The MIA complex is a conserved and novel dynein regulator essential for normal ciliary motility

• Type of Material: Article
• Authors: Ryosuke Yamamoto, Emory University; Kangkang Song, Brandeis University; Haru-aki Yanagisawa, University of Tokyo; Laura Fox, Emory University; Toshiki Yagi, University of Tokyo; Maureen Wirschell, Emory University; Masafumi Hirono, University of Tokyo; Ritsu Kamiya, University of Tokyo; Daniela Nicastro, Brandeis University; Winfield S Sale, Emory University
• Language: English
• Date: 2013-04-15
• Publisher: Rockefeller University Press
• Publication Version: Final Published Version
• Copyright Statement: © 2013 Yamamoto et al.
• License: Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported
• Final Published Version (URL): http://jcb.rupress.org/content/201/2/263
• Title of Journal or Parent Work: Journal of Cell Biology
• ISSN: 0021-9525
• Volume: 201
• Issue: 2
• Start Page: 263
• End Page: 278
• Grant/Funding Information: This study was supported by the National Institutes of Health (GM051173 to W.S. Sale and GM083122 to D. Nicastro), grants-in-aid from the Japan Society for Promotion of Science (22570157 and 23118706 to T. Yagi and 23570189 to R. Kamiya), and a TOYOBO Biotechnology Foundation Longterm Research Grant, Uehara Memorial Foundation Postdoctoral Fellowship, and Japan Society for the Promotion of Science Postdoctoral Fellowship for Research Abroad (to R. Yamamoto).
• Research Categories: Chemistry, Biochemistry; Biology, Cell

Abstract

Axonemal dyneins must be precisely regulated and coordinated to produce ordered ciliary/flagellar motility, but how this is achieved is not understood. We analyzed two Chlamydomonas reinhardtii mutants, mia1 and mia2, which display slow swimming and low flagellar beat frequency. We found that the MIA1 and MIA2 genes encode conserved coiled-coil proteins, FAP100 and FAP73, respectively, which form the modifier of inner arms (MIA) complex in flagella. Cryo–electron tomography of mia mutant axonemes revealed that the MIA complex was located immediately distal to the intermediate/light chain complex of I1 dynein and structurally appeared to connect with the nexin–dynein regulatory complex. In axonemes from mutants that lack both the outer dynein arms and the MIA complex, I1 dynein failed to assemble, suggesting physical interactions between these three axonemal complexes and a role for the MIA complex in the stable assembly of I1 dynein. The MIA complex appears to regulate I1 dynein and possibly outer arm dyneins, which are both essential for normal motility.