Functional phosphoproteomic analysis reveals cold-shock domain protein A to be a Bcr-Abl effector-regulating proliferation and transformation in chronic myeloid leukemia

• Published in: Cell death & disease 2010-11, Vol.1 (11), p.e93-e93
• Main Authors: Sears, D, Luong, P, Yuan, M, Nteliopoulos, G, Man, Y K S, Melo, J V, Basu, S
• Format: Article
• Language: English
• Subjects: 14-3-3 Proteins - metabolism; 631/136/2091; 631/45/475; 631/80/86; 692/699/67/1990/283/1896; Antibodies; Antineoplastic Agents - therapeutic use; Benzamides; Biochemistry; Biomedical and Life Sciences; CCAAT-Enhancer-Binding Proteins - metabolism; Cell Biology; Cell Culture; Cell Proliferation; Cell Transformation, Neoplastic; Fusion Proteins, bcr-abl - metabolism; Heat-Shock Proteins - metabolism; Humans; Imatinib Mesylate; Immunology; Leukemia, Myelogenous, Chronic, BCR-ABL Positive - drug therapy; Leukemia, Myelogenous, Chronic, BCR-ABL Positive - metabolism; Life Sciences; Mass Spectrometry - methods; Mitogen-Activated Protein Kinase Kinases - metabolism; Original; original-article; Phosphopeptides - analysis; Phosphorylation; Piperazines - therapeutic use; Proteome - analysis; Proto-Oncogene Proteins c-akt - metabolism; Pyrimidines - therapeutic use; Ribosomal Protein S6 Kinases, 90-kDa - metabolism; RNA Interference; RNA, Small Interfering - metabolism; Signal Transduction; Tumor Cells, Cultured
• ISSN: 2041-4889; 2041-4889
• DOI: 10.1038/cddis.2010.72

One proposed strategy to suppress the proliferation of imatinib-resistant cells in chronic myeloid leukemia (CML) is to inhibit key proteins downstream of Bcr-Abl. The PI3K/Akt pathway is activated by Bcr-Abl and is specifically required for the growth of CML cells. To identify targets of this pathway, we undertook a proteomic screen and identified several proteins that differentially bind 14-3-3, dependent on Bcr-Abl kinase activity. An siRNA screen of candidates selected by bioinformatics analysis reveals cold-shock domain protein A (CSDA), shown previously to regulate cell cycle progression in epithelial cells, to be a positive regulator of proliferation in a CML cell line. We show that Akt can phosphorylate the serine 134 residue of CSDA but, downstream of Bcr-Abl activity, this modification is mediated through the activation of MEK/p90 ribosomal S6 kinase (RSK) signaling. Inhibition of RSK, similarly to treatment with imatinib, blocked proliferation specifically in Bcr-Abl-positive leukemia cell lines, as well as cells from CML patients. Furthermore, these primary CML cells showed an increase in CSDA phosphorylation. Expression of a CSDA phospho-deficient mutant resulted in the decrease of Bcr-Abl-dependent transformation in Rat1 cells. Our results support a model whereby phosphorylation of CSDA downstream of Bcr-Abl enhances proliferation in CML cells to drive leukemogenesis.