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Subcellular Distribution of 65,000 Calmodulin‐Binding Protein (p65) and Synaptophysin (p38) in Adrenal Medulla
Author(s) -
Fournier S.,
Novas M. L.,
Trifaró J.M.
Publication year - 1989
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1989.tb07393.x
Subject(s) - synaptophysin , calmodulin , adrenal medulla , calcium binding protein , medulla , chemistry , microbiology and biotechnology , endocrinology , medicine , neuroscience , biology , biochemistry , calcium , immunohistochemistry , enzyme , catecholamine
Abstract: Both neuronal and endocrine cells contain secretory vesicles that store and release neurotransmitters and peptides. Neuronal cells release their secretory material from both small synaptic vesicles and large dense‐core vesicles (LDCVs), whereas endocrine cells release secretory products from LDCVs. Neuronal small synaptic vesicles are known to express three integral membrane proteins: 65,000 calmodulin‐binding protein (65‐CMBP) (p65), synaptophysin (p38), and SV2. A controversial question surrounding these three proteins is whether they are present in LDCV membranes of endocrine and neuronal cells. Sucrose density centrifugation of adrenal medulla was performed to study and compare the subcellular distribution of two of these small synaptic vesicle proteins (65‐CMBP and synaptophysin). Subsequent im‐munoblotting and 125 I‐Protein A binding experiments performed on the fractions obtained from sucrose gradients showed that 65‐CMBP was present in fractions corresponding t o granule membranes and intact chromaffin granules. Similar immunoblotting and 125 I‐Protein A binding experiments with synaptophysin antibodies showed that this protein was also present in intact granules and granule membrane fractions. However, an additional membrane component, equilibrating near the upper portion of the sucrose gradient, also showed strong immunoreactivity with anti‐synaptophysin and high 125 I‐Protein A binding activity. In addition, immunoblotting experiments on purified plasma and granule membranes demonstrated that 65‐CMBP was a component of both membranes, whereas synaptophysin was only present in granule membranes. Thus, there appears to be a different subcellular localization between 65‐CMBP and synaptophysin in the chromaffin cell.