An organelle K+ channel is required for osmoregulation in Chlamydomonas reinhardtii.
Fresh water protozoa and algae face hypotonic challenges in their living environment. Many of them employ a contractile vacuole system to uptake excessive water from the cytoplasm and expel it to the environment to achieve cellular homeostasis. K(+), a major osmolyte in contractile vacuole, is predicted to create higher osmolarity for water influx. Molecular mechanisms for K(+) permeation through the plasma membrane have been well studied. However, how K(+) permeates organelles such as the contractile vacuole is not clear. Here, we show that the six-transmembrane K(+) channel KCN11 in Chlamydomonas is exclusively localized to contractile vacuole. Ectopic expression of KCN11 in HEK293T cells results in voltage-gated K(+) channel activity. Disruption of the gene or mutation of key residues for K(+) permeability of the channel leads to dysfunction of cell osmoregulation in very hypotonic conditions. The contractile cycle is inhibited in the mutant cells with a slower rate of contractile vacuole swelling, leading to cell death. These data demonstrate a new role for six-transmembrane K(+) channels in contractile vacuole functioning and provide further insights into osmoregulation mediated by the contractile vacuole.
MOE Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
Feifei
F
Xu
Laboratory of Biomechanics, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
Xiaoan
X
Wu
School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK.
Lin-Hua
LH
Jiang
Laboratory of Biomechanics, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China panjunmin@tsinghua.edu.cn zhaohc@mail.tsinghua.edu.cn.
Hucheng
H
Zhao
MOE Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, Shandong Province 266071, China panjunmin@tsinghua.edu.cn zhaohc@mail.tsinghua.edu.cn.
Junmin
0000-0003-1242-3791
J
Pan
D020418:Algal Proteins / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000235:genetics / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D015388:Organelles / Q000378:metabolism*; D064587:Osmoregulation; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism*; D021381:Protein Transport; D014617:Vacuoles / Q000378:metabolism
D020418:Algal Proteins; D050505:Mutant Proteins; D015221:Potassium Channels
Chlamydomonas; Contractile vacuole; K+ channel; KCN11; Osmoregulation