An organelle K+ channel is required for osmoregulation in Chlamydomonas reinhardtii

J Cell Sci. 2016 Aug 1;129(15):3008-14. doi: 10.1242/jcs.188441. Epub 2016 Jun 16.

Abstract

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.

Keywords: Chlamydomonas; Contractile vacuole; K+ channel; KCN11; Osmoregulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algal Proteins / chemistry
  • Algal Proteins / metabolism
  • Amino Acid Sequence
  • Base Sequence
  • Cell Membrane / metabolism
  • Chlamydomonas reinhardtii / genetics
  • Chlamydomonas reinhardtii / metabolism*
  • Mutant Proteins / metabolism
  • Mutation / genetics
  • Organelles / metabolism*
  • Osmoregulation*
  • Potassium Channels / chemistry
  • Potassium Channels / metabolism*
  • Protein Transport
  • Vacuoles / metabolism

Substances

  • Algal Proteins
  • Mutant Proteins
  • Potassium Channels