A protein phosphorylation/dephosphorylation network regulates a plant potassium channel.
Potassium (K(+)) is an essential nutrient for plant growth and development. Plants often adapt to low K(+) conditions by increasing their K(+) uptake capability. Recent studies have led to the identification of a calcium signaling pathway that enables plants to act in this capacity. Calcium is linked to two calcineurin B-like calcium sensors (CBLs) and a target kinase (CBL-interacting protein kinase 23 or CIPK23) that, in turn, appears to phosphorylate and activate the potassium channel, Arabidopsis K(+) transporter 1 (AKT1), responsible for K(+) uptake in roots. Here, we report evidence that this regulatory mechanism is more elaborate than earlier envisaged. The recently described pathway is part of an extensive network whereby several CBLs interact with multiple CIPKs in the activation of the potassium channel, AKT1. The physical interactions among the CBL, CIPK, and AKT1 components provide a mechanism for specifying the members of the CBL and CIPK families functional in AKT1 regulation. The interaction between the CIPKs and AKT1 was found to involve the kinase domain of the CIPK component and the ankyrin repeat domain of the channel. Furthermore, we identified a 2C-type protein phosphatase that physically interacts and inactivates the AKT1 channel. These findings provide evidence that the calcium-sensitive CBL and CIPK families together with 2C-type protein phosphatases form a protein phoshporylation/dephosphorylation network that regulates the AKT1 channel for K(+) transport in plants.
Lee
Sung Chul
SC
Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA.
Lan
Wen-Zhi
WZ
Kim
Beom-Gi
BG
Li
Legong
L
Cheong
Yong Hwa
YH
Pandey
Girdhar K
GK
Lu
Guihua
G
Buchanan
Bob B
BB
Luan
Sheng
S
D017360:Arabidopsis / Q000502:physiology; D029681:Arabidopsis Proteins / Q000378:metabolism / Q000502:physiology; D008954:Models, Biological; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010940:Plant Proteins / Q000378:metabolism*; D015221:Potassium Channels / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism
D029681:Arabidopsis Proteins; D010750:Phosphoproteins; D010940:Plant Proteins; D015221:Potassium Channels; C074500:AKT1 protein, Arabidopsis; C507144:CIPK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases