Potassium Ion Channels of Chlorella Viruses Cause Rapid Depolarization of Host Cells during Infection

Authors

Florian Frohns, Institute of Botany, Darmstadt University of Technology, Darmstadt, Germany
Anja Kasmann, Institute of Botany, Darmstadt University of Technology, Darmstadt, Germany
Detlef Kramer, Institute of Botany, Darmstadt University of Technology, Darmstadt, Germany
Britta Schafer, Institute of Botany, Darmstadt University of Technology, Darmstadt, Germany
Mario Mehmel, Institute of Botany, Darmstadt University of Technology, Darmstadt, Germany
Ming Kang, University of Nebraska-LincolnFollow
James L. Van Etten, University of Nebraska-LincolnFollow
Sabrina Gazzarrini, Universita` degli Studi di Milano, Milan, Ital
Ana Morino, Universita` degli Studi di Milano, Milan, Ital
Gerhard Thiel, Institute of Botany, Darmstadt University of Technology, Darmstadt, GermanyFollow

Document Type

Article

Date of this Version

3-2006

Comments

Published in JOURNAL OF VIROLOGY, Mar. 2006, p. 2437–2444 Vol. 80, No. 5 0022-538X/06/$08.000 doi:10.1128/JVI.80.5.2437–2444.2006 Copyright © 2006, American Society for Microbiology. Used by permission.

Abstract

revious studies have established that chlorella viruses encode K⁺ channels with different structural and functional properties. In the current study, we exploit the different sensitivities of these channels to Cs⁺ to determine if the membrane depolarization observed during virus infection is caused by the activities of these channels. Infection of Chlorella NC64A with four viruses caused rapid membrane depolarization of similar amplitudes, but with different kinetics. Depolarization was fastest after infection with virus SC-1A (half time [t_1/2], about 9 min) and slowest with virus NY-2A (t_1/2, about 12 min). Cs⁺ inhibited membrane depolarization only in viruses that encode a Cs⁺-sensitive K⁺ channel. Collectively, the results indicate that membrane depolarization is an early event in chlorella virus-host interactions and that it is correlated with viral-channel activity. This suggestion was supported by investigations of thin sections of Chlorella cells, which show that channel blockers inhibit virus DNA release into the host cell. Together, the data indicate that the channel is probably packaged in the virion, presumably in its internal membrane. We hypothesize that fusion of the virus internal membrane with the host plasma membrane results in an increase in K⁺ conductance and membrane depolarization; this depolarization lowers the energy barrier for DNA release into the host.