@article{MTMT:3023309,
	title = {Molecular motions that shape the cardiac action potential: Insights from voltage clamp fluorometry},
	url = {https://m2.mtmt.hu/api/publication/3023309},
	author = {Zhu, W and Varga, Zoltán and Silva, J R},
	doi = {10.1016/j.pbiomolbio.2015.12.003},
	journal-iso = {PROG BIOPHYS MOL BIO},
	journal = {PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY},
	volume = {120},
	unique-id = {3023309},
	issn = {0079-6107},
	year = {2016},
	eissn = {1873-1732},
	pages = {3-17}
}

@article{MTMT:2948507,
	title = {Direct Measurement of Cardiac Na+ Channel Conformations Reveals Molecular Pathologies of Inherited Mutations.},
	url = {https://m2.mtmt.hu/api/publication/2948507},
	author = {Varga, Zoltán and Zhu, W and Schubert, AR and Pardieck, JL and Krumholz, A and Hsu, EJ and Zaydman, MA and Cui, J and Silva, JR},
	doi = {10.1161/CIRCEP.115.003155},
	journal-iso = {CIRC-ARRHYTHMIA ELEC},
	journal = {CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY},
	volume = {8},
	unique-id = {2948507},
	issn = {1941-3149},
	abstract = {BACKGROUND: -Dysregulation of voltage-gated cardiac Na+ channels (NaV1.5) by inherited mutations, disease-linked remodeling, and drugs causes arrhythmias. The molecular mechanisms whereby the NaV1.5 voltage-sensing domains (VSDs) are perturbed to pathologically or therapeutically modulate Na+ current (INa) have not been specified. Our aim was to correlate INa kinetics with conformational changes within the four (DI-DIV) VSDs to define molecular mechanisms of NaV1.5 modulation. METHOD AND RESULTS: -Four NaV1.5 constructs were created to track the voltage-dependent kinetics of conformational changes within each VSD, using voltage-clamp fluorometry (VCF). Each VSD displayed unique kinetics, consistent with distinct roles in determining INa. In particular, DIII-VSD deactivation kinetics were modulated by depolarizing pulses with durations in the intermediate time domain that modulates late INa. We then used the DII-VSD construct to probe the molecular pathology of two Brugada Syndrome (BrS) mutations (A735V and G752R). A735V shifted DII-VSD voltage-dependence to depolarized potentials, while G752R significantly slowed DII-VSD kinetics. Both mutations slowed INa activation, even though DII-VSD activation occurred at higher potentials (A735V) or at later times (G752R) than ionic current activation, indicating that the DII-VSD allosterically regulates the rate of INa activation and myocyte excitability. CONCLUSIONS: -Our results reveal novel mechanisms whereby the NaV1.5 VSDs regulate its activation and inactivation. The ability to distinguish distinct molecular mechanisms of proximal BrS mutations demonstrates the potential of these methods to reveal how inherited mutations, post-translational modifications and anti-arrhythmic drugs alter NaV1.5 at the molecular level.},
	year = {2015},
	eissn = {1941-3084},
	pages = {1228-1239}
}

@article{MTMT:2573825,
	title = {The Xenopus Oocyte Cut-open Vaseline Gap Voltage-clamp Technique With Fluorometry.},
	url = {https://m2.mtmt.hu/api/publication/2573825},
	author = {Rudokas, MW and Varga, Zoltán and Schubert, AR and Asaro, AB and Silva, JR},
	doi = {10.3791/51040},
	journal-iso = {JOVE-J VIS EXP},
	journal = {JOVE-JOURNAL OF VISUALIZED EXPERIMENTS},
	unique-id = {2573825},
	issn = {1940-087X},
	abstract = {The cut-open oocyte Vaseline gap (COVG) voltage clamp technique allows for analysis of electrophysiological and kinetic properties of heterologous ion channels in oocytes. Recordings from the cut-open setup are particularly useful for resolving low magnitude gating currents, rapid ionic current activation, and deactivation. The main benefits over the two-electrode voltage clamp (TEVC) technique include increased clamp speed, improved signal-to-noise ratio, and the ability to modulate the intracellular and extracellular milieu. Here, we employ the human cardiac sodium channel (hNaV1.5), expressed in Xenopus oocytes, to demonstrate the cut-open setup and protocol as well as modifications that are required to add voltage clamp fluorometry capability. The properties of fast activating ion channels, such as hNaV1.5, cannot be fully resolved near room temperature using TEVC, in which the entirety of the oocyte membrane is clamped, making voltage control difficult. However, in the cut-open technique, isolation of only a small portion of the cell membrane allows for the rapid clamping required to accurately record fast kinetics while preventing channel run-down associated with patch clamp techniques. In conjunction with the COVG technique, ion channel kinetics and electrophysiological properties can be further assayed by using voltage clamp fluorometry, where protein motion is tracked via cysteine conjugation of extracellularly applied fluorophores, insertion of genetically encoded fluorescent proteins, or the incorporation of unnatural amino acids into the region of interest(1). This additional data yields kinetic information about voltage-dependent conformational rearrangements of the protein via changes in the microenvironment surrounding the fluorescent molecule.},
	year = {2014},
	eissn = {1940-087X}
}