scholarly journals PKA-catalyzed phosphorylation of tomosyn and its implication in Ca2+-dependent exocytosis of neurotransmitter

2005 ◽  
Vol 170 (7) ◽  
pp. 1113-1125 ◽  
Author(s):  
Takeshi Baba ◽  
Toshiaki Sakisaka ◽  
Sumiko Mochida ◽  
Yoshimi Takai
Keyword(s):  
Neurotransmitter Release ◽  
Regulatory Protein ◽  
Snare Complex ◽  
Snare Proteins ◽  
Dependent Protein Kinase ◽  
Readily Releasable Pool ◽  
Pituitary Adenylate Cyclase ◽  
Electrophysiological Studies ◽  
Cervical Ganglion ◽  
Dependent Protein

Neurotransmitter is released from nerve terminals by Ca2+-dependent exocytosis through many steps. SNARE proteins are key components at the priming and fusion steps, and the priming step is modulated by cAMP-dependent protein kinase (PKA), which causes synaptic plasticity. We show that the SNARE regulatory protein tomosyn is directly phosphorylated by PKA, which reduces its interaction with syntaxin-1 (a component of SNAREs) and enhances the formation of the SNARE complex. Electrophysiological studies using cultured superior cervical ganglion (SCG) neurons revealed that this enhanced formation of the SNARE complex by the PKA-catalyzed phosphorylation of tomosyn increased the fusion-competent readily releasable pool of synaptic vesicles and, thereby, enhanced neurotransmitter release. This mechanism was indeed involved in the facilitation of neurotransmitter release that was induced by a potent biological mediator, the pituitary adenylate cyclase-activating polypeptide, in SCG neurons. We describe the roles and modes of action of PKA and tomosyn in Ca2+-dependent neurotransmitter release.

scholarly journals Role of Ca2+/Calmodulin-Dependent Protein Kinase Kinase in Adrenal Aldosterone Production

Endocrinology ◽  
2015 ◽  
Vol 156 (5) ◽  
pp. 1750-1756 ◽  
Author(s):  
Kazutaka Nanba ◽  
Andrew Chen ◽  
Koshiro Nishimoto ◽  
William E. Rainey
Keyword(s):  
Calcium Signaling ◽  
Regulatory Protein ◽  
Ang Ii ◽  
Dependent Protein Kinase ◽  
Adrenal Cell ◽  
Aldosterone Production ◽  
Dependent Protein ◽  
Steroidogenic Acute Regulatory ◽  
Protein Kinase Kinase

There is considerable evidence supporting the role of calcium signaling in adrenal regulation of both aldosterone synthase (CYP11B2) and aldosterone production. However, there have been no studies that investigated the role played by the Ca2+/calmodulin-dependent protein kinase kinase (CaMKK) in adrenal cells. In this study we investigated the role of CaMKK in adrenal cell aldosterone production. To determine the role of CaMKK, we used a selective CaMKK inhibitor (STO-609) in the HAC15 human adrenal cell line. Cells were treated with angiotensin II (Ang II) or K+ and evaluated for the expression of steroidogenic acute regulatory protein and CYP11B2 (mRNA/protein) as well as aldosterone production. We also transduced HAC15 cells with lentiviral short hairpin RNAs of CaMKK1 and CaMKK2 to determine which CaMKK plays a more important role in adrenal cell regulation of the calcium signaling cascade. The CaMKK inhibitor, STO-609, decreased aldosterone production in cells treated with Ang II or K+ in a dose-dependent manner. STO-609 (20μM) also inhibited steroidogenic acute regulatory protein and CYP11B2 mRNA/protein induction. CaMKK2 knockdown cells showed significant reduction of CYP11B2 mRNA induction and aldosterone production in cells treated with Ang II, although there was no obvious effect in CaMKK1 knockdown cells. In immunohistochemical analysis, CaMKK2 protein was highly expressed in human adrenal zona glomerulosa with lower expression in the zona fasciculata. In conclusion, the present study suggests that CaMKK2 plays a pivotal role in the calcium signaling cascade regulating adrenal aldosterone production.

scholarly journals Complexin-1 regulated transition in the assembly of single neuronal SNARE complex

2021 ◽  
Author(s):  
Hao Tongrui ◽  
Feng Nan ◽  
Gong Fan ◽  
Liu Jiaquan ◽  
Lu Ma ◽  
...  
Keyword(s):  
Synaptic Vesicle ◽  
Molecular Mechanism ◽  
Optical Tweezers ◽  
Neurotransmitter Release ◽  
Snare Complex ◽  
Snare Proteins ◽  
Synaptic Vesicle Exocytosis ◽  
Sensitive Factor ◽  
Vesicle Exocytosis ◽  
Vesicle Pool

Neurotransmitter release is mediated by the synaptic vesicle exocytosis. Important proteins in this process have been identified including the molecular machine Synaptic-soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins, and other regulators. Complexin (Cpx) is one of the vital regulators in this process. The functions of Cpx are proposed to maintain a proper primed vesicle pool by preventing its premature depletion, which facilitates the vesicle fusion in the presence of Ca2+. However, the molecular mechanism remains unclear. Using dual-trap optical tweezers, we detected the interaction of complexin-1 (CpxI) with SNARE. We found that the CpxI stabilizes partially folded SNARE complexes by competing with C-terminal of Vamp protein and interacting with the C-terminal of t-SNARE complex.

scholarly journals SNAREs and Synaptotagmin cooperatively determine the Ca2+ sensitivity of neurotransmitter release in fixed stoichiometry modules

2021 ◽  
Author(s):  
Zachary A McDargh ◽  
Ben A O'Shaughnessy
Keyword(s):  
Molecular Dynamics ◽  
Neurotransmitter Release ◽  
Release Site ◽  
Snare Complex ◽  
Snare Proteins ◽  
Stoichiometric Ratio ◽  
Release Rates ◽  
Vesicle Tethering ◽  
Fusion Site ◽  
Dynamics Simulations

Neurotransmitter release is accomplished by a multi-component machinery including the membrane-fusing SNARE proteins and Ca2+-sensing Synaptotagmin molecules. However, the Ca2+ sensitivity of release was found to increase or decrease with more or fewer SNARE complexes at the release site, respectively, while the cooperativity is unaffected (Acuna et al., 2014; Arancillo et al., 2013), suggesting that there is no simple division of labor between these two components. To examine the mechanisms underlying these findings, we developed molecular dynamics simulations of the neurotransmitter release machinery, with variable numbers of Synaptotagmin molecules and assembled SNARE complexes at the release site. Ca2+ uncaging simulations showed that increasing the number of SNARE complexes at fixed stoichiometric ratio of Synaptotagmin to SNAREs increased the Ca2+ sensitivity without affecting the cooperativity. The physiological cooperativity of ~4-5 was reproduced with 2-3 Synaptotagmin molecules per SNARE complex, suggesting that Synaptotagmin and SNAREs cooperate in fixed stoichiometry modules. In simulations of action potential-evoked release, increased numbers of Synaptotagmin-SNARE modules increased release probability, consistent with experiment. Our simulations suggest that the final membrane fusion step is driven by SNARE complex-mediated entropic forces, and by vesicle-tethering forces mediated by the long Synaptotagmin linker domains. In consequence, release rates are increased when more SNARE complexes and Synaptotagmin monomers are present at the fusion site.

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