This Article Full Text Full Text (PDF) Supplementary Data All Versions of this Article: 0008-5472.CAN-09-1976v1 69/20/8200    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Wang, D. Articles by Jang, D.-J. PubMed PubMed Citation Articles by Wang, D. Articles by Jang, D.-J.

Protein Kinase CK2 Regulates Cytoskeletal Reorganization during Ionizing Radiation–Induced Senescence of Human Mesenchymal Stem Cells

Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California

Requests for reprints: Daojing Wang, Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 977-250, Berkeley, CA 94720. Phone: 510-486-6592; Fax: 510-495-2535; E-mail: djwang{at}lbl.gov.

Key Words: mesenchymal stem cells • ionizing radiation • senescence • cytoskeletal reorganization • CK2

Human mesenchymal stem cells (hMSC) are critical for tissue regeneration. How hMSC respond to genotoxic stresses and potentially contribute to aging and cancer remain underexplored. We showed that ionizing radiation induced cellular senescence of hMSC over a period of 10 days, showing a critical transition between days 3 and 6. This was confirmed by senescence-associated β-galactosidase staining, protein expression profiles of key cell cycle regulators (retinoblastoma protein, p53, p21^waf1/Cip1, and p16^INK4A), and senescence-associated secretory phenotypes (interleukin-8, interleukin-12, GRO, and MDC). We observed dramatic cytoskeletal reorganization of hMSC through reduction of myosin-10, redistribution of myosin-9, and secretion of profilin-1. Using a SILAC-based phosphoproteomics method, we detected significant reduction of myosin-9 phosphorylation at Ser¹⁹⁴³, coinciding with its redistribution. Importantly, through treatment with cell-permeable inhibitors (4,5,6,7-tetrabromo-1H-benzotriazole and 2-dimethylamino-4,5,6,7-tetrabromo-1H-benzimidazole) and gene knockdown using RNA interference, we identified CK2, a kinase responsible for myosin-9 phosphorylation at Ser¹⁹⁴³, as a key factor contributing to the radiation-induced senescence of hMSC. We showed that individual knockdown of CK2 catalytic subunits CK2 and CK2' induced hMSC senescence. However, only knockdown of CK2 resulted in morphologic phenotypes resembling those of radiation-induced senescence. These results suggest that CK2 and CK2' play differential roles in hMSC senescence progression, and their relative expression might represent a novel regulatory mechanism for CK2 activity. [Cancer Res 2009;69(20):8200–7]