Evidence that SHIP-1 contributes to phosphatidylinositol 3,4,5-trisphosphate metabolism in T lymphocytes and can regulate novel phosphoinositide 3-kinase effectors.
The leukemic T cell line Jurkat is deficient in protein expression of the lipid phosphatases Src homology 2 domain containing inositol polyphosphate phosphatase (SHIP) and phosphatase and tensin homolog deleted on chromosome ten (PTEN). We examined whether the lack of expression of SHIP-1 and PTEN is shared by other leukemic T cell lines and PBLs. Analysis of a range of cell lines and PBLs revealed that unlike Jurkat cells, two other well-characterized T cell lines, namely CEM and MOLT-4 cells, expressed the 5'-phosphatase SHIP at the protein level. However, the 3-phosphatase PTEN was not expressed by CEM or MOLT-4 cells or Jurkat cells. The HUT78 cell line and PBLs expressed both SHIP and PTEN. Jurkat cells exhibited high basal levels of phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P(3); the lipid substrate for both SHIP and PTEN) as well as saturated protein kinase B (PKB) phosphorylation. Lower levels of PI(3,4,5)P(3) and higher levels of phosphatidylinositol 3,4-bisphosphate (PI(3,4)P(2)) as well as unsaturated constitutive phosphorylation of PKB were observed in CEM and MOLT-4 cells compared with Jurkat cells. In PBLs and HUT78 cells which express both PTEN and SHIP-1, there was no constitutive PI(3,4,5)P(3) or PKB phosphorylation, and receptor stimuli were able to elicit robust phosphorylation of PKB. Expression of a constitutively active SHIP-1 protein in Jurkat cells was sufficient to reduce both constitutive PKB membrane localization and PKB phosphorylation. Together, these data indicate important differences between T leukemic cells as well as PBLs, regarding expression of key lipid phosphatases. This study provides the first evidence that SHIP-1 can influence the constitutive levels of PI(3,4,5)P(3) and the activity of downstream phosphoinositide 3-kinase effectors in T lymphocytes.
Freeburn
Robin W
RW
Department of Pharmacy and Pharmacology, Bath University, Claverton Down, Bath, BA2 7AY, UK.
Wright
Karen L
KL
Burgess
Steven J
SJ
Astoul
Emmanuelle
E
Cantrell
Doreen A
DA
Ward
Stephen G
SG
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001798:Blood Proteins / Q000378:metabolism; D018106:CD28 Antigens / Q000276:immunology / Q000378:metabolism; D017252:CD3 Complex / Q000276:immunology / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018984:Epitopes, T-Lymphocyte / Q000378:metabolism; D006801:Humans; D007295:Inositol Phosphates / Q000502:physiology; D000072181:Inositol Polyphosphate 5-Phosphatases; D019169:Jurkat Cells; D008024:Ligands; D051379:Mice; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010716:Phosphatidylinositols / Q000096:biosynthesis / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011948:Receptors, Antigen, T-Cell / Q000502:physiology; D016176:T-Lymphocyte Subsets / Q000201:enzymology* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains / Q000276:immunology; D000099182:Phosphoinositide 5-Phosphatases
D000911:Antibodies, Monoclonal; D001798:Blood Proteins; D018106:CD28 Antigens; D017252:CD3 Complex; D004791:Enzyme Inhibitors; D018984:Epitopes, T-Lymphocyte; D007295:Inositol Phosphates; D000072181:Inositol Polyphosphate 5-Phosphatases; D008024:Ligands; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D000072183:Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases; D010716:Phosphatidylinositols; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011948:Receptors, Antigen, T-Cell; D025521:Tumor Suppressor Proteins; D014443:Tyrosine; D000099182:Phosphoinositide 5-Phosphatases; C060974:phosphatidylinositol 3,4,5-triphosphate; C039077:platelet protein P47; C051854:inositol 3,4-bisphosphate; C494929:PTEN protein, human; C000606430:INPP5D protein, human; C098706:INPPL1 protein, human; C000606433:Inpp5d protein, mouse