Key result
The Cardiovirus leader protein hijacks cellular RSK kinases and retargets them to directly phosphorylate nucleoporins NUP98 and NUP214, perturbing nucleocytoplasmic trafficking.
Why the study?
To explore whether pathogen proteins hijack RSKs to redirect the kinase toward a specific substrate, using the Cardiovirus leader protein as a paradigm.
Cardiovirus leader proteins hijack and retarget cellular RSK kinases toward specific substrates like NUP98 and NUP214 to perturb nucleocytoplasmic traffic.
Answers are grounded in this paper and cite their sources.
May guide antiviral development targeting L-RSK-NUP interactions; hypothesis-generating for cardiovirus pathogenesis in animal models.
Proteins from some unrelated pathogens, including small RNA viruses of the family Picornaviridae, large DNA viruses such as Kaposi sarcoma-associated herpesvirus and even bacteria of the genus Yersinia can recruit cellular p90-ribosomal protein S6 kinases (RSKs) through a common linear motif and maintain the kinases in an active state. On the one hand, pathogens' proteins might hijack RSKs to promote their own phosphorylation (direct target model). On the other hand, some data suggested that pathogens' proteins might dock the hijacked RSKs toward a third interacting partner, thus redirecting the kinase toward a specific substrate. We explored the second hypothesis using the Cardiovirus leader protein (L) as a paradigm. The L protein is known to trigger nucleocytoplasmic trafficking perturbation, which correlates with hyperphosphorylation of phenylalanine-glycine (FG)-nucleoporins (FG-NUPs) such as NUP98. Using a biotin ligase fused to either RSK or L, we identified FG-NUPs as primary partners of the L-RSK complex in infected cells. An L protein mutated in the central RSK-interaction motif was readily targeted to the nuclear envelope whereas an L protein mutated in the C-terminal domain still interacted with RSK but failed to interact with the nuclear envelope. Thus, L uses distinct motifs to recruit RSK and to dock the L-RSK complex toward the FG-NUPs. Using an analog-sensitive RSK2 mutant kinase, we show that, in infected cells, L can trigger RSK to use NUP98 and NUP214 as direct substrates. Our data therefore illustrate a novel virulence mechanism where pathogens' proteins hijack and retarget cellular protein kinases toward specific substrates, to promote their replication or to escape immunity.
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Lizcano-Perret et al. (2022) studied this question. Cardiovirus leader protein (L) was evaluated on Interaction and phosphorylation of FG-NUPs by L-RSK complex. The Cardiovirus leader protein hijacks cellular RSK kinases and retargets them to directly phosphorylate nucleoporins NUP98 and NUP214, perturbing nucleocytoplasmic trafficking.
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