The fatty acid-binding heterocomplex FA-p34 formed by S100A8 and S100A9 isthe major fatty acid carrier in neutrophils and translocates from the cytosol to the membrane upon stimulation

Since no data are available concerning fatty acid (FA) transport in neutrop hils we studied the presence of possible FA carriers. The kFA-p34 complex, composed of S100A8 and S100A9, has been implicated in the intracellular tra nsport of arachidonic acid and its precursors in human keratinocytes. Here, we show that FA-p34 is the major FA carrier in human neutrophils (nFA-p34) . The complex is highly expressed in resting neutrophils (2.65% of cytosoli c proteins) and translocates to the membrane fraction upon stimulation with opsonized zymosan. Comparison of purified nFA-p34 with kFA-p34 shows that both complexes are composed of nearly the same subunits and possess similar binding properties for oleic acid. Densito-metrical analyses of 2D gels sh ow that n and kFA-p34 contain twice as much S100A8 and S100A9 suggesting an estimated stoichiometry of (S100A8),S100A9. A method is described allowing to distinguish n and kFA-p34 from S100A8/S100A9 homo- and heteromer comple xes that are devoid of FA-binding properties. After solvent extraction, we find by GC analysis linoleic acid as major endogenous Ligand of purified kF A-p34. Our results suggest that nFA-p34, might be involved in the shuttling of unsaturated FA between the cytosol and the plasma membrane of neutrophi ls. (C) 1999 Academic Press.