Regulation of protein kinase CK1αLS by dephosphorylation in response to hydrogen peroxide

Low levels of hydrogen peroxide (H2O2) are mitogenic to mammalian cells and stimulate the hyperphosphorylation of heterogeneous nuclear ribonucleoprotein C (hnRNP-C) by protein kinase CK1α. However, the mechanisms by which CK1α is regulated have been unclear. Here it is demonstrated that low levels of H2O2 stimulate the rapid dephosphorylation of CK1αLS, a nuclear splice form of CK1α. Furthermore, it is demonstrated that either treatment of endothelial cells with H2O2, or dephosphorylation of CK1αLS in vitro enhances the association of CK1αLS with hnRNP-C. In addition, dephosphorylation of CK1αLS in vitro enhances the kinase’s ability to phosphorylate hnRNP-C. While CK1α appears to be present in all metazoans, analysis of CK1α genomic sequences from several species reveals that the alternatively spliced nuclear localizing L-insert is unique to vertebrates, as is the case for hnRNP-C. These observations indicate that CK1αLS and hnRNP-C represent conserved components of a vertebrate-specific H2O2-responsive nuclear signaling pathway.