title: Myosins II and V in chromaffin cells: myosin V is a chromaffin vesicle molecular motor involved in secretion.
abstract: The presence of myosin II and V in chromaffin cells and their subcellular distribution is described. Myosin II and V distribution in sucrose density gradients showed only a strong correlation between the distribution of myosin V and secretory vesicle markers. Confocal microscopy images demonstrated colocalization of myosin V with dopamine beta-hydroxylase, a chromaffin vesicle marker, whereas myosin II was present mainly in the cell cortex. Cell depolarization induced, in a Ca2+ and time-dependent manner, the dissociation of myosin V from chromaffin vesicles suggesting that this association was not permanent but determined by secretory cycle requirements. Myosin II was also found in the crude granule fraction, however, its distribution was not affected by cell depolarization. Myosin V head antibodies were able to inhibit secretion whereas myosin II antibodies had no inhibitory effect. The pattern of inhibition indicated that these treatments interfered with the transport of vesicles from the reserve to the release-ready compartment, suggesting the involvement of myosin V and not myosin II in this transport process. The results described here suggest that myosin V is a molecular motor involved in chromaffin vesicle secretion. However, these results do not discard an indirect role for myosin II in secretion through its interaction with F-actin networks.
authors.affiliation: Secretory Process Research Program, Department of Cellular & Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: Sergio D
authors.initials: SD
authors.lastname: Rosé
authors.forename: Tatiana
authors.initials: T
authors.lastname: Lejen
authors.forename: Luciana
authors.initials: L
authors.lastname: Casaletti
authors.forename: Roy E
authors.initials: RE
authors.lastname: Larson
authors.forename: Teodora Dumitrescu
authors.initials: TD
authors.lastname: Pene
authors.forename: José-María
authors.initials: JM
authors.lastname: Trifaró
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D002499:Centrifugation, Density Gradient; D019439:Chromaffin Cells / Q000737:chemistry / Q000378:metabolism*; D022162:Cytoplasmic Vesicles / Q000737:chemistry / Q000378:metabolism; D008856:Microscopy, Fluorescence; D024462:Myosin Type II / Q000032:analysis / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D024701:Myosin Type V / Q000032:analysis / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D011188:Potassium / Q000378:metabolism; D022142:Secretory Vesicles / Q000737:chemistry / Q000378:metabolism; D013347:Subcellular Fractions / Q000737:chemistry
chemical_list: D000906:Antibodies; D024462:Myosin Type II; D024701:Myosin Type V; D011188:Potassium; D002118:Calcium