Dear Editors

I want to express my serious concern related to this article

Please let me first introduce you to our work.
As you can see in the attached papers, already in 2010 and later in 2013 and 2014, we proposed and demonstrated that synaptotagmin (syt1) is the sensor of vesicle priming

For your convenience attached abstract of the first article, and summary of the second highlighting syt1 as vesicle priming protein:
Signaling role of the voltage-gated calcium channel as the molecular on/off-switch of secretion.
Atlas D.
Cell Signal. 2010 Nov;22(11):1597-603. doi: 10.1016/j.cellsig.2010.04.003. Epub 2010 Apr 11. Review.
“Abstract
Voltage-gated calcium channels (VGCC) are involved in a large variety of cellular Ca(2+) signaling processes, including exocytosis, a Ca(2+) dependent release of neurotransmitters and hormones. Great progress has been made in understanding the mode of action of VGCC in exocytosis, a process distinguished by two sequential yet independent Ca(2+) binding reactions. First, Ca(2+) binds at the selectivity filter, the EEEE motif of the VGCC, and second, subsequent to a brief and intense Ca(2+) inflow to synaptotagmin, a vesicular protein. Inquiry into the functional and physical interactions of the channels with synaptic proteins has demonstrated that exocytosis is triggered during the initial Ca(2+) binding at the channel pore, prior to Ca(2+) entry. Accordingly, a cycle of secretion begins by an incoming stimulus that releases vesicles from a releasable pool upon Ca(2+) binding at the pore, and at the same time, the transient increase in [Ca(2+)](i) primes a fresh set of non-releasable vesicles, to be fused by the next incoming stimulus. We propose a model, in which the Ca(2+) binding at the EEEE motif and the consequent conformational changes in the channel are the primary event in triggering secretion, while synaptotagmin acts as a vesicle docking protein. Thus, the channel serves as the molecular On/Off signaling switch, where the predominance of a conformational change in Ca(2+)-bound channel provides for the fast secretory process.”

Summary of the discussion of the paper:
(CaV2.1 (P/Q channel) interaction with synaptic proteins is essential for depolarization-evoked release.
Cohen-Kutner M, Nachmanni D, Atlas D.
Channels (Austin). 2010 Jul-Aug;4(4):266-77.

“In summary (1) Using Ca2+ -independent interactions in BAPTA-injected oocytes we have demonstrated that the P/Q- type Ca 2+ channel, could associate with Syt1, and the SNARE proteins to generate a distinct and kinetically active complex. We suggest that the long-winded Ca2+ -independent channel interactions with the synaptic proteins lead to the tethering of the vesicle to the channel. Under resting calcium concentrations, these channel-associated docked vesicles are non-releasable vesicles (2) We have reconstituted depolarization-evoked release in oocytes co-expressing P/Q-type with the t-SNARE’s and Syt1. The BotC1- and BotA-sensitive reconstituted release was observed without buffering of the intracellular Ca2+ (no BAPTA injection). We suggest that a rise of [Ca2+]I during an action potential would prime the channel-tethered vesicle (non-releasable) to a releasable vesicle by Ca2+-binding to Syt1 C2 domains. These releasable vesicles will remain readily docked at the membrane and will fuse only in response to an oncoming action potential. This is consistent with a model [14] in which, a cycle of secretion begins by an incoming stimulus that releases vesicles from a releasable pool and at the same time, primes a fresh set of non-releasable vesicles, to be fused by the next incoming stimulus. This cycle of events could provide for the well-resolved sub-millisecond time-scale of depolarization-evoked synaptic transmission.”

We further summarized this idea in:

The voltage-gated calcium channel functions as the molecular switch of synaptic transmission.
Atlas D.
Annu Rev Biochem. 2013;82:607-35. doi: 10.1146/annurev-biochem-080411-121438. Epub 2013 Jan 17. Review
See Overview

“OVERVIEW
Numerous studies have described multiple mechanisms of transmitter release driven by a variety of signals (e.g., membrane depolarization, caged calcium, ionomycin, the Gq-PLC-IP3 pathway, caffeine) (1, 2, 3, 4). However, many fundamental issues are unresolved, particularly with regard to the primary event that underlies action potential–driven synaptic transmission. The overall goal of this review is to highlight the role of Ca2+ binding at the voltage-gated calcium channel (VGCC) in signaling exocytosis, focusing mainly on the mechanism of secretion induced by membrane depolarization. The review discusses the excitosome model, in which the channel is assembled into the heteroprotein excitosome complex by syntaxin 1A (Sx1A), synaptosome-associated protein 25 kDa (SNAP-25), and synaptotagmin (syt1), and the vesicles are docked to the plasma membrane via unprimed (Ca2+-unbound syt1) or primed (Ca2+-bound syt1) excitosome complexes.
In this model, the channel operates as a Ca2+ sensor that triggers secretion while syt1 functions as a vesicle-priming protein. The current model suggests that syt1 is the Ca2+ sensor of secretion and the channel is the vehicle that introduces Ca2+ into the cell. We examine the molecular events underlying the coordinated, regulated process that resolve the Ca2+ binding site of the VGCC as the initial trigger of secretion. The proposed model identifies syt1 as a central player in vesicle priming and promotes the VGCC as the putative Ca2+ sensor of secretion.”

And finally, we specify the role of synaptotagmin as the calcium sensor of vesicle priming


Voltage-gated calcium channels function as Ca2+-activated signaling receptors.
Atlas D.
Trends Biochem Sci. 2014 Feb;39(2):45-52.

See section
“Syt1 functions as the Ca2+ sensor of vesicle priming
Most of the synaptic vesicles are found in the cytosol; only a few are docked to the presynaptic plasma membrane at the active zone. Docked vesicles can be further classified by the Ca2+ occupancy of syt1 C2 domains 8 and 60. Repelled by the negative charges of membrane phospholipids, Ca2+-free syt1 keeps the vesicle apart from the membrane [61] (Figure 1A, upper). Upon Ca2+ binding and syt1 insertion at the membrane, the gap between the vesicle and the plasma membrane closes (Figure 1A, lower; Figure 1B, upper). Therefore, vesicles associated with primed (i.e., Ca2+-bound syt1) or non-primed (i.e., Ca2+-free syt1) excitosome complexes provide a functional criterion to distinguish between non-releasable (docked/non-primed) and releasable (docked/primed) vesicles 8 and 60.
In this context, Ca2+ entry during an action potential primes the vesicle by binding to syt1, defining syt1 as a prospective Ca2+ sensor of vesicle priming. Regulating the availability of synaptic vesicles for release, syt1 can be viewed as the regulator of synaptic strength of the neuronal cell. Ca2+ binding to syt1 can potentially explain how Ca2+ influx regulates the effective size of the releasable pool and the synaptic strength of the cell [62].
Within this molecular framework, the releasable pool represents only a small percentage of all docked vesicles (1–5%) [63], known to be triggered by an action potential at a conformational speed of 60–200 μs. Correspondingly, conformational changes induced at the Ca2+-bound channel within the primed excitosome trigger fusion of the releasable pool (Figure 1B, lower). The spatiotemporal efficacy of conformationally-induced vesicle fusion supports the view that priming of vesicles within the secretory pathway is an earlier, separated step (for review, see [64])”.


Ca2+ independent interactions of synaptotagmin with the SNRAEs were published even earlier

See also
The C2A domain of synaptotagmin alters the kinetics of voltage-gated Ca2+ channels Ca(v)1.2 (Lc-type) and Ca(v)2.3 (R-type).
Cohen R, Elferink LA, Atlas D.
J Biol Chem. 2003 Mar 14;278(11):9258-66.

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Our excitosome model includes the Ca2+ channel as a member of the exocytotic complex. Accordingly, the Ca2+ channel is the Ca2+ sensor of secretion while synaptotagmin (Syt1) is the sensor responsible for maintaining primed vesicles.
In contrast, the model promoted by Dr. Sudhof is missing the major Ca2+ senor, namely the Ca2+ channel.
In all his early studies Dr. Sudhof insisted that Syt1 is the sensor of exocytosis, whereas, we demonstrated that Syt1 is the sensor of vesicle priming, and the sensor of exocytosis is the calcium channel.

It is pleasing that he finally recognizes one part of our model, shown in the present study, confirming that Syt1 is the sensor responsible for maintaining primed vesicle. However, I am deeply hurt and disappointed that he failed to cite any of our work.
I strongly maintain that publishing in October 2015 that Syt1 is also the sensor of primed vesicles as a novel finding without giving credit to prior publications, which appwaered already in 2010, 2013 and 2014 is unethical.
Dr. Sudhof who is familiar with our work, is not overlooking our work but rather seems to actively ignoring them.

I find it also disturbing that the reviewers failed to insist on keeping fairness in science.

In the future if Dr. Sudhof will adopt the first part of our model, namely that the channel is the Ca2+ sensor of release, I hope that he will be instructed by the reviewers to properly acknowledge his colleagues.

Sincerely,
Daphne Atlas