Nck-1 interacts with PKR and modulates its activation by dsRNA.
Activation of the double-stranded RNA (dsRNA)-activated protein kinase PKR results in inhibition of general translation through phosphorylation of the eukaryotic initiation factor 2 alpha-subunit on serine 51 (eIF2alphaSer51). Previously, we have reported that the adaptor protein Nck-1 modulates eIF2alphaSer51 phosphorylation by a subset of eIF2alpha kinases, including PKR. Herein, we demonstrate that Nck-1 prevents efficient activation of PKR by dsRNA, revealing that Nck-1 acts at the level of PKR. In agreement, Nck-1 impairs p38MAPK activation and attenuates cell death induced by dsRNA, in addition to diminish eIF2alphaSer51 phosphorylation. Our data show that the inhibitory effect of Nck-1 on PKR is reversible, as it could be overcome by increasing levels of dsRNA. Interestingly, we found that Nck-1 interacts with the inactive form of PKR, independently of its Src homology domains. Furthermore, we uncovered that Nck-1 is substrate of PKR in vitro. All together, our data provide the first evidence identifying Nck-1 as a novel endogenous regulator of PKR and support the notion that Nck-1-PKR interaction could be a way to limit PKR activation.
Experimental Medicine Department, Polypeptide Laboratory, McGill University, Montreal, Que, Canada.
Eric
E
Cardin
Louise
L
Larose
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D006367:HeLa Cells; D006801:Humans; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D012330:RNA, Double-Stranded / Q000378:metabolism*; D019892:eIF-2 Kinase / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C078332:Nck protein; D015513:Oncogene Proteins; D012330:RNA, Double-Stranded; D019892:eIF-2 Kinase; D048051:p38 Mitogen-Activated Protein Kinases