Reversibility of gelsolin/actin interaction in macrophages. Evidence of Ca2+-dependent and Ca2+-independent pathways.
We have developed an immunoadsorption technique for quantitating EGTA-resistant gelsolin/actin complexes in macrophages extracted with Triton X-100. We report here that the proportion of gelsolin complexed irreversibly to actin is low in freshly harvested macrophages. The amount of the EGTA-resistant complex increases spontaneously during incubation of the cells in suspension at 37 degrees C, or after exposure to the Ca2+ ionophore ionomycin. On the other hand, exposure of suspended cells to the chemotactic oligopeptide, FMLP, or plating of the cells onto tissue culture dishes causes the EGTA-resistant complex to dissociate rapidly. Plating even prevents Ca2+ ionomycin-treated cells with elevated intracellular Ca2+ from inducing this complex. Therefore, our results suggest that macrophages possess a mechanism, not directly involving Ca2+, for dissociating actin/gelsolin EGTA-resistant complexes. This mechanism may be a Ca2+-independent signal for leukocyte activation.
D000199:Actins / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000502:physiology*; D002465:Cell Movement; D003599:Cytoskeleton / Q000502:physiology*; D004987:Ethers / Q000494:pharmacology; D018260:Gelsolin; D015759:Ionomycin; D008264:Macrophages / Q000502:physiology* / Q000648:ultrastructure; D008840:Microfilament Proteins / Q000502:physiology*; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D011817:Rabbits
D000199:Actins; D002135:Calcium-Binding Proteins; D004987:Ethers; D018260:Gelsolin; D008840:Microfilament Proteins; D015759:Ionomycin; D009240:N-Formylmethionine Leucyl-Phenylalanine; D002118:Calcium