Electrical Oscillations of Isolated Brain Microtubules

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. Significance StatementMicrotubules (MTs) are important cytoskeletal structures engaged in a number of specific cellular activities. Recent in vitro electrophysiological studies indicate that different brain MT structures generate highly synchronous electrical oscillations. However, no information is available as to whether isolated MTs also engage in electrical oscillations. In the present study, we provide evidence that non-taxol stabilized isolated MTs generated electrical oscillations with richer frequency spectrum as compared to MT sheets. Thus, structured MT complexes may render more coherent responses at given oscillatory frequencies, suggesting entrainment in combined MT structures. The present study provides to our knowledge the first experimental evidence for electrical oscillations of single brain MTs.