Phosphoinositides provide a regulatory mechanism of surface charge and active transport.
Yeast cells, when grown in the presence of arsenate, are capable of accumulating phosphoinositides (PI) at the expense of inhibiting their degradation more than their synthesis. PI levels return to normal when the cells are cultured or exposed to media without arsenate. These reversible changes are employed as a tool to test the effect of inositide accumulation and dynamics on several membrane properties. In the PI-rich cells, phosphate and arsenate transport from low external concentrations (high affinity systems), as well as the transport of glycine, which enter the cells accompanied by protons, were increased. The proton ejection energized by glucose is also enhanced in the PI-rich cells that show a more efficient potassium inflow at pH 4.0-4.5. The membrane surface potential of the PI-rich cells was found to be 2-times higher than that of the normal cells, in agreement with the 2-fold increment in the PI. All the above mentioned alterations in membrane properties are reverted when the PI content of the PI-rich cells is reduced to the level of normal cells. The results show the participation of the phosphoinositides in the formation, maintenance and regulation of the membrane surface potential and their possible influence upon transport mechanisms.
D001149:Arsenates / Q000378:metabolism / Q000494:pharmacology; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000502:physiology; D005998:Glycine / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007292:Inosine Nucleotides / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials; D010710:Phosphates / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000502:physiology*; D011188:Potassium / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology
D001149:Arsenates; D007292:Inosine Nucleotides; D010710:Phosphates; D010716:Phosphatidylinositols; D011188:Potassium; D005998:Glycine