Live cell imaging of signaling and metabolic activities

Depaoli, Maria R.; Bischof, Helmut; Eroğlu, Emrah; Burgstaller, Sandra; Ramadani‐Muja, Jeta; Rauter, Thomas; Schinagl, Maximilian; Waldeck-Weiermair, Markus; Hay, Jesse; Graier, Wolfgang F.; Malli, Roland

doi:10.1016/j.pharmthera.2019.06.003

Cited by 49 publications

(47 citation statements)

References 355 publications

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“…The fatty acids have been grafted onto the precursor complex [Ir(ppy) 2 (TzPyNH 2 )] by the formation of a secondary amide bond. The photophysical properties reveals a green-yellow phosphorescent emission for all the complexes that was derived from a mixture of 3 MLCT and 3 LC excited states, which was comparable to the one recorded for the precursor [Ir(ppy) 2 (TzPyNH 2 )]. Temperature-dependent lifetime measurements on [Ir(ppy) 2 (TzPyNHC 16cis )] have suggested that the excited states might be partially quenched via thermally activated higher-lying dark states.…”

Section: Discussionsupporting

confidence: 65%

“…We have previously published an analogous Ir complex bearing a nitrile substituent in the 5 position of the pyridine ring [23], [Ir(ppy) 2 (TzPyCN)], as opposed to the currently reported complexes bearing an amine/amide group in the same position. When comparing measurements from dichloromethane solutions, the emission profile of [Ir(ppy) 2 (TzPyCN)] was red-shifted (typical broad and structureless 3 MLCT emission with a maximum at 618 nm) compared to the emission profiles of the complexes bearing an amine/amide group. This trend can be easily rationalised by taking into account the electron-withdrawing nature of the nitrile substituent, stabilising the π* system of the pyridyltetrazolato ligand.…”

Section: Temperature-dependent Emission Lifetimesmentioning

confidence: 99%

“…Cellular probes for optical imaging are predominantly based on fluorescent organic compounds [1][2][3][4]. While a large variety of these probes are commonly available and routinely used, there are significant shortfalls that depend on the imaging modality and cellular conditions.…”

Section: Introductionmentioning

confidence: 99%

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Photophysical and Biological Properties of Iridium Tetrazolato Complexes Functionalised with Fatty Acid Chains

et al. 2020

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Five cyclometalated Ir(III) tetrazolato complexes functionalised with fatty acid chains (octanoic, palmitic, stearic, palmitoleic, and oleic) have been synthesised. The fatty acids were chosen to evaluate the potential effect of the length and degree of unsaturation on the biological properties of the complexes for use as cellular imaging agents. The complexes were analysed in both organic and aqueous media to determine if the presence and nature of the fatty acid chains had a significant effect on their photophysical properties. The complexes display green–yellow emission in dichloromethane solutions with relatively long excited state decays, within the range 360–393 ns, and quantum yields between 5.4% and 6.7% (from degassed solutions). Temperature-dependent photophysical studies suggest that the emitting excited states of the complexes might be quenched by the thermal population of dark states. In water, the quantum yields drop within the range of 0.5%–2.4%, and the photophysical measurements are influenced by the variable degrees of aggregation. In general, the entire series displayed low cytotoxicity and relatively high photostability, which are favourable attributes in the design of cellular imaging agents. Images of live HeLa cells were obtained for all the complexes, but those functionalised with palmitic and stearic acids had limitations due the lower solubility conferred by the saturated aliphatic chains. The complexes were mainly detected within the endoplasmic reticulum.

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Section: Discussionsupporting

confidence: 65%

Section: Temperature-dependent Emission Lifetimesmentioning

confidence: 99%

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Photophysical and Biological Properties of Iridium Tetrazolato Complexes Functionalised with Fatty Acid Chains

et al. 2020

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“…Nonetheless, significant progress has been made over the past 40 years or so: several fundamental second messengers and pathways for calcium signaling have been identified [Pozzan 1994, Clapham 2007, Berridge 2012, Balla 2013, Carafoli 2016, Galione 2019, and the understanding of specific receptors [Rossi 2018 and channels [Kozak andPutney 2017, Galione 2019] has improved. Experimental methods, particularly calcium imaging techniques, have been developed [Depaoli 2019, Siciliano 2019. It has been shown that stimulus induces characteristic transient calcium blips, puffs (more generically known as calcium sparks or spikes) [Rose 2006], which in turn, through repetition, can give rise to calcium waves and oscillations [Dupont 2011, Gaspers 2014.…”

Section: Introductionmentioning

confidence: 99%

Role of Protons in Calcium Signaling

Molinari¹,

Nervo²

2020

Preprint

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36 years after the publication of the important article by Busa and Nuccitelli on the variability of intracellular pH (pHi) and the interdependence of pHi and intracellular Ca2+ concentration ([Ca2+]i), little research has been carried out on pHi and calcium signaling. Moreover, the results appear to be contradictory. Some authors claim that the increase in [Ca2+]i is due to a reduction in pHi, others that it is caused by an increase in pHi. The reasons for these conflicting results have not yet been discussed and clarified in an exhaustive manner. Variations in pHi have a significant impact on the increase in [Ca2+]i and hence on some of the basic biochemical mechanisms of calcium signaling. This paper focuses on the possible triggering role of protons, highlighting the mechanisms potentially involved and the open issues that could be clarified by research.

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“…Some older reports have demonstrated that the inhibition of ATP generation could strongly impact the secretory transport of particular cargo proteins [ 34 , 35 , 36 , 37 ]. While a mutual interrelation between the secretory rate and metabolic activity is frequently discussed [ 38 , 39 ], studies that aim at characterizing such crosstalk and its dynamics are rare. However, recent advances in the development of high-resolution live-cell imaging tools and techniques [ 38 ] have opened the door for meaningful experiments that could improve our understanding of metabolic implications in signaling and protein trafficking.…”

Section: Introductionmentioning

confidence: 99%

ER-to-Golgi Transport in HeLa Cells Displays High Resilience to Ca2+ and Energy Stresses

Rauter

Burgstaller

Gottschalk

et al. 2020

Cells

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One third of all human proteins are either transmembrane or soluble secretory proteins that first target the endoplasmic reticulum (ER). These proteins subsequently leave the ER and enter the Golgi apparatus via ER-Golgi intermediate vesicular structures. Live-cell imaging of cargos fused to fluorescent proteins (FPs) enables the high-resolution visualization and characterization of secretory transport processes. Here, we performed fluorescence time-lapse imaging to assess the Ca2+ and energy dependency of ER-to-Golgi transport in living HeLa cells, a cancer cell model which has been well investigated. Our data revealed that ER-to-Golgi transport remained highly efficient in the absence of ATP-generating substrates, despite clear reductions in cytosolic and mitochondrial ATP levels under these energy stress conditions. However, cell treatment with 2-deoxy-D-glucose (2-DG), which severely diminished subcellular ATP levels, abolished ER-to-Golgi transport. Interestingly, while 2-DG elevated cytosolic Ca2+ levels and reduced long-distance movements of glycosylphosphatidylinositol (GPI)-positive vesicles, robust short-term ER Ca2+ mobilizations, which strongly affected the motility of these vesicles, did not considerably impair ER-to-Golgi transport. In summary, we highlight that ER-to-Golgi transport in HeLa cells remains functional despite high energy and Ca2+ stress levels.

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Live cell imaging of signaling and metabolic activities

Cited by 49 publications

References 355 publications

Photophysical and Biological Properties of Iridium Tetrazolato Complexes Functionalised with Fatty Acid Chains

Photophysical and Biological Properties of Iridium Tetrazolato Complexes Functionalised with Fatty Acid Chains

Role of Protons in Calcium Signaling

ER-to-Golgi Transport in HeLa Cells Displays High Resilience to Ca2+ and Energy Stresses

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