Chlorella virus MT325 encodes water and potassium channels that interact synergistically

doi:10.1073/pnas.0600848103

Chlorella virus MT325 encodes water and potassium channels that interact synergistically

^†Dipartimento di Biologia and Istituto di Biofisica–Consiglio Nazionale delle Ricerche, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy;
^‡Department of Plant Pathology and Nebraska Center of Virology, University of Nebraska, Lincoln, NE 68583-0722;
^¶Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, ON, Canada M5S 3B2;
^‖Institute of Botany, Darmstadt University of Technology, 64287 Darmstadt, Germany; and
^††Istituto Nazionale per la Fisica della Materia, Unità di Milano-Università, Via Celoria 16, 20133 Milan, Italy

Contributed by James L. Van Etten, February 3, 2006

Abstract

Fast and selective transport of water through cell membranes is facilitated by water channels. Water channels belonging to the major intrinsic proteins (MIPs) family have been found in all three domains of life, Archaea, Bacteria, and Eukarya. Here we show that Chlorella virus MT325 has a water channel gene, aqpv1, that forms a functional aquaglyceroporin in oocytes. aqpv1 is transcribed during infection together with MT325 kcv, a gene encoding a previously undescribed type of viral potassium channel. Coexpression of AQPV1 and MT325-Kcv in Xenopus oocytes synergistically increases water transport, suggesting a possible concerted action of the two channels in the infection cycle. The two channels operate by a thermodynamically coupled mechanism that simultaneously alters water conductance and driving force for water movement. Considering the universal role of osmosis, this mechanism is relevant to any cell coexpressing water and potassium channels and could have pathological as well as basic physiological relevance.

Footnotes

^§To whom correspondence should be addressed at:
Department of Plant Pathology, 406 Plant Sciences Hall, University of Nebraska, Lincoln, NE 68583-0722.
E-mail: jvanetten{at}unlnotes.unl.edu
Author contributions: S.G., M.K., J.L.V.E., G.T., and A.M. designed research; S.G., M.K., S.E., and A.M. performed research; M.K. and J.L.V.E. contributed the clones; S.G., M.K., S.E., J.L.V.E., J.D., G.T., and A.M. analyzed data; and J.L.V.E., J.D., G.T., and A.M. wrote the paper.
Conflict of interest statement: No conflicts declared.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. DQ195162 for AQPV1 and DQ195163 for MT325-Kcv).
Abbreviations:

Abbreviations:

AQPV1,

aquaglyceroporin virus 1;

Osm,

osmolar;

PBCV-1,

Paramecium bursaria Chlorella virus.
Freely available online through the PNAS open access option.