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Lysophospholipid Transacetylase in the Regulation of Paf Levels in Human Monocytes and Macrophages

Luigi Servillo^*, Ciro Balestrieri^*, Alfonso Giovane^*, Paola Pari^*, Davide Palma^*, Giorgio Giannattasio, Massimo Triggiani and Maria Luisa Balestrieri^*,1

^* Department of Biochemistry and Biophysics, Second University of Naples; and

Division of Allergy and Clinical Immunology, University of Naples Federico II, Naples, Italy

¹Correspondence: Department of Biochemistry and Biophysics, Second University of Naples, via L. De Crecchio 7, Naples 80138, Italy. E-mail: mluisa.balestrieri{at}unina2.it

ABSTRACT

The transacetylase (TA), reported to be identical to platelet-activating factor (PAF) acetylhydrolase (II), is a multifunctional enzyme with three catalytic activities: lysophospholipid transacetylase (TA_L), sphingosine transacetylase (TA_S), and acetylhydrolase (AH). We report that TA_L activity participates in the control of PAF levels in monocytes and macrophages and that its regulation differs in these two types of cells. In monocytes, LPS or granulocyte-macrophage colony-stimulating factor (GM-CSF) specifically increased the TA_L activity. Western blot analysis and enzyme assays on immunoprecipitates revealed that the increased activity can be ascribed to PAF-AH (II) and that both translocation from cytosol to membranes and p38/ERKs-mediated phosphorylation regulate the enzyme activation. Instead, in macrophages differentiated in vitro from monocytes by incubation with FCS, an increase of both TA_L and AH activities was observed. Moreover, activation of ERKs and p38 MAP kinase was not required for the up-regulation of PAF-AH (II) in differentiated macrophages. The differences observed in macrophages as compared to monocytes can be explained by 1) p38/ERKs-independent phosphorylation of PAF-AH (II) and 2) appearance of plasma PAF-AH in the course of macrophage differentiation.—Servillo L., Balestrieri C., Giovane A., Pari P., Palma D., Giannattasio G., Triggiani M., Balestrieri M. L. Lysophospholipid transacetylase in the regulation of PAF levels in human monocytes and macrophages.

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