Effects on capacitance by overexpression of membrane proteins

Zimmermann, D.; Zhou, Aihua; Kiesel, M.; Feldbauer, Katrin; Terpitz, Ulrich; Haase, Winfried; Schneider‐Hohendorf, Tilman; Bamberg, Ernst; Sukhorukov, Vladimir L.

doi:10.1016/j.bbrc.2008.02.153

Cited by 76 publications

(56 citation statements)

References 18 publications

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“…Determining whether or not a given level of expression (e.g., as governed by gene dosage, promoter choice, and duration of expression) causes toxicity or other side effects is complicated because such effects may depend on factors including species, brain region, cell type, and age of the animal. High expression of a protein may alter electrophysiology as well as cell health: in studies examining the effects of expressing opsins at high levels in mammalian human embryonic kidney 293 (HEK293) cells in vitro, changes were reported in the capacitance of the membrane (Zimmermann et al 2008). Drosophila have expressed opsins under 20 copies of a conditional enhancer the upstream activating sequence (UAS), which may support a recent report of high light sensitivity of neurons in such flies for optogenetic activation .…”

Section: Cell-autonomous Side Effects Protein Expressionmentioning

confidence: 78%

Principles of designing interpretable optogenetic behavior experiments

2015

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Over the last decade, there has been much excitement about the use of optogenetic tools to test whether specific cells, regions, and projection pathways are necessary or sufficient for initiating, sustaining, or altering behavior. However, the use of such tools can result in side effects that can complicate experimental design or interpretation. The presence of optogenetic proteins in cells, the effects of heat and light, and the activity of specific ions conducted by optogenetic proteins can result in cellular side effects. At the network level, activation or silencing of defined neural populations can alter the physiology of local or distant circuits, sometimes in undesired ways. We discuss how, in order to design interpretable behavioral experiments using optogenetics, one can understand, and control for, these potential confounds.

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Section: Cell-autonomous Side Effects Protein Expressionmentioning

confidence: 78%

Principles of designing interpretable optogenetic behavior experiments

2015

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“…2,7,37 C M was in more recent studies found to be depending on viability and physiological state. 22,24 It also changes after viral infection and increases significantly after overexpression of cation channels, 30,49 being particularly affected by processes directly concerning cellular membrane properties, for example, exocytosis (loss of microvilli), viral release, and apoptosis. 20,29,38 One study reports that changes in C M might, in combination with a rather small drop in cell size, be responsible for changes in permittivity.…”

Section: Multifrequency Permittivity Measurements and Analysis Of Calmentioning

confidence: 99%

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Ansorge

Esteban

Schmid

2009

Biotechnology Progress

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Lab and pilot scale batch cultivations of a CHO K1/dhfr À host cell line were conducted to evaluate on-line multifrequency permittivity measurements as a process monitoring tool. The b-dispersion parameters such as the characteristic frequency (f C ) and the permittivity increment (De max ) were calculated on-line from the permittivity spectra. The dual-frequency permittivity signal correlated well with the off-line measured biovolume and the viable cell density. A significant drop in permittivity was monitored at the transition from exponential growth to a phase with reduced growth rate. Although not reflected in off-line biovolume measurements, this decrease coincided with a drop in OUR and was probably caused by the depletion of glutamine and a metabolic shift occurring at the same time. Sudden changes in cell density, cell size, viability, capacitance per membrane area (C M ), and effects caused by medium conductivity (r m ) could be excluded as reasons for the decrease in permittivity. After analysis of the process data, a drop in f C as a result of a fall in intracellular conductivity (r i ) was identified as responsible for the observed changes in the dual-frequency permittivity signal. It is hypothesized that the b-dispersion parameter f C is indicative of changes in nutrient availability that have an impact on intracellular conductivity r i . On-line permittivity measurements consequently not only reflect the biovolume but also the physiological state of mammalian cell cultures. These findings should pave the way for a better understanding of the intracellular state of cells and render permittivity measurements an important tool in process development and control.

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“…More recent studies found, however, that C M changes after the viral infection and overexpression of cation channels [23,64]. Therefore, it seems to be particularly affected by processes involving the cellular membrane properties, such as exocytosis (loss of microvilli), viral release, and apoptosis [42,65].…”

Section: Multifrequency Permittivity Spectramentioning

confidence: 99%

Monitoring lentiviral vector production kinetics using online permittivity measurements

Ansorge¹,

Lanthier²,

Transfiguracion³

et al. 2011

Biochemical Engineering Journal

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Lentiviral vectors (LVs) are effective delivery vehicles that have been successfully used in gene and cell therapy. LVs are most commonly produced via the transient transfection of several plasmid constructs in adherent cell cultures. Recently, we described an efficient and scalable LV production in serum-free suspension cultures. To further facilitate the translation of LV-based interventions to the clinic, the robustness of the production process needs to be ensured to ultimately achieve a specified quality and quantity of LV production lots. However, routine processes are largely empirical, and strategies to monitor LV production kinetics in real-time have not yet been described.In this work, in situ real-time permittivity measurements were assessed to document the production of LVs. Characteristic process phases that were closely associated with LV production kinetics were identified. The permittivity signal evolution was interpreted by exploiting various independent online and offline monitoring measurements. Cellular membrane properties and, to a lesser extent, cell size were the main factors contributing to the permittivity variations. It is concluded that the permittivityrelated parameters can be used for the detection of viral release, allowing real-time assessment of process performance. The technology should thus greatly facilitate process development and optimization.Crown

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Effects on capacitance by overexpression of membrane proteins

Cited by 76 publications

References 18 publications

Principles of designing interpretable optogenetic behavior experiments

Principles of designing interpretable optogenetic behavior experiments

Multifrequency permittivity measurements enable on‐line monitoring of changes in intracellular conductivity due to nutrient limitations during batch cultivations of CHO cells

Monitoring lentiviral vector production kinetics using online permittivity measurements

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