LEUKOSIALIN (CD43, SIALOPHORIN) REDISTRIBUTION IN UROPODS OF POLARIZED NEUTROPHILS IS INDUCED BY CD43 CROSS-LINKING BY ANTIBODIES, BY COLCHICINE OR BY CHEMOTACTIC PEPTIDES

We investigated a possible association of leukosialin (CD43), the majo r surface sialoglycoprotein of leukocytes. with neutrophil cytoskeleto n, We first analysed the solubility of CD43 in Triton X-100 and observ ed that CD43 of resting neutrophils was mostly soluble, The small prop ortion of CD43 molecules, which 'spontaneously' precipitated in Triton , appeared associated with F-actin, as demonstrated by the fact that t his insolubility did not occur when cells were incubated with cytochal asin B or when F-actin was depolymerized with DNase I in the Triton pr ecipitate, Cell stimulation with anti-CD43 mAb (MEM59) enhanced this C D43-cytoskeleton association, By immunofluorescence as well as by elec tron microscopy, we observed a redistribution of CD43 on the neutrophi l membrane, initially in patches followed by caps, during anti-CD43 cr oss-linking at 37 degrees C, This capping did not occur at 4 degrees C and was inhibited by cytochalasin B and by a myosin disrupting drug b utane-dione monoxime, thus providing evidence that the actomyosin cont racile sytem is involved in the capping and further suggesting an asso ciation of CD43 with the cytoskeleton. Some of the capped cells exhibi ted a front-tail polarization with CD43 caps located in the uropod at the rear of the cell, Surprisingly, colchicine and the chemotactic fac tor fNLPNTL which induce neutrophil polarization associated with cell motility, also resulted in a clustering of CD43 in the uropod, indepen dently of a cross-linking of the molecule by mAbs, An intracellular re distribution of F-actin, mainly at the leading front and of myosin in the tail, was observed during CD43 clustering induced by colchicine an d in cells polarized by anti-CD43 mAbs cross-linking, We conclude that neutrophil CD43 interacts with the cytoskeleton, either directly or i ndirectly, to redistribute in the cell uropod under antibodies stimula tion or during cell polarization by colchicine, thus highly suggesting that CD43 may be involved in cell polarization.