The Ca$ sp{2+}$ binding protein, calmodulin, has been implicated in several Ca$ sp{2+}$ dependent processes during secretion in many different secretory systems. One area where calmodulin is suggested to play a role is the fusion of the secretory granule with the plasma membrane during exocytosis. Calmodulin may mediate the interaction or fusion through specific calmodulin-binding proteins (CMBPs) present in these two membranes. / CMBPs present in bovine chromaffin cell granule membranes were characterized using the techniques of calmodulin affinity chromatography and $ sp{125}$I calmodulin overlay. Several CMBPs were detected in these membranes. One of these proteins, of molecular mass 65 kilodaltons (65-CMBP), was found to be immunologically identical to a protein previously identified in rat brain synaptic vesicles termed "p65". / Recent studies have debated the subcellular localization of 65-CMBP (p65) as well as another synaptic vesicle protein, synaptophysin (p38). A controversial question surrounding these proteins is whether or not they are present in large dense core secretory granules of neurons and endocrine cells, or exclusively localized on small synaptic or synaptic-like vesicles present in these tissues. Subcellular fractionation studies of adrenal medulla showed that both 65-CMBP and p38 were present in fractions corresponding to granule membranes and intact granules. However, an additional membrane fraction equilibrating near the upper portion of the sucrose gradient, also showed strong immunoreactivity with an antibody to p38. / CMBPs were also isolated from bovine posterior pituitary neurosecretory granules and rat brain synaptic vesicles. These membranes were also found to contain the 65-CMBP (63 kDa in rat brain synaptic vesicles). / Chromaffin cell membranes were isolated using positively charged microcarriers. The 65-CMBP (p65) was also identified in this structure. In addition, immunoblots of plasma and granule membranes showed that the 65-CMBP was a component of both membranes, whereas p38 was only present in granule membranes. Thus, there appears to be a different subcellular localization between the 65-CMBP and p38 in chromaffin cells. / These findings on the 65-CMBP are discussed in relation to its possible role as a mediator of the fusion step of the exocytotic process.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.75881 |
| Date | January 1988 |
| Creators | Fournier, Sue. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Pharmacology and Therapeutics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000913340, proquestno: AAINL52188, Theses scanned by UMI/ProQuest. |
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