A synaptojanin‐homologous region of Salmonella typhimurium SigD is essential for inositol phosphatase activity and Akt activation

FEBS Letters

Steele-Mortimer, Olivia³  Finlay, B.Brett¹  Marcus, Sandra L.¹  Wenk, Markus R.² 

[1] Biotechnology Laboratory, University of British Columbia, Wesbrook Building 237, 6174 University Boulevard, Vancouver, BC, Canada V6T 1Z3;Yale University School of Medicine, Department of Cell Biology, 295 Congress Avenue, New Haven, CT 06510, USA;Department of Cell Biology and Physiology, Washington University, P.O. Box 8228, 660 S. Euclid, St. Louis, MO 63110, USA

关键词: SopB;    IpgD;    PKB;    Synaptojanin;    Phosphatidylinositol 3-kinase;    Shigella;    PKBα;    serine–threonine kinase Akt;    PI3K;    phosphatidylinositol 3-kinase;    PtdIns(3;    4;    5)P3;    phosphatidylinositol 3;    4;    5-triphosphate;    PtdIns(3;    4)P2;    phosphatidylinositol 3;    4-biphosphate;    PtdIns(4;    5)P2;    phosphatidylinositol 4;    5-biphosphate;    PtdIns(3;    5)P2;    phosphatidylinositol 3;    5-biphosphate;    Ins(1;    3;    4;    5)P4;    inositol 1;    3;    4;    5-tetrakisphosphate;    Ins(1;    3;    4;    5;    6)P5;    inositol 1;    3;    4;    5;    6-pentakisphosphate;    TTSS;    type III secretion system;    SPI;    Salmonella pathogenicity island;    PBS;    phosphate-buffered saline;    TBS;    Tris-buffered saline;   

DOI  :  10.1016/S0014-5793(01)02356-0

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The Ser–Thr kinase Akt is activated in epithelial cells by Salmonella enterica serovar typhimurium. The bacterial effector SigD, which is translocated into host cells via the specialized type III secretion system, is essential for Akt activation. Here, we investigated the inositol phospholipid substrate preferences of SigD. Recombinant SigD preferentially dephosphorylated phosphatidylinositol 3,5-biphosphate and phosphatidylinositol 3,4,5-triphosphate over other phosphatidylinositol lipids. Phosphatidylinositol 3-phosphate was not a substrate, suggesting the 5′ phosphate moiety is one of the preferred substrates. Database searches revealed that SigD bears a small region of homology to the mammalian type II inositol 5-phosphatase synaptojanin. Mutation of two conserved residues in this region, Lys527 and Lys530, decreased or abrogated phosphatase activity, respectively. The Shigella flexneri SigD homologue, IpgD, displayed a similar activity in vitro and also activated Akt when used to complement a ΔsigD Salmonella strain. A mutation in IpgD at Lys507, analogous to Lys530 of SigD, also failed to activate Akt. Thus, we have characterized a region near the carboxyl-terminus of SigD which is important for phosphatase activity. We discuss how dephosphorylation of inositol phospholipids by SigD in vivo might contribute to the activation of Akt.

【 授权许可】

Unknown