The K protein domain that recruits the interleukin 1-responsive K protein kinase lies adjacent to a cluster of c-Src and Vav SH3-binding sites. Implications that K protein acts as a docking platform.
The heterogeneous ribonucleoprotein particle (hnRNP) K protein interacts with multiple molecular partners including DNA, RNA, serine/threonine, and tyrosine kinases and the product of the proto-oncogene, Vav. The K protein is phosphorylated in vivo and in vitro on serine/threonine residues by an interleukin 1 (IL-1)-responsive kinase with which it forms a complex. In this study we set out to map the K protein domains that bind kinases. We demonstrate that the K protein contains a cluster of at least three SH3-binding sites (P1, PPGRGGRPMPPSRR, amino acids 265-278; P2, PRRGPPPPPPGRG, 285-297; and P3, RARNLPLPPPPPPRGG, 303-318) and that each one of these sites is capable of selectively engaging c-Src and Vav SH3 domains but not SH3 domains of Abl, p85 phosphatidylinositol 3-kinase, Grb-2, and Csk. We demonstrate that the K protein domain that recruits and is phosphorylated in an RNA-dependent manner by the IL-1-responsive kinase, designated KPK for K protein kinase, is contained within the 338-425-amino acid stretch and thus is contiguous but does not include the cluster of the SH3-binding sites. K protein and KPK co-immunoprecipitate from cell extracts with either c-Src or Vav, suggesting that K protein-KPK-c-Src and K protein-KPK-Vav complexes exist in vivo. Furthermore, in the context of K protein, c-Src can reactivate KPK in vitro. The succession of kinase-binding sites contained within the K protein that allow it to form multienzyme complexes and facilitate kinase cross-talk suggest that K protein may serve as a docking platform that promotes molecular interactions occurring during signal transduction.
Van Seuningen
I
I
Department of Medicine, University of Washington, Seattle 98195, USA.
Ostrowski
J
J
Bustelo
X R
XR
Sleath
P R
PR
Bomsztyk
K
K
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D018797:Cell Cycle Proteins; D004789:Enzyme Activation; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology*; D051379:Mice; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D018909:src Homology Domains
D018797:Cell Cycle Proteins; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D007375:Interleukin-1; D011518:Proto-Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; C496619:Vav1 protein, mouse; D011494:Protein Kinases