Actin filament turnover regulated by cross-linking accounts for the size, shape, location, and number of actin bundles in Drosophila bristles

• Published in: Molecular biology of the cell 2003-10, Vol.14 (10), p.3953-3966
• Main Authors: Tilney, Lewis G, Connelly, Patricia S, Ruggiero, Linda, Vranich, Kelly A, Guild, Gregory M
• Format: Article
• Language: English
• Subjects: Actin Cytoskeleton - metabolism; Actin Cytoskeleton - ultrastructure; Animals; Cell Membrane; Cell Surface Extensions - metabolism; Cell Surface Extensions - ultrastructure; Depsipeptides; Drosophila; Drosophila melanogaster - embryology; Drosophila melanogaster - metabolism; Drosophila melanogaster - ultrastructure; Microscopy, Electron; Models, Molecular; Peptides, Cyclic - pharmacology
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.E03-03-0158

Drosophila bristle cells are shaped during growth by longitudinal bundles of cross-linked actin filaments attached to the plasma membrane. We used confocal and electron microscopy to examine actin bundle structure and found that during bristle elongation, snarls of uncross-linked actin filaments and small internal bundles also form in the shaft cytoplasm only to disappear within 4 min. Thus, formation and later removal of actin filaments are prominent features of growing bristles. These transient snarls and internal bundles can be stabilized by culturing elongating bristles with jasplakinolide, a membrane-permeant inhibitor of actin filament depolymerization, resulting in enormous numbers of internal bundles and uncross-linked filaments. Examination of bundle disassembly in mutant bristles shows that plasma membrane association and cross-bridging adjacent actin filaments together inhibits depolymerization. Thus, highly cross-bridged and membrane-bound actin filaments turn over slowly and persist, whereas poorly cross-linked filaments turnover more rapidly. We argue that the selection of stable bundles relative to poorly cross-bridged filaments can account for the size, shape, number, and location of the longitudinal actin bundles in bristles. As a result, filament turnover plays an important role in regulating cytoskeleton assembly and consequently cell shape.