title: c-Abl tyrosine kinase binds and phosphorylates phospholipid scramblase 1.
abstract: Phospholipid scramblase 1 (PLSCR1) is a plasma membrane protein that has been proposed to play a role in the transbilayer movement of plasma membrane phospholipids. PLSCR1 contains multiple proline-rich motifs resembling Src homology 3 (SH3) domain-binding sites. An initial screen against 13 different SH3 domains revealed a marked specificity of PLSCR1 for binding to the Abl SH3 domain. Binding between intracellular PLSCR1 and c-Abl was demonstrated by co-immunoprecipitation of both proteins from several cell lines. Deletion of the proline-rich segment in PLSCR1 (residues 1--118) abolished its binding to the Abl SH3 domain. PLSCR1 was Tyr-phosphorylated by c-Abl in vitro. Phosphorylation was abolished by mutation of Tyr residues Tyr(69)/Tyr(74) within the tandem repeat sequence (68)VYNQPVYNQP(77) of PLSCR1, implying that these residues are the likely sites of phosphorylation. Cellular PLSCR1 was found to be constitutively Tyr-phosphorylated in several cell lines. The Tyr phosphorylation of PLSCR1 was increased upon overexpression of c-Abl and significantly reduced either upon cell treatment with the Abl kinase inhibitor STI571, or in Abl-/- mouse fibroblasts, suggesting that cellular PLSCR1 is a normal substrate of c-Abl. Cell treatment with the DNA-damaging agent cisplatin activated c-Abl kinase and increased Tyr phosphorylation of PLSCR1. The cisplatin-induced phosphorylation of PLSCR1 was inhibited by STI571 and was not observed in Abl-/- fibroblasts. These findings indicate that c-Abl binds and phosphorylates PLSCR1, and raise the possibility that an interaction between c-Abl and plasma membrane PLSCR1 might contribute to the cellular response to genotoxic stress.
authors.affiliation: Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: J
authors.initials: J
authors.lastname: Sun
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: M A
authors.initials: MA
authors.lastname: Schwartz
authors.forename: J Y
authors.initials: JY
authors.lastname: Wang
authors.forename: T
authors.initials: T
authors.lastname: Wiedmer
authors.forename: P J
authors.initials: PJ
authors.lastname: Sims
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D016313:Genes, abl; D005982:Glutathione Transferase / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D016315:Proto-Oncogene Proteins c-abl / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D014162:Transfection; D014443:Tyrosine; D018909:src Homology Domains
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D005982:Glutathione Transferase; D016315:Proto-Oncogene Proteins c-abl