Potassium ion channels of Chlorella viruses cause rapid depolarization of host cells during infection.
Previous 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.
Frohns
Florian
F
Institute of Botany, Department of Biology, Darmstadt University of Technology, Germany.
Käsmann
Anja
A
Kramer
Detlef
D
Schäfer
Britta
B
Mehmel
Mario
M
Kang
Ming
M
Van Etten
James L
JL
Gazzarrini
Sabrina
S
Moroni
Anna
A
Thiel
Gerhard
G
D002462:Cell Membrane / Q000502:physiology*; D002708:Chlorella / Q000502:physiology* / Q000821:virology*; D004279:DNA, Viral / Q000378:metabolism; D007700:Kinetics; D008564:Membrane Potentials; D017862:Phycodnaviridae / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*
D004279:DNA, Viral; D026902:Potassium Channel Blockers; D015221:Potassium Channels