Actin filaments modulate electrical activity of brain microtubule protein two‐dimensional sheets

Cantiello

Cantero

2020

Preprint

Significance Statement. Microtubules (MTs) are important cytoskeletal structures engaged in a number of specific cellular activities. Recent in vitro electrophysiological studies indicate that different brain MT structures, including two-dimensional sheets and bundles, generate highly synchronous electrical oscillations. However, no information has been heretofore available as to whether isolated MTs also engage in electrical oscillations. In the present study, a broader spectrum of fundamental frequencies was always observed in isolated MTs as compared to the MT sheets. This interesting finding is consistent with the possibility that more structured MT complexes (i.e. bundles, sheets) may render more coherent response at given oscillatory frequencies and raise the hypothesis that combined MTs may tend to oscillate and entrain together. The present study provides to our knowledge the first experimental evidence for electrical oscillations of single brain MTs.Abstract. Microtubules (MTs) are important cytoskeletal structures engaged in a number of specific cellular activities, including vesicular traffic and motility, cell division, and information transfer within neuronal processes. MTs also are highly charged polyelectrolytes. Recent in vitro electrophysiological studies indicate that different brain MT structures, including two-dimensional (2D) sheets (MT sheets) and bundles, generate highly synchronous electrical oscillations. However, no information has been heretofore available as to whether isolated MTs also engage in electrical oscillations, despite the fact that taxol-stabilized isolated MTs are capable of amplifying electrical signals. Herein we tested the effect of voltage clamping on the electrical properties of isolated non-taxol stabilized brain MTs. Electrical oscillations were observed on application of holding potentials between ±200 mV that responded accordingly with changes in amplitude and polarity. Frequency domain spectral analysis of time records from isolated MTs disclosed a richer oscillatory response as compared to that observed in voltage clamped MT sheets from the same preparation. The data indicate that isolated brain MTs are electrical oscillators that behave as "ionic-based" transistors whose activity may be synchronized in higher MT structures. The ability of MTs to generate, propagate, and amplify electrical signals may have important implications in neuronal computational capabilities.

Section: Resultssupporting

confidence: 76%

Electrical Oscillations of Isolated Brain Microtubules

Cantiello

Cantero

2020

Preprint

“…In both cases, the oscillatory behavior peaked at frequencies around 40 Hz and 90 Hz. The findings are in general agreement with the oscillatory behavior of mammalian brain MT sheets (Cantero et al, 2016 , 2020 ) and membrane-permeabilized murine hippocampal neurons (Cantero et al, 2018 ). A couple of differences are worth noting, however.…”

Section: Discussionsupporting

confidence: 86%

Honeybee Brain Oscillations Are Generated by Microtubules. The Concept of a Brain Central Oscillator

Almenar

Martínez

et al. 2021

Front. Mol. Neurosci.

Self Cite

Microtubules (MTs) are important structures of the cytoskeleton in neurons. Mammalian brain MTs act as biomolecular transistors that generate highly synchronous electrical oscillations. However, their role in brain function is largely unknown. To gain insight into the MT electrical oscillatory activity of the brain, we turned to the honeybee (Apis mellifera) as a useful model to isolate brains and MTs. The patch clamp technique was applied to MT sheets of purified honeybee brain MTs. High resistance seal patches showed electrical oscillations that linearly depended on the holding potential between ± 200 mV and had an average conductance in the order of ~9 nS. To place these oscillations in the context of the brain, we also explored local field potential (LFP) recordings from the Triton X-permeabilized whole honeybee brain unmasking spontaneous oscillations after but not before tissue permeabilization. Frequency domain spectral analysis of time records indicated at least two major peaks at approximately ~38 Hz and ~93 Hz in both preparations. The present data provide evidence that MT electrical oscillations are a novel signaling mechanism implicated in brain wave activity observed in the insect brain.

“…Previous studies from our laboratory showed that different mammalian brain MT structures including 2D-sheets and bundles generate strong electrical oscillations [22,23] that resemble those observed in isolated MTs [24]. This electrical behavior of MTs is mechanistically consistent with electrochemical transistors that support both amplification and self-sustained current-(and voltage-) oscillations [22,23,24,25,26]. From a structural viewpoint, the distinct electrical activity of the various brain MT structures [22,23] is linked to the particular ensemble of MT subunits.…”

Section: Introductionsupporting

confidence: 73%

“…Voltage-clamped bundles of brain MTs display electrical oscillations with a prominent fundamental frequency at ~39 Hz that progress through various periodic regimes. Membrane-permeabilized neurites of cultured mouse hippocampal neurons also generate electrical oscillations conducted along their length [23,25,26]. Thus, the electrical activity of MTs remains evolutionarily conserved, despite functional heterogeneity of the different tubulin genes, encoding isotypes in the various tissues, and diverse posttranslational modifications of the tubulins [46,47,48].…”

Section: Discussionmentioning

confidence: 99%

The Primary Cilium is a Microtubule-Driven Electrical Antenna. The Case of Renal Epithelial Cells

Cantiello

Scarinci

et al. 2022

Preprint

The primary cilium is a non-motile sensory organelle that acts as a transducer of environmental cues into cellular responses. It comprises an axoneme, which is a core of microtubules (MTs), coated by a specialized membrane populated by receptors and a high density of ion channels. Dysfunctional primary cilia generate several diseases known as ciliopathies. However, the nature of ciliary signaling remains largely unknown. Herein, we determined by the patch-clamp technique, the electrical activity of cytoplasmic and axonemal MTs from LLC-PK1 renal epithelial cells. We observed electrical oscillations with fundamental frequencies at ~39 Hz and ~93 Hz in sheets of cytoplasmic MTs. We also studied isolated and in situ intact and Triton X-permeabilized primary cilia, observing electrical oscillations with peak frequencies at either 29-49 (non-permeabilized) or ~40-49 Hz (permeabilized) and ~93 Hz (both). The axonemal electrical oscillations changed with maneuvers that modify ciliary length, including addition of external Ca2+ and Li+. We also applied Continuous Wavelet Transform (CWT) and cross-correlation analyses in the Time-Frequency domain to assess the coherence between cytoplasmic and axonemal MT electrical oscillations. The evidence indicates that the primary cilium is an electrical antenna that produces MT-based electrical oscillations regulated by ciliary channels and receptors.