Biomedical subjects
Xin-Liang Zhou
Publications and source records attributed to Xin-Liang Zhou.
Heterologously expressed fungal transient receptor potential channels retain mechanosensitivity in vitro and osmotic response in vivo.
The budding yeast Saccharomyces cerevisiae has a mechanosensitive channel, TrpY1, a member of the Trp superfamily of channels associated with various sensations. Upon a hyperosmotic shift, a yeast cell releases Ca(2+) from the vacuole to the cytoplasm through this channel. The TRPY1 gene has orthologs in other fungal genomes, including TRPY2 of Kluyveromyces lactis and TRPY3 of Candida albicans. We subcloned TRPY2 and TRPY3 and expressed them in the vacuole of S. cerevisiae deleted of TRPY1. The osmotically induced Ca(2+) transient was restored in vivo as reported by transgenic aequorin. Patch-clamp examination showed that the TrpY2 or the TrpY3 channel was similar to TrpY1 in unitary conductance, rectification properties, Ca(2+) sensitivity, and mechanosensitivity. The retention of mechanosensitivity of transient receptor potential channels in a foreign setting, shown here both in vitro and in vivo, implies that these mechanosensitive channels, like voltage-gated or ligand-gated channels, do not discriminate their settings. We discuss various mechanisms, including the possibility that stress from the lipid bilayer by osmotic force transmits forces to the transmembrane domains of these channels.
The transient receptor potential channel on the yeast vacuole is mechanosensitive.
Ca2+ is released from the vacuole into the yeast cytoplasm on an osmotic upshock, but how this upshock is perceived was unknown. We found the vacuolar channel, Yvc1p, to be mechanosensitive, showing that the Ca2+ conduit is also the sensing molecule. Although fragile, the yeast vacuole allows limited direct mechanical examination. Pressures at tens of millimeters of Hg (1 mmHg = 133 Pa) activate the 400-pS Yvc1p conductance in whole-vacuole recording mode as well as in the excised cytoplasmic-side-out mode. Raising the bath osmolarity activates this channel and causes vacuolar shrinkage and deformation. It appears that, on upshock, a transient osmotic force activates Yvc1p to release Ca2+ from the vacuole. Mechanical activation of Yvc1p occurs regardless of Ca2+ concentration and is apparently independent of its known Ca2+ activation, which we now propose to be an amplification mechanism (Ca2+-induced Ca2+ release). Yvc1p is a member of the transient receptor potential-family channels, several of which have been associated with mechanosensation in animals. The possible use of Yvc1p as a molecular model to study mechanosensation in general is discussed.