 1995; Ryan et al., 1996).”

“Removal of rabphilin in mice has no detectable influence on synaptic transmission (Schluter et al., 1999), and deletion of Rim1 in mice causes a change of other parameters compared with Rab3-deficient mice (Schoch et al.”

“This finding is consistent with a previous study showing that release probabilities of the asynchronous and synchronous components are similar (Otsu et al., 2004).”

“During repetitive stimula - tion the ratio is shifted progressively toward asynchronous release ( Hagler and Goda , 2001 ; Pyott and Rosenmund , 2002 ) .”

“During repetitive stimulation the ratio is shifted progressively toward asynchronous release (Hagler and Goda, 2001; Pyott and Rosenmund, 2002).”

“Other factors that affect STP include feedback activation of presynaptic receptors (von Gersdorff et al., 1997), presynaptic Ca 2ϩ handling (Edmonds et al., 2000; Rozov et al., 2001; Blatow et al., 2003; Sippy et al., 2003), heterogeneous release probability (Trommershauser et al., 2003), Ca 2ϩ…”

“A third example is the role in auditory processing: precise regulation of short-tem plasticity features participates in distinguishing static from dynamic qualities of the auditory signal process in the primary auditory cortex (Atzori et al., 2001).”

“, 2003), heterogeneous release probability (Trommershauser et al., 2003), Ca 2 -dependent Ca 2 channel inactivation (Xu and Wu, 2005), and postsynaptic”

“A change in synaptic strength during spike trains may have strong impact on many aspects of synaptic encoding, one of such examples may be the precision of timing of neuronal excitation (Silberberg et al., 2004) or the cortical processing of sensory information.”

“A possible additional effector of Rab3 could be Synapsin I, which was shown to bind to Rab3a and modulate its function in vitro (Giovedi et al., 2004).”

“Four Rab3 paralogs (Rab3A, Rab3B, Rab3C, and Rab3D) are expressed in the brain (Touchot et al., 1987; Zahraoui et al., 1989; Baldini et al., 1995; Schluter et al., 2002) and are apparently functionally redundant.”

“Importantly, Rab3a is abundant at the neuromuscular junction (Mizoguchi et al., 1992).”

“We were particularly interested in the function of Syx1A, because together with Rab3a, this protein targets the exocytosis of synaptic vesicles at the presynaptic active zone (37, 38).”

“On the other hand, the relationship between pr and short-term plasticity is not always clear and is dependent on other factors (Geppert et al., 1997; von Gersdorff et al., 1997; Blatow et al., 2003; Xu and Wu, 2005; Schlüter et al., 2006).”

“We have identified 42 probes that can be divided into two groups, those that seem to be increasingly downregulated with AD severity (CABP1 [235,236,237,238,239,240,241,242,243], CADPS2 [244,245,246, 247,248,249], COLQ [250], DMD [251,252,253,254,255,256], ELOVL2 [257], FAIM2/LFG [258,259,260,261], GABBR2 [262, 263,264…”

“In hippocampal synapses, superpriming was shown to depend on the presence of at least one isoform of rab3 (32).”

“This subset of docked SVs would then be in a privileged location, efficiently coupled to calcium influx, similar to the RAB3-dependent “super-primed” pool, previously described at vertebrate synapses (Schlüter et al., 2006).”

“and functions to increase release probability of a subset of synaptic vesicle”

“In excitatory hippocampal neurons, the deletion of all Rab3 isoforms leads to a 40% decrease in synaptic release probability without affecting the number of primed vesicles (Schluter et al. 2004, 2006).”

“…of GTP-locked mutant Rab3A significantly decreases the number of vesicles docked at the plasma membrane without altering the kinetics of individual exocytotic events (Schluter et al., 2006; Tsuboi and Fukuda, 2006; Coleman et al., 2007; Handley et al., 2007; van Weering et al., 2007).”

“Isoforms of Rab3A, the most abundant Rab in the brain, and its effectors are involved in Ca2+-dependent exocytosis during neurotransmitter release from nerve terminals [83], [84].”

“Whether the interaction of Rab3 with its effectors, including synapsin I, underlies the enhancement of SV priming remains to be investigated (Schluter et al., 2006).”

“Rab3s do perform a regulatory role in neurotransmitter release (Schluter et al., 2006), as do many other proteins, including complexins and CAPS (Südhof, 2013; Rizo and Xu, 2015).”

“(23) speculate that Rab3 “superprimes” a subset of vesicles, specifically increasing their release probability.”

“E–E3 Rab3, a family of vesicular fusion and transport proteins (Schluter et al, 2006), was found co-localized with secretagogin (arrowheads) in the median eminence.”

“Studies using quadruple Rab3 KO mice revealed that Rab3 is essential for the normal dynamics of neurotransmitter release (17, 18).”

“More specifically, Rab3 seems to play a role in superpriming since it increases the calcium sensitivity of docked and primed SVs, making it more likely that they get released in response to an AP (Schlüter et al., 2006).”

“For example, loss of Rab3a in mice reduces the probability of synaptic vesicle release following a train of action potentials 43 , thereby increasing synaptic depression, and increases non-REM sleep 44 .”

“Additional evidence for a slow process of maturation of high-p vesicles comes from a knock-out study of Rab3 proteins in hippocampal neurons that suggested that Rab3 acts to increase the intrinsic release probability of readily releasable vesicles (“superpriming”) (Schlüter et al., 2006).”

“Rab3A and SNAP-29 colocalize at presynaptic terminals, and it is conceivable that their interaction modulates neurotransmitter release (Pan et al., 2005; Schlüter et al., 2006).”

“Fourth, the small GTPbinding protein rab3B that regulates calcium-dependent exocytosis and synaptic vesicle release has also been shown to present at the tight junction [110-112].”

“In general, both overexpression as well as null mutation of Rab3 isoforms appears to inhibit the final step: overexpression of Rab3 isoforms reduce secretion in PC-12 and chromaffin cells [11,12], but null mutation of all four Rab3 genes also reduces secretion in cultured neurons, probably of a subpopulation of synapt…”

“…are Ca2+ channel levels and the physical distance between Ca2+ channels and release-ready vesicles (Brandt et al., 2005; Sakaba et al., 2005; Schlüter et al., 2006; Wadel et al., 2007; Bucurenciu et al., 2010; Weber et al., 2010; Lee et al., 2013; Schmidt et al., 2013; Ishiyama et al.,…”

“…in the mouse, in contrast to that in C. elegans, do not appear to be required for synaptic vesicle trafficking to the active zone per se but rather may affect neurotransmitter release by increasing the release probability of a subset of primed vesicles (Nonet et al. 1997; Schluter et al. 2006).”

“…that are involved in the docking or priming process could function as downstream effectors of Ca2+ and/or cAMP, including synapsins (Sun et al. 2006), Munc18 (Toonen et al. 2006), Rim (Calakos et al. 2004), or Rab3 and other Ras-related GTPases (Owe-Larsson et al. 2005; Schlüter et al. 2006).”

“Proteins such as Rab3A-D and Munc13–3 increase Pr (Schlüter et al., 2004; Schlüter et al., 2006; Ishiyama et al., 2014), whereas”

“(41) to describe the effects of quadruple knockout of all Rab3 isoforms.”

“This strongly suggests that maturation-promoting mechanotransductive events might be triggered specifically by the nanotopography and not by the material.”

“Distinguishing between these two potential modes of superpriming, which are not mutually exclusive, remains a challenging experimental task (Schlüter et al., 2006).”

“Although beyond the scope of this study, p-Syn I is involved in multiple stages of vesicle cycling, including vesicle mobilizing, docking, priming, and fusion [35,36].”

“…in intracellular fusion reactions (Zerial and McBride, 2001; Frontiers in Cellular Neuroscience www.frontiersin.org January 2012 | Volume 5 | Article 32 | 1 Pfeffer and Aivazian, 2004), and to control release probability, with implications for synaptic plasticity (Schluter et al., 2004, 2006).”

“to failure of LG docking at the IS (11,12), reminiscent of the Rab3 phenotype in neuronal synapses (13).”

“A possible way to reduced short-term depression experimentally is the depletion of the pool of release-ready vesicles with trains of presynaptic stimuli right before the long-term induction activity patterns, or by reducing the pause (10 s in [2] and 4 s in [3]) between the burst of spike-pairs, or by using genetic ma…”

“…vesicular release probability RIM defines the efficiency of release by recruiting Ca21 channels (Han et al., 2011; Kaeser et al., 2011), binding to PIP2 rich membranes (de Jong et al., 2018) and interacting with Rab3 (Y. Wang et al., 1997; X. Wang et al., 2001; Fukuda, 2003; Schluter et al., 2006).”

“Interestingly, the C-terminal region of synapsin has been reported to interact with Rab3A, a SV-associated GTPase regulating the final steps of release (Geppert et al., 1997; Giovedì et al., 2004a; Giovedì et al., 2004b; Schluter et al., 2006).”

“Presynaptic modulation, which occurs during ongoing synaptic transmission and results in changes in transmitter release, may be mediated by changes in release probability and/or in recruitment of vesicles into the readily releasable vesicle pool (RRP) (Zucker & Regehr, 2002; Südhof, 2004; Schweizer & Ryan, 2006).”

“Several presynaptic protein molecules such as Munc13, Rab3, synaptotagmin, and kainate, have been suggested to mediate the calciumdependent transmitter release (Fernández-Chacón et al. 2001; Rosenmund et al. 2002; Schlüter et al. 2006; Sun and Dobrunz 2006).”

“…a vesicle-associated protein involved in both long- and short-term plasticity (Castillo et al., 1997; Geppert et al., 1997; Nonet et al., 1997; Leenders et al., 2001; Schlüter et al., 2004, 2006; accelerate replenishment by quickening the transition of vesicles to release sites at the ribbon base.”

“In neurons, ablation of Rab3 proteins or infusion of GTP-locked mutants causes a shift in short-term plasticity toward short-term facilitation (13,17,32).”

“And, indeed, this prediction seems to hold in several recent studies (Molder and Mennerick 2005; Schluter et al. 2006; Toonen et al. 2006).”

“Pvr can be also be elevated by increasing the fraction of “superprimed” SVs (within the RRP), which are more competent for release than normally primed vesicles (34, 46).”

“…studies have revealed effects during repeated rounds of neurotransmitter release (Geppert et al., 1997) and there are alterations in short-term (Schlüter et al., 2006) and long-term synaptic plasticity (Castillo et al., 1997; Lonart et al., 1998) that are associated with learning and memory…”

“This observation is consistent with the proposed role of the Rab3a protein in targeting vesicles to Ca 2 channels (Schlüter et al., 2006) and with the impaired Ca 2 sensitivity observed at the neuromuscular synapse of Rab3a( ) animals (Coleman et al., 2007; Coleman and Bykhovskaia, 2009).”

“Furthermore, it was proposed that vesicle “superpriming” or targeting to the clusters of Ca2+ channels is mediated by Rab3a (Schluter et al., 2006, Gracheva et al., 2008; Coleman and Bykhovskaia, 2009b).”

“…probability reflects a smaller complement of high release probability SVs (“tightly docked” or “super-primed” SVs (Neher and Brose, 2018)) we followed a previously described analysis that found a reduction of SV super-primed SVs upon genetic deletion of all rab3 isoforms (Schlüter et al., 2006).”

“Theta burst stimulation included 4 trains, each containing 10 bursts of 4 stimuli at 100 Hz delivered every 200 ms. Trains were repeated every 10 s.”

“The existence of a Rab3-dependent superprimed vesicle pool was first established on the basis of recordings from mouse hippocampal neurons from Rab3 quadruple knockouts [39].”

“[14].”

“It is puzzling that the only mechanistic difference for the final stages of either pathways is the critical requirement of RAB3A in DCV but not SV exocytosis (Schlüter et al., 2004, 2006; Persoon et al., 2018).”

“We believe that our findings can be explained by the model where Rab3a mediates vesicle superpriming (Schluter et al., 2006), more specifically, vesicle targeting to the clusters of Ca channels.”

“…when better reagents become available, because perturbations of Rab3a alone have significant effects on exocytosis in secretory cells (Yaekura et al., 2003), but significant changes in neuronal exocytosis were observed only in the absence of all four Rab3 isoforms (Schluter et al., 2004, 2006).”