Mechanosensory Transduction in Ciliates (Protozoa)

Abstract

Most living cells are mechanosensitive in that mechanical strain exerted on their plasma membrane results in a transient change in electrical conductance of the membrane. In cells unspecialized for mechanoreception, a mechanically induced “injury” would result in a membrane potential change due to traumatic leak currents. In specialized mechanoreceptor tissue, however, the mechanical energy input results in the opening and/or closing of specific sensory ion channels in the membrane; this may provide a very high sensitivity to a mechanical stimulus. The gating of these mechanosensitive channels results in a defined change in ion conductance, and consequently, in a shift of the membrane potential. The steps of mechanoelectrical coupling are summarized by the following scheme: mechanical energy input — deformation of the sensitive structure — gating of mechanosensory ion channels — change in membrane ion conductance — receptor current flow — receptor potential — voltage-sensitive modification and integration — motor output.