Reorientation of the golgi apparatus and the microtubule‐organizing center inside macrophages subjected to a chemotactic gradient

Mouse peritoneal macrophages subjected to gradients of activated mouse serum were found by immunofluorescence observations to have their Golgi apparatus and their microtubule‐organizing center largely oriented in the direction of the gradient. By analogy with similar results obtained with motile fibroblasts, it is proposed that these two organelles are rapidly and coordinately reoriented inside the macrophages in order to direct the insertion of new membrane mass, via vesicles derived from the Golgi apparatus, into the leading edge of the cell. Consistent with the importance of such membrane insertion to cell migration, we found that the ionophore monensin, an inhibitor of Golgi functions, inhibited cell motility in the chemostactic gradient. It was further shown that several inhibitors of chemotaxis (monensin, cytochalasin D, cycloheximide) did not inhibit the reorientation of the Golgi apparatus/microtubule‐organizing center in cells exposed to a chemotactic gradient, and that the reorientation required extracellular Ca⁺².