title: Chromaffin granule membrane-F-actin interactions and spectrin-like protein of subcellular organelles: a possible relationship.
abstract: The membrane of chromaffin granule, the secretory vesicle of adrenal medullary cells storing catecholamines, enkephalins, and many other components, interacts with F-actin. Using low shear falling ball viscometry to estimate actin binding to membranes, we demonstrated that mitochondrial and plasma membranes from chromaffin cells also provoked large increases in viscosity of F-actin solutions. Mitochondrial membranes also had the capacity to cause complete gelation of F-actin. In addition, vasopressin-containing granules from neurohypophysial tissue were shown to bind F-actin and to increase the viscosity of F-actin solutions. Using an antibody directed against human erythrocyte spectrin, it was found that a spectrin-like protein was associated with secretory granule membrane, mitochondrial membrane, and plasma membrane. The chromaffin granule membrane-associated spectrin-like protein faces the cytoplasmic side, is composed of two subunits (240 kD and 235kD ), the alpha-subunit (240 kD, pHi5 .5) being recognized by the antibody. Nonionic detergents such as Triton X-100 or Nonidet P40 failed to release fully active spectrin-like protein. In contrast, Kyro EOB , a different nonionic detergent, was found to release spectrin-like protein while keeping intact F-actin binding capacity, at least below 0.5% Kyro EOB concentration. Chromaffin cells in culture were stained with antispectrin antibody, showing the presence of spectrin-like protein in the cell periphery close to the cell membrane but also in the cytoplasm. We conclude that in living cells the interaction of F-actin with chromaffin granule membrane spectrin observed in vitro is important in controlling the potential function of secretory vesicles.
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D002458:Cell Fractionation; D002837:Chromaffin Granules / Q000378:metabolism*; D002838:Chromaffin System / Q000378:metabolism*; D004299:Dopamine beta-Hydroxylase / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007425:Intracellular Membranes / Q000378:metabolism*; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D008995:Monoamine Oxidase / Q000378:metabolism; D011485:Protein Binding; D013049:Spectrin; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D000199:Actins; D008565:Membrane Proteins; C041393:spectrin-like proteins; D013049:Spectrin; D004299:Dopamine beta-Hydroxylase; D008995:Monoamine Oxidase; D000110:Acetylcholinesterase