A non-catalytic herpesviral protein reconfigures ERK-RSK signaling by targeting kinase docking systems in the host

Abstract

The Kaposi’s sarcoma associated herpesvirus protein ORF45 binds the extracellular signal-regulated kinase (ERK) and the p90 Ribosomal S6 kinase (RSK). ORF45 was shown to be a kinase activator in cells but a kinase inhibitor in vitro, and its effects on the ERK-RSK complex are unknown. Here, we demonstrate that ORF45 binds ERK and RSK using optimized linear binding motifs. The crystal structure of the ORF45-ERK2 complex shows how kinase docking motifs recognize the activated form of ERK. The crystal structure of the ORF45-RSK2 complex reveals an AGC kinase docking system, for which we provide evidence that it is functional in the host. We find that ORF45 manipulates ERK-RSK signaling by favoring the formation of a complex, in which activated kinases are better protected from phosphatases and docking motif-independent RSK substrate phosphorylation is selectively up-regulated. As such, our data suggest that ORF45 interferes with the natural design of kinase docking systems in the host.

Cardiovirus leader proteins retarget RSK kinases toward alternative substrates to perturb nucleocytoplasmic traffic

“…Recent work showed that some proteins expressed by unrelated viruses and bacteria hijack host RSK kinases through a conserved DDVF linear motif that likely emerged in those proteins by convergent evolution (Sorgeloos et al, 2022, Alexa et al, 2022). Occurrence of the DDVF motif in RHBDF1, a known target of RSKs suggests that some proteins, either from pathogens or from the host cell, can associate with RSK through the DDVF motif to promote their own phosphorylation by RSKs (Alexa et al, 2022).…”

“…Recent work showed that some proteins expressed by unrelated viruses and bacteria hijack host RSK kinases through a conserved DDVF linear motif that likely emerged in those proteins by convergent evolution (Sorgeloos et al, 2022, Alexa et al, 2022). Occurrence of the DDVF motif in RHBDF1, a known target of RSKs suggests that some proteins, either from pathogens or from the host cell, can associate with RSK through the DDVF motif to promote their own phosphorylation by RSKs (Alexa et al, 2022). In the case of TMEV L protein, a point mutation in the C-terminal domain of the protein (L M60V ) abrogated L activities although this mutation affected neither L-RSK interaction nor RSK activation by L (Ricour et al, 2009a, Sorgeloos et al, 2022).…”

“…After phosphorylation, such proteins would act as effectors to the benefit of the pathogen (Figure 1A) (Sorgeloos et al, 2022). In an alternative model, proteins interacting with RSK through the conserved DDVF motif could directly act as preferential substrates for RSK-mediated phosphorylation (Figure 1B), as was suggested for protein RHBDF1 (Rhomboid 5 homolog 1) (Alexa et al, 2022).…”

“…Proteins encoded by several unrelated pathogens, including RNA viruses, DNA viruses and bacteria, were recently shown to use a common short linear motif (D/E-D/E-V-F, referred to as DDVF hereafter) to recruit members of the cellular p90-ribosomal S6 protein kinases (RSKs) family: RSK1, RSK2, RSK3 and RSK4 (Sorgeloos et al, 2022, Alexa et al, 2022). Interestingly, competition and cross-linking experiments, as well as crystallography data show that these pathogens’ proteins, the leader (L) protein (cardioviruses), ORF45 (Kaposi sarcoma-associated herpes virus - KSHV) and YopM ( Yersinia ) use a common interface to recruit RSKs.…”

“…Interestingly, competition and cross-linking experiments, as well as crystallography data show that these pathogens’ proteins, the leader (L) protein (cardioviruses), ORF45 (Kaposi sarcoma-associated herpes virus - KSHV) and YopM ( Yersinia ) use a common interface to recruit RSKs. Binding of the pathogens’ proteins prevents RSK dephosphorylation by cellular phosphatases, thereby maintaining RSK in an active state (Sorgeloos et al, 2022, Alexa et al, 2022). Although infection with all three pathogens leads to RSK activation, the outcome of this activation differs according to the protein bound to RSK.…”