Mechanically gated channel activity in cytoskeleton-deficient plasma membrane blebs and vesicles from Xenopus oocytes.

Abstract

1. A novel technique involving hypertonic stress causes membrane 'blebbing' of the Xenopus oocyte and the shedding of plasma membrane vesicles (PMVs). 2. Confocal fluorescence microscopy, immunocytochemistry and electron microscopy indicate that blebs and PMVs lack cortical cytoskeleton and are deficient in cytoskeleton proteins and devoid of microvilli. 3. Patch recordings from PMVs consistently reveal mechanically gated (MG) channel activity. The MG channels display the same single-channel conductance as control recordings but differ in terms of reduced mechanosensitivity and adaptation to sustained stimulation. 4. Whole PMV recordings show rapid and reversible activation of mechanosensitive currents in response to pressure pulses. The maximal currents activated in PMVs are consistent with MG channel activity recorded in patches. 5. The discrepancy between MG channel activity recorded in whole PMVs and oocytes most probably reflects their different membrane geometry and ability to develop activating bilayer tensions. 6. We propose that membrane blebbing, which is known to occur under specific physiological and pathological conditions (e.g. mitosis and apoptosis), may increase mechanosensitivity independently of the intrinsic properties of membrane proteins.