Regulation of the Src Homology 2 Domain-containing Inositol 5′-Phosphatase (SHIP1) by the Cyclic AMP-dependent Protein Kinase*

AUTOR(ES)

Zhang, Jun

FONTE

American Society for Biochemistry and Molecular Biology

RESUMO

Many agents that activate hematopoietic cells use phos pha tidyl ino si tol 3,4,5-trisphosphate (PtdIns 3,4,5-P3) to initiate signaling cascades. The SH2 domain-containing inositol 5′ phosphatase, SHIP1, regulates hematopoietic cell function by opposing the action of phos pha tidyl ino si tol 3-kinase and reducing the levels of PtdIns 3,4,5-P3. Activation of the cyclic AMP-de pend ent protein kinase (PKA) also opposes many of the pro-inflammatory responses of hematopoietic cells. We tested to see whether the activity of SHIP1 was regulated via phos pho ryl a tion with PKA. We prepared pure recombinant SHIP1 from HEK-293 cells and found it can be rapidly phos pho ryl a ted by PKA to a stoichiometry of 0.6 mol of PO4/mol of SHIP1. In 32P-labeled HEK-293 cells transfected with SHIP1, stimulation with Sp-adenosine 3′,5′-cyclic monophosphorothioate triethylammonium salt hydrate (Sp-cAMPS) or activation of the β-adrenergic receptor increased the phos pho ryl a tion state of SHIP1. Inhibition of protein phosphatase activity with okadaic acid also increased the phos pho ryl a tion of SHIP1. Phosphorylation of SHIP1 in vitro or in cells by PKA increased the 5′ phosphatase activity of SHIP1 by 2–3-fold. Elevation of Ca2+ in DT40 cells in response to B cell receptor cross-linking, an indicator of PtdIns 3,4,5-P3 levels, was markedly blunted by pretreatment with Sp-cAMPS. This effect was absent in SHIP−/− DT40 cells showing that the effect of Sp-cAMPS in DT40 cells is SHIP1-de pend ent. Sp-cAMPS also blunted the ability of the B cell receptor to increase the phos pho ryl a tion of Akt in DT40 and A20 cells. Overall, activation of G protein-coupled receptors that raise cyclic AMP cause SHIP1 to be phos pho ryl a ted and stimulate its inositol phosphatase activity. These results outline a novel mechanism of SHIP1 regulation.

Documentos Relacionados

• Regulation of transcription by cyclic AMP-dependent protein kinase.
• src homology 2 domain–containing tyrosine phosphatase SHP-1 controls the development of allergic airway inflammation
• Regulation of 6-phosphofructo-2-kinase activity by cyclic AMP-dependent phosphorylation.
• Differential regulation of bovine brain calmodulin-dependent cyclic nucleotide phosphodiesterase isoenzymes by cyclic AMP-dependent protein kinase and calmodulin-dependent phosphatase.
• Regulation of phospholipid biosynthesis in Saccharomyces cerevisiae by cyclic AMP-dependent protein kinase.