Evaluating Methods and Protocols of Ferritin-Based Magnetogenetics

Abstract

FeRIC (Ferritin iron Redistribution to Ion Channels) is a magnetogenetic technique that uses radiofrequency (RF) waves to activate the transient receptor potential channels, such as TRPV1 and TRPV4, coupled to cellular ferritins. In cells expressing ferritin-tagged TRPV, RF stimulation increases the cytosolic Ca2+ levels via a biochemical pathway. The interaction between RF and ferritin increases the free cytosolic iron level that in turn, triggers chemical reactions producing reactive oxygen species and oxidized lipids that activate the ferritin-tagged TRPV. In this pathway, it is expected that experimental factors that disturb the ferritin expression, the ferritin iron load, the TRPV functional expression, or the cellular redox state will impact the RF efficacy to activate ferritin-tagged TRPV. Here, three in vitro protocols were compared for using FeRIC to remotely activate ferritin-tagged TRPV. Further, several experimental factors were examined that either enhance or abolish the RF control of ferritin-tagged TRPV. The findings may help establish reproducible magnetogenetic experimental protocols.

Controlling the bioelectrical properties of neurons with ferritin-based Magnetogenetics

“…1C -E) and decreases the electrical interference transmitted to the patch-clamp electrode by up to 50% compared with the 5 cm diameter coil we used in previous studies (Fig. 1B) (5). The 180 MHz voltages induced on the head stage input impedance due to the electromagnetic fields were simulated to be less for the smaller coil for a variety of electrode wire geometries (Fig.…”

“…Low to mid-frequency (kHz and MHz) magnetic fields are safe and can freely penetrate through tissues (1, 2) allowing wireless, noninvasive, and ondemand control of cell activity. Some magnetogenetic approaches use the transient receptor potential vanilloid 1 and 4 channels (TRPV1 and TRPV4, respectively) coupled with ferritin as magnetic actuators (3)(4)(5)(6)(7)(8)(9)(10). TRPV1 and TRPV4 are non-selective cation channels activated by heat, pH changes, mechanical stimulus, and a diversity of endogenous lipids (11)(12)(13)(14)(15).…”

“…Several studies have reported the magnetic activation of ferritin-coupled TRPV1 and TRPV4 in vitro and in vivo. Because these channels are permeable to Ca 2+ , their magnetic activation has been examined by monitoring the intracellular Ca 2+ levels (3)(4)(5)(6)(7)(8)(9)(10) or by detecting the expression of Ca 2+responsive genes (6,7). The magnetic control of neurons has been examined in vivo by monitoring the behavioral output from animal models expressing ferritin-coupled TRPV1 or TRPV4 in specific neuronal populations.…”

“…The negative results from experiments using Magneto2.0 add uncertainty to the field of Magnetogenetics. Moreover, there is no Ephys characterization of other ferritin-coupled ion channels, such as the αGFP-TRPV1/GFP-ferritin (6) or the FeRIC channels (3)(4)(5), which have been reported to be activated with RF. This is, in part, due to the technical challenge caused by the electromagnetic interference between the RF setup and the Ephys system.…”

Localized nanoscale induction by single domain magnetic particles

“…suggests that the release of Fe 2+ ions from its core and subsequent oxidation of lipids are likely involved in the indirect stimulation of TRPV channel proteins (Fig. 4a) [33,34,45]. This suggested mechanism would be more satisfactory if the role of magnetic fields in this process could be elucidated.…”