Immunosuppressants implicate protein phosphatase regulation of K+ channels in guard cells.

AUTOR(ES)

Luan, S

RESUMO

The elevation of Ca2+ levels in the cytoplasm inactivates inward-rectifying K+ channels that play a central role in regulating the apertures of stomatal pores in higher plants. However, the mechanism for the Ca(2+)-mediated inhibition of K(+)-channel function is unknown. Using patch-clamp techniques, we show that cyclophilin-cyclosporin A and FK506-binding protein-FK506 complexes, which are highly specific inhibitors of protein phosphatase 2B (calcineurin), block Ca(2+)-induced inactivation of K+ channels in Vicia faba guard cells. A constitutively active calcineurin fragment that is Ca(2+)-independent inhibits K(+)-channel activity in the absence of Ca2+. We have also identified an endogenous Ca(2+)-dependent phosphatase activity from V. faba that is inhibited by the cyclophilin-cyclosporin A and FK506-binding protein-FK506 complexes. Our findings implicate a Ca(2+)-dependent, calcineurin-like protein phosphatase in a Ca2+ signal-transduction pathway of higher plants.

Documentos Relacionados

• Evidence for protein phosphatase 1 and 2A regulation of K+ channels in two types of leaf cells.
• Voltage-dependent K+ channels as targets of osmosensing in guard cells
• Inward-rectifying K+ channels in guard cells provide a mechanism for low-affinity K+ uptake.
• Voltage dependence of K+ channels in guard-cell protoplasts
• Evidence for G-Protein Regulation of Inward K+ Channel Current in Guard Cells of Fava Bean.