Phosphorylation of serine palmitoyltransferase long chain-1 (SPTLC1) on tyrosine 164 inhibits its activity and promotes cell survival.
In BCR-ABL-expressing cells, sphingolipid metabolism is altered. Because the first step of sphingolipid biosynthesis occurs in the endoplasmic reticulum (ER), our objective was to identify ABL targets in the ER. A phosphoproteomic analysis of canine pancreatic ER microsomes identified 49 high scoring phosphotyrosine-containing peptides. These were then categorized in silico and validated in vitro. We demonstrated that the ER-resident human protein serine palmitoyltransferase long chain-1 (SPTLC1), which is the first enzyme of sphingolipid biosynthesis, is phosphorylated at Tyr(164) by the tyrosine kinase ABL. Inhibition of BCR-ABL using either imatinib or shRNA-mediated silencing led to the activation of SPTLC1 and to increased apoptosis in both K562 and LAMA-84 cells. Finally, we demonstrated that mutation of Tyr(164) to Phe in SPTLC1 increased serine palmitoyltransferase activity. The Y164F mutation also promoted the remodeling of cellular sphingolipid content, thereby sensitizing K562 cells to apoptosis. Our observations provide a mechanistic explanation for imatinib-mediated cell death and a novel avenue for therapeutic strategies.
['Taouji|Saïd|S|', 'Higa|Arisa|A|', 'Delom|Frédéric|F|', 'Palcy|Sandrine|S|', 'Mahon|François-Xavier|FX|', 'Pasquet|Jean-Max|JM|', 'Bossé|Roger|R|', 'Ségui|Bruno|B|', 'Chevet|Eric|E|']
D019943:Amino Acid Substitution D000818:Animals D000970:Antineoplastic Agents D017209:Apoptosis D001549:Benzamides D002467:Cell Nucleus D002470:Cell Survival D002518:Ceramides D004285:Dogs D019008:Drug Resistance, Neoplasm D004721:Endoplasmic Reticulum D016044:Fusion Proteins, bcr-abl D055785:Gene Knockdown Techniques D006056:Golgi Apparatus D006801:Humans D000068877:Imatinib Mesylate D020014:K562 Cells D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive D008861:Microsomes D010446:Peptide Fragments D010766:Phosphorylation D019000:Phosphotyrosine D010879:Piperazines D011499:Protein Processing, Post-Translational D021381:Protein Transport D020543:Proteome D011743:Pyrimidines D034741:RNA, Small Interfering D051102:Serine C-Palmitoyltransferase D014158:Transcription, Genetic
SPTLC1 Sphingolipid Endoplasmic Reticulum (ER) Imatinib Apoptosis Protein Kinases Protein Phosphorylation