HUMAN-NEUTROPHILS CONTAIN AN INTRACELLULAR POOL OF PUTATIVE RECEPTORS FOR THE CHEMOATTRACTANT N-FORMYL-METHIONYL-LEUCYL-PHENYLALANINE

  • 1 January 1983
    • journal article
    • research article
    • Vol. 62  (4) , 792-799
Abstract
Purified human peripheral blood neutrophils were disrupted by N2 cavitation or sonication and fractionated on sucrose density gradients to separate the plasma membranes and granule fractions. Quantitatively, the fractions containing the specific granules by marker enzyme/protein enrichment contained the most tritiated fMet-Leu-[3H]Phe binding activity. Competitive binding experiments using unlabeled formyl peptide analogs indicated that the intracellular binding sites display the same structure-function specificity as formyl peptide receptors on intact polymorphonuclear leukocytes (PMN) or isolated plasma membranes. Analysis of the fractions for membrane, primary and secondary granule markers, as well as the distribution of 125I-labeled plasma membranes in sucrose density gradients, indicated that the specific fMet-Leu-[3H]Phe binding to granule-containing fractions was not due to contamination by plasma membranes. In addition, membranes isolated from PMN previously stimulated with phorbol myristate acetate (PMA) demonstrated increased binding sites, while isolated membranes exposed to PMA under the same conditions failed to show such increases. There apparently is an intracellular pool of Met-Leu-Phe receptors that serves as a source of new surface membrane constituents and receptor material that may allow PMN to maintain functional responsiveness during chemotaxis.