title: The role of myosin 1c and myosin 1b in surfactant exocytosis.
abstract: Actin and actin-associated proteins have a pivotal effect on regulated exocytosis in secretory cells and influence pre-fusion as well as post-fusion stages of exocytosis. Actin polymerization on secretory granules during the post-fusion phase (formation of an actin coat) is especially important in cells with large secretory vesicles or poorly soluble secretions. Alveolar type II (ATII) cells secrete hydrophobic lipo-protein surfactant, which does not easily diffuse from fused vesicles. Previous work showed that compression of actin coat is necessary for surfactant extrusion. Here, we investigate the role of class 1 myosins as possible linkers between actin and membranes during exocytosis. Live-cell microscopy showed translocation of fluorescently labeled myosin 1b and myosin 1c to the secretory vesicle membrane after fusion. Myosin 1c translocation was dependent on its pleckstrin homology domain. Expression of myosin 1b and myosin 1c constructs influenced vesicle compression rate, whereas only the inhibition of myosin 1c reduced exocytosis. These findings suggest that class 1 myosins participate in several stages of ATII cell exocytosis and link actin coats to the secretory vesicle membrane to influence vesicle compression.
authors.affiliation: Institute of General Physiology, Ulm University, Albert-Einstein Allee 11, Ulm 89081, Germany.
authors.forename: Nadine
authors.initials: N
authors.lastname: Kittelberger
authors.affiliation: Institute of General Physiology, Ulm University, Albert-Einstein Allee 11, Ulm 89081, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Breunig
authors.affiliation: Department of Chemistry, Technische Universität Dresden, Bergstr. 66, Dresden 01069, Germany.
authors.forename: René
authors.initials: R
authors.lastname: Martin
authors.affiliation: Department of Chemistry, Technische Universität Dresden, Bergstr. 66, Dresden 01069, Germany.
authors.forename: Hans-Joachim
authors.initials: HJ
authors.lastname: Knölker
authors.affiliation: Institute of General Physiology, Ulm University, Albert-Einstein Allee 11, Ulm 89081, Germany pika.miklavc@uni-ulm.de.
authors.forename: Pika
authors.initials: P
authors.lastname: Miklavc
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D056809:Alveolar Epithelial Cells / Q000502:physiology*; D000818:Animals; D012634:Bodily Secretions; D002478:Cells, Cultured; D005089:Exocytosis / Q000235:genetics; D008297:Male; D008561:Membrane Fusion / Q000235:genetics; D024461:Myosin Type I / Q000235:genetics / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D022142:Secretory Vesicles / Q000502:physiology*
chemical_list: C104297:Myo1b protein, rat; C088340:Myo1c protein, rat; D011663:Pulmonary Surfactants; D024461:Myosin Type I
keywords: Exocytosis; Myosin 1; Surfactant secretion