Dr. Shai D.  Silberberg: Research Interest

Involvement of membrane conductances in mucociliary activation and regulation.

The mucociliary system is responsible for maintaining the airways clean of inhaled particles and pathogens.  This immense task is performed by ciliated cells, which transport the mucus from the lungs to the upper airways. Ciliary Beat Frequency (CBF) is strongly regulated by hormones and neurotransmitters, thus providing fine control over the efficiency of mucus transport. In collaboration with Prof. Zvi Priel from the Department of Chemistry we aim to elucidate the biochemical mechanisms underlying the stimulation of mucociliary beating by extracellular nucleotides.  To this end, we are using the patch-clamp technique to control the composition of the intracellular environment of single freshly dissociated rabbit airway ciliated cells, and then monitor the effects of ATP and UTP on membrane conductances. We are also simultaneously measuring ciliary activity in the same cell.  The combination of patch-clamp recording with CBF measurements provides a unique means to investigate the relationship between the transduction pathway and the end biological effect in the same cell.

Elucidate the molecular structure and subunit composition of the P2X_cilia receptor.

The unraveling physiological importance of purinergic receptors in airway mucociliary function, has promoted interest in the mechanisms underlying stimulation of mucociliary clearance by ATP, and has led to the development of new strategies to treat obstructive airway disorders such as cystic fibrosis (CF).  Thus, inhalants containing either UTP or UTP analogs, which target a P2Y receptor in the ciliated cells, are being developed. Our recent discovery that airway ciliated cells express an UTP-insensitive P2X receptor (P2X_cilia receptor), which is modulated by Na⁺, lends way to the development of novel treatments targeting this P2X pathway.  The rational development of such drugs, and the unraveling of the mechanism of Na⁺ inhibition, would be greatly facilitated if the molecular structure of P2X_cilia receptor were known. Hence, in collaboration with Dr. Soto from the Department of Molecular Biology of Neuronal Signals, Max-Planck Institute for Experimental Medicine, Göttingen, we are attempting to elucidate the molecular structure and subunit composition of the P2X_cilia receptor. 

Regulation of mechanosensitive channels by voltage.

Mechanosensitive (MS) channels are implicated in a variety of cellular functions including volume regulation and mechanoreception.  MS channels activated by membrane stretch typically activate rapidly (within ms) and deactivate rapidly when the stretch is removed.  Using the patch clamp technique, we found that MS channels in Xenopus oocytes can have an uncommonly slow response to step changes in voltage in the absence of applied stretch.  The mechanisms underlying this slow cooperative activation of MS channels by voltage and the steady state voltage-dependence of the MS channels are being investigated.