Specific and Azurophilic Granules from Rabbit Polymorphonuclear Leukocytes. II. Cell Surface Localization of Granule Membrane and Content Proteins before and after Degranulation
The compositional relationship between the cell surface of rabbit polymorphonuclear leukocytes (PMNs) and the membranes of PMN cytoplasmic granules has been investigated. Heterophilic PMNs obtained from peritoneal exudates contained 13 cell surface polypeptides ranging in molecular weight from 220,0...
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Veröffentlicht in: | The Journal of cell biology 1983-04, Vol.96 (4), p.1040-1046 |
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Sprache: | eng |
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Zusammenfassung: | The compositional relationship between the cell surface of rabbit polymorphonuclear leukocytes (PMNs) and the membranes of PMN cytoplasmic granules has been investigated. Heterophilic PMNs obtained from peritoneal exudates contained 13 cell surface polypeptides ranging in molecular weight from 220,000 to 12,000 daltons as determined by lactoperoxidase-catalyzed protein iodination and gel electrophoresis. Of these, four polypeptides co-migrated with proteins identified as the major constituents of specific (SpG) and azurophilic (AzG) granule membranes. The most notable of these were cell surface proteins of 145,000 and 96,000 daltons that co-migrated with SpG membrane proteins and a 48,000-dalton protein that was also a major component of AzG membranes. Also, four iodinated cell surface proteins co-migrated with proteins identified as granule content proteins released from PMNs during exocytosis. Extensive washing did not remove these proteins from the cell surface. Iodination of PMNs after the release of SpG and AzG contents by calcium ionophore-induced exocytosis revealed that there was not a dramatic qualitative change in the proteins on the cell surface. Instead, there were large, quantitative increases in the relative amounts of 125 I that were incorporated into several pre-existing cell surface proteins; all of these cell surface proteins co-migrated as a set with those polypeptides identified as either granule membrane or content proteins. Although nearly all of the major polypeptides of SpG and AzG had counterparts on the cell surface of freshly isolated peritoneal exudate PMNs, there were several polypeptides that were unique to the cell surface. Thus, the PMN has at least three membrane compartments with strikingly different protein compositions. |
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ISSN: | 0021-9525 1540-8140 |
DOI: | 10.1083/jcb.96.4.1040 |