The juxtamembrane region of synaptotagmin 1 interacts with dynamin 1 and regulates vesicle fission during compensatory endocytosis in endocrine cells

McAdam, Robyn; Varga, Kelly; Jiang, Zhong-Jiao; Young, Fiona B.; Blandford, Vanessa; McPherson, Peter S.; Gong, Lin; Sossin, Wayne S.

doi:10.1242/jcs.161505

Cited by 9 publications

(9 citation statements)

References 26 publications

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“…The structural differences between unphosphorylated and phosphorylated core region residues in Syt 1 also provide potential insight into a recent report of the IDR interacting with the PH domain of dynamin 1, a GTPase known for facilitating fission of vesicles that are being endocytosed (6). That study showed that a T112E missense mutation in the IDR abolishes the binding interaction, suggesting that phosphorylation is a regulatory mechanism for the interaction.…”

Section: Discussionmentioning

confidence: 67%

“…Because the Syt 1 IDR exerts allosteric influence over C2A, structural or disordered ensemble transitions that occur there may be important for modulating C2 domain functions that in turn influence exocytosis (5). Additionally, the IDR was recently shown to bind to the PH domain of dynamin 1, implicating its sequence in an important protein-protein interaction of endocytosis (6).…”

Section: Introductionmentioning

confidence: 99%

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Structural Impact of Phosphorylation and Dielectric Constant Variation on Synaptotagmin’s IDR

Fealey

Binder

Uversky

et al. 2018

Biophysical Journal

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We used time-resolved Förster resonance energy transfer, circular dichroism, and molecular dynamics simulation to investigate the structural dependence of synaptotagmin 1's intrinsically disordered region (IDR) on phosphorylation and dielectric constant. We found that a peptide corresponding to the full-length IDR sequence, a ∼60-residue strong polyampholyte, can sample structurally collapsed states in aqueous solution, consistent with its κ-predicted behavior, where κ is a sequence-dependent parameter that is used to predict IDR compaction. In implicit solvent simulations of this same sequence, lowering the dielectric constant to more closely mimic the environment near a lipid bilayer surface promoted further sampling of collapsed structures. We then examined the structural tendencies of central region residues of the IDR in isolation. We found that the exocytosis-modulating phosphorylation of Thr disrupts a local disorder-to-order transition induced by trifluoroethanol/water mixtures that decrease the solution dielectric constant and stabilize helical structure. Implicit solvent simulations on these same central region residues testing the impact of dielectric constant alone converge on a similar result, showing that helical structure is formed with higher probability at a reduced dielectric. In these helical conformers, lysine-aspartic acid salt bridges contribute to stabilization of transient secondary structure. In contrast, phosphorylation results in formation of salt bridges unsuitable for helix formation. Collectively, these results suggest a model in which phosphorylation and compaction of the IDR sequence regulate structural transitions that in turn modulate neuronal exocytosis.

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Section: Discussionmentioning

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Structural Impact of Phosphorylation and Dielectric Constant Variation on Synaptotagmin’s IDR

Fealey

Binder

Uversky

et al. 2018

Biophysical Journal

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“…; McAdam et al . ). Synaptotagmin can also bind with the accessory proteins of endocytosis, such as AP2 and Stone 2 (Fergestad and Broadie ).…”

Section: Discussionmentioning

confidence: 97%

Myosin light chain kinase facilitates endocytosis of synaptic vesicles at hippocampal boutons

Yue

et al. 2016

Journal of Neurochemistry

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At nerve terminals, endocytosis efficiently recycles vesicle membrane to maintain synaptic transmission under different levels of neuronal activity. Ca2+ and its downstream signal pathways are critical for the activity-dependent regulation of endocytosis. An activity- and Ca2+-dependent kinase, myosin light chain kinase (MLCK) has been reported to regulate vesicle mobilization, vesicle cycling and motility in different synapses, but whether it has a general contribution to regulation of endocytosis at nerve terminals remains unknown. We investigated this issue at rat hippocampal boutons by imaging vesicle endocytosis as the real-time retrieval of vesicular synaptophysin tagged with a pH-sensitive green fluorescence protein. We found that endocytosis induced by 200 action potentials (5 – 40 Hz) was slowed by acute inhibition of MLCK and downregulation of MLCK with RNA interference, while the total amount of vesicle exocytosis and somatic Ca2+ channel current did not change with MLCK downregulation. Acute inhibition of myosin II similarly impaired endocytosis. Furthermore, downregulation of MLCK prevented depolarization-induced phosphorylation of myosin light chain, an effect shared by blockers of Ca2+ channels and calmodulin. These results suggest that MLCK facilitates vesicle endocytosis through activity-dependent phosphorylation of myosin downstream of Ca2+/calmodulin, probably as a widely existing mechanism among synapses. Our study suggests that MLCK is an important activity-dependent regulator of vesicle recycling in hippocampal neurons, which are critical for learning and memory.

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“…As such, it will be important to determine the conditions during which phosphorylation of SV2A's N-terminal domain (T84) occurs, and if this process occurs at the PM. Importantly, Syt1 has been shown to control endocytic events (Li et al, 2017;Nicholson-Tomishima and Ryan, 2004;Poskanzer et al, 2003) and recruit endocytic machinery during endocytosis in endocrine cells (McAdam et al, 2015). The C2 domains of Syt1 regulate the kinetics of vesicle internalisation in a calcium-dependent manner, similar the action of the C2 domains during exocytosis (Yao et al, 2012).…”

Section: Sv2a-mediated Nanoclustering Promotes Syt1 Trafficking To Rab5-positive Early Endosomesmentioning

confidence: 99%

SV2A-Syt1 interaction controls surface nanoclustering and access to recycling synaptic vesicles

Small

Harper

Kontaxi

et al. 2021

Preprint

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Following exocytosis, the recapture of vesicular proteins stranded at the plasma membrane in recycling synaptic vesicles (SVs) is essential to sustain neurotransmission. Nanoclustering is emerging as a mechanism through which proteins may be pre-assembled prior to endocytosis, to ensure high fidelity of retrieval for subsequent rounds of vesicle fusion. Here, we used single molecule imaging to examine the nanoclustering of synaptotagmin-1 (Syt1) and synaptic vesicle protein 2A (SV2A). Syt1 forms surface nanoclusters through interaction of its C2B domain (K326/K328) with SV2A, as demonstrated by mutating Syt1 (K326A/K328A) and knocking down endogenous SV2A. Blocking cognate interaction with Syt1 (SV2AT84A) also decreased SV2A clustering. Impaired nanoclustering of Syt1 and SV2A leads to accelerated endocytosis of Syt1, altered intracellular sorting and decreased trafficking of Syt1 to a Rab5-positive endocytic pathway. We conclude that the interaction between SV2A and Syt1 locks both molecules into surface nanoclusters, controlling their entry into recycling SVs.

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The juxtamembrane region of synaptotagmin 1 interacts with dynamin 1 and regulates vesicle fission during compensatory endocytosis in endocrine cells

Cited by 9 publications

References 26 publications

Structural Impact of Phosphorylation and Dielectric Constant Variation on Synaptotagmin’s IDR

Structural Impact of Phosphorylation and Dielectric Constant Variation on Synaptotagmin’s IDR

Myosin light chain kinase facilitates endocytosis of synaptic vesicles at hippocampal boutons

SV2A-Syt1 interaction controls surface nanoclustering and access to recycling synaptic vesicles

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