Whereas neuronal M-type K(+) channels composed of KCNQ2 and KCNQ3 subunits regulate firing properties of neurons, presynaptic KCNQ2 subunits were demonstrated to regulate neurotransmitter release by directly influencing presynaptic function. Two interaction partners of M-channels, syntaxin 1A and calmodulin, are known to act presynaptically, syntaxin serving as a major protein component of the membrane fusion machinery and calmodulin serving as regulator of several processes related to neurotransmitter release. Notably, both partners specifically modulate KCNQ2 but not KCNQ3 subunits, suggesting selective presynaptic targeting to directly regulate exocytosis without interference in neuronal firing properties. Here, having first demonstrated in Xenopus oocytes, using analysis of single-channel biophysics, that both modulators downregulate the open probability of KCNQ2 but not KCNQ3 homomers, we sought to resolve the channel structural determinants that confer the isoform-specific gating downregulation and to get insights into the molecular events underlying this mechanism. We show, using optical, biochemical, electrophysiological, and molecular biology analyses, the existence of constitutive interactions between the N and C termini in homomeric KCNQ2 and KCNQ3 channels in living cells. Furthermore, rearrangement in the relative orientation of the KCNQ2 termini that accompanies reduction in single-channel open probability is induced by both regulators, strongly suggesting that closer N-C termini proximity underlies gating downregulation. Different structural determinants, identified at the N and C termini of KCNQ3, prevent the effects by syntaxin 1A and calmodulin, respectively. Moreover, we show that the syntaxin 1A and calmodulin effects can be additive or blocked at different concentration ranges of calmodulin, bearing physiological significance with regard to presynaptic exocytosis.
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http://dx.doi.org/10.1523/JNEUROSCI.2666-11.2011 | DOI Listing |
Elife
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Department of Neurology, Baylor College of Medicine, Houston, United States.
Neurobiol Dis
December 2024
The Florey Institute of Neuroscience and Mental Health, Parkville, Victoria 3052, Australia. Electronic address:
Background: Developmental and epileptic encephalopathies (DEE) are rare but severe neurodevelopmental disorders characterised by early-onset seizures often combined with developmental delay, behavioural and cognitive deficits. Treatment for DEEs is currently limited to seizure control and provides no benefits to the patients' developmental and cognitive outcomes. Genetic variants are the most common cause of DEE with KCNQ2 being one of the most frequently identified disease-causing genes.
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Department of Neuroscience, Section of Pharmacology, University of Naples Federico II, Naples 80131, Italy.
Pathogenic variants in encoding Kv7.2 voltage-gated potassium channel subunits cause developmental encephalopathies (-encephalopathies), both with and without epilepsy. We herein describe the clinical, in vitro, and in silico features of two encephalopathy-causing variants (A317T, L318V) in Kv7.
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January 2025
Graduate School of Medicine, Osaka University, Japan; Graduate School of Frontier Biosciences, Osaka University, Japan.
Phosphatidylinositol 4,5-bisphosphate (PIP) is a key membrane lipid regulating various ion channel activities. Currently, several molecular tools are used to modulate PIP levels, each of which has distinct advantages and drawbacks. In this study, we proposed a novel methodology using heterologous Xenopus oocytes to precisely manipulate PIP levels using phospholipase C (PLC)-ζ, which hydrolyzes PIP.
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October 2024
Department of Neurology, Children's Hospital of Nanjing Medical University, Nanjing, China.
Recent advances in exome and targeted sequencing have significantly improved the aetiological diagnosis of epilepsy, revealing an increasing number of epilepsy-related pathogenic genes. As a result, the diagnosis and treatment of epilepsy have become more accessible and more traceable. Voltage-gated potassium channels (Kv) regulate electrical excitability in neuron systems.
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